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1.
Hydrogen Ion Concentration (pH) :
The Hydrogen Ion Concentration (pH) is valuable parameter in the
operation of biological units. The pH of fresh domestic sewage is
slightly more than that of the water supplied to the community.
However, the on setting up of the septic conditions the pH get reduced
to some extent. The pH of all the samples vary between 6.96 to 7.7
and is within permissible limit.
2.
Chemical Oxygen Demand (COD) : The
chemical Oxygen demand (COD) test gives a measure of oxygen required
for chemical oxidation. This test does not differentiate between
biological oxidisable and non-oxidisable material. However, the
ratio of the COD to BOD does not change significantly for a particular
waste and hence this test could be used conveniently for interpreting
performance efficiencies of the treatment units. In the situations
where the presence of tank materials is likely to interfere with
the BOD, this test is very useful. On comparison of results of 7
tests conducted it can be noted that COD of sewage Treatment Plants
is 100 mg/lit and that of conventional Septic tanks is 360 mg/lit
while that in EverClean Shankar Septic Tank varies between 208 to
230 mg/lit. This shows the system reduces COD to 57.8% to 63.9%
of the conventional septic tank. Though the value is more than two
times to the value of sewerage treatment plant but it will come
down when waste water from the house will be mixed to the effluent
(say one sixth i.e. 35 to 40 mg/lit.).
3.
Biochemical Oxygen Demand (BOD) :
The Biochemical Oxygen Demand (BOD) of sewage or of polluted water
is the amount of oxygen required for the biological decomposition
of biodegradable organic matter under aerobic conditions. The oxygen
consumed in the process is related to the amount of decomposable
organic matter. Greater reliance is placed on BOD test when
putrefaction
of the sewage is to be determined. The tests were conducted on all
the 7 samples collected from different sources. It can be seen from
the above test results that the BOD in the effluent of conventional
septic tank is 262 mg/lit while that in case of EverClean Shankar
Septic Tank varies from 112 to 136 mg/lit i.e. 42.75% to 51.01%
(say half) of the conventional septic tank. When compared with the
sample from University of Roorkee drain 82.2 mg/lit. and Sewage
Treatment Plants (BOD 62.20 mg/lit.) the BOD of EverClean Shankar
Septic Tank is about one and a half to two times. The effluent in
their cases is diluted by the waste water coming from bathroom,
kitchen and other washing activities, which will also reduce the
BOD of the effluent of Septic Tank latrine when added. In the case
of EverClean Shankar Septic Tank the waste water from bathroom etc.
when added and mixed in the effluent will reduce the BOD to one
sixth. i.e. 19 to 23 mg/lit. This waste water will also be carrying
its own BOD which may slightly raise the above value and bring it
almost at par with, if not less than, that of sewerage treatment
plant or less.
4.
Solids :
Though the municipal sewage contains only 0.1 percent solids, the
rest being water, still the nuisance caused by the solids cannot
be overlooked as they are highly putrefactionable and therefore need
proper disposal. The sewage solids may be classified into suspended
and dissolved fraction which may be further sub divided into volatile
and non-volatile solids. A knowledge of volatile or organic fraction
of solid which are putrefactionable becomes necessary as this constitute
the load on biological treatment unit or oxygen resources of a stream
when sewage is disposed off by dilution. The estimation of suspended
solids both organic and inorganic fraction is to be considered when
sewage is used for land irrigation or reuse of sewage is planned.
The tests conducted on seven samples shows the following relative
performance of these systems.
(A) Total Solids : The total solids
found in the effluent of conventional Septic Tank were 2922 mg/lit
while that in case of Sewage Treatment Plant were 665.7 mg/lit.
The total solids in case of four samples from EverClean Shankar
Septic Tank varied between 985 to 1110.6 mg/lit which are almost
at par to that of University of Roorkee open drains and Slightly
more than Sewage Treatment Plant. The reduction in total solid varies
between 33.7% to 38% of conventional septic tank. This percentage
will further be reduced substantially when the waste water will
be added.
(B) Suspended Solids : The suspended
solids in case of conventional septic tank are 587 mg/lit and only
61.4 mg/lit in case of sewerage treatment plant. They vary between
126 to 363 mg/lit in case of EverClean Shankar Septic Tank, thus
the reduction is 21.5% to 61.8% of the conventional septic tank
and is about two times of sewage treatment plant. The dilution of
effluent by waste water will further reduce.
(C) Volatile Solids : The volatile
solids present in the effluent of conventional septic tank were
found to be 105.4 mg/lit and in case of sewerage treatment plant
as 21.5 mg/lit. The figure varied from 29.5 to 72.10 mg/lit in case
of EverClean Shankar Septic Tank, This indicated that reduction
is up to 28% to 68% of conventional septic tank and one and a quarter
to three times of sewerage treatment plant. Further reduction will
take place when dilution will be affected by adding the waste water.
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