Biological Waste water Treatment Fundamentals and Recent developmentin Nutrient Removal.pdf

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Biological Wastewater Treatment: Fundamentals and Recent development in
Nutrient Removal
Presentation · February 2024
DOI: 10.13140/RG.2.2.21857.07529
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Prem Baboo
The Institution of Engineers (India)
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Biological Wastewater Treatment: Fundamentals and
Recent development in Nutrient Removal
By
Prem Baboo
Fellow of Institution of Engineers(India)
Former DGM (Production & Process) Dangote Fertilizers Ltd. Nigeria
&
Former Sr. Manager (Prod) National Fertilizers Ltd., India
Introduction
A type of treatment that uses substances made
from living organisms to treat waste and waste
water. These substances may occur naturally in
the body or may be made in the laboratory.
Biological treatment is the sustainable
treatment of waste. Biological treatment is an
attractive and useful technology that results in
the complete conversion of organic compounds
into less harmful end products such as CO2 and
H2O. It is considered low-cost and
environmentally friendly compared to physical
or chemical methods for removing
contaminants without any harmful chemicals.
The biological waste management technologies
include composting, incineration, landfill,
anaerobic digestion, and bioconversion to
produce biofuels, i.e., bioethanol, biodiesel,
biogas, methane production etc.
Keywords –Bacteria, pollution, anaerobic,
Environment, Biological.
National fertilizers limited, Viajipur (India) has
developed and commercialized a unique and
efficient process for control of pollution in the
urea plant discharge from the fertilizers plant.
The process known as Bio hydrolyser process.
Urea is waste product generated in urea plant.
Some bacteria (like Hafnia Alvie 1426), which
splits the urea molecule into carbon dioxide and
ammonia. It is the 1st of its kind installed in the
country and is very simple. The mixed cutler of
urea hydrolyser micro-organism HAFNIA
ALVIE1426 BACTERIA has been developed
in laboratory under established parameters
maintained in liquid medium. The bio culture is
highly resistant even to as high concentration of
urea as 20000 ppm present in effluent. It can be
hydrolysed 99% urea in to Nitrogen in 4 to 5
hours, as shown in the figure No. In Fertilizers
Industries urea waste is treated with bio
hydrolyser.
NH2CONH2 + Bacteria Hafnia Alvie 1426
+H2O = CO2+2NH3
The urea waste from Line-I & line-II plant is
collected in concrete Buffer tank; the system
comprises three concrete tank in series having
weir for increasing residence e time. The
ammonia is removed in air stripping tower and
bottom waste sent to urea hydrolyser through
buffer tank. The waste feed in Bio hydrolyser
subjected to 5-6 hrs. Residence time. The
treated waste goes to cleaned pond B, if
ammonia content is more than recycle to
stripper, this is gravity flow.
Urea effluent from urea plant Line-I & II (200-
900ppm) urea. Name of Bacteria-“HAFNIA
ALVIE 1426” Residence time-5-6 hrs.PH range
6.5 to 9.5 Temperature range-10-500
C The urea
waste from line-I & line-II plant is collected in
concrete Buffer tank; the system comprises
three concrete tank in series having weir for
increasing residence time. The ammonia is
removed in air stripping tower and bottom
waste sent to urea hydrolyser through buffer
tank. The waste feed in Bio hydrolyser
subjected to 5-6 hrs. Residence time. The
treated waste goes to cleaned pond B, if
ammonia content is more than recycle to
stripper, this is gravity flow.

Fig-1
Advantages of Bio Hydrolyser
1. No chemical required for urea waste.
2. Low installation cost & No running cost.
3. Low space required compared to
conventional clarifier.
Different Bacteria for waste Treatments.
The treatment of water in ponds gram-
positive Bacillus spp. are generally more
efficient in converting organic matter back to
CO2 than are gram-negative bacteria, which
would convert a greater percentage of organic
carbon to bacterial biomass or slime. Biological
wastewater treatment is the most common
sanitation method in the world. Saprophytic
bacteria and fungi can convert organic matter
into living cell mass, carbon dioxide, water and
a range of metabolic by-products. These
saprophytic organisms may then be predated
upon by protozoa, rotifers and, in cleaner
waters, Bryozoa which consume suspended
organic particles including viruses and
pathogenic bacteria. Clarity of the water may
begin to improve as the protozoa are
subsequently consumed by rotifers and
cladocera. Purifying bacteria, protozoa, and
rotifers must either be mixed throughout the
water or have the water circulated past them to
be effective. Sewage treatment plants mix these
organisms as activated sludge or circulate water
past organisms living on trickling filters or
rotating biological contactors. This technology
uses different types of bacteria and other
microorganisms for the treatment and
purification of polluted water. Bacillus sp.,
Aeromonas sp., and Pseudomonas sp. are the
dominant bacterial species to involve in the
denitrification processes. Another has also
confirmed that Pseudomonas sp. is the
predominant heterotrophic bacteria involved in
denitrification during activated
sludge treatment. All of these factors create
quantitative changes between autotrophic and
heterotrophic bacteria. In municipal wastewater
treatment plants, for example, gram-negative
bacteria of the proteo bacteria type are
predominant (21-65%) of which Betaproteo
bacteria is the most abundant class, largely
responsible for the elimination of organic
elements and nutrients. The other branches are
Bacteroidetes, Acidobacteria and Chloroflexi.
The most numerous types of bacteria are
Tetrasphaera, Trichococcus, Candidatus
Microthrix, Rhodoferax, Rhodobacter,
Hyphomicrobium.

