Environmental Microbiology Lab (Ese 2104)

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JATIYA KABI KAZI NAZRUL ISLAM UNIVERSITY
TRISHAL, MYMENSINGH
Assignment On: Biological Treatments of Water
Course Name: Environmental Microbiology-Lab
Course Code: ESE-2104
SUBMITTED TO
Rtn.Md.Nakibul Hasan Khan
Assistant Professor
Department of Environmental Science & Engineering
Jatiya Kabi kazi Nazrul Islam University
SUBMITTED BY
Name Roll
Mimtaz Afsana Mim 20103427
Mozakkir Azad 20103429
Md Khairul Haque 20103430
2nd
Year,1st
Semester, Session:2019-20
Department of Environmental Science & Engineering
Jatiya Kabi Kazi Nazrul Islam University
Date of Submission: 22/12/2022

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Content
SL No Topic Name Page No
1. Abstract 02
2. Introduction 02
3. Water Treatment 3
4. Method of Biological Water Treatment 4-6
5. Phytoremediation Method 7
6. Importance of Wastewater Treatment 8
7. Conclusion 9
8. Keywords 9
9. References 10
Figure List
SL No Name of Figure Page No
1. Schematic Diagram view of a water treatment process 3
2. Aerobic Treatment Principle 5
3. Anaerobic Treatment Principle 7

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Abstract: Biological treatment systems in which mixed populations of micro-organisms are
used to break down organic material. A general account of pollution and pollution control is
first presented, and specific attention is given to the need for waste-water treatment,
alternatives to on-site waste treatment, the causes of pollution, the evaluation of oxygen
demand, and the measurement of dissolved oxygen. A chapter is devoted to oxygen demand,
this being the key to aerobic biological purification processes. The activated sludge process is
described in outline, after which several models are presented, each representing a different
aspect of the process. Two advanced activated sludge processes (advances involve an
increase in oxygen partial pressure in the gas phase) are described; this is followed by an
outline account of biological-film systems, which basically aim to bring wastewater into
contact with mixed microbial populations present in a slime film attached to a solid support
medium. Nitrogen and phosphorus pollution in effluent and processes for its removal are
considered. Finally, problems of sludge treatment and disposal, and anaerobic sludge
treatment processes are discussed.
Introduction:
Biological treatment is an important and integral part of any wastewater treatment plant that
treats wastewater from either municipality or industry having soluble organic impurities or a
mix of the two types of wastewater sources. The obvious economic advantage, both in terms
of capital investment and operating costs, of biological treatment over other treatment
processes like chemical oxidation; thermal oxidation etc. has cemented its place in any
integrated wastewater treatment plant. Biological treatment using aerobic activated sludge
process has been in practice for well over a century. Increasing pressure to meet more
stringent discharge standards or not being allowed to discharge treated effluent has led to
implementation of a variety of advanced biological treatment processes in recent years. The
title of this article being very general, it is not possible by any means to cover all the

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biological treatment processes. It is recommended that interested readers, for deeper reading
and understanding, refer to well-known reference books e.g.
Water Treatment
Water treatment is any process that improves the quality of water to make it appropriate for a
specific end-use. The end use may be drinking, industrial water supply, irrigation, river flow
maintenance, water recreation or many other uses, including being safely returned to the
environment.
Figure 1:Schematic Diagram view of a water treatment process

