Waste Water Treatment

Wastewater treatment is a process, which is used to convert wastewater into a useful

effluent (with no negligible health and environmental issues), which is then returned
back to the water-cycle or in other words, it can be reused.

From: Advanced Oxidation Processes for Waste Water Treatment, 2018

Related terms:

Contaminant, Reuse, Biomass, Effluent, Micro-Organism, Sewage, Sewage Sludge,

Wetland

View all Topics

Wastewater Treatment
J. Jeffrey Peirce, ... P. Aarne Vesilind, in Environmental Pollution and Control (Fourth
Edition), 1998

CENTRAL WASTEWATER TREATMENT

The objective of wastewater treatment is to reduce the concentrations of specific
pollutants to the level at which the discharge of the effluent will not adversely affect
the environment or pose a health threat. Moreover, reduction of these constituents
need only be to some required level. Although water can technically be completely
purified by distillation and deionization, this is unnecessary and may actually be
detrimental to the receiving water. Fish and other organisms cannot survive in
deionized or distilled water.

For any given wastewater in a specific location, the degree and type of treatment are
variables that require engineering decisions. Often the degree of treatment depends
on the assimilative capacity of the receiving water. DO sag curves can indicate how
much BOD must be removed from wastewater so that the DO of the receiving water
is not depressed too far. The amount of BOD that must be removed is an effluent
standard (discussed more fully in Chapter 11) and dictates in large part the type of
wastewater treatment required.
To facilitate the discussion of wastewater, assume a “typical wastewater” (Table 8-1)
and assume further that the effluent from this wastewater treatment must meet the
following effluent standards:

BOD ≤ 15 mg/L

SS ≤ 15 mg/L

P ≤ 1 mg/L

Additional effluent standards could have been established, but for illustrative pur-
poses we consider only these three. The treatment system selected to achieve these
effluent standards includes

• Primary treatment: physical processes that remove nonhomogenizable solids

and homogenize the remaining effluent.
• Secondary treatment: biological processes that remove most of the biochem-
ical demand for oxygen.
• Tertiary treatment: physical, biological, and chemical processes to remove nu-
trients like phosphorus and inorganic pollutants, to deodorize and decolorize
effluent water, and to carry out further oxidation.

> Read full chapter

Biological Wastewater Treatment Sys-

tems
M. Pell, A. Wörman, in Encyclopedia of Ecology, 2008

Wastewater treatment today probably is more focused on removing phosphorus and

nitrogen than pathogens since these elements contribute to eutrophication and de-
terioration of our natural water ecosystems. A great number of biological wastewater
treatment techniques exist, from natural and constructed wetlands at one end to
high-technology solutions based on the activated sludge process at the other end.
The core of all wastewater treatment processes involves active microbial cells con-
centrated at biofilms or flocs. Knowledge of the cell and the structure and function
of the microbial community is necessary in the design of effective conventional
and new treatment systems. In this article, the importance of respiration, nitro-
gen mineralization, nitrification, denitrification, and biological phosphorus removal
processes is emphasized. Equally important is knowledge and theoretical modeling
of water movement through the wastewater ecosystems. The understanding of the
contact between the microbe and wastewater is a prerequisite for kinetic modeling
of various enzyme reactions to describe the water purification process. Emphasis is
given to the function of constructed wetlands and activated sludge processes. The
future challenge of sustainable wastewater treatment is to design techniques that
recycle the content of valuable plant nutrients. In addition, wastewater treatment
by constructed wetlands will contribute in maintaining biological diversity in the
ecosystem as well as ideally to create easy accessible recreational and educational
meetings between urban citizens and the ecosystem.