In old urea process through crystallization
the crystallizer waste through vapour
directly condensed in cooling water
resulting there is loss of energy and
pollution problem. The crystallizer vapour
can be condensed in indirectly and
generated waste can be treated in
distillation tower and urea hydrolyser. As
per attached diagram. Rapid
industrialization is going all over the world,
especially in the developing countries.
Because, the major source of country’s
income will come through the industries.
The increasing in the number of the
industries, pollute the environment by
releasing the toxic gases and toxic waste
into the air and water thus contributing the
air and water pollution respectively. As a
result, the air and water quality of the
surrounding villages will be put in danger.
So, periodic survey has to be done by the
industry/government/state or central
pollution control boards, in order to
investigate the concentration of various air
and water pollutants in the industry
surrounding villages. Recovery of Waste
Water - Around 450-480 Kg of liquid
effluents (water) is generated for metric ton
of urea. This water is pumped into a
distillation tower. The feed in this column
then preheated before entering into the
column. Due to volatility difference the
water and urea was separated in the tower,
water can be drawn from the bottom of the
tower and the urea vapors goes to the top.
Due to the presence of reboiler in the top
section urea decomposed into ammonia and
carbon dioxide which is further fed into a
feed section. The Urea waste also treated in
Bio-Hydrolyser. Urea can be irritating to
skin when it is contact with skin. Repeated
and prolonged contact with urea in fertilizer
form on the skin may cause dermatitis.
High concentration in the blood will cause
damage of blood cells. So, to overcome
these problems the efficient treatment of
wastes is needed. The Urea waste also
treated in Bio-Hydrolyser as shown in the
figure-1.
Fig-2

Fig-3
Biological Wastewater Treatment: in
Dangote Fertilizers Ltd
“The Dangote group” has acquired the requisite
industrial land in the Lekki Free Trade Zone,
for setting up the Fertilizer Complex. To meet
the water requirement of Fertilizer plant, there
is a Raw Water Treatment Plant. The Dangote
Fertilizer Project Site is located in Nigeria,
Lagos State, and Lekki Free Trade Zone. The
Lekki Lagoon is a large expanse of shallow
fresh water located in both Lagos and Ogun
state of Nigeria. This lagoon is considered to be
a reservoir of relatively fresh water but TDS
varies from low values in wet season to high
value in dry season. The DANGOTE GROUP
has ventured into the business of manufacturing
and marketing of fertilizers. The proposed
Fertilizer complex consists of Ammonia and
Urea plants with associated facilities and
infrastructures.
The plant, located in Lekki free trade zone,
Okunraye, Ibeju at Lagos state. State will be an
excellent example of how to utilize a substantial
amount of the country’s significant gas
resources, as a raw material in the Ammonia-
Urea fertilizer process. Ultimately, the project,
when completed will make the country self-
sufficient in fertilizer production, thereby
saving it the huge foreign reserves presently
spent on importation of fertilizer. Dangote
Group is one of the most diversified business
conglomerates in Africa with a hard - earned
reputation for excellent business practices and
products’ quality.
The Raw Water Treatment Plant will
comprise of the following:
1. Intake System from Lekki Lagoon
2. Biological Treatment System (SBR)
3. Dual Media Filters
4. Ultrafiltration (UF) System
5. Reverse Osmosis system

