UNIVERSITI TEKNOLOGI MARA

FACULTY OF APPLIED SCIENCES

MIC 548 INDUSTRIAL APPLICATIONS OF

MICROORGANISMS

MINI REVIEW: WASTEWATER TREATMENT BY

MICROORGANISM

LECTURER: DR. MUHAMMAD NAZIZ BIN SAAT

NO NAME STUDENT ID

1 ALISSA REENDA ANAK JAMPANG 2021110289

2 NURUL ALIYAH BINTI ZAINUDDIN 2021114819

3 ALIESHA AISAR BINTI SHAH FINAL 2021125933

4 NURIN MUNIRAH BINTI MOHAMMAD ALLAWI 2021101457

5 NUR ZULAIKA BINTI ZULKEFLI 2021120233

SUBMITTED ON: 3𝑟𝑑 JULY 2022

Introduction to wastewater treatment management

The purpose of wastewater treatment is to protect the environment from:

● High amount of suspended solids

● High loads of organic matter and consequent low oxygen levels

● High amount of nutrients (N and P) causing eutrophication

● Substantial loads of hazardous non-biodegradable compounds

● Serious contamination with pathogenic microorganisms

Thus, in treating the wastewater it helps create a healthy aquatic environment and improves

public health by preventing transmissions of water-borne diseases. It also allows humankinds to

utilize water resources for different purposes, such as water supply, recreation, fishing,

navigation, irrigation, and etc.

The microbial sp. involved

Microbes cause various diseases in animals and plants, but these tiny creatures are far more

important to us in a variety of ways. One important application is in sewage treatment

plants.Untreated wastewater can be harmful to the environment. This is because human and

animal waste is a source of several types of waterborne diseases and bacterial contamination.

Various microorganisms are used in sewage treatment plants, but these three types of bacteria

play an important role in keeping sewage clean. Each of these contributes to the treatment

process in a unique way, ensuring minimal environmental impact. Microbes found in wastewater

treatment plants include:

Bacteria:

Small prokaryotic organisms with no cell nucleus or organelles, form the "backbone" of the

wastewater treatment plant because they are the most common organisms and do the majority of

the work in converting pollutants into non-hazardous forms. System temperature, pH, inlet

chemical makeup, dissolved oxygen, and other environmental factors influence the species.

Typically, wastewater bacteria are classified according to their ability to grow at different

temperatures: psychrophiles, mesophiles, and thermophiles. As well as their ability to use

oxygen or another electron acceptor for cellular respiration: aerobic, facultative anaerobic, and

obligate anaerobe.

Fungi:

Fungi, a more complex organism than bacteria, can be unicellular, like yeasts, or multicellular,

with hyphae. Fungi concentrations are typically higher in waste treatment under low pH

conditions (pH 5.0). Other factors that can benefit fungi include complex organics such as lignin

and other complex biopolymers, as well as low concentrations of macronutrients such as nitrogen

and phosphorus. Fungi are typically found in much lower concentrations in wastewater than

bacteria.

Archaea:

Archaea microbes have distinct cell membranes and chemistry and can be found in a variety of

environments including ocean thermal vents, hot springs, anaerobic digesters, ruminant digestive

systems, and others. Archaea are frequently found in methane-producing microbes in anaerobic

digesters during waste treatment. Methane is produced by these methanogens from short-chain
organic acids and H2 produced by facultative and obligate anaerobic bacteria. Methanogen

activity is critical for COD/BOD reduction in anaerobic digesters and methane gas production.

Most other archaea are found in low concentrations in wastewater treatment plants and are only

second in importance to bacteria.

Process of wastewater treatment

● Aerobic process

Aerobic treatment of wastewater is a biological process that uses oxygen to break down organic

contaminants and other pollutants like nitrogen and phosphorus. The organic stuff in the

wastewater is subsequently consumed by aerobic bacteria which convert it to carbon and

biomass, which may then be removed. There are 3 types of aerobic wastewater treatment

systems:

1. Conventional activated sludge

2. Moving bed biofilm reactor (MBBR)

3. Membrane bioreactor (MBR)

 Figure 1: Aerobic wastewater treatment process (Membrane bioreactor, MBR)

Figure 1 shows the membrane bioreactor (MBR) which involves a cutting-edge technique that

combines the activated sludge and membrane filtration processes. The process starts with

screening the sewage to remove objects such as rags, paper, plastics, and metal to prevent

damage and clogging of downstream equipment. Then, it goes into a primary sedimentation tank

which allows suspended particles to settle out of water or wastewater as it flows slowly through

the tank.

