Indirect Reuse of Wastewater for Drinking by Restoring a Lake, (Including Mitigation of Methane in Anaerobic Treatment) which was Fed with Untreated Wastewater Using Combination of UASB Reactor and Natural Purification Systems with Mitigation of Green

摘要

Madivala Lake is one of the biggest lakes in south of Bangalore with a plan area of 116 acres. This lake was fed with untreated water to an extent of 14 MLD. The lake is restored now. The wastewater entry to the lake before restoration work was measured and found to be average of 14 MLD and overflow of the lake water on the waste weirs were measured and recorded as 6 MLD during non rainy days. The difference 8 MLD was due to seepage and evapo-transpiration. The evapo-transpiration loss estimated at 2 MLD and rest 4 MLD is estimated to seepage into ground water drawn by bore wells surrounding the lake. The lake was restored by setting up a recycling plant to supply the water to the lake with less than 5 mg/lit BOD and SS & with least ' Operation and maintenance' costs. The lake is surrounded by dense population with out any water net work and mainly dependent on the ground water fed by this lake. The influent BOD of 400 mg/L of wastewater entering the recycling plant is reduced to < 5 mg/lit BOD. Care has been taken to consider phosphorus reduction for avoiding eutrification in the designs. The lake has regained the flora and fauna also attracting migratory birds round the globe. This restoration work can be a role model for many lakes in the country fed with untreated wastewater. The paper highlight the concepts considered in design, the method of execution and performance of the recycling plant with economics. The methane gas produced in the UASB reactor could be mitigated also for generating the power as an additional advantage.