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Method of Biological Water Treatment
Aerobic & Anaerobic
Before we go into the discussions of various aerobic biological treatment processes, it is
important to briefly discuss the terms aerobic and anaerobic. Aerobic, as the title suggests,
means in the presence of air (oxygen); while anaerobic means in the absence of air (oxygen).
These two terms are directly related to the type of bacteria or microorganisms that are
involved in the degradation of organic impurities in each wastewater and the operating
conditions of the bioreactor. Therefore, aerobic treatment processes take place in the presence
of air and utilize those microorganisms (also called aerobes), which use molecular/free
oxygen to assimilate organic impurities i.e., convert them into carbon dioxide, water and
biomass. The anaerobic treatment processes, on other hand take place in the absence of air
(and thus molecular/free oxygen) by those microorganisms (also called anaerobes) which do
not require
air (molecular/free oxygen) to assimilate organic impurities. The pictures in Fig. 1 and 2
depict simplified principles of the two processes. Table I summarizes the major differences in
these two types of processes. From the summary in Table 1, it can be concluded. hat it is not
anaerobic or aerobic treatment, but a combination of the two types of the technologies that
give an optimum configuration for those wastewater treatment applications where the organic
impurities are at a relatively higher concentration.
Aerobic Biological Treatment Technologies
There are multitudes of aerobic biological treatment processes and technologies in literature
and practice; however, for the purpose of this article, following four biological treatment
technologies are described. After description of each process and corresponding
advantages/highlights, a qualitative comparison of these technologies is tabulated. This
comparison is based on an actual wastewater treatment application for a refinery project,
where the treatment requirement was meant for discharge of treated effluent to the sea.

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A. Conventional Activated Sludge Process (ASP) System:
Figure 2: Aerobic treatment principle
This is the most common and oldest biotreatment process used to treat municipal and
industrial wastewater. Typically, wastewater after primary treatment i.e., suspended
impurities removal is treated in an activated sludge process based biological treatment system
comprising aeration tank followed by secondary clarifier. The aeration tank is a completely
mixed or a plug flow (in some cases) bioreactor where specific concentration of biomass
(measured as mixed liquor suspended solids (MLSS) or mixed liquor volatile suspended
solids (MLVSS)) is maintained along with sufficient dissolved oxygen (DO) concentration
(typically 2 mg/l) to effect biodegradation of soluble organic impurities measured as
biochemical oxygen demand (BOD5) or chemical oxygen demand (COD).
The aeration tank is provided with fine bubble diffused
aeration pipework at the bottom to transfer required oxygen to the biomass and ensure
completely mixed reactor. Roots type air blower is used to supply air to the diffuser
pipework.
In several older installations, mechanical surface aerators have been used to meet the aeration
requirement. The aerated mixed liquor from the aeration tank overflows by gravity to the

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secondary clarifier unit to separate out the biomass and allow clarified, treated water to the
downstream filtration system for finer removal of suspended solids. The separated biomass is
returned to the aeration tank by means of return activated sludge (RAS) pump. Excess
biomass (produced during the biodegradation process) is wasted to the sludge handling and
dewatering facility.
B. Cyclic Activated Sludge System (CASSTM):
Cyclic Activated Sludge System (CASSTM) as the name suggests is one of the most popular
sequencing batch reactors (SBR) processes employed to treat municipal wastewater and
wastewater from a variety of industries including refineries and petrochemical plants.
Aquatec has an agreement with AECOM (erstwhile Earth Tech), UK, the licensor of this
technology to supply CASS™ technology in India on exclusive basis to both municipal and
industrial markets. This technology offers several operational and performance advantages
over the conventional activated sludge process. The CASS™ SBR process performs all the
functions of a conventional activated sludge plant (biological removal of pollutants,
solids/liquid separation and treated effluent removal) by using a single variable volume basin
in an alternating mode of operation, thereby dispensing with the need for final clarifiers and
high return activated sludge pumping capacity.

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Figure 3: Anaerobic treatment principle
Phytoremediation method
This is another biological method for wastewater treatment. The combination of two Latin
words―plant and remedy―gave rise to the term phytoremediation. The plant, plant origin
microbes, or associated microbiota are used to take up the contamination from soil or water.
The remediation is achieved either by retaining, elimination, or degradation in a natural way
as it happens in an ecosystem. Phytoremediation is a cheaper, eco-friendly, and feasibly
sustainable method for removal of dye pollutants. Moreover, the process requires little
nutrient cost and has aesthetic demand. However, the phytoremediation method is also not a
limitations-free method. The major disadvantage of the phytoremediation procedure is the
sluggish rate of ecological cleanup process, which may even last for more than a decade.
There may also be a substantial decrease in phytoremediation, generally during winter (plant
growth retards or hinders) and/or may be damage of vegetation because of weather, plant
diseases, or pests. Few reports regarding decolorization of pollutant in wastewater by
phytoremediation have been briefly illustrated in this section. Researchers exploited the
phytoremediation prospective of Petunia grandiflora Juss., for remediation of dye mixture
present in wastewater. Individual effects of three plant species, Sorghum vulgare, Phaseolus
mungo, and Brassica juncea, have been considered for decolorization efficacy of textile
runoffs, which showed color removal up to 79%, 53%, and 57%, respectively.