The next process is the biology tank which is the main process. This process is normally divided

into two zones, an anoxic and aerobic zone. In the aerobic zone where the air is dissolved, it is

fitted with bubbles that come from the process of air blower; leading to the aerobic zone with a

stream of air bubbles that provide the oxygen for microorganisms to survive.The solids are

stirred simultaneously to ensure that they are suspended and must settle out as secondary

clarifiers to achieve cell separation and return to the microbiological tank which normally goes to

the anoxic zone.

Basically, classical aerobic wastewater treatment has two processes, primary treatment which is

the sediment process; secondary treatment with the biological tank followed by the cell

separation stage. To achieve more quality in treatment water, a tertiary stage needs to be applied

which comprises a solid-liquid separation process followed by a disinfection process either

chlorine or UV disinfected to give the final effluent.

● Anaerobic process

Anaerobic treatment is a biological treatment process in which microbes convert the organic

matter in the absence of oxygen. The main goal of this process is to reduce the amount of sludge

that needs to be disposed of. These systems usually include a chamber in which an oxygen-free

environment is maintained. The decrease in chemical oxygen demand (COD) and biological

oxygen demand (BOD) is the final resulting effluent. There are 3 types of anaerobic wastewater

treatment systems which are anaerobic lagoons, anaerobic filter reactors, and anaerobic

sludge blanket reactors.

 Figure 2: Anaerobic lagoons

An anaerobic lagoon is a process that is placed in deep earthen basins or ponds that is used as an

anaerobic pretreatment system. The process started with raw wastewater entering near the

bottom of the pond and mixing with the active microbial mass in the sludge blanket. In some

situations, aeration is provided at the surface to control odors. The discharge port is located near

the side opposite the influent. The effluent is not suitable for discharge to receiving waters.

Anaerobic microorganisms involve two separate steps which are acid formation and methane

production. Acid formation or usually known as “acid formers” is a process of converting

complex organic compounds such as carbohydrates and proteins into simpler compounds, mainly

short-chain volatile organic acids (acetic acid, and lactic acid). In this phase, chemical oxygen

demand (COD) and biological oxygen demand (BOD) are reduced due to the short-chain fatty

acids and alcohol that can be used by many microorganisms.

The methane production phase is playing a role in converting the short-chain organic acids into

acetate, carbon dioxide, and hydrogen gas, this process is called acetogenesis where it is a

process involving acetate to produce either by the reduction of carbon dioxide or organic acids.

Besides acetogenesis, methanogenesis is the next process that converts acetate, hydrogen, and

carbon dioxide into methane gas through two major pathways.

1. Breakdown of acetic acid into methane and carbon dioxide

CH3COOH→ CH4 + CO2

2. Reduction of carbon dioxide by hydrogen to form methane

CO2 + 4H2 → CH4 +2H2O

Degradation will occur simultaneously in dynamic equilibrium if the systems work successfully.

The temperature of the system needs to be maintained within the range of 25 to 40℃. It is

because, at temperatures below 15℃, the anaerobic activity will decrease rapidly.
 Figure 3: Upflow Anaerobic Sludge Blanket (UASB) reactor

Upflow anaerobic sludge bucket is rapidly used due to its great performance compared to other

reactors (EGSB and SGBR). UASB is known as a reactor that uses a single tank process where

the wastewater will enter the reactor from the bottom and flow upward. There are

microorganisms in the sludge layer that role to degrade the organic compounds and as a result,

the methane and carbon dioxide gasses are then released. Bubbles mix rise into the sludge

without the assistance of any mechanical parts while the wall of sloped deflects the materials that

reach the top of the tank into downwards back. The effluent will extract from the above area of

the sloped wall at the top of the tank. The final effluent will go out through part at the top. Next,

the large granules of sludge that form during the process will act as filters for smaller particles as

the effluent rises through the cushion of sludge. Granule-forming organisms preferentially

accumulate as the others are washed out due to the upflow regime (Oakley, 2017).
 Figure 4: Anaerobic filter reactor

