C H A P T E R

2
Wastewater treatment as a process
and a resource
M.I. Pariente, Y. Segura, R. Molina, F. Martı́nez
Department of Chemical and Environmental Technology, Rey Juan Carlos University, Madrid, Spain

Introduction • Natural pollution: Consists of the presence

of various substances in the water (solid
Water is a natural and essential resource for particles, vegetable waste, animal
life. However, 97% of the world’s water excrements, etc.) without human
resources appears as salt water in seas and intervention, due to weather and natural life.
oceans. Only 3% can potentially be used for These pollutants are naturally degraded and
human needs (domestic, agricultural, livestock, eliminated through physical, chemical, and
and industrial uses); and a large part of this fresh biological processes.
water (about 90%) is in the form of glaciers and • Urban pollution: It is the result of the use of
polar caps, so it is not directly available to water in urban areas (housing, shops,
humans. Therefore, only 0.4% of the water hospitals, etc.). It is characterized by high
resources in the world are accessible to the needs content of fecal and food wastes and by
of mankind as part of aquifers, rivers, reservoirs, the presence of different common chemical
lakes, and the atmosphere, and <0.01% appears products (detergents, cosmetics, drugs,
as surface water. Although this number seems etc.).
minimal and insufficient, it is larger than current • Agricultural and livestock pollution: Results
demand and consequently water is considered a from the use of water in agriculture, leading
renewable resource. However, this renewable to the pollution of water with pesticides,
resource is threatened by its irregular distribu- biocides, and fertilizers. The most important
tion around the world, the growing demand contamination is due to organic wastes.
from the gradual increase in population, and • Industrial pollution: It is the result of the use
consequent deterioration of its quality, as a of water in industrial activities (process,
result of domestic and industrial uses. Water cleaning, and cooling waters). It usually
contamination may be classified into the follow- produces a strong effect on ecosystems,
ing groups: but this depends on the type of industry.

Wastewater Treatment Residues as Resources for Biorefinery Products and Biofuels 19 # 2020 Elsevier Inc. All rights reserved.
https://doi.org/10.1016/B978-0-12-816204-0.00002-3
20 2. Wastewater treatment as a process and a resource

It is important to highlight that the possible transfer with high bacterial densities, stress
numbers of compounds and polluting effects caused by pollutants, such as heavy metals
are very large. However, nutrients (nitrogen and antibiotics, and biofilms formed during
and phosphorus), organic matter, heavy metals, the purification process [6].
hydrocarbons, and endocrine disruptors (as part • Micropollutants of emerging concern are a
of the so-called microcontaminants of emerging broad group of different compounds that are
concern) can be considered as current major con- constantly released into the environment at
taminants in wastewater effluents, leading to low concentrations. They cover a wide range
adverse effects on the environment and human of pollutants, including pharmaceuticals,
health [1]: personal care products (PCPs), pesticides,
persistent organic pollutants, and
• Nutrients (nitrogen and phosphorus) are
disinfectant by-products, among others. Once
mainly responsible for the eutrophication
released in nature, many of these compounds
present in wastewater effluents. An excessive
are not totally or even partially eliminated in
nutrient proliferation can lead to the
wastewater treatment plants and can be
stimulation of algae growth and toxic
transported to places far away from the
cyanobacteria bloom, which can lead to
generated source. The presence of these
dissolved oxygen depletion, physical changes
chemicals remains a major challenge to the
to receiving water bodies, bioaccumulation
environment and human health. One major
and biomagnification of contaminants,
problem is that some of them act as endocrine
release of toxic substances, nutrient
disruptors (EDCs), which can alter the
enrichment effects, and increased cost of
normal functions of hormones, resulting in a
water purification [2]. Eutrophication and
variety of health effects [7].
global warming are the two most commonly
assessed impacts in life cycle assessment The quality of the water is a fundamental
(LCA) studies for wastewater treatment descriptive variable used for its environmental
plants [3]. characterization, also necessary for hydrological
• The content of organic matter is very planning and management. It is defined as the
important in all water treatment processes, as set of physical, chemical, and biological charac-
well as for the self-purification characteristics teristics that make water suitable for a specific
of natural waters. Organic matter and other use. For each use, there are a series of require-
forms of contaminants create a breeding ments, which are mostly related to concentra-
ground for most pathogenic organisms, such tions of the same chemical, physical, and
as bacteria, fungi, protozoa, nematodes, and biological principles. If the water does not meet
viruses, which are among the major health these requirements, it is said to be unacceptable
problems associated with water and or of poor quality. It must be borne in mind that
wastewater. It should be pointed out that the the quality of the water can be modified both by
majority of waterborne microorganisms natural and anthropogenic causes. In the latter
causing human disease are from fecal wastes. case, contamination, as discussed and generally
Additionally, wastewater treatment plants speaking, is more serious, far-reaching, and per-
are already identified as sources of antibiotic sistent. In addition to the different parameters
resistant bacteria (ARB) and antibiotic used to describe and quantify water quality,
resistance genes (ARGs) among pathogenic the properties and composition of the different
and nonpathogenic bacteria [4, 5]. The types of water must be taken into account. As
wastewater treatment process creates there are different ways to measure water qual-
conditions that may favor horizontal gene ity, the assessment process consists of obtaining

I. Wastewater treatment as a process and a resource

 Introduction 21
an appreciation of the physical, chemical, and Similarly, the US EPA (Environmental Protec-
biological nature of the water in relation to nat- tion Agency) gathers the federal rules and rec-
ural quality, effects on man, and ultimate use [8]. ommendations [12]; the regulatory authority
There are two main purposes of treating falls to individual states, which have indepen-
wastewater [9]. The first and most common is dently developed water reclamation criteria
the need for safe disposal of the treated waste- and, therefore, there are variations among the
water into the environment. The second goal is different state regulations. The first water recla-
wastewater reuse. Apart from compulsory rules mation and reuse standards were adopted by
in each country, there are several national and the state of California in 1918. This state has
international organizations that publish recom- continually revised its water reuse standards
mendations to be used as references. These and it even includes requirements for monitor-
are, for example, WHO (World Health Organi- ing constituents of emerging concern, and limits
zation), FAO (Food and Agricultural Organiza- depend on end use [13].
tion), and ISO (International Organization for The quality requirements depend on the use
Standardization), among others. The European of wastewater (discharge or reuse). Biochemical
Union (EU) and the United States (US) apply dif- oxygen demand (BOD5), chemical oxygen
ferent regulations concerning the collection, demand (COD), total phosphorus, total nitro-
treatment, and discharge of urban wastewater. gen, and total suspended solids (TSS) are the
EU legislation establishes different standards main physicochemical parameters used in
in order to protect the environment from the wastewater discharge regulations. Related to
adverse effects of wastewater discharges [10]. water reuse, microbiological parameters are also
Also, discharge to a surface body of water, as taken into account, such as E. coli, Legionella
in “waters of the United States” (a legal defini- spp., fecal coliforms, and intestinal nematodes
tion), must comply with the CWA (Clean Water (pathogens). In the United States, chlorine
Act) and NPDES (National Pollution Discharge contact time and residual, as well as dissolved,
Elimination System). The water discharge per- oxygen, pH, and temperature are also consid-
mits provide for two levels of control: ered important parameters for water reuse.
technology-based limits and water quality- On the other hand, knowledge gained in the
based limits. last decades on the presence and effects of com-
The reuse of treated reclaimed wastewater, as pounds discharged by different wastewater
a technology, appeared during the 20th century treatment plants (WWTPs) raises the question
(indications for utilization of wastewater for of the appropriateness of the current approaches
agricultural irrigation extend back approxi- to evaluate water quality [14]. In recent years, an
mately 5000 years), complying at the same time increased number of anthropogenic chemicals
with specific regulations. EU legislation encour- are being disposed and detected, increasing
ages water reuse through: (a) the Urban Waste the evidence of adverse environmental effects.
Water Treatment Directive, which provides that Therefore, it is important to consider new
“treated wastewater shall be reused whenever methodologies in which engineering, environ-
appropriate”; and (b) the Water Framework mental, ecotoxicological, and microbiological
Directive, which lists water reuse as a possible expertise are taken into account to assess the
measure to be included in the programs of mea- overall quality of wastewater.
sures for each river basin. However, EU legisla- It is also important to stress the latest progress
tion does not specify conditions for water reuse. in analytical chemistry that has led to the deve-
The European Commission proposed on May lopment of technologies that enable detection of
2018 new regulations on minimum require- contaminants of emerging concern in the trace
ments for water reuse [11]. range. The large presence of those and other

I. Wastewater treatment as a process and a resource

22 2. Wastewater treatment as a process and a resource

contaminants in water samples and their toxico- Table 2.1 shows the typical composition of a
logical relevance emphasize the need for bioana- domestic wastewater. The main contaminants
lytical assessment to complement the analysis to be removed are biodegradable organics
[15]. The toxicological impact of substances is (BOD5/COD >0.4), that correspond with a high
mainly dependent on concentration, bioavail- percentage of volatile solids (60%–70% of the
ability, duration of exposure, critical windows total solids). Pathogen and salts concentrations
of exposure, and species-specific sensitivity [16]. are usually high, the latter being measured as
In this context, chemical approaches should dissolved solids (70% of the total solids) [20].
include target, nontargeted and suspect ana- WWTPs include many logically arranged and
lyses, identification of transformation products, separated physical, chemical, and biological
modeling, as well as toxicity identification eva- processes [21], which are joined in primary, se-
luation. Similarly, water quality assessment condary, and tertiary treatments (Fig. 2.1).
methods, including in vitro or in vivo assays,
have been developed to detect ecotoxicological
effects on a variety of endpoints and trophic TABLE 2.1 Typical composition of a domestic
levels [17–19]. wastewater.
Parameter Value

Processes of wastewater treatment plant COD (mg L
1) 200–800

1
BOD (mg L ) 110–350
The configuration of a WWTP is highly
1
TKN (mg L ) 8–70
dependent on the characteristics of the wastewa-

1
ter and the desirable quality of the final effluent. N-NH+4 (mg L ) 7–45
Conditioning and distribution of water for resi- TP (mg L )
1
4–12
dential, commercial, and industrial uses is nec-
pH 7.3–7.5
essary in all human communities. Although

1
urban wastewater treatment is a well- TS (mg L ) 390–1900
established practice, water treatment is nowa- TDS (mg L
1) 270–1300
days subject to multiple changes. Application
TSS (mg L
1) 120–400
of more restrictive limitations on the quality of
the effluents and the potential use of those efflu- Conductivity (μS cm
1) 10,000–13,000
ents as water sources for industry, agriculture, Oil and fats (mg L
1) 50–100
and urban uses have opened new topics and
Cl
(mg L
1) 30–240
perspectives that will lead research in future

1
years [20]. SO2

4 (mg L ) 20–250
Sewage treatment refers to the processing of Total coliforms (nº/100 mL) 106–1010
primarily domestic wastewater produced by
Abbreviations: COD, chemical oxygen demand; BOD, biochemical
typical community and household activities. oxygen demand; TKN, total Kjeldahl nitrogen; TP, total phosphorus;
The flow of sewage to be treated may approxi- TS, total solids; TDS, total dissolved solids; TSS, total suspended
mate the flow of municipal water supplied to solids.
(Based on X. Yan, C. Zhu, B. Huang Q. Yan, Q. Zhang, Enhanced nitrogen
the community, being in the range of about removal from electroplanting tail wastewater through two-staged anoxic-
380 L/day per capita in rural areas, to 570 L/ oxic (A/O) process, Bioresour. Technol. 247 (2018) 157–164; F.M. Kemmer,
day in urban areas with industrial uses [20], The Nalco Water Handbook. McGraw-Hill Inc, USA, 1987; G.
Tchobanoglous, F.L. Burton, H.D. Stensel, Wastewater Engineering:
although losses due to infiltration and poor state Treatment and Reuse. 4th ed., McGraw-Hill. Metcalf & Eddy, Inc.,
of pipelines must be taken into account. New York, 2003.)

I. Wastewater treatment as a process and a resource

 Processes of wastewater treatment plant 23

FIG. 2.1 General scheme of an urban wastewater treatment plant.