> Read full chapter

Industrial Wastewater Treatment, Recy-

cling, and Reuse—Past, Present and Fu-
ture
Vivek V. Ranade, Vinay M. Bhandari, in Industrial Wastewater Treatment, Recycling
and Reuse, 2014

14.2 The Past

Wastewater treatment philosophy dates back thousands of years and was part of
many ancient civilizations, such as those of Rome and the Indus Valley (Vigneswaran
et al., 2011; http://www.lenntech.com/history-water-treatment.htm). Located near
the Indus River in the ancient Indian region, Mohenjo-Daro represents one of
the oldest known systems of wastewater management, as it is believed to date
to around 1500 BC (Wiesmann, 2007). At that time, the local population settled
in the vicinity of rivers that ensured easier supply and discharge of waters. These
ancient settlements were believed to have water supplies and sewerage facilities.
The development of water transport systems of various forms was crucial and was
supplemented by treatment methods. The primary focus in the past was sewage
wastewater treatment, and major treatment processes included segregation, di-
lution, and filtration in different forms. Though India is facing severe wastewater
treatment problems, and water scarcity today, it is believed to have history and prior
art of water management, disposal of waste, and health issues that find mention in
various forms of literature, beginning with the Vedas, one the most ancient pieces
of literature on Earth. However, modern world wastewater treatment arrived only
a few centuries back, in about the sixteenth century. The development of physical,
chemical, and biological treatments started gradually. The twentieth century saw the
main thrust in this area, and the understanding of wastewater evolved through the
1900s to the present date.

In the early 1900s, wastewater treatment mainly involved filtration, settling, and
septic tank use. The design of wastewater treatment plants was also consid-
ered, along with the application of disinfection methods, largely in the form of
chlorination. The biological treatment method also emerged during this period,
and the first use of the activated sludge process (ASP) was reported in 1916
in the USA (http://civil.colorado.edu/~silverst/cven5534/History%20of%20Waste-
water%20Treatment%20in%20the%20US.pdf; http://www.activatedsludgeconfer-
ence.com/downloads/OneHundredYearsofActivatedSludge-Abriefhistory.pdf). In
the following years, increased understanding of wastewaters led to the evolution
of various treatment methods, especially for the removal of odor, color, and solids.
The main methods included adsorption, ion exchange, coagulation, and chemical
treatment. The application of the ASP created a secondary treatment problem in
the form of sludge generation, and methods were researched to minimize sludge
production, compacting, and other undesired results. The importance of dissolved
oxygen was also realized during this period.

After 1950, waste water treatment scenario changed dramatically. Global industrial
development also increased in speed and scale, largely due to the emergence of
technologies in the form of novel materials, processes, and equipment configura-
tions and devices. During this period, communities also developed new regulations
for the release and treatment of wastewaters, fuelling further advances in water
management. An increased understanding of biological oxygen demand and chem-
ical oxygen demand propelled the development of methodologies for reducing the
organic load in wastewaters, as well as the classification of pollutants in different
forms. The membrane separation process also started in this period, with simple
symmetric membranes acting merely as filtration medium. Asymmetric membranes
followed, allowing for increased flux, as did membranes with diverse materials,
better characteristics, and improved mechanical and chemical properties. Eventually,
more complex hybrid membranes systems emerged, providing facilitated transport
and reactive membranes for highly specific applications. This development, need-
less to say, widened the scope of application tremendously for industrial waste-
water treatment (Microfiltration, Ultrafiltration, Nanofiltration, Reverse Osmosis,
emulsion liquid membranes, membrane distillation) and also altered biological
treatments in the form of membrane bioreactors. Aside from the developments in
technology and instrumentation, overall awareness about environmental pollution
and more particularly water pollution increased tremendously in the late twentieth
century.

> Read full chapter

Synthetic Polymers☆
J.P. Carbone, K.H. Reinert, in Reference Module in Earth Systems and Environmental
Sciences, 2015
Aquatic Acute Ecotoxicity
Wastewater treatment will be an important removal process for p(AA) materials.
Therefore an analysis of the toxicity of these polycarboxylates to wastewater treat-
ment facility (WWTF) biomass is of critical importance. An IC50 of > 100 mg l− 1 p(AA)
4500 has been reported and thus the likelihood of significant biomass toxicity as a
result of entry of p(AA) of this molecular weight or larger into a WWTF is likely to be
minimal.

A number of acute fish and aquatic invertebrate toxicity studies are available for poly-
acrylates. Ninety-six hour LC50 data for rainbow trout (Salmo gairdneri, O. mykiss)
and bluegill sunfish (Lepomis macrochirus) were reported as 315 and > 450 mg l− 1
p(AA) 4500. Generally these materials are characterized according to United States
Environmental Protection Agency (USEPA) Toxic Substances Control Act (TSCA)
criteria as of low toxicity to aquatic organisms. Table 3 illustrates additional acute
fish and invertebrate (D. magna) toxicity data for a variety of molecular weight
polyacrylates.