An anaerobic filter comes with a biofilm system that aims to remove non-settleable and dissolves

solids. This method comprises a watertight tank containing more than one layer of submerged

media, which provides surface area for bacteria to settle down. The wastewater enters the filter

from the bottom to the top or known as an "up-flow," where it interacts with the biomass and is

degraded anaerobically. Anaerobic filters have a few chambers and baffles in order to ensure the

upflow goes smoothly so that the settleable and dissolved solids are also treated as they are

brought into close contact with the active bacterial mass fixed on the filter material. On the

reactor wall, bacteria tend to fix themselves and anaerobically digest the dispersed organic matter

within a short retention time.

Impact of the process

● Aerobic process

The aerobic process in wastewater treatment by microorganisms can help to remove dissolved

organic matter and suspended solids from water. The aerobic process in wastewater treatment by

microorganisms involves the use of aerobic bacteria to break down organic matter in water. This

process can help to remove dissolved organic matter and suspended solids from water, making

it cleaner and safer to drink. In addition, the aerobic process can also help to reduce the levels of

harmful bacteria and viruses in water, making it safer for human consumption. This process

also can help in reducing the concentrations of ammonia and other nitrogenous compounds in

water. In the presence of oxygen, microorganisms are used in the aerobic wastewater treatment

process to break down organic materials in water. The treatment system's microbes use the

organic material as food, converting it to carbon dioxide and water in the process. Ammonia and

other nitrogenous chemical concentrations in water may be decreased using this approach. A

typical treatment method for industrial and municipal wastewater is the aerobic process. A

variety of water characteristics, including sewage, food processing effluent, and water from

agricultural operations, can be treated using this method. Aerobic treatment systems come in a

variety of forms, such as trickling filters, rotating biological contactors, and activated sludge

systems. Last but not least, aerobic processes also help to reduce the concentrations of

phosphorus in water. The aerobic process can also aid in lowering the phosphorus levels in

water. Plants require the nutrient phosphorus for growth. But an excess of phosphorus in water

can harm the ecology. By dissolving the phosphorus-containing molecules, the aerobic process

can aid in lowering the phosphorus levels in water.

 ● Anaerobic process

Process in which the bacteria breakdown the organic matter in the absence of oxygen is called as

anaerobic process. The organic matter may contain wastewater biosolids, animal manure and

others. Anaerobic bacteria is used in the wastewater treatment process because, to reduce the

volume of the sludge, it produces methane gas from it. Both the aerobic and anaerobic

wastewater treatment methods and processes have proved fruitful in their overall results. But the

anaerobic methods employed are more cost effective, result oriented and best suited for all types

of wastewater treatments. Anaerobic wastewater treatment is carried out by the application of

various microorganisms. The first impact of anaerobic process is it produces methane gas

during the process of wastewater treatment using anaerobic bacteria. The best part of the

anaerobic treatment processes is the production of methane that can be efficiently used as an

alternative source of energy. The biogas methane produced during the waste water treatment by

the anaerobic organisms such as methanogens ,easily grows in the lack of oxygen in the waste

water , this biogas can be used as fuel. Next, as compared to aerobic treatments, anaerobic

treatment processes are more efficient in terms of energy requirements and need less energy for

operation. The oxygen concentration in the biological reaction tank needs to be constantly and

properly controlled. The electricity required to supply sufficient dissolved oxygen for treating 1

kg of chemical oxygen demand (COD) is 1.1 kWh, which accounts for most of the energy

consumption in removal for wastewater treatment facilities. On the other hand, anaerobic

treatment does not require oxygen, and therefore does not require electricity for supplying

oxygen. Although both treatments use electricity for stirring and pumping operations, these

operations require very little power. Thus, anaerobic decomposition is more energy-saving and