Physical/chemical treatments cover a variety of Primary treatment

processes aiming at the removal of different pol-
lutants producing an effluent that could be The primary process is the first step in the
appropriately treated in the following steps, municipal sewage treatment plant. The tech-
commonly through biological processes. Biolog- niques included in the primary process are
ical treatment is the succeeding method after designed to reduce the suspended and floating
physical/chemical treatment to lower high solids in the wastewater by either mechanical
levels of BOD, COD, and organic matter. These devices or gravity action. Filters and static and
processes have the production of sludge as a moving screens block floating bulky debris that
common by-product that should be treated could clog further pipes or pumps in the WWTP.
and dewatered for subsequent disposal or Grit chambers slow down the flow, allowing the
reutilization. settling of sand and similar fine solids. The
The possible treatment steps, modifications, remaining grease and oil, responsible for odor,
and operational conditions that can be applied are normally removed in skimming tanks. Addi-
vary considerably [22–24]. Table 2.2 shows tionally, natural settling of suspended solids can
many treatment processes that can be used in be enhanced by the addition of chemicals in
WWTPs, according to the target pollutant. Cur- coagulation and flocculation tanks [25]. Finally,
rent applications vary greatly, with some of the wastewater goes to the primary settling tank
them being more intensively applied over others (clarifier or sedimentation tank), where about
that are still under development or in the proof- 98% of settable solids, 60%–80% suspended
of-concept stage. Nevertheless, WWTP configu- solids, and 30%–50% of oxygen demand can
rations are under continuous improvement and be removed from the wastewater in the form
some of the processes are becoming more impor- of primary sludge [26].
tant in addressing a sustainable and environ- Sedimentation is an effective process for se-
mentally favorable depuration. paration of the primary sludge and produces a

I. Wastewater treatment as a process and a resource

24 2. Wastewater treatment as a process and a resource

TABLE 2.2 Classification of common wastewater treatment processes according to target pollutants.
Target
pollutant/
objective Physical process Chemical process Biological process

Suspended Settling, flotation, sieving, filtration,

particles microfiltration, centrifuging, hydrocycloning,
magnetic separation
Soluble organic Adsorption, absorption, stripping, nanofiltration Electrochemical Anaerobic
compounds oxidation biodegradation,
aerobic
biodegradation
Ammonia Stripping, ion exchange Precipitation (struvite), Nitrification/
electrodialysis denitrification

Soluble Crystallization, ion exchange, evaporation Precipitation,

minerals electrodialysis

Soluble Crystallization, adsorption Precipitation Concentration in

phosphate biomass
Dissolved Crystallization, ion exchange Precipitation, reduction,
sulfur and partial oxidation
compounds
Decolorization Adsorption, absorption, reverse osmosis, Oxidation, Anaerobic and aerobic
filtration, nanofiltration, flotation electrochemical biological
treatment degradation
Disinfection UV, ultrasound (US), gamma radiation Oxidation
Heavy metal Cementation, ultrafiltration after complexation, Electrolysis, precipitation
ions adsorption, absorption
Toxic soluble Stripping of volatile compounds Advanced oxidation Anaerobic
organic processes, pretreatment
pollutants electrochemical
treatment
(Based on W. Rulkens, Increasing significance of advanced physical/chemical processes in the development and application of sustainable wastewater
treatment systems, Front. Environ. Sci. Eng. China 2 (4) (2008) 385–396.)

significant reduction of the overall emissions of industries implement this technology for their
CO2 equivalents and energy demand in the fol- wastewater treatment process: paper mills,
lowing stages of wastewater treatment [27]. chemical-mechanical polishing (CMP), the meat
However, dissolved air flotation (DAF) is also industry, the seafood industry, and oil refinery
considered an interesting method, based on wastewaters [28–31]. DAF clarifiers remove
the production of bubbles by dissolving air in suspended solids more rapidly than conven-
the wastewater under pressure, followed by tional primary sedimentation and are cost
releasing the air at atmospheric pressure in a flo- effective from an engineering standpoint. For
tation tank [28]. DAF is usually designed in com- these reasons, there are many commercial
bination with coagulation. A variety of solutions based on this technology, such as the

I. Wastewater treatment as a process and a resource

 Processes of wastewater treatment plant 25
IDRAFLOT flotation unit [32] and the poseidon conventional aeration tank (HRT time 1–3 h) [5].
PPM and Saturn DAF clarifier units from SUEZ The inorganic phosphorus is released from cells
Water Technologies [33, 34]. as a result of polyphosphate hydrolysis in the
anaerobic zone. The soluble phosphorus is taken
up by bacteria in the aeration tank, synthesizing
Secondary treatment
polyphosphates, using the energy released from
Secondary treatment consists of biological BOD oxidation. The sequencing batch reactor
degradation of dissolved degradable organic (SBR), such as the Cyclor technology from
matter and remaining suspended solids by SUEZ [39], is a modification of an activated
microorganisms, reducing the organic loading sludge system for wastewater treatment,
in terms of COD and BOD, as well as the number which includes five stages (fill, react, settle,
of pathogens. The conventional active sludge decant, and idle) occurring in a single reactor
(CAS) process has been the most used wastewa- tank. Several conditions (anaerobic, aerobic,
ter technology for removing nutrients, carbona- anoxic) can occur during SBR operation,
ceous biological matter, and nitrogenous matter allowing the system not only to remove organic
for >100 years [35]. The main reason is its matter but also to carry out nitrification, denitri-
flexibility of use for any kind of wastewater, fication, or even phosphorus and polyhydrox-
producing an effluent of high quality that meets yalkanoates accumulation [40].
the increasingly stringent effluent standards. As an alternative to suspended growth sys-
Biomass generated from the CAS along with tems, fixed growth technologies offer smaller
the overflow effluent is taken to a secondary reactors with lower land space needs and
settling tank. Some of the sludge is recycled to greater simplicity of operation and process sta-
the CAS and used as an inoculum for primary bility. The trickling filter is an aerobic treatment
effluent. The remainder of the sludge, known that utilizes microorganisms attached to a filtra-
as secondary sludge, is removed. tion media made of a bed of rock, slag, or plastic.
Activated sludge processes can be modified The wastewater percolates down and bacteria
for nitrogen removal, by promoting nitrification grow on the media, utilizing organic matter
followed by denitrification [36]. The establish- and nitrogen from the wastewater [41]. BOD
ment of a nitrifying population in activated removal by trickling filters is approximately
sludge depends on the wastage rate of the 85% for low-rate filters [42]. Effluent from the
sludge (BOD loading rate, mixed liquor sus- trickling filter usually passes into a final clarifier
pended solids (MLSS), and retention time), to further separate solids from effluent. Another
although nitrification is expected at sludge age recent fixed growth technology, implemented in
>4 days [37]. Nitrification must be followed by industrial wastewater treatment systems, is
denitrification to remove nitrogen from waste- moving bed bioreactors (MBBR). The MBBR
water. The Bardenpho process uses a series of principle involves growing a fixed biofilm on
four tanks to promote nitrification, denitrifica- plastic elements that move freely in the biologi-
tion, and carbonaceous oxidation, as a sole bio- cal reactor. Compared to other fixed growth
logical system. The Bardenpho process can technologies, this system shows no clogging
also be modified to simultaneously remove problems and lower head losses [15]. A further
nitrogen and phosphorus during operation step is a hybrid process consisting of a fluidized
[38]. This alternative is based on the A/O pro- fixed biofilm media and an activated sludge pro-
cess, consisting of a modified activated sludge cess taking place in a single aeration tank, called
system that includes an anaerobic zone (hydrau- integrated fixed film activated sludge (IFAS).
lic retention time (HRT) 0.5–1 h) upstream of the The IFAS process can be operated at low solid

I. Wastewater treatment as a process and a resource

26 2. Wastewater treatment as a process and a resource

retention time (SRT) and still achieve nitrifica- disadvantage, however, of these processes is
tion [43]. The IFAS technology and the combina- membrane fouling and its consequences in
tion of anaerobic and IFAS systems have also terms of plant maintenance and operating costs,
been proposed for enhanced biological phos- which limit the widespread application
phorus removal (EBPR) or even micropollutant of MBRs.
removal [44, 45]. Technologies combining fixed
growth (MBBR, IFAS) and suspended growth
Tertiary treatment
(activated sludge) systems in series are popular,
especially in the United States [46]. That is the The aim of tertiary treatment is to enhance the
case with Hybas technology [47], combining quality of the treated water in order to fulfill reg-
MBBR and CAS, and the METEOR IFAS/MBBR ulations for its discharge into the environment
from SUEZ [48]. These combinations take or reuse as water source. It includes the removal
advantage of the high-quality effluent associ- of turbidity and organics, nutrients (phosphorus
ated with suspended growth systems, the sim- and nitrogen), and heavy metals by adsorption
plicity of operation and process stability of on carbon filter, filtration, reverse osmosis, or
fixed film processes, the possibility of nitrogen other physicochemical processes.
removal, and the production of sludge with Disinfection of pathogens remaining in the
good settling properties. effluent of the secondary treatment is also con-
Finally, the membrane bioreactor (MBR) is sidered part of the ternary treatment. Actually,
the latest technology, which combines the con- disinfection is the last step in selectively destroy-
ventional activated sludge with a membrane fil- ing disease-causing organisms. Chlorination is
tration system that replaces the conventional extensively used as a disinfectant in municipal
settling tank. Membrane filtration provides a sewage treatment plants due to its effectiveness,
positive barrier to suspended biosolids, which low cost, and ease of application [51]. However,
can be maintained at 3 to 4 times that of CAS disinfection by-products in chlorinated waste-
(10,000 to 2500 mg L
1). Thus, aeration tank waters can be toxic and may have a deleterious
size in the MBR system can be smaller than that impact on aquatic organisms [52]. Thus, alterna-
used in conventional activated sludge systems. tive technologies based on ozone and UV radia-
Due to membrane filtration, the treated effluent tion are gaining increasing attention as suitable
quality is far superior in MBR as compared to methods for disinfection in WWTPs [53, 54].
CAS (BOD <5 mg L
1, turbidity <0.2 nephelo- Ozone is one of the strongest oxidation agents
metric turbidity units, NTU). Due to these fac- on the market (50% more powerful than chlo-
tors, MBR reduces the cost of operation and rine) and is an environmentally friendly techno-
the required footprint, as well as providing a logy that does not create any chlorinated
remarkable reduction of soluble organic matter. disinfection by-products (mainly when bromine
The MBR technology has been in extensive use is absent). Thus, a variety of commercial ozone
for treatment of domestic sewage and, more technologies have emerged during the last
recently, in industrial applications, with a vari- decade, such as the Ozonia Ozone Generation
ety of commercial alternatives available depend- Systems (CFV, M or XF models) from SUEZ
ing on the specific application: for urban for disinfection [55]. At the same time, UV tech-
wastewater, the BIOSEP (Veolia) [49], the nology allows the treatment of those microor-
LEAPmbr series of products [50] and the Mem- ganisms resistant to chlorination, such as
Pulse MBR (MEMCOR); for industrial wastewa- Criptosporidios and Giardia, and there are tech-
ter, the ADI MBR (ADI Systems) or AMBR LE nologies designed for small to large wastewater
(Aqua Bio Ltd), among others. The main treatment plants, like the TrojanUV series from

I. Wastewater treatment as a process and a resource

 Biological sludge as a bioresource 27
Trojan Technologies [56] or the Aquaray Ultra- nanofiltration (NF), reverse osmosis (RO), and
violet systems from SUEZ [57]. forward osmosis (FO), are used to treat a variety
Adsorption, mainly by activated carbon, is a of wastes, including sewage, organic and inor-
common practice in order to retain soluble water ganic matter, and water-soluble oil wastes.
compounds not sufficiently removed in previ- Commercial technologies, such as the MEM-
ous treatments, such as emerging pollutants, COR product line (Evoqua) for microfiltration
dyes in textile industries, polar organic sub- and ultrafiltration installations or UFLEX (Veo-
stances, or heavy metals [58, 59]. The interest lia) provide turbidity reduction up to <0.01
in new adsorbents has been growing in recent NTU, and viruses, bacteria, and protozoa
years, looking for materials suitable for removal removals of 99.9% from the influent [49].
of organic pollutants from wastewater streams. Finally, precipitation techniques are used to
Nevertheless, activated carbon-based technolo- remove heavy metals from industrial wastewa-
gies are mainly used in WWTPs, due to the high ters [67, 68] and, more frequently, phosphorus
efficiency in removing organic compounds, as soluble phosphate. The phosphate precipita-
chlorine, and micropollutants (ACTIFLO CARB tion can be either integrated as simultaneous
or ACTIFLO TWIN CARB from Veolia [60] or precipitation into the biological treatment or
Siemens’ PACT technology [61]). added as a subsequent separate process to
Advanced oxidation processes (AOPs) have recover phosphorus, magnesium, and potas-
emerged as promising alternatives for the sium as struvite [69], such as the Struvia Phos-
removal of micropollutants from urban and phorus Recovery and Harvesting system from
industrial wastewaters [24]. The main types of Veolia [70].
AOPs for wastewater treatment are based on
the generation of highly oxidizing and nonselec-
tive hydroxyl radicals (HO•) that react with Biological sludge as a bioresource
organic pollutants. Hydroxyl radicals can be
generated by a variety of technologies, including The physical, chemical, and biological treat-
those based on chemical, photochemical, sono- ment routes produce a solid by-product that
chemical, and electrochemical systems [62]. can be categorized into two main groups, pri-
Emerging contaminants (pharmaceuticals, per- mary and secondary (waste-activated) sludge.
sonal care products), herbicides and pesticides, Primary sludge is generated by postmechanical
and other recalcitrant or toxic organic molecules treatment after the primary stage, whereas
are the major target pollutants of these technol- waste-activated sludge is generated via biologi-
ogies [63]. Free radicals generated in AOPs are cal treatment by transformation of soluble
also used for the treatment of wastewater con- contamination (mainly C, N, and P) into particu-
taining chlorinated organics, perchlorate, chro- late biomass. Thus, sewage sludge is the main
mate, nitrate, nitrite, arsenate, selenate, by-product generated in WWTPs and it is a
bromate, chlorate, and a number of radionu- potential source of secondary environmental
clides [64]. Examples of commercial solutions contamination [71]. Although part of it is
are Xylem’s Wedeco MiPro eco3 AOP system, recycled in the WWTP operation, the sewage
which comprises a Wedeco ozone system and sludge in excess needs to be managed and
an H2O2 dosing unit [65], or the static and removed from the wastewater treatment plants
dynamic hydro reactors from Novexx Pte [72]. Fig. 2.2 shows typical processes involved
Ltd. [66]. in sewage sludge treatment at WWTPs.
Membrane-based technologies based on The main methods of sewage sludge manage-
multifiltration (MF), ultrafiltration (UF), ment in the European Union and United States