Outfall piping & sub-sea diffuser piping for
Reject disposal
Fig-4
INTAKE SYSTEM
The Intake taken from the lagoon by a canal.
The maximum design flow of water is 3300
m3/hr considering total requirement of fertilizer
plant. At the lagoon side near intake point, there
is window bar type screen with a mesh size of
100 mm provided to prevent entry of biological
mass like hyacinth. At the entry point of the
Intake well, the canal is divided into two
sections, each section designed for 50% of the
total flow. Both sections of the canal are
provided with 1 no. of 50 mm bar screen,
followed by an Automatic Mechanical screen
(25 mm). Isolation gates are provided at
upstream of 50 mm manual screen &
downstream of Automatic Mechanical Screen.
Mechanical bar/rake screens have been
provided at the entrance to each canal to
segregate the weeds and wastes. The depth of
the lagoon is considered based on lagoon top
level +1 meter and lagoon bottom level -1m and
the average water depth of the lagoon is
considered to be approx. 2 m at intake canal.
The canal will empty into a fore bay to convey
the water into the sump of the pump house.
Vertical Turbine pumps are installed in the
pump house to ensure cavitation free operation.
Individual pump sump has been designed for
each pump with sluice gate for isolation
purpose. Chlorination provision of raw water
given in canal before entering in to fore bay.
Only shock dosage provision is provided so as
to avoid any biological growth inside the Intake
well.
SEQUENTIAL BATCH REACTOR (SBR)
After Raw water pumping station, the water is
distributed through splitter box to four SBR
Basins (4W). The basins receive influent during
all phases of the cycle. Surplus activated sludge
(SAS) is disposed directly from each basin. The
raw water flows to the SBR basins via splitter
box. The chamber splits the flow to each basin
via manual gate/penstocks. The influent pipe
passes into the pre-react chamber and
terminates in a bell mouth mid-way along the
pre-react chamber. Influent to the SBR basins is
continuous during all stages of the cycle. Float
switches in each basin is detect a High-High
level and having generate alarm; manual action
to be taken by operator to stop the flow to that

www.researchgate.net 5th
Feb. 2024
basin by closing the gate/penstock. Suitable
bypass arrangement is provided to bypass the
feed raw water during lean season, as this is
seasonal variation, full flow will be bypassed
the SBR & send to filter feed tank during lean
period. A provision has been made to dose
carbon source & phosphoric acid in Splitter
Box. Air Blowers, Surplus Activated Sludge
(SAS) Pumps, Decanter & Motorized Air Line
Valves will be automatically controlled by
PLC. Treated water from SBR will be send to
Filter Feed Tank.
SBR PROCESS
A typical SBR process consists of the following
time-based phases; it is designed with a normal
cycle of 240 minutes or 4 hours. Each cycle has
120 minutes of react phase as aeration phase
with DO control to achieve simultaneous
nitrification and de-nitrification, the remaining
time is made up of 60 minutes of settle phase,
and 60 minutes of decant phase:
1. Aeration: Raw water from screening in
the Canal flows into the basin. The
basin is aerated while filling and
biological oxidation takes place
simultaneously.
2. Sedimentation: Aeration is stopped and
the solids settle to the bottom of the
basin leaving clear water on top. The
basin continuously receives the
influent.
3. Decantation: The clear water is
discharged from the top of the basin,
while the basin continuously receives
the influent. Sludge shall be disposed to
UF CEB waste sump during this phase.
Influent is received continuously
during all phases of the cycle, including
sedimentation and decantation. The
duration of each cycle and segment of
each operating cycle are the same
among all basins in a time-based
system
Fig. 5
SBR BASIN
The SBR basin is divided into two zones, the
pre-react zone and the main react zone. A baffle
wall with openings at the bottom is constructed
to divide the SBR basin into the two zones. The
raw water flows continuously into the pre-react
zone and is directed down through orifice
openings at the bottom of the baffle wall into
the main react zone. The prereact wall baffles
the incoming flow and prevents short-
circuiting. The volume of the pre react zone is
typically 10 to 15 percent of the total basin
volume. For the stabilization of SBR system,
sludge recirculation line from SAS pump outlet
to Inlet of SBR shall be provided.
1. Pre-react zone- The pre-react zone also
provides pre-treatment of the wastewater
before it enters the main react zone. Since

