3/13/2021 0 Comments 1970 Septic Tank Cement Design
Settling and anaerobic processes reduce solids and organics, but the treatment efficiency is only moderate (referred to as primary treatment).Septic tank systems are a type of simple onsite sewage facility (OSSF).
They can be used in areas that are not connected to a sewerage system, such as rural areas. ![]() However, groundwater pollution may occur and can be a problem. ![]() Therefore, the accumulated fecal sludge must be periodically removed which is commonly done with a vacuum truck. The liquid capacity of tank is taken as 130 liters to 70 liters per head. A septic tank is usually provided with brick wall in which cement mortar not less than 20 cm (9 inch) thick and the foundation floor is of cement concrete 1:2:4. Both inside and outside faces of the wall and top of the floor are plastered with minimum thickness of 12 mm (one-half inch) thick cement mortar 1:3 mix. Water proofing agent such as Impermo, Cem-seal or Accoproof etc. Water proofing agent is to be added in similar proportion in to the concrete also for making floor of the tank. For proper convenience in collection and removal of the sludge, the floor of septic tank is given a slope of 1:10 to 1:20 towards the inlet side. Which means that floor of the outlet side will be on the higher elevation than the floor at inlet side. The rate of flow of effluent must be equal to the rate of flow of influent. For outlet pipe an elbow or T type of 100 mm diameter pipe is submerged to a depth of 200-500 mm below the liquid level. The baffle wall is generally extended 150 mm above to scum level and 400-700 mm below it. Scum being light, generally floats at the water level in the tank. Circular manholes of 500 mm clear diameter are provided for inspection and desludging. In case of rectangular opening clear size is kept as 600 X 450 mm. Top of the ventilation pipe is provided with a mosquito proof wire mess or cowl. Fig: Sectional plan ZZ shoes the typical layout of the septic tank.
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