Waste water treatment is a process to convert waste water – which is water no longer needed or suitable for its most recent use into an effluent that can be either returned to the water cycle with minimal environmental issues or reused.

1. Waste Water Treatment
Practices
VIKAS KUMAR UJJANIA
(M.F.Sc.)
Dept. of Aquaculture
College of Fisheries, MPUAT, Udaipur

2. Waste water:-
Waste water is any water that has been adversely affected in
quality by anthropogenic influence.
Waste water can originate from a combination of domestic ,
industrial , commercial or agricultural activities , surface runoff or
storm water , and from sewer inflow or infiltration.
Waste water treatment:-
Waste water treatment is a process to convert waste water – which
is water no longer needed or suitable for its most recent use into an
effluent that can be either returned to the water cycle with minimal
environmental issues or reused.

3. Waste water treatment consists of a combination of physical
chemical, and biological processes and operations to remove solids,
organic matter and, sometimes, nutrients from waste water.
General terms used to describe different degrees of treatment , in
order of increasing treatment level, are preliminary , primary ,
secondary, and tertiary or advanced waste water treatment.
Preliminary treatment-
The objective of preliminary treatment is the removal of coarse
solids and other large materials often found in raw waste water.
Preliminary treatment operations typically include coarse
screening, grit removal and ,in some cases , comminution of large
objects.
Waste water treatment processes

4. Primary treatment-
• The objectives of primary treatment is the removal of
settleable organic and inorganic solids by sedimentation ,
and the removal of materials that will float by skimming.
• Approximately 25% to 50 % of the incoming biochemical
oxygen demand (BOD), 50 to 70 % of the total suspended
solids (SS), and 65% of the oil and grease are removed
during primary treatment.
• Some organic nitrogen , organic phosphorous and heavy
metals associated with solids are also removed during
primary sedimentation . but colloidal and dissolved
constituents are not affected.
• The effluent from primary sedimentation units is referred to
as primary effluent.

5. Secondary treatment:-
• The objective of secondary treatment is the further
treatment of the effluent from primary treatment to remove
the residual organics and suspended solids.
• In most cases, secondary treatment follows primary
treatment and involves the removal of bio-degradable
dissolved and colloidal organic matter using aerobic
biological treatment processes.
• Aerobic biological treatment is performed In the presence of
oxygen by aerobic micro-organisms (bacteria) that
metabolize the organic matter in the waste water, thereby
producing more micro organisms and inorganic end
products (CO2, NH3 and H2O).

6. • High rate biological processes are characterized by relatively
small reactor volumes and high concentrations of micro
organisms compared with low rate processes.
• Common high rate processes include the activated sludge
processes, trickling filters or biofilters, and rotating biological
contactors(RBC).
• A combination of two of these processes in series(e.g., biofilter
followed by activated sludge ) is sometimes used to treat
municipal waste water containing a high concentration of organic
materials from industrial source.
Activated sludge-
In the activated sludge process, the dispersed growth reactor is an
aeration tank or basin containing a suspension of the waste water
and micro organisms, the mixed liquor.

7. Trickling filters-
• A trickling filter or biofilter consists of a basin or tower filled
with support media such as stones, plastic shapes, or wooden
slates.
• Waste water is applied intermittently, or sometimes
continuously, over the media.
Rotating biological contactors
• Rotating biological contactors (RBC) are fixed film reactors
similar to biofilters in that organisms are attached to support
media.
• In the case of the RBC, the support media are slowly rotating
discs that are partially submerged in flowing waste water in
the reactor.

8. Tertiary or advanced treatment :-
• Tertiary or advanced waste water treatment is employed when
specific waste water constituents which cannot be removed by
secondary treatment must be removed .
• Individual treatment processes are necessary to remove
nitrogen, phosphorus, additional suspended solids, heavy
metals and dissolved solids .
• Because advanced treatment usually follows high rate
secondary treatment, it is some times referred to as tertiary
treatment .

9. Types of waste water:-
• Waste water usually produced from by-products of otherwise
purposeful human activities.
• Main types of waste water-
Sewage (domestic waste water)
Industrial waste water
Aquaculture waste water and agriculture waste water.

10. Sewage (Domestic waste water) :-
• Sewage is a type of wastewater that includes household waste liquid
from baths, showers, kitchens, and sinks draining into sewers. In
many areas, sewage also includes liquid waste from industry and
commerce.

11. Industrial waste water:-
• All waste water that is not defined as domestic waste water is
considered industrial waste water.
• Source of industrial waste water include manufacturing ,
commercial business, mining, agricultural production and
processing, and waste water from cleanup of petroleum and
chemical contaminated sites.

