Waste water treatment is a process used to convert wastewater into an effluent that can be returned to the water cycle with minimum impact on the environment, or directly reused. The latter is called water reclamation because treated wastewater can then be used for other purposes.

1. SHRI SHANKARACHARYA MAHAVIDYALAYA
JUNWANI, BHILAI NAGAR(C.G.)

2. 1. INTRODUCTION
2. TYPES OF SEWAGE
3. COMPOSITION OF SEWAGE
4.CHARACTERSTIC OF SEWAGE
5.OBJECTIVES OF SEWAGE
6. COLLECTION OF SEWAGE
7. PROPERTIES OF SEWAGE
8.SEWAGE TREATMENT METHOD
9. CONCLUTION
10. REFERENCE

3. 1. INTRODUCTION:- Sewage is the waste water of a
community. There are two classes of sewage, namely domestic &
industrial. There is a considerable variation in the composition of
domestic & industrial sewage, there fore, each type requires
separate discussion.
2.TYPES OF SEWAGE:- There are two main type of sewage-
A) DOMASTIC SEWAGE:- It is composed of human wastes
( faces & urine) & waste waters resulting from personal washing,
food preparation, laundry & the washing of kitchen utensils. It is
generally relatively low in solids, usually being more then 99%
water. Fresh sewage is a grey, turbid liquid with an earthy odors.
Approximate analyses of human faces & urine are given in table -

4. B) INDUSTRIAL SEWAGE:- It contains both organic & compounds.
The nature & amount of these compounds depend upon the type of
product that a factory produces, & also the nature of the process
involved in it. For example, organic compounds are discharged by
sugar factories, paper mills, creameries, breweries, slaughter
houses, etc. On the other hand, inorganic substances are added by
mines and metal industries. E.g.:- acids & salts of metals.
FACES URINE
MOISTURE 66-80 93-96
NITROGEN 5.0-7.0 15-19
CARBON 44-55 11-17
CALCIUM( AS CaO) 4.5 4.5-6.0

5. 3. COMPOSITION OF SEWAGE:- The composition of sewage, in
simpler form.

6. 4) CHARACTERSTICS OF SEWAGE:- Organic matter in the sewage
serves as food for micro-organism. These micro-organisms oxidize the
waste, & this requires oxygen supply. This may be represented by the
following general equation:
Organic matter of sewage + oxygen
Treated sewage + new micro organism
BOD (Biological Oxygen Demand):-
The amount of oxygen required for the oxidation of the organic
matter of the sewage by micro-organism is called Biological Oxygen
Demand (BOD).
There exists a gradient for the requirement of oxygen, depending
upon the amount of organic matter in the sewage.

7.  COD (Chemical Oxygen Demand):-
 There is an alternate test for measuring the load of organic matter
in sewage i.e., Chemical Oxygen Demand (COD) test.
 COD is determined by oxidizing the waste (organic matter) with a
boiling acid dichromate solution.
 Almost all organic compounds undergo oxidization with the
formation of carbon dioxide & water.
Usually, the reaction proceeds to more than 95%
completion. COD measurements are made very quickly. But there
are two disadvantages with this test, namely-
a) Such measurements do not give any information on the proportion
of bio-degradable waste,
b) COD tests do not provide any information regarding the rate at
which bio-oxidation may take place.
A COD test is described in the Appendix I.

8. 5. OBJECTIVES OF SEWAGE TREATMENT:-
Sewage cannot be disposed of without proper treatment.
However, many communities & municipalities dump improperly
treated sewage into natural bodies of water (e.g. lakes river, etc.). It
is believed that sewage gets diluted in a large body of water & thus
prevents hazards to society. actually, the dilution method for
sewage disposal is not a reliable method. In other words, the
solution for pollution is not dilution. Therefore, sewage should be
adequately treated before its ultimate disposal in a receiving
watercourse in order to:
I) Reduce the spread of pathogenic micro-organism,
II) Prevent the pollution of ground & surface waters,
III) Prevent the contamination of oysters & other shell-fish which are
used for human consumption,
IV) Maintain the oxygen balance of the receiving watercourse,
permitting the aquatic life to survive,

9. V) Avoid health & aesthetic hazards while swimming & boating in
the water.
6) COLLECTION OF SEWAGE:- Sewage is conveyed through
pipes, known as sewers, from its place of production to its
place of treatment & disposal. There are three types of
sewage system. They are as under:
a) Sanitary sewers:- These sewers carry only domestic & industrial
sewage,
b) Storm sewers:- These are meant for dumping storm & surface
waters, &
c) Combined sewers:- These are designed to carry all the sewage
through a single system of sewers.
Large towns & cities may have a provision for a separate
storm sewerage systems, under which the high value
commercial buildings in the centre of the town are