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Importantance of wastewater treatment
Wastewater treatment is crucial to protect our environment and the health of both humans and
animals. When wastewater is not treated properly, it can pollute our water sources, damage
natural habitats, and cause serious illnesses. Effectively, wastewater treatment plants do as
describe; they treat the water that goes down our drains before discharging it back into the
environment. Regardless of the efforts that are being made to install these plants worldwide,
more is required. Water is one of our most important resources and it’s being squandered.
There are multiple ways to treat wastewater, and the better the process, the higher the
percentage that can be reused before it gets dumped into the ocean.
The public has begun to stand up to oil companies about fracking and wastewater and the
rules are slowly changing, especially in terms of transparency and its effects on the
environment. It’s a good thing that the industry is under scrutiny as the more transparency
that’s required by law, the better. We need to raise the levels of expectation for oil
companies, mines, and other large-scale industries as they’ve been unregulated and sold to
the highest bidder for too long.

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CONCLUSION
Biological treatment processes have a proven track record of dealing adequately with various
kinds of wastes generated by human activities. They mimic natural processes occurring in
streams and rivers. Waste treatment processes are increasingly engineered in such a way that
they per-form this task efficiently with a minimal input of energy. Traditionally, treatment
has relied on technological ap-proaches designed to mimic aerobic processes occurring in the
water column of streams and rivers. To become truly sustainable, however, we must move
away from energy-consuming aerobic processes and switch to an-aerobic treatment
processes, again mimicking natural pro-cesses, but now those occurring in the anaerobic
sediments of the streams and rivers. For example, there is a new focus in the water industry
to integrate these two processes into systems where the waste is initially di-gested in an
anaerobic step followed by an aerobic pol-ishing step. Only by integrating these two
processes, and variants thereof such as partial nitrification and Anammox wastewater
treatment, will waste treatment become truly energy efficient and sustainable. Finally, it
should be noted that anaerobic digestion to methane is not the only sustain-able option. Great
strides are now being made in microbial fuel cell technology within waste treatment with
chemi-cal energy from wastes being captured as electricity.
Keywords:
Wastewater Treatment, Biological treatment, Aerobic, Aenorobic, Phytoremediation, Cyclic
Activated Sludge System, Conventional Activated Sludge Process (ASP) System, Aerobic
Biological Treatment Technologies.

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REFERENCES
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2.Tchobanoglous, G.; Burton, F.L.; Stensel, H.D.; Metcalf and Eddy, Inc. Fundamentals
of biological treatment. In Wastewater Engineering: Treatment, Disposal, Reuse, 6th Ed.;
McGraw-Hill: New York, 2003.
3.Lettinga, G. Anaerobic digestion and wastewater treatment systems. Antonie van
Leeuwenhoek 1995, 67, 3–28
4.Lettinga, G. Sustainable integrated biological wastewater treatment. Water Sci. Technol.
1996, 33, 85–98.
5.Jewell, W.J. Resource-recovery wastewater treatments with biological systems.
Proceedings of the Workshop on Sus-tainable Municipal Wastewater Treatment Systems,
ETC-WASTE, Leusden, the Netherlands, 1996; 67–101.
6.Qasim, S.R. Wastewater Treatment Plants: Planning, De-sign and Operation; Holt,
Rinehart and Winston: New York, 1985.
7.WPCF, Natural Systems for Wastewater Treatment. Manual for Practice, prepared by Task
Force on Natural System