Wastewater from domestic, industrial, and agricultural sources can pollute the environment if not properly treated. It contains organic matter, pathogens, nutrients, and other pollutants that can deplete oxygen in water bodies and threaten human and ecological health. The document outlines various wastewater characteristics and treatment processes like primary sedimentation, activated sludge process, trickling filters, and waste stabilization ponds that remove pollutants through physical, chemical, and biological means to produce effluent that meets quality standards for discharge or reuse. Proper wastewater treatment is important to protect water resources and public health.

1. EFFECTS OF WASTEWATER
ON THE ENVIRONMENT AND
THE TREATMENT
PROCESSES
BY
AUDU SULEMAN JOSEPH
ENGR II
NATIONAL ENVIRONMENTAL STANDARDS AND REGULATIONS
ENFORCEMENT AGENCY (NESREA)
OWERRI, IMO-STATE.
A Presentation at the monthly In-House Training Programme.
April 2011

2. PRESENTATION OUTLINE
• INTRODUCTION
• WASTEWATER POLLUTANTS
• WASTEWATER TREATMENT
• CONCLUSION
• RECOMMENDATIONS

3. INTRODUCTION
• Wastewater can simply be defined as water that
has been used and disposed. Basically, it is water
that lost its natural or original quality and this
quality could either be physical, chemical or
biological.
• Wastewater can be broadly classified by their
origin as domestic, agricultural and industrial.
• Domestic wastewater is that which is discharged
from residential and commercial establishments,
where as industrial wastewater is that which is
discharged from manufacturing plants.
• Agricultural wastewater results from washing of
agricultural chemicals used on farms.

4. • Normally waste water is conducted to
treatment plants for removing
undesirable components which include
both organic and inorganic matter as
well as soluble and insoluble material.
• These pollutants if discharged directly
or with improper treatment can interfere
with the self-cleaning mechanisms of
water bodies or affect the quality of the
environment.

5. • But often either a pollutant does not
degrade naturally or the sheer volume
of the pollutant discharged is sufficient
to overwhelm the self-cleaning process.
• Also the microbial population can be
destroyed by toxic wastes discharged
into the water way. If that happens, the
pollutant concentrations will build up
and reach high enough levels that will
prevent re-establishment of a microbial
population.

6. • The water quality thus becomes
permanently degraded. Various
constituents of wastewater are potentially
harmful to the environment and human
health. In the environment, the pollutants
may cause destruction of animal and plant
life and aesthetic nuisance.
• Drinking water sources are often
threatened by increasing concentration of
pathogenic organisms as well as by many
toxic chemicals disposed of by industry
and agriculture.
• Thus the treatment of these wastes is of
paramount importance.

7. WASTEWATER CHARACTERISTICS AND
TESTS
PHYSICAL CHARACTERISTICS
• Total Solids
• Suspended solids
• Total dissolved solids
• Settleable solids
• Colour
• Odour
• Temperature

8. CHEMICAL CHARACTERISTICS
• Chemical Oxygen Demand (COD)
• Chloride
• Sulphate
• Nitrogen compounds
• pH
• Heavy metals

9. BIOCHEMICAL CHARACTERISTICS
• Biochemical oxygen demand (BOD)
• Nitrogenous oxygen demand (NOD)
BIOLOGICAL CHARACTERISTICS
• Coliform organisms
• Specific organisms (viruses, protista)

10. COMPOSITION OF WASTEWATER
• Floating materials: Papers, leaves, etc
• Organic matter: Compounds of
Carbon, Hydrogen, Oxygen, Nitrogen,
Sulphur (CHONS) and a-times
phosphorus.
• Inorganic materials: Metals, non-
metals, sand, silt etc.

11. POLLUTANTS CATEGORIZATION
Pollutants can be categorized as follows;
• Oxygen demanding wastes
• Disease causing agents
• Synthetic organic compounds
• Plant nutrients
• Inorganic chemicals and minerals
• Sediments
• Oil

12. OXYGEN DEMANDING WASTE
• When these substances enter a water
way, dissolved oxygen is consumed in
their breakdown by micro-organisms, so
the organic substances can be said to
exert a demand on the availability of
dissolved oxygen.
• The more the oxygen required for the
breakdown of the substances, the greater
will be the de-oxygenation of the water
way. Pollution results when the oxygen
demand exceeds the available oxygen.

13. BIOCHEMICAL OXYGEN DEMAND (BOD)
• The Biochemical Oxygen Demand is a
measure of the oxygen demand of organic
waste in waste water. It is the most widely
known measure for assessing the water
pollution potential of a given organic waste.
On an average the demand for oxygen is
directly proportional to the amount of organic
waste which has to be broken down.
• A standard way to measure BOD is to
determine the amount of oxygen required by
the bacteria during the first five days of
decomposition at 20°C. The result is known
as the 5-day BOD at 20°C commonly
abbreviated as BOD5.