10. Protected form floods by allowing the storm water
falling in this area, to enter the storm sewers.

11. 7) SEWAGE TREATMENT METHOD:-
There are many different method available for the
treatment of raw sewage. The selection of the method
requires many factors to be considered. All these factors are
peculiar to each situation. The under mentioned factors are
kept in mind at the time of selecting a method:
I) The quantity & nature of the raw sewage,
II) The cost of the plant & its operation,
III) Sanitary requirements by state health department &
IV)Circumstances regarding the natural body of water for final
disposal purposes.

12. SINGLE DWELLING UNITS:-
SEPTIC TANKS:- They are small, rectangular chamber. They are
usually sited just below ground level. Two purposes are served
by such tanks, namely sedimentation, as well as bio-
degradation of the sediment sludge. The raw sewage is
allowed to come into the tank, where the retention time is
from 1 to 3 days. The tank must be dislodged at regular
intervals, usually once in every 1-5 years. The effluent from
septic tanks requires further treatment before disposal.

13. MUNICIPAL SEWAGE TREATMENT METHOD:-
Municipal raw sewage passes through three major
steps before its disposal. The nature of treatment in each
step is a unique property of respective operations. The
different serial operations in modern municipal sewage.
A) PRIMARY TREATMENT:- Raw sewage contains two types of
solid material: coarse solid material & settle able solid
materials. Coarse solid materials are removed by a variety of
mechanical methods(e.g. screening, grit chamber, grinding
etc). Settle able solid material are removed by holding the
sewage in sedimentation units (e.g. tanks & basins) for an
appropriate time.

14. B) SECONDARY TREATMENT:- The liquid portion, effluent,
resulting from primary treatment operation still contains some
small amount of solids & soluble putrescible matter. In other
words, the effluent is highly unstable &, therefore, cannot be
dumped into a natural body of water without stabilization.
UNSTABLE MATTER STABILIZED MATTER
There are different methods employed in the secondary
treatment. They are:
1. BIOFILTRATION : a) INTERMITTENT SAND FILTERS
b) TRICKLING FILTERS &
c) CONTACT FILTERS

15. 2. AERATION BY THE ACTIVATED SLUDGE PROCESS
3. LAGOONS.
TRICKLING FILTERS:- The trickling filter has been designed on the
basis of experiments carried out at the Lawrence Experiment
station in 1894. It consists of a bed of coarse pieces of stone,
gravel & slag or related material. The depth of the bed is 1 to 3
inches. This leaves a great many open spaces in the bed for
the penetration of air. The tank is equipped with drains
underneath. These filters have been described as a pile of
rocks over which sewage or organic wastes slowly trickle.
Settled sewage + oxygen Oxidized effluent +
new bacteria cells

17. 2) ACTIVATED SLUDGE PROCESS:- This process was developed
in 1912 at the Lawrence experiment station. The process is
based on vigorous aeration of sewage. This practice of
vigorous aeration causes the finer partials to clump into flocks.
Such flocs are allowed to settle & then, added to fresh sewage
that is vigorously aerated. This result in more rapid
flocculation than, before & thus time is saved.
ADVANTAGES:-
I) This sewage treatment method requires a small land area.
II) Effluent resulting from an activated sludge unit has a low BOD,
& therefore, does not require high dilution for its disposal.
Also there is great reduction of suspended solids.

18. 3) Lagoons:- Lagoons are also known as oxidation ponds or
stabilization ponds. Lagoonization is now being practiced by a
large number of smaller communities in the Middle West. It is
without doubt, the most important method of sewage
treatment in hot climates where sufficient land is normally
available. The preliminary treatment to the sewage is given to
remove most of the solids. The sewage effluent resulting from
the preliminary treatment stage is dumped into a large pond
having a depth of 2 to 4 ft. Lagoonazation is a natural process
of sewage purification, because oxidation of putrescible
matter occurs though symbiotic action of algae & aerobic
bacteria present in the effluent.

20. C) FINAL TREATMENT:- The organic matter remaining after
sludge digestion is stabilized & is not easily decomposed
further. It is black & without any appreciable odors. Stabilized
sludge may be dried & sold as fertilizer, or it may be burned or
buried.
The effluent is chlorinated(5 to 10 ppm), & is generally
dumped into some water channel for final disposal.
Satisfactory chlorination can kill the bacteria more then 99%
of the original bacterial population.