Feb. 2024
2. influent flows continuously into the pre-
react zone, a high concentration
3. of soluble BOD is available to the
microorganisms in a relatively small basin
volume. This situation creates a high
“Food to Microorganisms” (F: M) ratio.
The high F:M ratio encourages the
maximum bio-sorption of food by the
microorganisms. The pre-react zone
therefore acts as a biological selector
encouraging the proliferation of the most
desirable organisms.
4. Buffer Zone- The design volume of the
basin is based on a combination of the
volume required for the hydraulics based
on the peak flow conditions and the
volume occupied by the sludge. A “Buffer
Zone” is included in the design as a safety
factor to ensure the SBR process’s ability
to withstand the unusual flows and
loadings. This zone is typically a minimum
of three feet deep, extending from the top
of sludge blanket to the BWL after
decanting.
5. Auto DO Control- SBR use auto DO
control for plant operation. There are two
DO set points, one for first 90% of the react
phase & another for balance 10% of the
react phase. The DO for the last part of
aeration is higher in order to encourage the
growth of bacteria. For the first five
minutes of the react phase the blower
(VFD – starter) will run without DO
control. During this period the blower runs
at a speed of 50%. This is to ensure that the
basin contents are thoroughly mixed and
therefore that the DO reading is
representative of the basin as a whole.
After this period, the DO signal in SBR
basin is controlled against the DO set point
by the PLC. The PLC has a closed-loop
control function that incrementally adjusts
the speed of the blower in order to control
the measured DO against the set point DO.
Fig. -6
There are twin decanters mounted in each basin.
The decanters are mounted by way of a decanter
wall plate seal and bearing ring assembly
anchored onto the concrete wall. Each decanter
utilizes a connecting rod to an actuator. Each
actuator has a motor drive. Effluent flows from
the decanters into an outlet pipe through the
basin wall to the Filter Feed Tank. The Filter
Feed tank is an integrated Tank

to the SBR basin. The decanter is controlled on
a timed basis. However, the limits of travel are
ultimately controlled, as a fail-safe measure, by
position limit switches on each of the decanter
actuators.
SBR Dosing System:
Carbon Source (Molasses) dosing is provided in
Splitter Box before SBR due to variable levels
of BOD in the lake water. Carbon Source
(Molasses) dosing purpose is to provide food
for Bacteria. Carbon Source (Molasses) Dosing
system comprises of 2 Dosing Pumps Carbon
Source (Molasses) Bulk Storage tank along
with unloading cum transfer pumps are also
considered. Carbon Source (Molasses) will be
available in liquid form; its commercial
available concentration is 90-100%, same
concentration without dilution are considered
for dosing in SBR. Based on the daily
measurement of COD or TOC, Carbon Source
(Molasses) dosage & its frequency is decided.
PHOSPHORIC ACID DOSING SYSTEM:
Phosphoric Acid dosing is provided in Splitter
Box before SBR due to variable levels of
phosphorus in the lake water. Phosphoric Acid
will act as a nutrient to Bacteria. Phosphoric
Acid Dosing system comprises of 2 nos. Dosing
Pumps and 1 nos. of Dosing Tanks. Phosphoric
Acid is available in liquid form; its commercial
available concentration is 40%, same
concentration without dilution is considered for
dosing in SBR. Based on the daily measurement
of phosphorus in raw water phosphoric acid
dosage & its frequency decided.
Sewage Treatment Plant
Anaerobic bacteria are the most common type
of bacteria used. This type of bacteria helps to
drastically reduce the amount of sludge that is
created while also assisting in the production of
methane gas from the sludge. anaerobic
bacteria are an important element in the
wastewater treatment processes. They are
responsible for methane fermentation of
sewage sludge, facilitating decomposition of
macromolecular organic matter into simpler
compounds. The proportion of gram-negative
bacteria, particularly proteobacteria, is 21-65%.
Betaproteobacteria, the most abundant group,
have a major contribution to the elimination of
organic elements and nutrients. bacteria are the
heart of the process. And finally, a wastewater
treatment plant represents a small farm where
micro-organisms are cultivated on a large scale.
The presence of bad bacteria (or the absence of
good ones) can cause in particular:
1. Low biogas efficiency of the anaerobic
digester
2. Poor flocculation and sedimentation
3. An excess of filamentous bacteria
4. Excess of phosphorus
5. Low nitrogen removal efficiency
(NH4, NO3)
6. The production of unpleasant odors
7. Excess consumption of chemical
products
8. In an anaerobic digester, foam
production

Fig-7
Biological Treatment for railways coach
Toilets.
An Anaerobic biological toilet system. In this
technology anaerobic bacteria are used for de-
composition of fecal matter. These bacteria are
stored in tanks fitted to the under frame of the
coach to decompose the fecal matter. Biological
decomposition of Human waste is done in bio-
digester tanks with the help of anaerobic
bacteria which is developed at bacteria
generation plant at Workshop situated in many
cities. Bio toilet is completely different toilet as
compare to the traditional restrooms. It saves a
lot of water and helps in keeping the
environment clean. Bio-digester technology
treats human waste at the source. A collection
of anaerobic bacteria that has been adapted
to work at temperatures as low as -5°C and as
high as 50°C act as inocula (seed material) to
the bio-digesters and convert the organic
human waste into water, methane, and carbon-
dioxide gases. The anaerobic process
inactivates the pathogens responsible for water-
borne diseases and treats the shit without the
use of an external energy source. Under the bio-
toilet concept of the DRDO, the bio-digester
tank in every toilet is filled with inoculums.
containing four types of bacteria. The water trap
system in the toilet prevents air from getting
into the tank, the human waste is processed by
anaerobic bacteria in seven chambers in the
tank and the methane gas is allowed to escape
into the air.