Table 3. Acute aquatic toxicity of polyacrylates in fish and D. magna.

Polymer test- Zebra fish Golden orfe Bluegill Trout (Salmo Daphnia
ed (molecular (Brachy- (Leuciscus (Lepomis
weight, Da) gairdneri, magna 48 h
danio rerio) idus macrochirus-
On- EC50
96 h LC50 melanotus) ) 96 h LC50
(mg l− 1) (mg l− 1) corhynchus (mobility) (mg 
96 h LC50
(mg l− 1) mykiss) 96 h l− 1)
LC50 (mg l− 1)
p(AA) 1000 > 200 > 1000 > 1000 > 200
≥ 1000
p(AA) 2000 > 200 > 200
p(AA) 4500 > 200 > 1000 700 > 200
> 1000 > 1000
> 450
p(AA) 9400 > 1000
p(AA) 10 000 > 1000
p(AA) 23 000 > 1000
p(AA) 78 000 > 1000 1590 > 750
p(AA) 111 000 > 1000
p(AA) 152 000 > 1000
p(AA) 215 000 > 1000
p(AA) 12 000 > 200 > 200
p(AA) 70 000 > 100 > 200 > 200
> 1000 > 100
> 200
> 908
Data from Table 6 and Table 7 of ECETOC (1993). Joint assessment of commodity
chemicals, No. 23: Polycarboxylate polymers as used in detergents. Brussels: ECETOC
(ISSN-0773-6339-23).

A detailed survey of the toxicity of p(AA) polymers and additional wastewater

treatment polymers chemistries such as methacryloyloxy trimethyl ammonium
chloride (METAC), acryloyloxy trimethyl ammonium chloride (AETAC), epichloro-
hydrin/dimethylamine (EPI/DMA), diallyldimethyl ammonium chloride (DADMAC),
melamine formaldehyde and mannich (secondary amines) in Daphnia pulex, and
the fathead minnow (P. promelas) has been conducted. LC50 values for the D. pulex
ranged from 0.06 to 2.0 mg l− 1 for the majority of the polymers tested. Daphnia pulex
was much less sensitive to melamine formaldehyde and mannich polymers (LC50
values: 12.1–70.1 mg l− 1). Some of the D. pulex toxicity was apparently the result
of physical entrapment of the organism by the polymer. The fathead minnow was
generally less sensitive than the invertebrate. Polymer toxicity to the fathead minnow
appeared to be related to the charge of the polymer. Cationic polymers were found
to be clearly more toxic to P. promelas than anionic polymers with polymer toxicity
generally increasing with increasing positive charge density.

> Read full chapter

Advanced Treatment Technology and

Strategy for Water and Wastewater Man-
agement
Haresh Bhuta, in Industrial Wastewater Treatment, Recycling and Reuse, 2014

Abstract
Wastewater treatment is becoming increasingly complex because of the wide spec-
trum of pollutants generated by industries including chemical, biomedical, phar-
maceutical, textile, and other sectors. Biological methods, such as evaporation, have
fallen short of meeting stringent treatment standards and methods, and incinera-
tion has fallen short of its promise because of the secondary pollution it causes. The
advanced oxidation process can play an important role in helping industries meet
the strict treatment standards either by complementing a biological process or by
itself. Key features such as a small footprint, nonselective destruction of pollutants,
and high flexibility make it key to the future sustainable success of the chemical
industry. This chapter outlines promising advanced treatment technologies along
with possible strategies for their application in various industries.
> Read full chapter

Bacterial pathogen removal in waste-

water treatment plants
Tom Curtis, in Handbook of Water and Wastewater Microbiology, 2003

4 THE FATE OF PATHOGENIC BACTERIA IN WASTEWATER

TREATMENT PLANTS
Wastewater treatment can be divided into anaerobic systems (septic tanks, anaerobic
ponds and anaerobic digesters), aerobic systems with attached growth (typically
trickling filters) and aerobic suspended growth systems (typically activated sludge). A
primary sedimentation tank usually precedes these systems. An increasingly popular
alternative is the reed bed or wetland. Another well-established alternative tech-
nology is the waste stabilization pond (WSP) - a sort of very wetland. Both ponds
and wetlands are relatively easy to construct, biologically sophisticated and contain
both aerobic and anaerobic zones. Waste stabilization ponds and wetlands can be
designed to optimize pathogen removal. In this sense they are different from the
other wastewater treatment systems we will consider. In most wastewater treatment
systems any pathogen removal that occurs is a fortuitous by-product of the principal
design objective (usually organic carbon removal). Pathogen removal cannot usually
be refined in these systems without compromising this objective or at least the costs
of meeting this objective.

