plant check up is very important in respect of immersion depth of areator blades as excess immersion would cause increased load on the equipment which may lead to damage of gear and motor. Increased immersion after installation of areator would coour due to excess hydraulic laod to the areation tank. Hence it is a must ensure to allow the effluent equivalent to the designed flow rate.
The initial start up of the system is intended to develop the required solids (called as MLSS) to ixidise the putreasable organic matter present in the effluent. To develop the active biomass the areation tank is initially filled up with the waste by pumping for 4-6 hours and the feeding is stopped and the aerators are switched on to wotk for 4 hours to allow the formation of flocculated growth of biomass in areation tank. After areation of 4 hours the aerators are switched off and areator liquid in the areation tank is allowed to remain undisturbed for a period of 2 to 3 hours, to enable the newly formed flocs of biomass to settle at the bottom of the areation tank. Having ensured a quisent settling for the specified duration the liquid level in the areation tank is lowered down to depth that will be sufficient to be filled back by 4-8 hours fresh effluent.
Therafter the areation tank is fitted with the fresh neutralised effluent by switching on the raw effluent pumps and the conten by areation tank are aerated and the mixer liquor allowed to settle.
The process is repeated till a healthy biomass is developed. It will take 20-30 days for development of healthy biomass. Thus once the system is astablished with development of biomass, the plant can be put for reqular operation.
Undeer regular operation the plant units are subjected to continuous operation as described below.
The effluent to the treatment plant after passing through the screen is allowed into sump. the effluent is pumped from the sump to areation tanks wher the organic matters is aerobically oxidised. The aerated effluent is taken to a settling tank wher the biomass is seprated out in the form of settled sludge and is returned back to the aeration tanks by means of return sludge pumps. the under regular operation the areators and return sludge pumps willbe made to work continously irrespective of the raw waste flow into the treatment system. The supernatent resulting from the settling tank shall be discharged. however, the excess sludge from the system is required to be wasted. This shall be taken to the sludge drying beds.
Continous retur od settled sludge from the settling tank to the aeration tank leads to the build up mixed liquor volatile suspended solids (MLVSS) in the system in excess of its retention level and further leads to the purging of the excess suspended solids in the treated effluent thus deteriorating the quality of treated effluent in respect of suspended solids concentration and BOD. It would therfore be necessary to bleed off waste the excess sludge from the system. The excess sludge is taken to the sludge drying beds through the branch line provided on the return sludge line to aeration tank.
As stated earlier, the volatice suspended solids in excess of the desired maximum level of 4000 mg/lit.in the mixed liquor of areation tank wasted in the form of excess sludge from the return sludge.