relatively easier to control. Since, the biomass production during anaerobic processes is lower,
so less nutrients are required. In this way, expenses of nutrient supplementation, whenever and

wherever required during any stage of treatment process is less, as compared to aerobic one. The

other impact of anaerobic treatment processes are quick and respond to substrate addition more

quickly, ever after an extended off period. Examples of some anaerobic microorganisms that are

used in wastewater treatment include bacteria, fungi and algae can more efficiently be used to

carry out anaerobic treatment processes. Chlorella sp, a unicellular green algae species, is used

for treatment of sewage water. Scenedesmus sp is one more species of algae employed to carry

out the same processes. This whole process of wastewater treatment is carried out in order to

produce an effluent that will in no way affect any component of the surrounding environment.

The general process of treatment is completed in several stages, like, primary, secondary and

tertiary treatment stages. The role of anaerobic treatment starts generally at the tertiary stage,

when the wastewater after going through primary and secondary stages is shifted to sludge

treatment compartments that use microorganisms for anaerobic degradation.

Suggestion and Improvement

There are some ways to improve the wastewater treatment such as activated sludge, biofilm

method,biological contact oxidation method and immobilized microbiological method. All of

these methods are useful for dealing with the treatment of wastewater.

The newly proposed microbial niche nexus aims to effectively remove both known and unknown

pollutants by tuning microbial niches to accommodate various microbial communities. Apart

from infrastructure construction, microbial niche nexus could be used to overcome developing

difficulties. Furthermore, the establishment of characterization systems can be applied to the

treatment of biological wastewater such as the co-enrichment of r/K-strategists and the formation

of microenvironments with substrate gradients. Finally, components of microbial enrichment,

microbial function and metabolism identification, system design and operation control, also the

new technology development and application represents future development and outlook.

Activated sludge:

The most popular technique for using water to treat water pollution currently is activated sludge

method. This method refers to the employment of activated sludge in wastewater coagulation,

adsorption, oxidation, breakdown, and precipitation roles in wastewater management procedures

to remove organic contaminants. The term “activated sludge” describes a mixture of bacteria,

micro-animal-based-microorganisms, colloidal and suspended substances, and other substances

that put together to create a solid that is highly effective at adsorbing and decomposing organic

matter and settling flocculent particles. A complex microbial community is made up by a wide

range of microorganisms that may survive the activated sludge. Along with yeast, filamentous
fungi, cell algae, rotifer nematodes, and other microorganisms, both bacteria (mostly aerobic

heterotrophic bacteria) and protozoa make up the majority of microbes.

Source: Institute of Hydrobiology

The microbial effects of activated sludge can improve the role of water quality through the

secretion of certain protozoa, in the settlement process to encourage the flocculation of free

bacteria, and increase the settlement efficiency of bacteria and removal rate. Protozoan predator

bacteria increases the ability of bacteria to better absorb soluble organic materials. Both protozoa

and bacteria together commonly feed on pathogenic microorganisms.

Next, the role of activated sludge in the system is characterized by large flocculation, good

sedimentation, microscopic observations of the organism’s presence such as insects,

Streptococcus, all types of sucking insects, rotifers, eczema, oligosaccharides and other fixed

species or creeping species.

When the activated sludge degrades, the flocculation is tiny, and organisms such as the genus

Bombyxmori, and Trichomonas swims quickly. When the activated sludge is substantially

degraded, there is a bug region of death or nearly no sign of life, sludge settles and the ability to

treat water declines. Rose wood, tube leaf insects, and other slow moving or creeping critters are

examples of emerging organisms during the transition of activated sludge from degradation to

return to normal. The key agent responsible for the sludge’s expansion is when the activated

sludge itself expands. The activated sludge is cotton-like, the particles carefully separated, and

the color is somewhat shallow as the filamentous bacteria multiply (Dong et al., 2017).