Fig-8
Benefits of Bio-Toilets
1. In the traditional toilets; human excreta were
released on the rail tracks directly causing
damage to the metal of railway tracks as well as
spreading the dirt in the environment. Now it
will not happen.
2. Traditional toilets spent at least 10 to 15 liters
of water in one flush, while vacuum-based bio-
toilets need just half a liter of water.
3. India's stations will now become clean which
will support “Swachh Bharat Abhiyan” of
Government of India.
4. These bio toilets will provide respite to those
who manually clean the shit at the platforms.
It is expected that after reading the above
article, you must have come to know that what
is bio-toilet and why is it essential for the India
in the years to come.
Benefits of green toilet
1. Environment friendly
2. Preventing damages to tracks due to
corrosion
3. Improved aesthetics at Railway
Stations
Types of Environment friendly toilets are:
1. Bio toilets- The Bio toilet system,
discharge processed waste on track
2. Vacuum toilets: Based on the principle of
direct transport from the toilet bowl to the
tank aided by vacuum creation in the tank
and pipeline.
3. Zero discharge toilet systems: In Zero
Discharge toilet system, waste is collected
at terminus and then processed. Solid and
liquid separation is done in the tank itself
and liquid is recycled as flush water.
Advantage of Anaerobic bio-toilet:
1. Require less maintenance
2. Simple in design
3. Easier Retro fitment on existing coaches in
service
4. Can be in operation upto years together.
5. No oxygen and sunlight required for
processing.
Biological Treatments of Heavy metals.
Anaerobic biological processes relying on
the activity of sulfate reducing bacteria are
being considered for the treatment of AMD
and other heavy metal containing effluents.
The heavy metals (HMs) (chromium (Cr),
lead (Pb), zinc (Zn), cadmium (Cd),
mercury (Hg), copper (Cu), nickel (Ni),
etc.), and organic pollutants (phenolic
compounds, aromatic hydrocarbons,

surfactants, along with biocides). As heavy
metals aren't biodegradable, they tend to
stay in the environment for a long time,
causing them to build up in the food chain,
which can be bad for the environment and
our health. Microalgae are being used to
treat wastewater and make useful products.
Microalgae, for example, is a
promising renewable resource for
producing biomass from wastewater
nutrients because of its quick growth rate,
short life span, and high carbon dioxide
utilization efficacy. Microalgae-based
bioremediation has grown in importance in
the treatment of numerous types of
wastewater in recent years. This solar-
powered wastewater treatment technology
has huge potential. However, there are still
issues to be resolved in terms of land
requirements, as well as the process's
ecological feasibility and long-term
viability, before these systems can be
widely adopted. Due to cost and the need
for a faultless downstream process, it is
difficult to deploy this technology on a
large scale. Other recent breakthroughs in
wastewater microalgae farming have been
investigated, such as how varied pressures
affect microalgae growth and quality, as
well as the number of high-value
components produced. In this review, the
future of this biotechnology has also been
examined.
Fig-9
Bioremediation involves the removal of
the contaminated materials with the help of
bacteria, fungi, algae and yeast. Microbes
can grow at below zero temperature as well
as extreme heat in the presence of
hazardous compounds or any waste stream

Feb. 2024
Fig-10
Conclusion
Biological wastewater treatment is a modern
technique in which wastewater is treated with
microorganisms instead of chemicals.
Biological wastewater treatment method, also
known as the conventional method, Main
objectives of biological treatment to remove or
reduce the concentration of organic, inorganic
compounds nutrients specially nitrogen and
phosphorus and heavy metals. Biological
treatment in the batch system indicated that
hydrolyzer effluent is a nutritionally deficient
medium to sustain microbial growth, hence
supplementation with optimum levels of
nutrients is a prerequisite for high treatment
efficiency. In a continuous biological treatment
system urea and ammonia can be completely
removed from the hydrolyzer effluent at a
hydraulic retention time of 15–20 hours.
**************************************************
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