14. BOD/NOD CURVE
Time
Nitrification stage
NOD
Carbonaceous stage
BOD
BOD (mg/l)
A
B
Combined O2 demand
curve
A: Lag value often occurs until
micro organisms become
acclimated
B: Nitrification usually is
observed to occur from 5-8 days
after the start of the incubation
period

15. • The curve shown in the above figure is typical
of what is known as first stage BOD where
carbonaceous matter is degraded by
bacterial oxidation. But when nitrogenous
material is also present, nitrifying bacteria
exert an additional oxygen demand. This
causes a second hump in the curve called
the second stage BOD or nitrification.
• During the carbonaceous stage, ammonia is
produced by the breakdown of organic
nitrogen materials, but this process is so slow
that nitrifiers do not predominate until nearly
the end of the carbonaceous stage. Ammonia
(or ammonium ion) is then oxidized to nitrite
and then to nitrate by Nitrosomonas and
Nitrobacter micro-organisms respectively.

16. • The oxidation process speeds up towards
the end of the first stage and slows down
again as the ammonia is oxidized.
Ammonia exerts a very high demand,
requiring over 4.5 times its own weight of
oxygen for complete oxidation. Thus if
nitrification is allowed to occur in the
receiving stream, second-stage BOD
exerts its presence and a further decrease
in the oxygen resource will be
experienced.

17. NITRIFICATION
Nitrosomonas
2NH4
+ + 3O2 2NO2 + 2H2O + 4H+
Nitrobacter
2NO2
- + O2 2NO3
-

18. BACTERIA GROWTH GRAPH
Bacteria
Organic
matter
A
B
C
D
Key:
A= the lag phase
B= the log-growth
C= the stationary phase
D= the death phase

19. ANAEROBIC OXIDATION
New cells
Alkohol + Bacteria
(Organic
Acids)
New cells
CH4, NH3, CO2
Organic matter + Bacteria

20. AEROBIC OXIDATION
New cells
CO2, NH3, H2O
Organic matter + Bacteria + O2

21. DISEASE CAUSING AGENTS
• Water is a potential carrier of pathogenic
micro-organisms. These pathogens are
carried into the water bodies by sewage and
wastes from farms and various industries.
Some bacteria are water borne and these
include those responsible for causing
cholera, typhoid, amoebic dysentery and
gastro enteritis.
• Viruses are also found in water including
strains which are responsible for polio,
infectious hepatitis and coxsackie fever.
Water may also contain some animal
parasites including round worm and pork tape

22. • All these types of organisms occur in faeces and
so are present in the sewage. Although techniques
are available for identifying and enumerating many
types of pathogens commonly transmitted by
water, these methods are time consuming,
complex and expensive and hence are not
ordinarily used to evaluate the bacteriological
quality of water.
• Escherichia Coli (E. coli), belonging to the coliform
group, is essentially harmless bacteria found in
large numbers in human faeces. Since pathogens
leave the human body through body waste and
since coliforms commonly travel together with the
pathogens, a large concentration of E. coli in the
water indicates faecal contamination and a
presumptive evidence of the presence of
pathogens.

23. SYNTHETIC ORGANIC COMPOUNDS
• These include pesticides, synthetic
organic chemicals and detergents. These
compounds in contrast to the organic
wastes are not bio-degradable and may
persist for long periods.
• These are of great concern to
environmentalists because most of the
synthetic organic compounds are
accumulative toxic poisons and ultimately
reach objectionable levels in water or in
aquatic life.

24. PESTICIDES
• Pesticides can be classified into three main
classes of insecticides, herbicides and
fungicides. Pesticides are not common
constituents of sewage but result primarily
from surface run-off from agricultural lands,
waste discharge by pesticide manufacturers
and by other means.
• Because of their world wide usage, nearly all
the rivers and oceans of the world contain
pesticide residue. Pesticides residues in
water may reach humans through drinking
water but the concentration in most cases are
far below the harmful levels.

25. • The concentrations found in man have not
caused any ill-effects in man so far, but
there is experimental evidence of harmful
longer term effects in mammals. Several
pesticides have been shown to cause
cancer in mice and rats.

26. DETERGENTS
• Detergents contribute about 50% of the
phosphate present in sewage effluents.
When these phosphates are released into
streams and lakes, they act as plant
nutrients thus supporting eutrophication of
water bodies.