For any given system, there are essentially two factors in pathogen removal: how long
the pathogen stays in the system and how quickly it dies. The former is governed by
the hydraulic flow regime and the latter depends on the ecology of the reactor.

The simplest conception of hydraulic flow in a reactor is as a completely stirred reac-

tor in which any material entering into a system is immediately uniformly dispersed
within the reaction vessel. The effluent quality of a completely stirred reactor is the
same as the reactor quality and therefore some of the pathogens pass almost directly
from the inlet to the outlet. However, if a number of completely mixed reactors
are placed in series then they can begin to approximate plug flow reactors. In plug
flow reactors the material entering into the reactor proceeds through the wastewater
treatment plant without mixing with the material that has entered before or after. In
reality some mixing does occur, this is known as dispersed flow.

Low rate systems such as ponds and wetlands have long retention times (typically
days) and thus more opportunity to remove pathogens. However, they may have
inefficient hydraulic flow regimes. Processes such as activated sludge have much
lower hydraulic retention times, though some plants may be hydraulically very
efficient indeed.

> Read full chapter

Aquatic Environment
V.J. Inglezakis, ... A.N. Menegaki, in Environment and Development, 2016

3.10.1 Historical Background and Overview

Wastewater treatment is the process of removing contaminants from wastewater; it
includes mechanical, physical, chemical, and biological processes, and the objective
is to produce environmentally safe treated effluent.

Industrialization and urbanization in the 19th century in combination with poor

sanitation led to severe outbreaks of cholera causing heavy loss of life in large
European cities. A major reason was the contamination of drinking water resources
with pathogens originating from untreated municipal (urban) wastewater. Thus,
municipal wastewaters drew the attention, while industrial wastewaters had to wait
for several decades. From the first comprehensive sewer network in Europe in
Hamburg in 1848, it took 68 years to develop the activated sludge treatment in
1916, and since then, 74 additional years to the development of advanced wastewater
treatment technologies as membranes in the 1990s (Table 3.5). The technologies
developed for municipal wastewaters are also used for the treatment of industrial
wastewaters. Similar to municipal wastewaters, industrial wastewaters treatment has
been evolved following a series of phases, from no treatment and direct discharge
to reuse and recycling.

Table 3.5. Timeline for Modern Wastewater Treatment [52].

Year Development
1740 Chemical treatment of sewage discharges in Paris
using lime as the precipitant.
1853 First comprehensive sewerage system completed
in Hamburg, Germany.
1850–1910 Many patents applied for in the United Kingdom
and the United States for chemical treatment of
sewage.
1868–70 Frankland's tests on filtration of sewage through
soil and gravel.
1890 First true biological filter at Lawrence Experimen-
tal Station, Massachusetts State Board of Health,
the United States.
1906 Imhoff tank designed in Germany.
1916 First full-scale activated sludge plant at Worcester.
First full-scale AS plant in the United States at
Houston, Texas.
1936 Denitrification used in Sheffield.
1964 Development of basis for consistent nitrification
by Downing, Painter and Knowles, WPRL, Steve-
nage, the United Kingdom.
1972 Biological phosphorous removal described by
Barnard in South Africa.
1990s Membrane biological reactors developed in
Japan.

So, the development of wastewater treatment was driven by these outbreaks of wa-
terborne diseases (Fig. 3.13). Since then, the evolution of wastewater treatment was
driven by the need for environmental (water quality) protection; in particular, nutri-
ent removal in the 1960s and 1970s after recognizing wastewater as the major cause
for the eutrophication of surface waters, and removal of persistent organic pollutants
such as PCBs, PAHs, and heavy metals until the beginning of the 1990s [52,66]. This
evolution was supported by the emergence and development of the environmental
legislation in the 1970s, which—apart from municipal—also prompted industrial
wastewater treatment. Since the beginning of 2000, the attention was drawn to
the so-called contaminants of emerging concern (CEC), such as pharmaceuticals,
personal care products, and perfluorinated compounds. These chemicals were not
previously detected in municipal water or are being currently detected at levels that
may be significantly different than expected [66]. The situation is similar in industry
where new raw chemicals are used or produced, and industrial wastewaters now
contain fractions of these chemicals.
Figure 3.13. Drivers for wastewater treatment plants development and upgrade.