Biofilm method:

Biofilm is composed of microorganisms bound on solid supports via electrostatic contacts,

covalent bonds, and hydrophobic interactions to form a multi-layered structure. Fimbriae, cilia,

cell wall components, and extracellular polymeric substances (EPS) all aid in colonization. The

thickness of biofilm is determined by the depth to which both substrate and oxygen can penetrate

while mass transport in biofilm is primarily due to diffusion (Wu & Yin, 2020).
 Source: SpringerLink

The biofilm method is applied by placing a membrane-like biomect community on the surface of

an inert material in order to treat the wastewater. The biofilm serves the same purpose as

activated sludge in the activated sludge process and it has a comparable microbial composition.

The primary concept of wastewater treatment is based on the adsorption of organic materials in

wastewater and oxidative breakdown, which is linked to the surface of biofilm carrier surface. A

biological filter, biological turntable, tower biofilter, and other biofilm technologies are used to

interface the medium and water in diverse methods. The treatment concept is essentially the

same, relying on the surface of solid medium born to purify organic particles, thus referred to as

biological filtration. Substance transferred in the process for example:

Oxygen in the air → Wastewater → Biofilm

and waste produced by this method is less than the excessive sludge produced in the activated

sludge method.
Biofilm is made up of highly dense aerobic, anaerobic, and facultative bacteria, fungi, protozoa,

and algae along with other ecosystem components, adhered to a solid substrate called a filter or

carrier. Outside the gas layer, good gas layer, attached to the water layer, and flowing water layer

are the examples of biofilm that can be found in a filter. The concept of biofilm method, the

biofilm is first adsorbed by waterborne organic matter, next it is degraded by the aerobic gas of

the aerobic layer, and finally into the anaerobic layer for anaerobic breakdown. The goal for

wastewater treatment is accomplished by flushing the aged biofilm using a flowing water layer in

order to allow new biofilm development.

Biofilm method according to the media and water contact with different ways, a biological filter,

biological turntable, tower biofilter and so on. Its treatment principle is basically the same,

relying on the surface of the solid medium born to the purification of organic matter, therefore,

also known as biological filtration. Substance transfer in the process: Oxygen in the air →

Wastewater → Biofilm, this method produces less products than the excess sludge produced by

the activated sludge process (Dong et al., 2017).

Next, heavy compounds like oils and solids are not accepted by the biological treatment system

because they interfere with the treatment process. These compounds should be separated from

the waste before they go into the systems. Additionally, toxic and biological-resistant materials

must be handled carefully and may need to be treated in advance before being incorporated into

the biological wastewater system.

Biological contact oxidation method:

Biological contact oxidation (BCO) combines a biological filter with the conventional activated

sludge process. This process is frequently used to treat organic wastewater because it is tolerant

to high ammonia nitrogen and severe impact loading. The biological contact oxidation method is

from the biofilm method for treating wastewater. The biological contact oxidation tank filled

with a specific amount of filler, the use of habitat attached to the filler on the biofilm and fully

supplied oxygen, through biological oxidation role, the organic matter in the wastewater

oxidation decomposition, is used to achieve the purpose of purification (Dong et al., 2017).

Under anoxic and aerobic conditions, BCO process has been used for treatment of domestic

sewage, and industrial wastewater (Zhang et al., 2016).

There are two methods to improve the treatment effect of a biological contact oxidation reactor:

● By improving the gas or water ratio

● The biofilm biomass needs to be increased.

but the biofilm thickness will increase, and the transport efficiency of the reduced oxygen.

However, the aeration level will certainly grow, and energy consumption will rise as a result

(Jiang, S.Q et al.,2016).

Example diagram of BOC device

Source : Atlantis press

Immobilized microbiological method:

An immobilized microorganism is one that is stopped from moving independently of its

neighbors to all areas of the aqueous phase of the system by either natural or artificial means.

Immobilized microbial technology is a cutting-edge method of biological engineering that uses

physical or chemical ways to contain or locate free microorganisms in a particular area while

keeping their natural catalytic activity and allowing for repeated and continuous use (Dong et al.,

2017). The bioreactor's microbe concentration can be increased by using this technology for

sewage treatment. It offers the benefits of a high activity and stable seed culture of bacteria, an

easily controlled response, and the removal of organic materials and chemicals that are difficult

to decompose (Zhang, X. et al.,2016) . Adsorption, covalent bonding, cross-linking of the

microorganism, encapsulation in a polymer-gel, entrapment in a matrix, and other techniques can

be used to artificially immobilize the microorganism on the carriers.