I. Wastewater treatment as a process and a resource

28 2. Wastewater treatment as a process and a resource

FIG. 2.2 The sewage sludge treatment processes at wastewater treatment plant.

remain agricultural use and incineration [73]. In the total operation costs of these facilities [81].
the case of the EU, the current landfill Directive Moreover, a considerable increase of sludge
forbids the landfill practice of wastes, so a generation is expected because of growth in
decrease from 11% to 4% is expected for the worldwide population and living standards.
overall sludge managed with this method from This fact, as well as the promulgation of more
2010 to 2020 [71, 74]. A close look at the EU restricted disposal regulations, means that man-
reports shows that >10 million tons of dry solids agement methods involving storage are now
(DS) of sewage sludge per year have been pro- being replaced by methods leading to waste sta-
duced in the member states between 2008 bilization and safe recycling [82]. Moreover, the
and 2012. Approximately 36%–40% was used European Commission, in 1991 and 2008,
on land for soil conditioning and fertilization encouraged recycling and management
[72, 75, 76]. The production estimated in 2020 methods over the use of landfills. Actually, a
is around 10.5 million tons of DS of sewage reduction of 35% of biodegradable content in
sludge [76, 77]. The United States is the first sew- landfilling is necessary by 2020 [83].
age sludge producer in the world with an annual Fig. 2.3 shows a variety of common and inno-
production of 8 million tonnes of DS. The United vative sludge management strategies for energy,
States employs sewage sludge mainly for arable resource recovery, bioproducts generation, reu-
land application (55%), 30% landfilled and 15% tilization, and applications for pollution control
incinerated [78]. China, as the second largest [71, 84, 85].
sludge producer in the world (6.25 million
tonnes DS per year), is moving to arable land
application, sanitary landfill, anaerobic diges-
Sludge treatment for energy recovery
tion, and incineration as the main sludge mana- In terms of energy recovery, anaerobic diges-
gement strategies [79, 80]. tion, incineration, pyrolysis, gasification, and
In any case, the disposal of sewage waste the combination of sludge with microbial fuel
sludge represents a major problem in wastewa- cells are all extended and promising technolo-
ter treatment plants, accounting for 50%–60% of gies for the treatment of sludge. Anaerobic

I. Wastewater treatment as a process and a resource

 Biological sludge as a bioresource 29

FIG. 2.3 Common and innovative strategies for sludge treatment and management. (Based on A. Raheem, V.S. Sikarwar, J. He,
W. Dastyar, D.D. Dionysiou, W. Wang, M. Zhao, Opportunities and challenges in sustainable treatment and resource reuse of sewage
sludge: a review, Chem. Eng. J. 337 (2018) 616–641; M. Kacprzak, E. Neczaj, K. Fijałkowski, A. Grobelak, A. Grosser, M. Worwag,
A. Rorat, H. Brattebo, A. Almås, B.R. Singh, Sewage sludge disposal strategies for sustainable development, Environ. Res. 156 (2017)
39–46; B.M. Cie
slik, J. Namiesnik, P. Konieczka, Review of sewage sludge management: standards, regulations and analytical methods,
J. Clean. Prod. 90 (2015) 1–15.)

digestion is the most-used method for stabiliz- adsorbents [77, 87]. Gasification converts the
ing activated sludge and producing biogas as sludge into syngas, a gaseous biofuel with high
an energy product. The supernatant (liquid energy content, appropriate for heating or run-
phase) is commonly submitted to nitrification- ning steam turbines [88]. The main problem in
denitrification to remove the excess of ammo- application of these technologies is the high
nium and is recycled into the mainline, whereas energy requirements associated with the
the residual sludge (solid phase) is dewatered processes.
and further dried before combustion or applica- Finally, recent studies have demonstrated the
tion as land biofertilizer. applicability of microbial fuel cell technology to
Sludge incineration produces heat, a gas con- sewage sludge for bioelectricity production,
taining CO2, H2O, and ashes that can be used to reducing environmental problems commonly
produce building materials in combination with associated with the previously mentioned con-
cementitious materials. Vitrification at very high ventional thermal treatments [89, 90].
temperatures with addition of silica allows a com-
plete fixation of different pollutants, providing
another source for a strong ceramic material,
Recovery of nutrients and resources
which is environmentally safe [86]. Thermal con- Sewage sludge contains a considerable
version by pyrolysis transforms the sludge into amount of nutrients, particularly phosphorus
liquid, gas, and char products with different char- in the form of proteinaceous material [71]. Phos-
acteristics and applications, such as liquid biofuels phorus is a limited nonrenewable resource and
(bio-oil) or raw material for production of its exhaustion is predicted in <200 years, in the

I. Wastewater treatment as a process and a resource

30 2. Wastewater treatment as a process and a resource

more optimistic studies [75]. A recent review recovery after hydrolysis or acid extraction from
shows >30 types of technologies for phosphorus dried sludge [98, 99]. The Aqua Reci (AR) pro-
recovery from sewage sludge, with new ones cess combines supercritical water oxidation
often added [75, 91]. The authors classified all technology for phosphorus and energy recovery
these methods into two main groups, depending [100]. The SEPHOS process is an example of full-
on the origin of the sludge: (i) sewage sludge and scale technology from the ashes remaining after
leachates produced from sludge treatments, like sludge incineration [71, 75].
anaerobic digestion; and (ii) ashes from incinera- Resource recovery is not only limited to nutri-
tion of the sewage sludge. ents. Sewage sludge is a source of other valuable
The simplest method of phosphorus recovery compounds that can be recovered by applying
is the direct use of activated sludge or dried/ appropriate techniques. That is the case with
roasted sewage sludge as a fertilizer [92]. How- heavy metals. These chemicals cause a contam-
ever, the risk of soil pollution due to heavy ination problem in almost all sewage sludge
metals and toxic compounds contained in the management systems. However, this also offers
sludge or ashes makes additional solutions ne- the possibility of recovering valuable rare earth
cessary, to extract the phosphorus from the solid metals from sewage sludge incineration pro-
matter. Technologies based on disintegration cesses using high-temperature furnaces under
and solubilization of the sludge, releasing phos- oxidative or reductive conditions [101].
phate and also other nutrients, allow a subse-
quent selective precipitation of phosphorus in
the form of hydroxyapatites, calcium phos- Production of valuable biorefinery
phates, or magnesium ammonium phosphate compounds
(struvite), which can be used for fertilizer
About 60%–70% of the organic matter con-
formulations or directly for land application,
tained in domestic wastewater is formed by
in the latter case [93].
lipids and proteins. Consequently, the three
On the other hand, recent literature focuses
main biochemical families in sewage sludge
on phosphorus recovery in the sludge after ther-
are carbohydrates, proteins, and lipids, account-
mal treatment. The remaining ashes after sludge
ing for approximately 80% of the organic matter
incineration contain 20% more available phos-
[84]. This has motivated the formulation of a
phorus than the pretreated sludge, mainly due
biorefinery concept for recovering high value-
to the significant reduction of volume [94]. Phos-
added products from wastewater based on the
phorus recovery from ashes could be five to ten
anaerobic digestion of the sludge as core
times higher than in the case of activated sludge
technology.
directly [75]. Some approaches assume direct
use of ashes as a phosphorus source or fertilizer. • Protein is an essential component used in
However, the presence of heavy metals in the animal feed, supplying energy and nitrogen.
ashes makes extraction methods using mineral With up to 50% proteins as dry weight of
or organic acids the preferred phosphorus bacterial cells, sewage sludge has a
recovery technology [95, 96]. remarkable potential as protein source [102].
The large number of treatments for phospho- Methods combining alkali treatment with
rus recovery around the world has promoted the ultrasonication allow protein extraction
commercialization of several full-scale technolo- efficiencies from sludge higher than 80%,
gies. The OSTARA process allows recovering with nutrient composition comparable to
phosphorus from sludge streams using magne- commercial protein feeds.
sium chloride [97]. The KREPRO and BioCON • Enzymes are high-value products used as
processes (Veolia) are used for phosphorus biological catalysts in various industrial

I. Wastewater treatment as a process and a resource

 Industrial wastewater treatment plants 31
applications, such as pharmaceutical, food, Meat processing industry
diagnostics, cosmetics, detergent, and fine
chemical industries. Their high cost is The meat processing industry is one of the
usually attributed to preparation of a major consumers of fresh water in the agricul-
culture medium able to produce the specific tural and livestock industry. Meat processing
enzyme [103]. Thus, enzyme extraction facilities (slaughterhouse plants) may consume
from waste sludge is a potentially low-cost between 2.5 and 40 m3 of water per metric ton
option after taking into account some key of meat produced [107, 108], producing large
factors, such as the use of an appropriate amounts of wastewater with an extremely varia-
extraction process and the design of ble composition (see Table 2.3) from animal
suitable purification and concentration slaughtering and processing and cleaning of
methods. the slaughterhouse facilities. Likewise, the
• Bioplastics are other valuable products that wastewater volume in some plants can be low,
can be obtained from sewage sludge. but it can reach thousands of cubic meters per
Several microorganisms have the ability to day in others [113]. The slaughterhouse waste-
accumulate polyhydroxyalkanoates water is characterized by large content of
(PHAs), which exhibit properties organics and nutrients, with BOD values of
comparable to petroleum-based plastics. 150–5600 mg L
1 (COD of 500–15,900 mg L
1)
Thus strategies to promote PHA and total nitrogen and phosphorus quantities
accumulation, for example through of 50–840 and 25–200 mg L
1, respectively
operation of a biological reactor using [107]. Moreover, this type of industrial wastewa-
excess carbon and feast and famine ter also contains high concentrations of solids,
conditions, can be coupled with further such as fats, grease, hair, feathers, flesh, manure,
extraction and purification methods for grit, and undigested feed [114]. Pathogenic and
bioplastic production [104–106]. nonpathogenic microorganisms, pharmaceuti-
cals for veterinary purposes, disinfectants, and
cleaning agents can also be present in these
Industrial wastewater treatment plants effluents [115]. Fig. 2.4 shows the conventional
treatment processes typically applied for
Industrial wastewater coming from slaughterhouse wastewater.
manufacturing processes is characterized by a The processes are the same used in conven-
large variety of pollutants and concentrations tional wastewater treatment plants: primary,
(diluted and strongly concentrated), as can be secondary, and tertiary treatment, with a pre-
seen in Table 2.3 [107–112]. These pollutants liminary treatment always being required. The
can also be of different chemical nature preliminary treatment removes up to 30% of
(organics, inorganics) and can be presented as the BOD content, separating solids from the li-
soluble or suspended particles. Moreover, some quid. The most common processes for prelimi-
of them can be nonbiodegradable or toxic com- nary treatments are screeners, sieves, and
pounds (depending on concentration), which strainers, which retain a large amount of partic-
can make specific well-designed physicochemi- ulate matter (10–30 mm diameter). Thereafter,
cal pretreatments necessary. Thus the scheme of equalization and dissolved air flotation are the
the treatment processes can follow different most common physiochemical processes for
strategies depending on the characteristics of the removal of oil, fat, and grease.
the wastewater. This section reviews different The removal of soluble organic compounds
schemes of industrial wastewater treatment takes place during the secondary biological pro-
plants. cess. Anaerobic treatment is the preferred