The wastewater treatment can be conducted in centralized or decentralized systems.

Following treatment, the effluents are usually discharged to surface waters. Industri-
al wastewaters are usually treated on-site, although limited amounts are also sent to
centralized municipal systems [32]. The typical wastewater treatment plant is divided
into the following units (Fig. 3.14) [67–71]:

Figure 3.14. Unit operations in a typical wastewater treatment plant [67,68,70].Treat-

ment process diagram generated using PetWin version 4.1, EnviroSim Associates
Ltd.

•
Preliminary treatment—removal of large solids (rags, sticks, floatables, grease)•
by screening and removal of grit (sand, gravel, cinders, etc.). The processes
employed are purely mechanical.
Primary treatment—removal of a portion of suspended solids and organic •
matter by settling. While preliminary treatment is purely mechanical, primary
treatment may employ physicochemical methods as coagulation/flocculation
in order to enhance settling. Coagulation is a process of destabilization of
the charge of colloidal particles in wastewater so that to build up to larger
particles, which are easily settled. Flocculation produces larger particles from
small colloidal particles, which then could be easily removed by gravitational
settlement or filtration. More information on coagulation/flocculation process
is provided in Section 3.11. Flotation is a mechanical treatment unit that
removes solid or liquid particles from wastewaters with an aid of air. Air
bubbles attach to the particles that need to be removed and under the effect
of buoyant forces rise to the surface. Then, skimmers remove the waste at the
top of the flotation tank.
Secondary treatment—typically a biological treatment step for the removal •
of biodegradable organic matter (in solution or suspension) and suspended
solids, also combined with nutrients removal processes (often included in
tertiary step definition). The contaminants of major concern in the waste-
water are significantly reduced during this stage in terms of biochemical
oxygen demand (BOD) and chemical oxygen demand (COD). The objectives
of the biological treatment are the following: oxidation of particulate and
dissolved biodegradable constituents; capturing and converting suspended
and colloidal solids into a biological floc; removal of nutrients, eg, nitrogen,
phosphorous.
Tertiary treatment—removal of residual suspended solids by employing filters.•
Disinfection is also typical in this step. Moreover, an advanced treatment
step can be included in this definition where additional methods are used
for further purification of the wastewater, such as adsorption, ion exchange,
membrane separation, advanced oxidation, etc., for the removal of dissolved
and suspended materials. This step is crucial when the purpose is the reuse of
the treated wastewater.
Solids (sludge) treatment—collection, stabilization, and subsequent disposal.
This step includes the processes of thickening to increase the sludge solids
before treatment, anaerobic digestion, dewatering of the digestate, and final
treatment of the dewatered sludge by composting or drying (Fig. 3.15).Fig-
ure 3.15. Sludge treatment steps.

In the following paragraphs, the secondary and tertiary treatment steps will be
further analyzed.
> Read full chapter

Co-composting of sewage sludge and

wetland plant material from a con-
structed wetland treating domestic
wastewater
Anna Kwarciak-Kozłowska, in Industrial and Municipal Sludge, 2019

3 Constructed wetland
Wastewater treatment by using low-cost ecotechnology has gained importance in
recent years (Rana et al., 2011; Gomesa et al., 2014; Scholz, 2011). The methods of
environmental treatment based on phytotechnologies are gaining more and more
supporters due to their ecological character, easy operation, effectiveness, and op-
portunity for conducting the wastewater treatment in situ. In Europe, such systems
have been successfully used for municipal and industrial wastewater treatment and
removal of heavy metals from road drainage systems or dewatering of sewage
sludge (Manios et al., 2002; Vymazal and Kröpfelová, 2008; Herath and Vithanage,
2015; Brix, 1994; Manios, 2004; Obarska-Pempokowiak and Klimkowska, 1999). The
first experiments with wastewater treatment using macrophytes were conducted in
Germany in the early 1950s (Vymazal, 2011).

