The wastewater generated from various sections is to be segregated into two streams. (Sullage – wastewater from kitchens, wash waters from bathrooms etc. and Sewage – the wastewater from toilets) and treated.
The sullage would be let through bar screen chamber, grit-settling tank/oil and grease trap, and Sullage collection tank. From the sullage collection tank it is regulated and pumped to the chemical precipitation tank where coagulants are dosed using automatic dosing pumps. The overflow goes to the sullage settling tank and chlorination/filter feed tank where chlorination is done. From here it is pumped to pressure sand filter and pressure carbon filter for final polishing. The sludge from the settling tank is pumped periodically to the sludge tank. The non- biodegradable bar screenings like plastics, cloth pieces, rubbers etc to be removed and disposed to the solid waste disposal system. For Chlorination and Pressure Filtration same tank and same pressure filters are used for both sullage and sewage.
ANAEROBIC FOLLOWED BY AEROBIC ACTIVATED SLUDGE PROCESS
The sewage would be let through the bar screen chamber to the collection tank. The non- biodegradable bar screenings like plastics, cloth pieces, rubbers etc to be removed and disposed to the solid waste disposal system.
COLLECTION / PRIMARY SETTLING TANK
From the Collection/Primary settling tank the wastewater is pumped at the required regulated flow to the Anaerobic Tank
The anaerobic tank contains the high surface area fixed fill media, which is stationary and anaerobic reduction of organic matter takes place here. This ensures development of high anaerobic microbial bio-growth and the anaerobic microbial biomass reduces the initial organic load in sewage (From B.O.D 350 mg/l to 210 mg/l)
The overflow from the anaerobic tank overflows to the Diffused Aeration tank where the aerobic bacterial growth is allowed to grow in suspension and the process employed is Activated sludge process. The aerobic bacteria attain a high growth rate utilizing the oxygen supplied by the diffused aeration system and reduces the organic matter. Diffused aeration system comprises of diffusers, which are installed at the bottom of the aeration tank. Air from the blower at the desired rate and having the required pressure will be diffused through the diffusers. The diffuser is designed to ensure uniform permeability and to produce a flow of fine air bubbles. The diffusers used are the non-clog variety, which also ensures high oxygen transfer efficiency and very effective treatment of sewage. Re-circulation of bio-sludge from the settling tank is done to maintain MLSS of 3000-3500 mg/l in the Aeration Tank. Here aerobic Activated sludge process takes place resulting in high reduction of organic load. (From B.O.D 210 mg/l to 15 mg/l)
HOPPER BOTTOM SETTLING TANK
From the Aeration tank the water flows to the Hopper Bottom Settling tank, where the activated bio-sludge and the peeled off biomass is settled by sedimentation. Here the Settling tank is Hopper-bottom type, which helps in effective settling of suspended and fine solid particles. The activated sludge is re-circulated to the aeration tank. The overflow from the Hopper Bottom Settling tank is let to the Chlorination/Treated water tank.
CHLORINATION / DISINFECTION AND PRESSURE FILTERATION
The water after sedimentation is let to the Chlorination/Filter Feed tank and disinfected using Sodium Hypochlorite solution (5% solution at the rate of 3 ppm) by a dosing pump in the Chlorination/ Filter feed tank and pressure filtered through pressure sand filter and pressure carbon filter for final polishing and further reduction in B.O.D to 3 mg/l and S.S to 20 mg/l. The backwash of Pressure filters is let to the sludge tank. The treated water is let to the treated water tank and the final treated water can be used for irrigation, toilet flushing, and firefighting purposes and excess water to soak pit.
Sewage contains very small amount of solids in relation to the huge quantity of water (99.9%). The remaining solid matters (0.1%) become sludge. We have designed the two sludge tanks to collect and store the sludge for both sewage and sullage. This Sludge is pumped to the bio-gas plant by means of pump.
ADVANTAGES – ANAEROBIC FOLLOWED BY AEROBIC SYSTEM FOR SEWAGE
- Process is Eco-friendly, only natural growth of microorganisms and air essential.
- The treatment is ensured by the natural growth of microbes to feed on the effluent.
- Consistent high quality of treated water
- Simple operation and less maintenance required as there is no submerged moving parts within the aeration tank.
- An automatic electrical control panel is provided.
- Compact Design.
- Neat and clean environment around the plant.
- Tanks can be kept underground and the area above utilized for other purposes.