27. PLANT NUTRIENTS
• Nitrogen and Phosphorus are essential
elements which are required by plants and
animals for maintaining their growth and
metabolism.
• These compounds may enter the water
bodies from the manufacture and use of
fertilizers, and from the processing of
biological materials such as food and textiles
or via domestic sewage treatment plants.
• Thus, when unusually large concentrations of
nutrients are present in water bodies an
excess growth of algae known as algal bloom
appears. This produces an unsightly green

28. • The slime layer reduces light penetration and
restricts atmospheric re-oxygenation of the water.
The dense algal growth eventually dies and the
subsequent bio-degradation produces an oxygen
deficit which results in foul-smelling anaerobic
conditions.
• The anaerobic conditions created by rotting algae
can present a health hazard. Birds feeding on the
algae are killed by toxin produced by the
anaerobic bacterium Clostridium botulinum which
flourishes in the environment.
• Other problems resulting from heavy algal growth
are the clogging of filters in water treatment plants
and slowing down of stream flow by filamentous
weeds which can grow up to 12m long. These
weeds can trap solid particles carried by a stream
and if they are organic, a large decaying mass
accumulates which exerts a high oxygen demand.

33. INORGANIC CHEMICALS AND MINERALS
• This category of water pollutants includes
inorganic salts, mineral acids, finely divided
metals and metal compounds. These
pollutants enter the water bodies from
municipal and industrial wastewaters and
mine run-off. Acid Mine Drainage is an
important source of increased acidity in
natural waters.
• The detection of these substances produce
physiological poisoning by becoming
attached to the tissues of aquatic organisms
and accumulate consequently, their
increasing concentrations can build up in
food chains. The metals of particular concern
in industrial waste water are cadmium,
chromium, lead, mercury and silver.

34. SEDIMENTS
• Sediments include soil, sand and mineral
particles washed into the aquatic
environment by storms and flood waters. The
sediments erode pumping equipment and
power turbines and have the effect of
increasing turbidity and consequently
reducing the amount of sunlight reducing the
amount of sunlight available to green water
plants.
• In suspension, the solids may cause
thickening of fish gills which may lead to
eventual asphyxiation of the fish. On the river
bed, the sediment may interfere with

35. OIL
• Oil is an important commodity involved in
some way or other in virtually every
activity of contemporary life. Therefore,
there is obvious concern about its polluting
effects.
• Oil and oil wastes enter rivers and other
water bodies from several sources like
industrial effluents, oil refineries and
storage tanks, automobile waste oil and
petrochemical plants.
• All these make a significant contribution to
the pollution of the soil and aquatic

36. • Since oil is virtually insoluble in water, it
floats and spreads rapidly into a thin layer.
An oil slick on the surface of water can
prevent oxygen transfer from the
atmosphere and lead to very low DO
levels in the water due to microbial
oxidative attack on the hydrocarbon
molecules.
• Films of oil on the surface may be driven
in-shore through the action of wind and
tides, and may accumulate along the
shoreline where they pose aesthetic

37. WASTE WATER TREATMENT
• The purpose of waste water treatment is to
remove the contaminants from water so
that the treated water can meet the
acceptable quality standards. The quality
standards usually depend upon whether
the water will be reused or discharged into
a receiving stream.
• The WW treatment processes are
generally grouped according to the water
quality they are expected to produce.
These processes are usually grouped as;
Primary treatment, Secondary or
Biological treatment and

38. • Primary treatment removes identifiable
suspended solids and floating matter. In the
secondary treatment, also known as the
biological treatment, organic matter that is
soluble or in the colloidal form is removed.
• Advanced WW treatment may involve
physical, chemical or biological processes or
the various combinations depending on the
impurities to be removed.
• These advanced WW treatment processes
are expensive and are used only when water
produced is required to be of higher quality
than that produced by conventional
secondary treatment so that the treated water
can be reclaimed and put to some form of
direct use.

39. CONVENTIONAL WW TREATMENT
• Primary treatment: The primary treatment
comprises a pretreatment step and a
sedimentation step. Wastewater is pretreated
to remove large floating and suspended
solids which could interfere with the normal
operation of subsequent treatment
processes.
• Biological/Secondary treatment: Since much
of the organic matter in wastewater is
colloidal and dissolved, the primary treatment
processes are largely ineffective in removing
it. This organic material still represents a high
demand for oxygen which must be reduced
further so that the effluent may be rendered

40. • The micro-organisms are fixed while WW
is passed through (eg Waste Stabilization
Pond and Trickling filter).
• The WW body with micro-organisms is
introduced to the WW treatment facility
(Activated Sludge Process, ASP).

41. WASTE STABILIZATION POND (WSP)
• This consists of large shallow basins
enclosed by earthen embankments in
which raw sewage is treated entirely by
natural processes involving both bacteria
and algae. Three (3) types of ponds
connected in series namely; Facultative,
Maturation and anaerobic ponds.

42. WASTE STABILIZATION POND

43. ACTIVATED SLUDGE PROCESS (ASP)
• Waste water after primary treatment enters
an aeration tank where the organic matter is
brought into intimate contact with the sludge
from the secondary clarifier. This sludge is
heavily laden with micro-organisms which are
in active state of growth. Air is introduced into
the tank either in the form of bubbles through
diffusers or by surface aerators.
• The micro-organism utilize the oxygen in the
air and convert the organic matter into
stabilized, low-energy compounds such as
NO3, SO4, CO2 and synthesize new bacterial
cells.