Removal of contaminants in these natural systems occurs by a combination of

physical, chemical, and biological processes. The processes connected with the
removal of contaminants is sedimentation, sorption, evapotranspiration, photo-oxi-
dation, diffusion, and microbiological degradation (e.g., nitrification, denitrification,
reduction of sulfates, and carbon metabolism (Herath and Vithanage, 2015).

A classification of constructed wetlands can be presented in three ways (Fig. 4):

Fig. 4. Types of constructed wetlands for wastewater treatment (Vymazal, 2008;
Herath and Vithanage, 2015).

• According to the type of plants used (submerged, floating, floating leaves,

emergent).
• According to the direction of wastewater flow (horizontal, vertical, mixed).

• According to hydrological conditions (subsurface, surface, so-called free wa-

ter).

The most popular constructed wetland systems are surface flow (SF) systems, hori-
zontal subsurface flow (HSF), and vertical subsurface flow (VSF) systems.

• The surface flow systems (SF) are usually shallow ponds and ditches (often
from 20 to 40 cm) with water macrophytes. These systems are characterized by
low investment expenditures and uncomplicated use. However, they require a
large surface (up to 20 m2/PE). The problems occur with reduced performance
in the period other than growing season and releasing an unpleasant smell
and freezing.
• Horizontal subsurface flow (HSF) systems are cells filled with media (from 30
to 60 cm deep) in which aquatic vegetation is planted. This kind of wetland
is saturated and the water column is not exposed to the atmosphere, usually
remaining about 5–10 cm under the surface of the bed and therefore avoiding
fouling odors and the proliferation of vectors. In HSF systems, the contami-
nants contained in sewage sludge are removed mainly during the anaerobic
processes. The HSF systems require smaller surface (up to 5 m2/PE) and are
characterized by high resistance to freezing.
• Vertical subsurface flow systems (VSF), The subsurface VSF systems are cells
filled with coarse sand or fine gravel, usually from 60 to 100 cm deep, and
planted with aquatic vegetation. Due to the convenient conditions, quick and
efficient removal of organic contaminants (nitrification capabilities) can be
observed. Compared to other types of CW, they require the least surface, with
2–3 m2/PE. (De la Verga et al., 2017; Zhang, 2012; Vymazal, 2010; Ramachan-
dra et al., 2017).

The benefits of hydrophyte treatment plants include:

• Easy operation.

• Resistance to uneven flow of wastewater.

• Lower costs compared to conventional systems.

• Easy matching of the facilities with the present landscape.

• The lack of production of secondary wastewater treatment.

• Simultaneous removal of organic compounds, phosphorus, nitrogen, and

heavy metals.

The main drawbacks are:

• Demand for large surface area.

• Difficulties connected with the adaptation of plants in mineral soil and

the related long period that allows for a full development of the rhizosphere
(Sadecka, 2005; Davis, 1995). Hydrobiological plants develop in wetland, which
are oxygen-deficient. The very good adaptation of a substantial part of macro-
phytes to these conditions is due to the spongy tissue termed aerenchyma.
Aerenchyma is characterized by large air channels that represent containers
for air necessary for the breathing process. They are present in the entire
plant, thus facilitating oxygen transport from overground parts to underwater
organs. This helps supply this life-giving element to the entire plant, which
can grow in such unfavorable settings (Koutika and Rainey, 2015; Vymazal and
Kröpfelová, 2008; Wetzel, 2001)

The costs of treatment of this type of vegetation represent a particularly serious chal-
lenge to small rural communities. Macrophytes are mostly annual aquatic vascular
plants. Their life cycle ends in late autumn and their harvest should be planned for
this season of the year. At the moment of becoming the waste, it also becomes a
challenge for the managers of wastewater treatment plants. Among the methods
of their disposal is incineration (e.g., Salix viminalis) or use for the production of
enzymes, polymers, organic acids, fuel, and composting or vermicomposting (Fig.
5).
Fig. 5. Ways to dispose of plants from constructed wetlands (Sindu et al., 2017).