I. Wastewater treatment as a process and a resource

32 2. Wastewater treatment as a process and a resource

TABLE 2.3 Typical composition of types of industrial wastewater studied in this work.
Pharmaceutical wastewater(e)
Slaughterhouse Pulp and paper Chemical Oily
wastewater(a,b) wastewater(c,d) Fermentation process wastewater(f)

COD (mg L
1) 500–15,900 500–115,000 180–12,380 375–32,500 3,600–5,300

1
BOD (mg L ) 150–5,600 140–12,000 25–6,000 200–6,000 0.2–360

1
TKN (mg L ) 50–840 7–350 190–760 165–770 –

1
N-NH+4 (mg L ) 20–200 – 65.5–190 148–363 0.1–70
pH 4.9–8.1 6.1–8.3 3.3–11 3.9–9.2 8.3–8.9

1
TDS (mg L ) 1,130–3,500 1,150–1,260 1300–28,000 675–9,320 3,800–6,200

1
TSS (mg L ) 70–2,700 37–6,000 57–7,130 – 30–40
Conductivity (μS – – 1600–44,850 – 5,200–6,800
cm
1)
Oil and fats 23–1,200 – – – 1.1–3,000
(mg L
1)
Cl
(mg L
1) 650–1,000 0–200 182–2,800 760–4,200 –

1
SO42
(mg L ) – 3–5,100 160–9,000 890–1,500 14.5–16

Total phenol – 17–800 – – 160–185

(mg L
1)
Abbreviations: COD, chemical oxygen demand; BOD, biochemical oxygen demand; TKN, total Khejdal nitrogen; N-NH+4 , ammonium nitrogen;
TDS, total dissolved solids; TSS, total suspended solids.
(Based on (a) C.F. Bustillo-Lecompte, M. Mehrab, Slaughterhouse wastewater characteristics, treatment, and management in the meat processing
industry: a review on trends and advances, J. Environ. Manag. 161 (2015) 287–302. (b) D.I. Mass
e, L. Masse. Treatment of slaughterhouse wastewater
in anaerobic sequencing batch reactors, Can. Agric. Eng. 42 (2000) 131–137. (c) H. Vashi, O.T. Iorhemen, J.H. Tay, Aerobic granulation: a recent
development on the biological treatment of pulp and paper wastewater, Environ. Technol. Innov. 9 (2018) 265–274. (d) O. Ashrafi, L. Yerushalmi,
F. Haghighat, Wastewater treatment in the pulp-and-paper industry: a review of treatment processes and the associated greenhouse gas emission,
J. Environ. Manag. 158 (2015) 146–157. (e) C. Gadipelly, A. P
erez-González, G.D. Yadav, I. Ortiz, R. Ibáñez, V.K. Rathod, K.V. Marathe,
Pharmaceutical industry wastewater: review of the technologies for water treatment and reuse. Ind. Eng. Chem. Res. 53 (29) (2014) 11571–11592.
(f) M.H. El-Naas, S. Al-Zuhair, A. Al-Lobaney, S. Makhlouf, Assessment of electrocoagulation for the treatment of petroleum refinery wastewater, J.
Environ. Manag. 91 (2009) 180–185.)

FIG. 2.4 Conventional slaughterhouse wastewater treatment.

I. Wastewater treatment as a process and a resource

 Industrial wastewater treatment plants 33
biological treatment because of its effectiveness concentration introduced in the paper machine
in treating high-strength effluents, such as is 99% water and only 1% fiber. Although both
slaughterhouse wastewater, with low comple- processes (pulp and paper manufacturing) are
xity equipment [107, 116]. Besides, anaerobic intensive in water consumption, approximately
processes produce a lower quantity of sludge 72% of the industry wastewater comes from the
(5%–20%) and have low energy requirements pulp manufacturing process. The pulp and
compared to those of aerobic systems, with paper industry is the largest industrial wastewa-
potential nutrient and biogas recovery [108]. ter producer (42% as reported by the Forest
The complete stabilization of the organic mat- Products Association of Canada, FPAC) [117].
ter and the removal of the remaining organics, There are different stages in the pulping pro-
nutrients, and pathogens are needed to comply cess (wood handling, debarking and chip wash-
with required discharge limits. An aerobic bio- ing, wood cooking, pulp screening and washing,
logical treatment is frequently used after anaero- and pulp bleaching) and each one generates a
bic treatment, due to its fast biological rates, variety of pollutants that eventually end up in
which significantly reduce the hydraulic reten- the wastewater stream. The pulp and paper
tion time and land requirements. However, in industry uses different types of processes, wood
terms of operating costs, aerobic systems are materials, and technologies, which makes the
more expensive than anaerobic ones, due to characteristics and quantities of the wastewater
the maintenance and energy requirements of effluents different. The composition range of
artificial oxygenation, which strongly depend wastewater effluents for this industry is shown
on the strength of the pretreated effluent [108]. in Table 2.3. For instance, the COD of kraft mill
The combination of anaerobic-aerobic biological effluents is in the range of 1.1–2 g/L, with
processes usually results in 90% of BOD reduc- adsorbable organic halides (AOX), volatile
tion in the anaerobic treatment and over 98% organic compounds (VOCs), residual lignin,
after the following aerobic one [20]. and resin acid [109, 118]. Due to the toxicity of
The recovery of by-products in slaughter- these pollutants, kraft mill effluent is the most
house wastewater treatment plants is basically complex for biological treatment [119]. The
focused on energy biogas production, but water chemi-thermomechanical mill effluent tends to
recycling is also an important point in this be more concentrated, with COD in the range
industry, as it is a large consumer of fresh water. of 6–9 g/L [109]. These wastewaters also contain
In this sense, some slaughter wastewater treat- higher total suspended solid (TSS) concentra-
ment plants are evaluating additional tertiary tions, in the range of 300–510 mg L
1 [109, 120]).
treatments, such as advanced oxidation pro- In contrast, papermaking wastewater is of a
cesses (AOPs) to produce high-quality effluents relatively lower organic loading with a COD
that would enable the reuse of the regenerated value around 1 g/L, but has higher content of
water in the meat processing plant [107]. TSS [109, 121].
The conventional pulp and paper wastewater
treatment plant includes physicochemical and
Pulp and paper industry biological processes. The wastewater treatment
The pulp and paper industry is also a large plant installed in a pulp and paper mill industry
consumer of water. The pulp is washed with is generally quite comparable to that found for a
water at several points in the process, and water municipal treatment plant. As can be seen in
is used to convey the pulp fibers from their ini- Fig. 2.5, the primary clarifiers handle only those
tial production in the pulp mill through various wastes carrying a high concentration of sus-
refining operations. Moreover, the slurry pended solids (>50 mg L
1). After primary

I. Wastewater treatment as a process and a resource

34 2. Wastewater treatment as a process and a resource

FIG. 2.5 Typical process flowsheet for pulp mill wastewater treatment plant. (Based on K.P. Oliveira, M. Mori, R.E. Bruns
Simulation of an industrial wastewater treatment plant using artificial neural networks and principal components analysis, Braz. J. Chem.
Eng. 19 (2002) 365–370.)

sedimentation, sludge could be recycled to the treatment and the product quality. The quality
manufacturing process, or it could be dewatered of water required for reuse in the process varies
and sent to sludge treatment. After clarifying with the grades of paper being produced (fine,
these wastes, the effluent is combined with the kraft, ground-wood paper, or sulfate pulp)
remaining low solid streams and treated in bio- and the specifications for these grades (turbid-
logical processes [20]. Aerobic processes are ity, color, hardness, iron, total dissolved
usually applied for treating pulp and paper solids…). Normally, fine paper specifications
mills due to the ease of operation and relatively are higher than those for ground-wood paper.
low capital and operating costs [110, 122]. Acti- For example, TDS for fine paper (high-quality
vated sludge and aerated lagoons are commonly fine paper) in the recycled wastewater should
used in this industry [123]. Aerobic biological be lower than 200 mg L
1, whereas for ground-
processes based on ligninolytic fungi species wood paper (the lowest quality) the limit is
could be a promising alternative. However, the 500 mg L
1 [20].
ability of practical treatment with fungi can be In this sense, the major advances are based on
restricted under extreme conditions, such as the tertiary treatment. Different filtration tech-
alkaline pH or oxygen restrictions [119]. nologies have been implemented in closed-loop
Although the use of anaerobic processes in these recycling systems for zero discharge based on
types of effluents is not common, a number of sand filters, ultrafiltration, and inverse osmosis.
treatment processes employ anaerobic technolo- A wastewater recycling system consisting of aer-
gies because of their benefits: biogas production, ation tanks, surge tank, clarifiers, sand filters,
lower sludge generation, smaller area require- and carbon filters can reduce the discharge into
ments, and ease in further degradation of pollut- a water body by 99%, with over 85% of the water
ants [110]. The classical process discharges the being recycled [124]. Advanced oxidation pro-
effluents into a water body after secondary cesses using powerful oxidants such as ozone
treatment. or hydrogen peroxide have also been investi-
Water consumption in the classical process is gated [125]. However, the intensive energy
very high, so different options have been pro- input required is still the main disadvantage of
posed in order to close the water cycle in the these processes.
pulp and paper industries. The main goals are
to eliminate the discharge of wastewater into
Pharmaceutical industry
natural water bodies and to reduce the mill’s
dependence on river water or even potable The pharmaceutical industry is a high-tech,
water. Water reuse is restricted by the accumu- high investment, and high efficiency industry,
lation of dissolved solids that could affect the recognized as the most promising international

I. Wastewater treatment as a process and a resource

 Industrial wastewater treatment plants 35
industry [126]. This industry has developed ra- are characterized by high concentrations of
pidly in the past few decades due to the increase organic contaminants, solvents from extraction
in world population and the advances in medi- processes, and synthesis of product with high
cine to fulfill worldwide demands, reaching a values of BOD, COD (large differences in
production and revenue of 825 and 1143 billion BOD/COD ratio), NH3-N, suspended solids,
US dollars in 2017, respectively [127, 128]. Water and salinity (see Table 2.3) [131].
is a critical raw material in pharmaceutical and There are many alternatives for the treatment
chemical manufacturing operations, and this of wastewater generated in pharmaceutical
industry is also a serious source of water pollu- industries (Fig. 2.6), but they are specific to the
tion. However, wastewater produced in phar- pharmaceutical type and associated wastewater.
maceutical units varies in composition and The treatment alternatives of effluents coming
quantity, by plant, season, and even time, from both systems are usually grouped into
depending on the raw materials and the variety six general approaches: (i) recovery of valuable
of processes used in the manufacturing of prod- products, (ii) physical-chemical treatments, (iii)
ucts [111]. Bulk pharmaceuticals are produced aerobic/anaerobic biological treatment, (iv)
using a variety of processes, and pharmaceutical inactivation of active substances by oxidation,
industries can be classified into five main cate- (v) sterilization and decontamination of infec-
gories based on the process used: (i) fermenta- tious and bioactive substances from biotechnol-
tion plants; (ii) synthesized organic chemicals ogy, and (vi) new integrated treatment and
plants; (iii) fermentation/synthesized organic disposal facilities for particular wastewater
chemical plants (generally big plants); (iv) natu- treatment plants.
ral/biological product extractions (such as anti- The recovery of valuable products, such as
biotics); (v) drug formulation (tablets, capsules, solvents, acids, metals, fermentation residues,
etc.) [129]. and pharmaceutical products and ingredients
A water balance for the five categories of phar- comprise a very important waste control
maceutical industries would reveal that chemical strategy for pharmaceutical plants. These
synthesis and fermentation processes are among require intensive separation methods that
the pharmaceutical sectors with larger water improve the economics of the pharmaceutical
consumption and wastewater generation. Fer- industry. Organic solvents are one of the main
mentation plants usually produce high organic contributors to the BOD/COD content of
effluents called the spent fermentation broth, pharmaceutical effluents, and industries have
which contains considerable concentration of sol- their own solvent recovery systems based on
vents and excess of fungi or bacteria responsible distillation columns and solvent-solvent
for fermentation [129]. Organic-synthesis phar- evaporation systems [111, 129, 132]. The
maceutical plants generally produce complex recovery of pharmaceutical products and
waste streams with high COD, salinity, and lim- ingredients can be done by effective mem-
ited biodegradability, due to many operations brane technologies. Ultrafiltration has been
and reactions taking place in the reactor. Waste- used for the recovery of organic compounds
waters comprise cooling waters, condensed from fermentation process wastewaters, for
steam still bottoms, mother liquors, crystal end example alkaline protease (83% recovering),
product washes, and solvents, resulting from which accounts for 60% of the total enzymes
the process. Thus, the application of biological produced in the pharmaceutical industry
treatments is not effective, causing the release [111]. Nanofiltration can achieve permeates
to the environment of recalcitrant organic pol- of feed-water quality with rejections higher
lutants [130]. Summarizing, these wastewaters than 97% for antibiotics and 40% for COD.

