301 / 2024-02-29 11:22:28

Preventing contamination of drinking water sources by in-situ treatment of sanitary and kitchen wastewater.

drinking water and sanitation services,rural drinking water safety,sanitary waste,small carbon footprint

Many people in South 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 becomes important. Traditional sanitary waste treatment designs of septic tank (ST) coupled with soak pit systems for ground disposal,  worked well in the last 150 years, where primary treated sanitary wastewater was released to soil via soak pits. Pathogens in primary treated effluent did not survive few days travel (required for 18m minimum distance from a drinking well) through clayey soil matrix. Now 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. Also, many new houses are now constructed in marginal lands having high groundwater table and/ or low soil cover, limiting soil absorption of partially treated sanitary wastewater.



One solution is treatment of septic tank effluent in a water sealed anaerobic biological filter (AF) as the secondary treatment unit, and then release secondary treated effluent to soil or surface water. National standards were provided (and enforced) during last three decades, specifying treated wastewater quality required for surface discharge. This paper presents performance data of coupled ST & AF units, operated as a proven (legally and environmentally acceptable) technology. Application status of a medium scale system designed by one author, to treat both sanitary and kitchen wastewater in an international award winning eco-resort (with twenty guest rooms, population equivalent of 100) is discussed. Also the tertiary treatment (and aesthetic acceptance) provided by downstream constructed wetlands is presented.



The effluent data obtained after 3 years of operation show pH values within acceptable range. Effluent values of TSS, BOD, COD and oil & grease with 64%, 87%, 54% and 10% of limit respectively, are all well within acceptance limits, showing the efficacy of this mature treatment train.



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.



Why education of stakeholders is important is also discussed.



While this paper is targeted to South Asia (tropical climate), experience discussed will be useful for many countries in the developing world and rural areas of developed countries.