The characterization of the macrophytes used in CW presented in the Table 5

illustrates their potential as biomass, which can be successfully used in organic re-
cycling. Wetzel (2001) gives the following values of ash (as the dry mass percentage):
emergent species 12% (5%–25%), floating-leaved 16% (10%–25%), submerged
21% (9%–25%), average for all species 18%.

Table 5. Percentage of total biomass found in underground tissues of mature aquatic

macrophytes (Vymazal and Kröpfelová, 2008; Wetzel, 2001)

Type Species
% of total biomass (< 10)
Submerged Ceratophyllum demersum (Coontail)Elodea
canadensis (Common waterweed)
Emergent Cyperus fuscus (Browb cyperius)

% of total biomass (10–20)

Submerged Myriophyllum spicatum (Eurasian watermil-
foil)Potamogeton pectinatus (Sago pondweed)

Emergent Zizania aquantica (Annual wildrice)

% of total biomass (> 20)

Submerged Potamogeton perfoliatus (Read-head
grass)—31%–51%Vallisneria americana (Wild
celery)—48%Isoetes lacustris (Quill-
wort)—20%–52%
Floating Eichhornia crassipes (Water hy-
acinth)—10%–56%
Floating-leaved Nuphar spp. (Yellow water lily)—46%–80%-
Nymphaea spp. (Water lily)—48%–80%
Emergent Acorus calamus (Sweet flag)—49%–66-
%Alisma plantago-aquatica (Water plan-
tain)—40%Carex lasiocarpa (Hairy fruit-
ed sedge)—50%–78%Cyperus popy-
rus (Papyrus)—31%Eleocharis rostellata
(Small-beaked spikerush)—47%Equisetum f-
luviatile (Water horsetail)—40%–83%Typha an-
gustifolia (Broadleaf cattail)—32%–67%Typha
latifolia (Broadleaf cattail)—29%–82%

> Read full chapter

Measurement of Water Quality

J. Jeffrey Peirce, ... P. Aarne Vesilind, in Environmental Pollution and Control (Fourth
Edition), 1998

SOLIDS
Wastewater treatment is complicated by the dissolved and suspended inorganic
material the wastewater contains. In discussion of water treatment, both dissolved
and suspended materials are called solids. The separation of these solids from the
water is one of the primary objectives of treatment.

Strictly speaking, in wastewater anything other than water is classified as solid. The
usual definition of solids, however, is the residue after evaporation at 103°C (slightly
higher than the boiling point of water). The solids thus measured are known as total
solids. Total solids may be divided into two fractions: the total dissolved solids (TDS)
and the total suspended solids (TSS). The difference is illustrated in the following
example:

A teaspoonful of table salt dissolves in a glass of water, forming a water-clear

solution. However, the salt remains behind if the water evaporates. Sand, however,
does not dissolve and remains as sand grains in the water and forms a turbid
mixture. The sand also remains behind if the water evaporates. The salt is an example
of a dissolved solid, whereas the sand is a suspended solid.

Suspended solids are separated from dissolved solids by filtering the water through
a filter paper as seen in Figure 4-6. The suspended material is retained on the filter
paper, while the dissolved fraction passes through. If the initial dry weight of the
filter paper is known, the subtraction of this from the total weight of the filter and
the dried solids caught in the filter paper yields the weight of suspended solids,
expressed in milligrams per liter.

FIGURE 4-6. Elements of a filter photometer

Solids may be classified in another way: those that are volatilized at a high tem-
perature and those that are not. The former are known as volatile solids, the latter
as fixed solids. Volatile solids are usually organic compounds. Obviously, at 600°C,
the temperature at which the combustion takes place, some of the inorganics are
decomposed and volatilized, but this is not considered a serious drawback. The
relationship between total solids and total volatile solids is illustrated by Example
4.2.

Example 4.2
Given the following data:

• Weight of a dish = 48.6212 g.

• 100 mL of sample is placed in a dish and evaporated. Weight of the dish and
dry solids = 48.6432 g.
• The dish is then placed in a 600°C furnace, then cooled. Weight = 48.6300 g.

Find the total, fixed, and volatile solids.

(4.16b)

(4.16c)

(4.16d)

Measurement of the volatile fraction of suspended material, the volatile suspended

solids, is made by burning the suspended solids and weighing them again. The loss
in weight is interpreted as the volatile suspended solids.

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