I. Wastewater treatment as a process and a resource

36 2. Wastewater treatment as a process and a resource

FIG. 2.6 Alternative technologies for the treatment of pharmaceutical wastewater.

Finally, electrochemical processes have been organic matter with a COD concentration as
proposed for the recycling and recovery high as 7–12 g/L [137, 138].
of metals (Cd, Ni, Zn) in pharmaceutical The dilute streams from the manufacturing
industries [111]. units, recovery systems and pretreated effluents
Due to the low biodegradability of residual are mainly treated by biological methods,
organic water streams after the recovery pro- including both aerobic and anaerobic systems
cesses in the pharmaceutical industry, different [111]. CAS is the most widely used aerobic sys-
treatments have been developed as pretreat- tem, achieving COD and N removals higher
ments for biological processes, such as flotation than 98% in both cases, in effluents pretreated
[133], membrane filtration, activated carbon with advanced oxidation processes [139]. MBR
adsorption [134], and electrolysis [135]. AOPs systems exhibit a similar performance, in combi-
(photocatalysis and UV or solar irradiation, elec- nation with high removal of phosphorus (90%)
trooxidation, Fenton and photo-Fenton pro- and specific pharmaceutical compounds at trace
cesses, wet air oxidation, and ultrasound) have levels that are poorly eliminated by CAS, such as
been used either alone or combined with other estrogens (17-β-estradiol or estradiol valerate),
processes (physiochemical and/or biological), among others [140]. Anaerobic treatment for
depending on the objective for treatment, pharmaceutical wastewater purification has
whether destruction or transformation of the been done mainly in continuous stirred tank
organic matter [130, 136]. For example, homoge- reactors (anaerobic digestion), fluidized bed
neous Fenton oxidation produces >95% COD reactors, and upflow anaerobic sludge reactors.
removal in a pharmaceutical effluent generated The advantages of anaerobic systems over aero-
in the chemical synthesis of paracetamol (aceta- bic processes have been previously exposed. In
minophoene) (COD of 12 g/L), whereas catalytic this case, the ability to treat high-concentration
(copper) wet air oxidation of a wastewater from wastewater is one of the most important facts.
chemical synthesis showed a total removal of the Hybrid upflow anaerobic sludge blank reactors

I. Wastewater treatment as a process and a resource

 Future perspectives on wastewater treatment plants 37
allow high COD (65%–75%) and BOD (80%–94%) conventionally the activated sludge process,
removals even in very high concentration chemi- for the removal of biodegradable organics and
cal synthetic wastewater (40–60 g/L) with an residual sulfides, obtaining high reductions in
organic content up to 9 kg of COD/(m3day) [141]. COD (95%), TOC (85%), and suspended
solids (98%) [146]. At this point, the wastewa-
ter can be discharged into a water body. If, how-
Oil industry
ever, the goal is obtaining reclaimed water, a
Many complex processes are used in oil refine- range of effective tertiary methods are proposed
ries to convert crude oil into a different number of in the literature, including chlorination, mem-
refined products. These processes generate large brane processes (micro- and ultrafiltration) as
amounts of wastewater (0.4–1.6 times the volume well as reverse osmosis or sand filtration [147].
of processed oil). Thus, an appropriate treatment On the other hand, the sludge generated in
is required before the discharge into natural water the API/PPI/DAF as well as in the biological
bodies [142]; otherwise the discharge can have process is also treated. The sludge treatment
adverse impacts on the surrounding environment usually involves thickening (by a gravity thick-
due to its toxicity [143]. Although the pollutants ener) and then dewatering and storing before
present in the refinery wastewater depend on final disposal. In the clarification tank, the oil
the process conducted, the main pollutants coming from different treatment steps is condi-
include suspended solids, biodegradable and tioned and stored or forwarded to the oil recove-
refractory organic compounds, hydrocarbons, sul- red from the water.
fides, chlorides, cyanides, phenols, nitrogen com- Normally, the only valuable products
pounds, and some micropollutants, among obtained from the conventional approaches
others, as can be seen in Table 2.3 [142]. This com- implemented in the refinery facilities are oils
plex composition is a result of the mixture of recovered from the water and sludge separation
numerous waste effluents from different refining operations carried out in the API, PPIs, and DAF
processes, including the domestic sewage gener- systems. Those conventional processes (gravity
ated in the facility itself. water/oil separators, DAF and biological pro-
The conventional treatment of refinery waste- cess) result in effluents that can be discharged
water involves a sequence of physicochemical fulfilling required legislation limits. When,
processes followed by a biological treatment optionally, other more stringent (tertiary)
(Fig. 2.7) [142]. In a primary oil/water separa- advanced treatments are also implemented,
tion stage, most of the oil is separated from the the water can be reused. The sludge produced,
wastewater in API (American Petroleum Insti- treated as previously mentioned, is removed
tute) gravity separators and PPIs (parallel- from the facility by an authorized contractor.
plates-interceptors), where the wastewater is The contractor usually treats the sludge by incin-
clarified by the removal of suspended matter eration; otherwise, the sludge ends up in
such as solids and oils [144]. Secondary oil/ landfills.
water separation comprises flotation by air
(DAF) or dissolved gas (highly developed
patented technologies), for the elimination of Future perspectives on wastewater
sulfides, suspended solids, and residual hydro- treatment plants
carbons [142, 145]. In those first separation steps,
90% of the hydrocarbons can be recovered, gen- Wastewater treatment plants should be
erating two different (wastewater and sludge) focused not only on their performance for
streams. The resultant liquid effluent is con- removal of pollutants and pathogens but also
ducted to a biological treatment, which is on aspects of sustainability, such as the use of

I. Wastewater treatment as a process and a resource

38 2. Wastewater treatment as a process and a resource

FIG. 2.7 Typical diagram of the refinery wastewater treatment plant. API, American Petroleum Institute; PPIs, parallel-
plates-interceptors; DAF, dissolved air flotation.

ecofriendly products, reduction of energy alternative to redirect carbon (organic com-

demand, the recovery of energy and valuable pounds) towards energy as biogas. The basis
compounds (including the treated water for of the HRAS process is to enhance energy pro-
reuse), and low emission of greenhouse gases duction during operation, ideally obtaining an
[148]. This new perspective has changed the role energy-neutral process. Low SRT (0.1–1 days)
and significance of the advanced physical and values in HRAS increase the COD removal
chemical treatments, as a prerequisite to achiev- through high sludge production with minimal
ing a sustainable environmental process [149]. energy, producing a young and fast-growing
These advanced physical/chemical processes sludge easily digested in anaerobic
can be categorized into five different groups, digestion [154].
depending on their purpose within the scheme A new paradigm for wastewater treatment
of the WWTP: (i) improvement of further biolog- has been recently proposed as the partition-
ical treatments in the WWTP; (ii) achieving the release-recover concept. It is based on the
appropriate quality of the effluent for reuse or removal of nutrients and carbon from the liquid
discharge; (iii) recovering valuable components phase, using selective biological agents. This
from wastewater; (iv) removal of soluble mine- process enables the treatment of waste effluents
rals; and (v) treatment of the wastes (liquid, without energy input, and makes the recovery of
solid or semisolid) generated in a wastewater nitrogen, phosphorus, and value-added prod-
treatment process. ucts (organics or microbial) possible [8, 148].
Within the refurbishing of WWTPs to reduce The process of treating the wastewater could
energy consumption and recover resources, possibly result in four different resources: trea-
there are a number of broad biological process ted water, biogas, biosolids (mainly composed
options to attain lower energy wastewater treat- of inert organics, nonrecoverable nutrients,
ment, including high-footprint passive (wet- and excess metals), and a fertilizer stream. In
lands, lagoons) and low-energy anaerobic this sense, phototrophic anaerobic bacteria and
systems (e.g., the upflow anaerobic sludge blan- algae systems emerge as a promising alternative
ket (UASB), the expanded granular sludge bed to conventional biological processes, as they
(EGS), or the anaerobic MBR), as well as alterna- grow using light as the main energy source,
tive nitrogen removal methods, such as Ana- allowing accumulation of carbon and nutrients
mmox [150–152]. There are commercially from the wastewater [155, 156] and the in situ
available technologies combining UASB/EGSB, generation of value-added products [157, 158].
IFAS and Anammox (Biobed Advanced, ANITA Additionally, many alternatives and strate-
Mox and IFAS ANITA MOX from VEOLIA), gies can be proposed for successful sludge
devoted to these issues [153]. Within the context management. The technology selection is highly
of maximizing energy recovery, the high-rate dependent on social, economic, and environ-
activated sludge (HRAS) process is a new mental criteria, as well as development related

I. Wastewater treatment as a process and a resource

 References 39
to climate-change policy and renewable energy Contaminants of emerging concern: a review of new
[72]. Different technologies, such as anaerobic approach in AOP technologies, Environ. Monit. Assess.
189 (2017) 414–436.
digestion, dewatering, and thermal treatments [8] W. Rulkens, Increasing significance of advanced
by pyrolysis/gasification, can be efficiently physical/chemical processes in the development
coupled for the recovery of products for material and application of sustainable wastewater treatment
reuses and/or energy purposes [87]. These systems, Front. Environ. Sci. Eng. China 2 (4) (2008)
coupled technologies may have viable routes 385–396.
[9] G.T. Daigger, Evolving urban water and residuals
for full-scale applications, combining favorable management paradigms: water reclamation and reuse,
process economics and low energy require- decentralization, and resource recovery, Water Envi-
ments in an environmentally friendly solution. ron. Res. 81 (8) (2009) 809–823.
Among the different biological systems, [10] E. Commission, On the municipal sewage treatment
anaerobic digestion treatment could be the most dated on 21 May (Directive 91/271/EWG), Off. J.
Eur. Union (1991) 1–13.
promising one, as COD removal can be around [11] E. Commission, Proposal for a regulation of the Euro-
70%, the sludge is reduced, and biogas is pro- pean Parliament and of the Council on minimum
duced during the treatment [159]. On the other requirements for water reuse, 2018/0169 (COD),
hand, the use of anaerobic digestion for the pro- 2018, pp. 1–28.
duction of hydrogen is emerging as another [12] EPA, Guidelines for Water Reuse, United States Envi-
ronmental Protection Agency, 2012.
attractive option to treat high-strength industrial [13] Californian Department of Water Resources (DWR),
effluents. More specifically, different studies Policy for Water Quality Control for Recycled Water,
have been carried out for the effluents coming Available from: https://www.waterboards.ca.gov/
from the brewery industry [160]. water_issues/programs/water_recycling_policy/docs/
rwp_revtoc.pdf, 2013. (Accessed 21 February 2019).
[14] C. Prasse, D. Stalter, U. Schulte-Oehlmann,
References J. Oehlmann, T.A. Ternes, Spoilt for choice: a critical
review on the chemical and biological assessment of
[1] O.B. Akpor, D.A. Otohinoyi, T.D. Olaolu, Heavy current wastewater treatment technologies, Water
metal pollutants in wastewater effluents: sources, Res. 87 (2015) 237–270.
effects and remediation, Adv. Biosci. Bioeng. 2 (4) [15] K. Tang, G.T.H. Ooi, K. Litty, K. Sundmark,
(2014) 37–43. K.M.S. Kaarsholm, C. Sund, C. Kragelund,
[2] M. Le Moal, C. Gascuel-Odoux, A. M
enesguen, M. Christensson, K. Bester, H.R. Andersen, Removal


