Swachh Bharat Clean Sanitation
FERROCEMENT SEPTIC TANKS:
The FERROBUILD SEPTIC TANK System is a submerged anaerobic system, suitable for both domestic and commercial applications. The system is relatively simple, using proven technology, to give superior results. Our Septic Tank systems have 3 treatment zones, generally in one tank. In each zone a different stage of the treatment occurs. Wastewater from the dwelling, toilets, sinks, shower etc, enters the system and the purification process begins.
Stage 1: Primary settlement chamber
Anaerobic breakdown takes place in the primary settlement chamber where the wastewater is introduced into the system. The large volume of this chamber reduces velocity of the wastewater. This along with the long flow path allow the wastewater maximum time in the first chamber resulting in a higher settlement rate. Settlement occurs when the heavier solids, drop out of the wastewater and settle to the bottom of the tank to create sludge or when lighter solids, like fats or
oils, float to the top of the water to create a scum. Up to 70% of the solids are removed in primary settlement zone. Anaerobic breakdown begins to occur and improve the water quality.
A baffling system holds the sludge and scum in the primary settlement zone and ensures against short circuiting to the second chamber. The large sludge storage volume increases the de-sludging intervals.
Stage 2: Secondary Settlement – Sludge Digestion chamber
Stage 2 takes place in second settlement chamber. This chamber is relatively very calm and this is where the actual sludge digestion takes place in an anaerobic environment. There is a scum layer at the top and liquid below it. As the liquid flows to the second chamber small quantities of bacteria may be carried with the liquid. Before discharge from the system, these solids must be separated from the liquid. With the velocity of the liquid once again slowed down and the flow path maximised the bacteria is encouraged to settle to the bottom of the tank, like sludge, through the up flow nature of the zone.
After digestion, liquor passes to the third chamber.
Stage 3: Final settlement- Filtration chamber
The liquor coming from the second chamber is allowed to undergo a filtration process. This filtration process is important to bring down the dangerous pathogens still present in the liquor.
The remaining treated liquid now meets the required standard to be safely passed out of the Septic Tank Unit. The effluent may be discharged into a drain or into a field/garden.
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 FERROBUILD 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. The value will further 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 BOD in the effluent of conventional septic tank is 262 mg/lit while that in case of FERROBUILD Septic Tank varies from 112 to 136 mg/lit i.e. 42.75% to 51.01% (say half) of the conventional septic tank. In the case of FERROBUILD 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 Solid: 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 samples from FERROBUILD Septic Tank varies between 985 to 1110.6 mg/lit.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 from bathroom, kitchen etc 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 FERROBUILD 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 FERROBUILD 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 from bathroom and kitchen.