One of the simplest immobilization techniques is the adsorption of microbes onto the carriers,

which relies on a physical connection between the bacterium and the carrier surface. This is a

reversible process that could result in the removal of adsorbed bacteria while the procedure is

being performed. One of the most popular techniques for immobilizing microorganisms involves

the covalent attachment of reactive groups, such as -NH2 or -COOH groups, to the surface of

biological cells, such as proteins. The microorganism's stability will rise dramatically following

coupling immobilization, but its bioactivity will go off quickly during the recovery period. The

cross-linking technique, which uses multifunctional chemicals including glutaraldehyde, bis

diazo benzidine, and hexamethylene diisocyanate, was frequently employed to attach the

bio-macromolecular components to one another using covalent bonds. Although the

aforementioned technique is fairly straightforward, it can be challenging to execute correctly.

The bacteria were enclosed in a polymer-gel using the encapsulation process.

The immobilized microbial technique is distinguished from other environmental treatment

technologies by the following features: the high concentration and activity of microorganisms in

the reactor can be maintained through microbial immobilization, which can increase the

processing load and remove contaminants more effectively. Immobilized microorganism

technology helps to lessen the load of eventual sludge disposal by reducing sludge

production.The particle state, which is beneficial to the separation of the sludge process, creates

microbial immobilization. It will contain some industrial wastewater that can be effectively

treated by microbial immobilization.

Type of treatment Advantages Disadvantages

● High BOD and SS removal rate: ● Poor ability to adjust

up to 90% -95% (Suitable for to changes in water

demanding high water quality quality.

Activated sludge and stable wastewater) ● High infrastructure

costs.

● Produces huge

amounts of excess

sludge.

● Good stability, good ability to ● Poor operational

adjust to changes in water flexibility

quality. (Complicated

● No sludge expansion (Easy to man-made control)

Biofilm operate and manage) ● Low BOD removal

● Biofilm rich in biological rate: approximately

(biological population distributed 80% (Poor treatment

specifically) efficiency)

● More capacity and less residual ● Small carrier surface

sludge (Existence of high area and equipment

nutritional levels of volume load.

microorganisms) ● Low space efficiency.

● Natural ventilation oxygen

 ● Higher energy consumption ● Requires management and

Biological contact than biofilm that can increase maintenance of the

oxidation artificial aeration. microorganisms

● High concentration of ● The process is slow

microorganisms. (problems with kinetics)

Physical adsorption Physical adsorption

● Cheap ● Possible loss of

● High catalytic activity biomolecules

● Weak bonds might cause

desorption of biocatalyst

Immobilized
Cross linking Cross linking
microbial technology
● Can prevent leakage ● Diffusion limitations

● Higher stability ● Loss of enzyme activity

Covalent binding Covalent binding

● High heat stability ● Less effective

● Strong binding ● Support materials are not

renewable
Conclusion

Biological methods in wastewater treatment have several significant benefits compared to

conventional physical and chemical methods. Microorganisms are the best solutions to deal with

wastewater because they are small, diverse, metabolically efficient, easily versatile, adaptive, and

almost capable of using all natural substances in nature (Dong et al., 2017). Me(O)NPs, which

are emerging pollutants, are becoming more abundant in wastewater due to the growing use of

metal and metal oxide nanoparticles in consumer items.According to study, Me(O)NPs are

effectively removed at high rates by activated sludge thanks to the production of aggregates

during adsorption. Recent research suggests that nutrient removal processes like nitrification are

likely to be inhibited. Biofilm systems have received much less research, but they have the

ability to withstand Me(O)NP inhibition and remove materials by potential sorption retention.

The presence of organics, surface functionalization, and aggregation are just a few of the

elements that influence how bacteria and Me(O)NP interact. Since neither activated sludge nor

biofilm systems can completely remove Me(O)NPs at the levels currently predicted, various

biological communities in streams receiving wastewater effluents may be exposed to Me(O)NPs

for an extended period of time (Walden & Zhang, 2016).

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