Y. Souchon, C. Etrillard, A. Levain, F. Moatar, of pharmaceuticals in conventionally treated wastewa-
A. Pannard, P. Souchu, A. Lefebvre, G. Pinay, Eutro- ter by a polishing moving bed biofilm reactor (MBBR)
phication: a new wine in an old bottle? Sci. Total Envi- with intermittent feeding, Bioresour. Technol.
ron. 651 (Part 1) (2019) 1–11. 236 (2017) 77–86.
[3] A. Gallego-Schmid, R.R. Zepon Tarpani, Life cycle [16] N.N. Koopaei, M. Abdollah, Health risks associated
assessment of wastewater treatment in developing with the pharmaceuticals in wastewater. DARU, J.
countries: a review, Water Res. 153 (2019) 63–79. Pharm. Sci. 25 (9) (2017) 1–7.
[4] L. Rizzo, C. Manaia, C. Merlin, T. Schwartz, C. Dagot, [17] F.D.L. Leusch, N.H. Aneck-Hahn, J.E. Cavanagh,
M.C. Ploy, I. Michael, D. Fatta-Kassinos, Urban waste- D. Du Pasquier, T. Hamers, A. Hebert, P.A. Neale,
water treatment plants as hotspots for antibiotic resis- M. Scheurer, S.O. Simmons, M. Schriks, Comparison
tant bacteria and genes spread into the environment: a of in vitro and in vivo bioassays to measure thyroid
review, Sci. Total Environ. 447 (2013) 345–360. hormone disrupting activity in water extracts, Chemo-
[5] X. Yan, C. Zhu, B. Huang, Q. Yan, Q. Zhang, Enhanced sphere 191 (2018) 686–875.
nitrogen removal from electroplanting tail wastewater [18] R. Pedrazzani, G. Bertanza, I. Brnardi
c, Z. Cetecioglu,
through two-staged anoxic-oxic (A/O) process, Biore- J. Dries, J. Dvarionien_e, A.J. Garcia-Fernández,
sour. Technol. 247 (2018) 157–164. A. Langenhoff, G. Libralato, G. Lofrano, B. Škrbi
c,
[6] A. Karkman, T.T. Do, F. Walsh, M.P.J. Virta, Antibiotic- E. Martı́nez-López, S. Meriç, D.M. Pavlovi
c, M. Papa,
resistance genes in waste water, Trends Microbiol. P. Schr€oder, K.P. Tsagarakis, C. Vogelsang, Opinion
26 (3) (2018) 220–228. paper about organic trace pollutants in wastewater:
[7] M. Salimi, A. Esrafili, M. Gholami, A.J. Jafari, toxicity assessment in a European perspective, Sci.
R.R. Kalantary, M. Farzadkia, M. Kermani, H.R. Sobhi, Total Environ. 651 (2019) 3202–3221.

I. Wastewater treatment as a process and a resource

40 2. Wastewater treatment as a process and a resource

[19] P. Ragazzo, D. Feretti, S. Monarca, L. Dominici, wastewater, Resour. Conserv. Recycl. 52 (2008)
E. Ceretti, G. Viola, V. Piccolo, N. Chiucchini, 533–544.
M. Villarini, Evaluation of cytotoxicity, genotoxicity, [32] Veolia Water Technologies, IDRAFLOT® Advanced
and apoptosis of wastewater before and after disinfec- Multi-DAF Technology, Available on http://www.
tion with performic acid, Water Res. 116 (2017) 44–52. veoliawatertech.com/vwst-northamerica/ressources/
[20] F.M. Kemmer, The Nalco Water Handbook, McGraw- files/2/55293-IDRAFLOT_Flotation_Technology_EN-
Hill Inc., USA, 1987. 5.pdf, 2017. Accessed April 2019.
[21] S. Denisov, S. Maksimov, E. Gordeef, Improving the [33] Suez Water Technologies, Poseidon *PPM* dissolved
efficiency of biological treatment of domestic wastewa- air flotation units, Available at: https://my.
ter by using acoustic and hydrodynamic effect, Proce- suezwatertechnologies.com/s/content-download?
dia Eng. 150 (2016) 2399–2404. DN¼BRclposeidon_DAF_Saturn_EN.pdf, 2018
[22] Y. Lorenzo-Toja, I. Vázquez-Rowe, S. Chenel, Accessed April 2019.
D. Marı́n-Navarro, M.T. Moreir, G. Feijoo, Eco- [34] Suez Water Technologies, Poseidon *Saturn*
efficiency analysis of Spanish WWTPs using the LCA dissolved air flotation units, Available at: https://
+ DEA method, Water Res. 68 (2015) 651–666. my.suezwatertechnologies.com/s/content-download?
[23] M. Garfı́, L. Flores, I. Ferrer, Life cycle assessment of DN¼BRclposeidon_DAF_PPM_EN.pdf, 2018. Accessed
wastewater treatment systems for small communities: April 2019.
activated sludge, constructed wetlands and high rate [35] D. Jenkins, J. Wanner, Activated Sludge – 100 Years
algal ponds, J. Clean. Prod. 161 (2017) 211–219. and Counting, IWA Publishing, London, 2014.
[24] D.B. Miklos, C. Remy, M. Jekel, K.G. Linden, [36] C.J. Moretti, D. Das, B.T. Kistner, H. Gullicks,
J.E. Drewes, U. H€ ubner, Evaluation of advanced oxida- Y.-T. Hung, Activated sludge and other aerobic sus-
tion processes for water and wastewater treatment – a pended culture processes, Water 3 (2011) 806–818.
critical review, Water Res. 139 (2018) 118–131. [37] G. Bitton, Wastewater Microbiology, third ed., John
[25] C.S. Lee, J. Robinson, M.F. Chong, A review on appli- Wiley & Sons, Inc., Hoboken, 2005.
cation of flocculants in wastewater treatment, Process [38] R. Kumar, A.K. Sarmah, L.P. Padhye, Fate of pharma-
Saf. Environ. 92 (6) (2014) 489–508. ceuticals and personal care products in a wastewater
[26] B.-S. Zăbavă, N. Ungureanu, V. Vladut, M. Dincă, treatment plant with parallel secondary wastewater
G. Voicu, M. Ionescu, Experimental study of the sedi- treatment train, J. Environ. Manag. 233 (2019)
mentation of solid particles in wastewater, 649–659.
in: Scientific International Conferences, 2016. – The [39] Suez Water Technologies. Puritreat Pcf, A range of
12th Annual Meeting, Durable Agriculture – Agricul- automatic activated carbon filters to reduce chlorine,
ture of the Future, At Craiova, Vol. XLVI/2, 2016. organic contaminants and for general water condi-
[27] R. Gori, F. Giaccherini, L.-M. Jiang, R. Sobhani, tioning, Available at: https://www.suezwater.co.
D. Rosso, Role of primary sedimentation on plant- uk/wp-content/uploads/2017/01/SUEZ-PURITREAT-
wide energy recovery and carbon footprint, Water PCF-Datasheet-Nov-2016.pdf, 2016. Accessed April
Sci. Technol. 68 (4) (2013) 870–878. 2019.
[28] P. Palaniandy, M.N. Hj, H.A. Nadlan, M.F.M. Aziz, [40] S. Mace, J. Mata-Alvarez, Utilization of SBR technology
Dissolved air flotation (DAF) for wastewater treat- for wastewater treatment: an overview, Ind. Eng.
ment, in: Waste Treatment in the Service and Utility Chem. Res. 41 (3) (2002) 5539–5553.
Industries, CRC Press, Boca Raton, 2017, ISBN: 978- [41] H. Simsek, M. Kasi, J.B. Ohm, M. Blonigen, E. Khan,
1-4200-7237-2, pp. 145–182. Bioavailable and biodegradable dissolved organic nitro-
[29] M. Krofta, L.K. Wang, C.D. Pollman, Treatment of sea- gen in activated sludge and trickling filter wastewater
food processing wastewater by dissolved air flotation, treatment plants, Water Res. 47 (9) (2013) 3201–3210.
carbon adsorption and free chlorination, [42] EPA, Aerobic Biological Wastewater Treatment Facili-
in: Proceedings of the 43rd Purdue Industrial Waste ties. Process Control Manual, United States Environ-
Conference, Purdue University, West Lafayette, IN, mental Protection Agency, 1977.
1988, , pp. 535–550. [43] H. Eslami, M.R. Samaei, E. Shahsavani, A.A. Ebrahimi,
[30] A.I. Zouboulis, A. Avranas, Treatment of oil-in-water Biodegradation and fate of linear alkylbenzene sulfo-
emulsions by coagulation and dissolved-air flotation, nate in integrated fixed-film activated sludge using
Colloids Surf. A Physicochem. Eng. Asp. 172 (2000) synthetic media, Desalin. Water Treat. 92 (2017) 128–133.
153–161. [44] L.B. Stadler, A.S. Ernstoff, D.S. Aga, N.G. Love, Micro-
[31] I.R. de Nardi, T.P. Fuzi, V. Del Nery, Performance eval- pollutant fate in wastewater treatment: 3118 redefining
uation and operating strategies of dissolved-air flota- “removal” Environ. Sci. Technol. 46 (19) (2012)
tion system treating poultry slaughterhouse 10485–10486.

I. Wastewater treatment as a process and a resource

 References 41
[45] A. Arias, T. Alvarino, T. Allegue, S. Suárez, [57] Suez Water Technologies, Aquaray* Ultraviolet (UV)
J.M. Garrido, F. Omil, An innovative wastewater treat- Systems, Available at: https://www.suezwatert
ment technology based on UASB and IFAS for cost- echnologies.com/products/disinfection-oxidation/
efficient macro and micropollutant removal, J. Hazard. aquaray-uv-systems. Accessed April 2019.
Mater. 359 (2018) 113–120. [58] A.E. Burakov, E.V. Galunin, I.V. Burakova,
[46] P. Lessard, Y. Le Bihan, Handbook of Water and A.E. Kucherova, S. Agarwal, A.G. Tkachev,
Wastewater Microbiology, Academic Press, 2003. V.K. Gupta, Adsorption of heavy metals on conven-
School of Civil Engineering, University of Leeds, UK. tional and nanostructured materials for wastewater
[47] Veolia Water Technologies, Anoxkaldness Hybass™, treatment purposes: a review, Ecotox. Environ. Safe
Available on http://technomaps.veoliawatertechnolo 148 (2018) 702–712.
gies.com/hybas/en/. Accessed April 2019. [59] C.A. Sophia, E.C. Lima, Removal of emerging contam-
[48] Suez Water Technologies, Meteor* IFAS/MBBR Process, inants from the environment by adsorption, Ecotox.
Available at: https://www.suezwatertechnologies. Environ. Safe 150 (2018) 1–17.
com/products/biological/meteor-ifasmbbr. Accessed [60] R. Treguer, B. Blair, R. Klaper, S. Royer, C. Magruder,
April 2019. Evaluation of Actiflo® Carb Process for the Combined
[49] Veolia Water Technologies, Reclamation system in the Removal of Trace Organic Compounds and Phospho-
soft drinks manufacturing reduces water footprint, rous during Wastewater Tertiary Treatment, WEFTEC,
Available at: http://technomaps.veoliawatertechno New Orleans, 2015. Available at: https://www.veolia.
logies.com/processes/lib/pdfs/productbrochures/ ca/sites/g/files/dvc2386/files/document/2015/12/
aquafab_english/2731,31901,2013_Case_Study_Beverage_ 40590ActiFlo-presentation_0.pdf. Accessed April 2019.
Wate.pdf, 2013. Accessed April 2019. [61] Siemens, PACT® Systems, Available at: https://w3.
[50] Suez Water Technologies, Activated Sludge by siemens.com/markets/global/en/oil-gas/Publishing
Sequenced Batch Reactor (SBR) – Cyclor™, Available Images/technologies/water-technology/products/
at: https://www.suezwaterhandbook.com/degremont- PACT-Systems-When-Clean-Water-Matters.pdf, 2016.
R-technologies/wastewater-treatment/biological-pro Accessed April 2019.
cesses/activated-sludge-by-Sequenced-Batch-Reactor- [62] M.A. Oturan, J.J. Aaron, Advanced oxidation pro-
SBR-Cyclor. Accessed April 2019. cesses in water/wastewater treatment: principles
[51] Y. Li, M. Yang, X. Zhang, J. Jiang, J. Liu, C.F. Yau, and applications. A review, Crit. Rev. Environ. Sci.
N.J.D. Graham, X. Li, Two-step chlorination: a new Technol. 44 (23) (2014) 2577–2641.
approach to disinfection of a primary sewage effluent, [63] S.C. Ameta, R. Ameta, Advanced Oxidation Processes
Water Res. 108 (2017) 339–347. for Waste Water Treatment. Emerging Green Chemical
[52] K. Watson, G. Shaw, F.D. Leusch, N.L. Knight, Chlo- Technology, Academic Press (imprint of Elsevier),
rine disinfection by-products in wastewater effluent: ISBN: 978-0-12-810499-6, 2018.
bioassay-based assessment of toxicological impact, [64] B.P. Vellanki, B. Batchelor, A. Abdel-Wahab,
Water Res. 46 (18) (2012) 6069–6083. Advanced reduction processes: a new class of treat-
[53] J. Rodrı́guez-Chueca, A. Mediano, M.P. Ormad, ment processes, Environ. Eng. Sci. 30 (5) (2013)
R. Mosteo, J.L. Ovelleiro, Disinfection of wastewater 264–271.
effluents with the Fenton-like process induced [65] Wedeco Mipro™, The right advanced oxidation
by electromagnetic fields, Water Res. 60 (2014) solution for any kind of micropollutants, Available
250–258. at: http://www.eawater.com/droplets/eaw/2015/
[54] O.-M. Lee, H.Y. Kim, W. Park, T.-H. Kim, S. Yu, A com- february/brochure4.pdf, 2015. Accessed April 2019.
parative study of disinfection efficiency and regrowth [66] Novexx, Static Hydro reactors, Available at:
control of microorganism in secondary wastewater http://www.novexx.com.sg/static-hydro-reactor-shr/.
effluent using UV, ozone, and ionizing irradiation pro- Accessed April 2019.
cess, J. Hazard. Mater. 295 (2015) 201–208. [67] Q. Chen, Z. Luo, C. Hills, G. Xue, M. Tyrer, Precipita-
[55] Suez Water Technologies, Ozonia* Ozone Systems, tion of heavy metals from wastewater using simulated
Available at: www.suezwatertechnologies. flue gas: sequent additions of fly ash, lime and carbon
com/products/disinfection-oxidation/ozonia-ozone- dioxide, Water Res. 43 (2009) 2605–2614.
systems. Accessed April 2019. [68] Y.H. Wang, J.C. Gu, W.L. Lin, W.Y. Wang, Wastewater
[56] W. Lem, J. Muller, UV Disinfection for Municipal Waste- containing copper precipitation research, Appl. Mech.
water, Available at: https://www.resources.trojanuv. Mater. 368-369 (2013) 510–513.
com/wp-content/uploads/2018/07/Basic-Introduction- [69] J.D. Doyle, R. Philp, J. Churchley, S.A. Parsons, Anal-
to-UV-Disinfection-Brazil.pdf, 2018. Accessed April ysis of struvite precipitation in real and synthetic
2019. liquors, Process Saf. Environ. 78 (6) (2000) 480–488.