44. BACTERIA GROWTH GRAPH
Bacteria
Organic
matter
A
B
C
D
Key:
A= the lag phase
B= the log-growth
C= the stationary phase
D= the death phase

45. ASP FLOW DIAGRAM
A B C D E
I
J
K
F H
L
M
N
O
A-Screening E-Secondary settling
B-Grit chamber F-Filtration
C-Primary sedimentation tank H-Chlorine
contact
D-Aeration I-Floatation thickening
J-Anaerobic digestion K-Sludge
dewatering
L-Chlorine M-Effluent

46. ACTIVATED SLUDGE PROCESS

47. TRICKLING FILTER (TF)
• Conventional trickling filters normally
consist of a rock bed, 1-3m in depth, with
enough openings between the rocks to
allow air to circulate easily. The influent is
sprinkled over the bed packing which is
coated with a biological slime.
• As the liquid trickles over the packing,
oxygen and the dissolved organic diffuse
into the film to be metabolized by the
micro-organisms in the slime layer. End
products such as CO2, NO2 etc diffuse
back, out of the film and appear in the filter
effluent.

48. A B D
C
F
E
J
G
H I
K
TRICKLING FILTER FLOW
DIAGRAM
A-Primary settling tank F-Sludge
B-Primary filter G-Raw water
C-Secondary filter H-Recirculation
D-Secondary settling tank I-Recirculation
E-Effluent J-Sludge return

49. TRICKLING FILTER

50. ADVANCED WASTEWATER TREATMENT
• The effluent from a typical secondary
treatment plant still contains 20-40 mg/l
suspended solids and 20-40 mg/l BOD, which
may be objectionable in some streams.
Suspended solids, in addition to contributing
to BOD, may settle on the stream bed and
inhibit certain forms of aquatic life.
• The BOD, if discharged into a stream with
low flow, can cause damage to aquatic life by
reducing the dissolved oxygen content. In
addition, the secondary effluent contains
significant amounts of plant nutrients and
dissolved solids. If the wastewater is of
industrial origin, it may contain traces of
organic chemicals, heavy metals and other

51. • The recent trend towards the formulation
of regulations for the discharge of specific
compounds and the increased emphasis
on recovery of valuables from industrial
wastewaters have, created the need for
treatment beyond the conventional
secondary treatment stage.
• Advanced treatment processes are
expensive at the present level of their
development. Their need in a particular
situation should, therefore, be assessed in
the light of the circumstances relevant to
that situation.

52. • A wide variety of methods are used in
advanced wastewater treatment to satisfy
any of several specific goals, which
include the removal of;
• Suspended solids
• BOD
• Plant nutrients
• Dissolved solids and
• Toxic substances.

53. • These methods may be introduced at any
stage of the total treatment process as in
the case of industrial wastewaters or may
be used for complete removal of pollutants
after the secondary treatment.
• Some of the methods used in advanced
wastewater treatment include:
Microstraining
Coagulation and Filtration(aluminum
sulfate, ferric chloride)

54.  Adsorption on Activated Carbon
 Solvent extraction
 Ion exchange
 Reverse osmosis
 Electrodialysis
 Ammonia stripping
 Phosphorus removal

55. CONCLUSION
• Wastewater, when not properly treated and
discharged into the environment affects
plants, animals and the environment in a lot
of negative ways. Toxic chemicals kill plants
and animals, in some cases they accumulate
in the tissues of aquatic animals which could
be consumed by man, pathogens cause
various diseases in man, polluted water
makes the cost of treating water for drinking
high etc.
• With the aforementioned problems, there is
therefore the need for sensitization of the
public and industries of the problems
associated with discharging untreated
wastewater into the environment and also
carry out enforcement as the case arise for a

56. RECOMMENDATIONS
• NESREA should give high priority to
monitoring of activities around rivers,
wetlands, and water sheds to ensure that
they are not polluted.
• The Agency should ensure that States and
LGAs carry out their responsibilities in
establishing sanitation and waste
management facilities.
• NESREA should intensify efforts in
ensuring that tanneries and abattoirs
provide some degree of treatment to their
wastewater before discharging into water
bodies.

57. • Sensitization programs on the appropriate use
of herbicides, pesticides and fertilizers should
be carried out by the Agency and also
encourage keeping the required distance
between farmlands, settlements and river
banks.
• NESREA should discourage indiscriminate
mining activities and existing mines should be
assessed to ascertain the level of toxicity of the
substances present at the sites.
• The Agency should ensure strict compliance by
industries on the stoppage of the use of
banned chemicals as contained in the National

58. THANK
YOU