12. Aquaculture waste water:-
• Aquaculture activities are well known to be the major contributor
to the increasing level of organic waste and toxic compounds in
the aquaculture industry.
• The main contaminants of the waste water effluent are metals,
suspended solids, ammonium, organic nitrogen and phosphorus.

13. Characteristics of aquaculture waste water-
• In aquaculture system, especially in extensive culture the primary
source of nitrogen and phosphorus in the pond water is derived
from feed applications.
• The pollutant load discharged into the environment from
aquaculture system has been calculated and found that one ton of
produced fish generates 0.8 kg of nitrogen/day and 0.1 kg of
phosphorus /day.
• In intensive shrimp culture, 11.56% nitrogen and 14.11%
phosphorus of nutrient input remained in water body, nitrite is a
naturally occurring intermediate product of the nitrification
process.
• The nitrate ion (NO3-)is the most oxidized form of nitrogen in
nature and is relatively non-toxic to fishes.

14. Waste water use in aquaculture-
Biota in aquaculture ponds
Food chains
• The objective in fertilizing an aquaculture pond with excreta, night
soil or waste water is to produce natural food for fish.
• Since several species of fish feed directly on faecal solids, use of raw
sewage or fresh night soil as influent to fish ponds should be
prohibited for health reasons.
Fish species
• The selection reflects local culture rather than fish optimally-suited to
such environments. For example, Chinese carps and Indian major
carps are the major species in excreta -fed systems in china and India,
respectively.
• In some countries, a polyculture of several fish species is used.

15. Aquatic plants-
• Aquatic macrophytes grow readily in ponds fed with human
waste and their use in waste water treatment has been
discussed.
Effect of aquaculture waste water -
• The major impact on the receiving water bodies are
eutrophication, oxygen depletion and toxicity of ammonia
and sulfide.
• High organic load increases the oxygen demand in water
bodies. This eventually reduces dissolved oxygen levels in
aquaculture system.
• The urine and faeces from the aquatic animals can cause
high content of ammonia, nitrogen and an increase of BOD.
• Nitrite is naturally occurring intermediate product of the
nitrification process.
• Ammonia is the main nitrogenous waste that is produced by

16. Treatment of aquaculture waste water-
Removal of organic matter
• Removing of organic matter from waste water can be accomplished
by two main processes that are aerobic and anaerobic.
• Aerobic process is suitable for the waste water if the concentration
of BOD is less than 1000 mg /l, and
• Anaerobic process is suitable if the concentration of BOD is more
than 1000mg/l.
Nitrogen removal
• Ammonia is the principal excretory product of most aquatic
organisms.
• Ammonia and nitrite is toxic to fish and invertebrates and should be
maintained below 0.1 mg/l .
• Nitrate is the end product of nitrification.

17. Nitrification
• Nitrification involves the two step conversion of ammonia to
nitrite and nitrite to nitrate by autotrophic aerobic
microorganisms which are nitrosomonas sp.and nitrobactor sp.
Denitrification
• Biologically denitrification occurs naturally when certain
bacteria use nitrate as terminal electron acceptor in their
respiratory process, in the absence of oxygen .
• Denitrification consists of a sequence of enzymatic reaction
leading to the evolution of nitrogen gas .
Phosphate removal
• Phosphorus is released from bacterial biomass in the anaerobic
stage and is assimilated by these bacteria in excess as
polyphosphate during the aerobic stage.

18. Waste water reuse for aquaculture-
• Waste water reuse for aquaculture has been practiced in many
countries for a considerable period of time.
• It has the potential of wider application in the tropics.
• There is great diversity of systems involving cultivation of aquatic
species(mainly fish), and plants(mainly aquatic vegetables).
• Farmers and local communities have developed most reuse systems,
the primary motivating factor has been reuse of nutrients for food
production rather than waste water treatment, and with scant
attention to either waste treatment or to public health.
• In most aquaculture systems, waste water is not reused directly in
aquaculture and the nutrients contained in the waste water are used
as fertilizers to produce natural food such as plankton for fish.
• Waste water provides a source of nutrients for aquaculture .

19. Problems in waste water reuse
Problems in waste water reuse for aquaculture relate to non
availability of guidelines for selection of species and stocking
density.
Fig:- Schematic of waste water reuse strategies (Edwards 2000)

20. Reference :-
• Google scholar
• Patterson, James w. (1980). Waste water and waste
water treatment.
• Klein Gomes, waste water management(book), page
no. 2-9, 237-239
• Elizabeth Emanuel, international best practices in
waste water treatment, page no.54-56
• Freshwater aquaculture (R.K. rath)
• Handbook of fisheries and aquaculture
• www.slideshare.net