I. Wastewater treatment as a process and a resource

42 2. Wastewater treatment as a process and a resource

[70] K. Zhou, M. Barjenbrunch, C. Kabbe, G. Inial, C. Remy, [83] C. Valderrama, R. Granados, J.L. Cortina, C.M. Gasol,
Phosphorus recovery from municipal and fertilizer M. Guillem, A. Josa, Comparative LCA of sewage
wastewater: China’s potential and perspective, J. Envi- sludge valorisation as both fuel and raw, J. Clean.
ron. Sci. 52 (2017) 151–159. Prod. 51 (2013) 205–213.
[71] A. Raheem, V.S. Sikarwar, J. He, W. Dastyar, [84] V.K. Tyagi, S.-L. Lo, Sludge: a waste or renewable
D.D. Dionysiou, W. Wang, M. Zhao, Opportunities source for energy and resources recovery? Renew.
and challenges in sustainable treatment and resource Sust. Energ. Rev. 25 (2013) 708–728.
reuse of sewage sludge: a review, Chem. Eng. J. [85] J. Chen, R.D. Tyagi, J. Li, X. Zhang, P. Drogui, F. Sun,
337 (2018) 616–641. Economic assessment of biodiesel production from
[72] M. Kacprzak, E. Neczaj, K. Fijałkowski, A. Grobelak, wastewater sludge, Bioresour. Technol. 253 (2018)
A. Grosser, M. Worwag, A. Rorat, H. Brattebo, 41–48.
A. Almås, B.R. Singh, Sewage sludge disposal [86] E. Bernardo, R. Dal Maschio, Glass-ceramics from vit-
strategies for sustainable development, Environ. Res. rified sludge pyrolysis residues and recycled glasses,
156 (2017) 39–46. Waste Manag. 31 (2011) 2245–2252.
[73] Eurostat, Sewage sludge production and disposal from [87] L. Spinosa, A. Ayol, J.C. Baudez, R. Canziani,
urban wastewater (in dry substance (d.s)), 2015. P. Jenicek, A. Leonard, W. Rulkens, G. Xu, L. van
[74] E. Commission, On the landfill of waste dated on 26 Dijk, Sustainable and innovative solutions for sewage
April 1999 (Directive 99/31/EC), Off. J. Eur. Union sludge management, Water 3 (2011) 702–717.
(1999) 1–19. [88] F. Kokalj, B. Arbiter, N. Samec, Sewage sludge gasifi-
[75] B.M. Cie
slik, P. Konieczka, A review of phosphorous cation as an alternative energy storage model, Energy
recovery methods at various steps of wastewater treat- Convers. Manag. 149 (2017) 738–747.
ment and sewage sludge management. The concept of [89] L. Borea, S. Puig, H. Monclús, V. Naddeo, J. Colprim,
“no solid waste generation” and analytical methods, J. V. Belgiorno, Microbial fuel cell technology as a down-
Clean. Prod. 142 (part 4) (2017) 1728–1740. stream process of a membrane bioreactor for sludge
[76] E. Commission, Environmental, economic and social reduction, Chem. Eng. J. 15 (2017) 222–230.
impacts of the use of sewage sludge on land; Final [90] B. Xiao, M. Luo, X. Wang, Z. Li, H. Chen, J. Liu, X. Guo,
Report; Part III: Project Interim Reports. In: W. a. R. Electricity production and sludge reduction by inte-
f. t. E. C. Milieu Ltd, DG Environment under Study grating microbial fuel cells in anoxic-oxic process,
Contract DG ENV.G.4/ETU/2008/0076r (Ed.), 2008. Waste Manag. 69 (2017) 346–352.
[77] M.C. Samolada, A.A. Zabaniotou, Comparative assess- [91] D. Cordell, A. Rosemarin, J.J. Schr€ oder, A.L. Smit,
ment of municipal sewage sludge incineration, gasifi- Towards global phosphorous security: a systems
cation and pyrolysis for a sustainable sludge-to-energy framework for phosphorous recovery and reuse
management in Greece, Waste Manag. 34 (2014) options, Chemosphere 84 (6) (2011) 747–758.
411–420. [92] R. Li, J. Yin, W. Wang, Y. Li, Z. Zhang, Transformation
[78] A.K. Venkatesan, H.Y. Done, R.U. Halden, United of phosphorous during drying and roasting of sewage
States National Sewage Sludge Repository at Ari- sludge, Waste Manag. 34 (2014) 1211–1216.
zona State University—a new resource and research [93] Z. Yuan, S. Pratt, D.J. Batstone, Phosphorous recovery
tool for environmental scientists, engineers, and from wastewater through microbial processes, Curr.
epidemiologists, Environ. Sci. Pollut. Res. Opin. Biotechnol. 23 (2012) 878–883.
22 (2015) 1577–1586. [94] L.M. Ottosen, G.M. Kirkelund, P.E. Jensen, Extracting
[79] G. Yang, G. Zhang, H. Wang, Current state of sludge phosphorous from incinerated sewage sludge ash rich
production, management, treatment and disposal in in iron or aluminum, Chemosphere 91 (2013) 963–969.
China, Water Res. 78 (2015) 60–73. [95] H. Weigand, M. Bertau, W. H€ ubner, F. Bohndick,
[80] X. Lishan, T. Tao, W. Yin, Y. Zhilong, L. Jiangfu, Com- A. Bruckert, RecoPhos: full-scale fertilizer production
parative life cycle assessment of sludge management: a from sewage sludge ash, Waste Manag. 33 (2013)
case study of Xiamen, China, J. Clean. Prod. 192 (2018) 540–544.
354–363. [96] K. Gorazda, B. Tarko, Z. Wzorek, H. Kominko,
[81] W.Q. Guo, S.S. Yang, W.S. Xiang, X.J. Wang, N.Q. Ren, A.K. Nowak, J. Kulczycka, A. Henclik, M. Smol, Ferti-
Minimization of excess sludge production by in-situ lisers production from ashes after sewage sludge
activated sludge treatment processes—a comprehen- combustion – a strategy towards sustainable develop-
sive review, Biotechnol. Adv. 31 (8) (2013) 1386–1396. ment, Environ. Res. 154 (2017) 171–180.
[82] B.M. Cie
slik, J. Namiesnik, P. Konieczka, Review of [97] Nutrient Management Solution, Available at: https://
sewage sludge management: standards, regulations ostara.com/. Accessed April 2019.
and analytical methods, J. Clean. Prod. 90 (2015) [98] B. Hultman, E. Levlin, E. Plaza, K. Stark, Phosphorus
1–15. recovery from sludge in Sweden – possibilities to meet

I. Wastewater treatment as a process and a resource

 References 43
proposed goals in an efficient, sustainable and eco- of pulp and paper wastewater, Environ. Technol.
nomical way No 10: 19-28, Available at www.lwr. Innov. 9 (2018) 265–274.
kth.se/forskningsprojekt/Polishproject/JPS10s19.pdf, [110] O. Ashrafi, L. Yerushalmi, F. Haghighat, Wastewater
2003. Accessed April 2019. treatment in the pulp-and-paper industry: a review
[99] Y. Kalogo, H. Monteith, State of Science Report: of treatment processes and the associated greenhouse
Energy and resource recovery from sludge, Water gas emission, J. Environ. Manag. 158 (2015) 146–157.
Environ. Res. Foundation, Global Water Res. Coali- [111] C. Gadipelly, A. P
erez-González, G.D. Yadav, I. Ortiz,
tion, 2008. R. Ibáñez, V.K. Rathod, K.V. Marathe, Pharmaceutical
[100] K. Stendahl, S. J€afverstr€
om, Recycling of sludge with industry wastewater: review of the technologies for
the Aqua Reci process, Water Sci. Technol. 49 (10) water treatment and reuse, Ind. Eng. Chem. Res.
(2004) 233–240. 53 (29) (2014) 11571–11592.
[101] M. Osaka, C.-H. Jung, Thermodynamic behavior of [112] M.H. El-Naas, S. Al-Zuhair, A. Al-Lobaney,
rare metals in the melting process, Chemosphere S. Makhlouf, Assessment of electrocoagulation for
69 (2007) 279–288. the treatment of petroleum refinery wastewater, J.
[102] J. Jimenez, F. Vedrenne, C. Denis, A. Mottet, D. D
el
eris, Environ. Manag. 91 (2009) 180–185.
J.P. Steyer, J.A.C. Rivero, A statistical comparison of [113] R. Marı́n, Procesos Fı́sico Quı́micos en Depuración de
protein and carbohydrate characterisation methodol- Aguas: Teorı́a, Práctica y Problemas Resueltos, Edi-
ogy applied on sewage sludge samples, Water Res. ciones Diaz de Santos, Madrid, 2012.
47 (2013) 1751–1762. [114] M.A. Bull, R.M. Sterritt, J.N. Lester, The treatment of
[103] R. Singh, M. Kumar, A. Mittal, P.K. Mehta, Microbial wastewaters from the meat industry: a review, Envi-
enzymes: industrial progress in 21st century, 3 Biotech ron. Technol. Lett. 3 (3) (1982) 117–126.
6 (2) (2016) 174. [115] E. Debik, T. Coskun, Use of the static granular bed
[104] F. Morgan-Sagastume, M. Hjort, D. Cirne, F. Gerardin, reactor (SGBR) with anaerobic sludge to treat poultry
S. Lacroix, G. Gaval, L. Karabegovic, T. Alexandersson, slaughterhouse wastewater and kinetic modeling,
P. Johansson, A. Karlsson, Integrated production of Bioresour. Technol. 100 (11) (2009) 2777–2782.
polyhydroxyalkanoates (PHAs) with municipal [116] P.D. Jensen, S.D. Yap, A. Boyle-Gotla, J. Janoschka,
wastewater and sludge treatment at pilot scale, Biore- C. Carney, M. Pidou, Anaerobic membrane bioreactors
sour. Technol. 181 (2015) 78–89. enable high rate treatment of slaughterhouse wastewa-
[105] S. Bengtsson, A. Karlsson, T. Alexandersson, ter, Biochem. Eng. J. 97 (2015) 132–141.
L. Quadri, M. Hjort, P. Johansson, F. Morgan- [117] FPAC, FPAC Sustainability Report, Forest Products
Sagastume, S. Anterrieu, M. Arcos-Hernandez, Association of Canada, Ottawa, ON, Canada, 2009.
L. Karabegovic, A process for polyhydroxyalkanoate http://www.fpac.ca/index.php/en/publications.
(PHA) production from municipal wastewater treat- [118] R. C
espedes, A. Maturana, U. Bumann, M. Bronfman,
ment with biological carbon and nitrogen removal B. González, Microbial removal of chlorinated phenols
demonstrated at pilot-scale, New Biotechnol. during aerobic treatment of effluents from radiata pine
35 (2017) 42–53. Kraft pulps bleached with chlorine-based chemicals,
[106] A. Werker, S. Bentsson, L. Korving, M. Hjort, with or without hemicellulases, Appl. Microbiol. Bio-
S. Anterrieu, T. Alexandersson, P. Johansson, technol. 46 (1996) 631–637.
A. Karlsson, L. Karabegovic, P. Magnusson, [119] M. Kamali, T. Gameiro, M. Elisabete, V. Costa,
F. Morgan-Sagastume, L. Sijstermans, M. Tietema, I. Capela, Anaerobic digestion of pulp and paper mill
C. Visser, E. Wypkema, Y. van der Kooij, A. Deeke, wastes – an overview of the developments and
C. Uijterlinde, Consistent production of high quality improvement opportunities, Chem. Eng. J. 298 (2016)
PHA using activated sludge harvested from full scale 162–182.
municipal wastewater treatment – PHARIO, Water [120] X. Qu, W.J. Gao, M.N. Han, A. Chen, B.Q. Liao, Inte-
Sci. Technol. 78 (11) (2018) 2256–2269. grated thermophilic submerged aerobic membrane
[107] C.F. Bustillo-Lecompte, M. Mehrab, Slaughterhouse bioreactor and electrochemical oxidation for pulp
wastewater characteristics, treatment, and manage- and paper effluent treatment – towards system clo-
ment in the meat processing industry: a review on sure, Bioresour. Technol. 116 (2012) 1–8.
trends and advances, J. Environ. Manag. 161 (2015) [121] M.S. Nasser, F.A. Twaiq, S.A. Onaizi, Effect of poly-
287–302. electrolytes on the degree of flocculation of papermak-
[108] D.I. Mass
e, L. Masse, Treatment of slaughterhouse ing suspensions, Sep. Purif. Technol. 103 (2013) 43–52.
wastewater in anaerobic sequencing batch reactors, [122] N. Buyukkamaci, E. Koken, Economic evaluation of
Can. Agric. Eng. 42 (2000) 131–137. alternative wastewater treatment plant options for
[109] H. Vashi, O.T. Iorhemen, J.H. Tay, Aerobic granula- pulp and paper industry, Sci. Total Environ.
tion: a recent development on the biological treatment 408 (2010) 6070–6078.

