530 / 2024-06-30 19:03:14

Preventing Contamination of Drinking Water Sources by In-situ Treatment of Sanitary and Kitchen Wastewater

septic tank,upflow anaerobic filters, constructed wetland,,sanitary wastewater

Subtheme 1: Water-related Hazard and Risk Reduction > Topic 5: Resilient City Against Water Hazard

Many people in Asia do not have reticulated safe drinking water or reticulated sewerage. To avoid the drinking water sources (shallow wells, open ponds, streams) getting contaminated, in-situ treatment of sanitary and domestic wastewater using traditional sanitary waste treatment designs of septic tank (ST) coupled with soak pit systems for ground disposal,  worked well in the last 150 years. Pathogens in primary treated effluent did not survive few days travel (required for 18m minimum distance from a drinking well) through clayey soil matrix. With increasing population density, the land plot sizes are reducing, and traditional treatment systems do not have enough soil volume to treat the ST effluent. One solution is treatment of septic tank effluent in a water sealed anaerobic biological filter (AF) as the secondary treatment unit, with tertiary treatment (and aesthetic acceptance) provided by downstream constructed wetlands, finally releasing treated effluent to soil or surface water. National standards specify treated wastewater quality for surface discharge. Effluent data obtained after 7 years of operation, for an eco-resort (with twenty guest rooms, population equivalent of 100) show pH and temperature within acceptable range. Effluent values of TSS, BOD, COD, N, P and Oil & grease are 24%, 28%, 6%, 1%, 58% and 1% of maximum allowed limit respectively. Reducing the water inputs from ablution and flushing, minimized the size of treatment units. The use of gravity flow helps to reduce the Operation and Maintenance costs, while also helping to reduce the carbon footprint of waste treatment.