I. Wastewater treatment as a process and a resource

44 2. Wastewater treatment as a process and a resource

[123] D. Pokhrel, T. Viraraghavan, Treatment of pulp and [137] M.I. Badawy, R.A. Wahaab, Fenton-biological treat-
paper mill wastewater – a review, Sci. Total Environ. ment processes for the removal of some pharmaceuti-
333 (2004) 37–58. cals from industrial wastewater, J. Hazard. Mater.
[124] T.K. Das, Toward Zero Discharge – Innovative Meth- 167 (2009) 567–574.
odology and Technologies for Process Pollution Pre- [138] K.-H. Kim, S.-K. Ihm, Heterogeneous catalytic wet
vention, Wiley Interscience, 2005. air oxidation of refractory organic pollutants in indus-
[125] D. Hermosilla, N. Merayo, A. Gasco, A. Blanco, The trial wastewaters: a review, J. Hazard. Mater. 186
application of advanced oxidation technologies to (2011) 16–34.
the treatment of effluents form the pulp and paper [139] Y.Z. Peng, Y.Z. Li, C.Y. Peng, S.Y. Wang, Nitrogen
industry: a review, Environ. Sci. Pollut. R. 22 (2015) removal from pharmaceutical manufacturing waste-
168–191. water with high concentration of ammonia and free
[126] C.G. Zhang, Research on the technology of pharma- ammonia via partial nitrification and denitrification,
ceutical wastewater treatment, IOP Conf. Ser. Earth Water Sci. Technol. 50 (2004) 31–36.
Environ. Sci. (2018). [140] A.M. Deegan, B. Shaik, K. Nolan, K. Urell,
[127] J. Wang, S. Wang, Removal of pharmaceuticals and M. Oelgem€ oller, J. Tobin, A. Morrisey, Treatment
personal care products (PPCPs) from wastewater: options for wastewater effluents from pharmaceutical
a review, J. Environ. Manag. 182 (2016) 620–640. companies, Int. J. Environ. Sci. Technol. 8 (3) (2011)
[128] Global Pharmaceuticals, 2017 Industry Statistics Hard- 649–666.
man&co, 2018. Available online: https://www.statista. [141] J. Bezawada, S. Yan, R.P. John, R.D. Tyagi, R.
com/statistics/263102/pharmaceutical-market-world Y. Surampalli, Recovery of Bacillus licheniformis alka-
wide-revenue-since-2001/; https://www.hardmanand line protease from supernatant of fermented wastewa-
co.com/wp-content/uploads/2018/09/global-pharma ter sludge using ultrafiltration and its characterization,
ceuticals-2017-industry-stats-april-2018-1.pdf. Biotechnol. Res. Int. (2011) 1–11.
[129] S.K. Gupta, S.K. Gupta, Y.-T. Hung, Treatment of phar- [142] C.E. Santos, A. Fonseca, E. Kumar, A. Bhatnagar, V.J.
maceutical wastes, in: Waste Treatment in the Process P. Vilar, C.M.S. Botelho, A.R. Boaventura, Performance
Industries, CRC Press, Boca Raton, 2005, pp. 167–233. evaluation of the main units of a refinery wastewater
[130] F. Martı́nez, R. Molina, I. Rodrı́guez, M.I. Pariente, treatment plant – a case study, J. Environ. Chem.
Y. Segura, J.A. Melero, Techno-economical assessment Eng. 3 (2015) 2095–2103.
of coupling Fenton/biological processes for the treat- [143] C. Machin-Ramirez, A.I. Okohc, D. Morales,
ment of a pharmaceutical wastewater, J. Environ. K. Mayolo-Deloisa, R. Quintero, M.R. Trejo-
Chem. Eng. 6 (2018) 485–494. Hernandez, Slurry-phase biodegradation of weath-
[131] Z. Li, P. Yang, Review on physicochemical, chemical, ered oily sludge waste, Chemosphere 70 (2008)
and biological processes for pharmaceutical wastewa- 737–744.
ter, IOP Conf. Ser. Earth Environ. Sci. 113 (2018). [144] F. Renault, B. Sancey, P.-M. Badot, G. Crini, Chitosan
[132] S. Perez-Vega, E. Ortega-Rivas, I. Salmeron-Ochoa, for coagulation/flocculation processes—an eco-
P.N. Sharratt, A system view of solvent selection in friendly approach, Eur. Polym. J. 45 (2009) 1337–1348.
the pharmaceutical industry: towards a sustainable [145] M.H. El-Naas, M.A. Alhaija, S. Al-Zuhair, Evaluation
choice, Environ. Dev. Sustain. 15 (1) (2012) 1–21. of a three-step process for the treatment of petroleum
[133] S. Suarez, J. Lema, F. Omil, Pre-treatment of hospital refinery wastewater, J. Environ. Chem. Eng. 2 (2014)
wastewater by coagulation–flocculation and flotation, 56–62.
Bioresour. Technol. 100 (7) (2009) 2138–2146. [146] C.E. Santo, V.J.P. Vilar, A. Bhatnagar, E. Kumar, C.M.
[134] J.R. Andrade, M.F. Oliveira, M.G.C. da Silva, M.G. S. Botelho, R.A.R. Boaventura, Biological treatment by
A. Vieira, Adsorption of pharmaceuticals from water activated sludge of petroleum refinery wastewaters,
and wastewater using nonconventional low-cost mate- Desalin. Water Treat. 51 (34–36) (2013) 6641–6654.
rials: a review, Ind. Eng. Chem. Res. 57 (9) (2018) [147] B.H. Hasan Diyauddeen, W.M.A.W. Daud, A.R.
3103–3127. A. Aziz, Treatment technologies for petroleum refin-
[135] J. Yi-zhong, Z. Yue-feng, L. Wei, Experimental study ery effluents: a review, Process Saf. Environ.
on micro-electrolysis technology for pharmaceutical 89 (2011) 95–105.
wastewater treatment, J. Zhejiang Univ. 3 (2002) [148] D.J. Batstone, T. H€ ulsen, C.M. Mehta, J. Keller, Plat-
401–404. forms for energy and nutrient recovery from domestic
[136] J.A. Melero, F. Martı́nez, J.A. Botas, R. Molina, M. wastewater: a review, Chemosphere 140 (2015) 2–11.
I. Pariente, Heterogeneous catalytic wet peroxide oxi- [149] W.H. Rulkens, H.V.M. Hamelers, Design and selection
dation systems for the treatment of an industrial phar- of closed water loop systems to abate environmental
maceutical wastewater, Water Res. 43 (2009) pollution in industrial production processes, in:
4010–4019. H.F. Schr€ oder (Ed.), Ecohazard 2003—Proceedings of

I. Wastewater treatment as a process and a resource

 Further reading 45
the 4th IWA Specialized Conference on Assessment [156] T. H€ ulsen, E.M. Barry, Y. Lu, D. Puyol, J. Keller,
and Control of Hazardous Substances in Water, Insti- D.J. Batstone, Domestic wastewater treatment with
tute of Water and Waste Manage. Aachen University, purple phototrophic bacteria using a novel continuous
Aachen, 2003, , pp. 31/1–31/8. photo anaerobic membrane bioreactor, Water Res.
[150] J.A. Alvarez, I. Ruiz, M. Gomez, J. Presas, M. Soto, 100 (2016) 486–495.
Start-up alternatives and performance of an UASB [157] D. Puyol, D.J. Batstone, T. H€
ulsen, S. Astals, M. Peces,
pilot plant treating diluted municipal wastewater at J.O. Kr€omer, Recovery from Wastewater by biological
low temperature, Bioresour. Technol. 97 (2006) technologies: opportunities, challenges, and prospects,
1640–1649. Front. Microbiol. 7 (2017) 1–23.
[151] V. Kalyushnyi, V.V. Fedorovich, P. Lens, Dispersed [158] S. Lage, Z. Gojkovic, C. Funk, F.G. Gentili, Algal bio-
plug flow model for upflow anaerobic sludge bed reac- mass from wastewater and flue gases as a source of
tors with focus on granular sludge dynamics, J. Ind. bioenergy, Energies 11 (3) (2018) 664.
Microbiol. Biotechnol. 33 (2006) 221–237. [159] W.M. Budzianowski, Negative carbon intensity of
[152] B. Wett, A. Omari, S.M. Podmirseg, M. Han, renewable energy technologies involving biomass or
O. Akintayo, G.M. Brandón, S. Murthy, C. Bott, carbon dioxide as inputs, Renew. Sust. Energ. Rev.
M. Hell, I. Takács, G. Nyhuis, M. O’Shaughnessy, 16 (2012) 6507–6521.
Going for main stream deammonification from bench [160] M.K. Arantes, H.J. Alves, R. Sequinel, E.A. da Silva,
to full scale for maximized resource efficiency, Water Treatment of brewery wastewater and its use for bio-
Sci. Technol. 68 (2013) 283–289. logical production of methane and hydrogen, Int. J.
[153] G.R. Zoutberg, R. Frankin, Anaerobic treatment of Hydrog. Energy 42 (2017) 26243–26256.
chemical and brewery waste water with a new type
of anaerobic reactor; the biobed® EGSB reactor, Water
Sci. Technol. 34 (1996) 375–381. Further reading
[154] J. Jimenez, M. Miller, C. Bott, S. Murthy,
H. DeClippeleir, B. Wett, High-rate activated sludge [161] G. Tchobanoglous, F.L. Burton, H.D. Stensel, Waste-
system for carbon management – evaluation of crucial water Engineering: Treatment and Reuse, fourth ed.,
process mechanisms and design parameters, Water McGraw-Hill. Metcalf & Eddy, Inc., New York, 2003.
Res. 87 (2015) 476–482. [162] K.P. Oliveira, M. Mori, R.E. Bruns, Simulation of an
[155] T. Cai, S.Y. Park, Y. Li, Nutrient recovery from waste- industrial wastewater treatment plant using artificial
water streams by microalgae: status and prospects, neural networks and principal components analysis,
Renew. Sust. Energ. Rev. 19 (2013) 360–369. Braz. J. Chem. Eng. 19 (2002) 365–370.

I. Wastewater treatment as a process and a resource