The Potential for Ground Water Contamination from Septic Effluents

Large populations in both rural and urban areas rely on septic tank soil-absorption treatment systems as the principal disposer of domestic waste materials. Potential ground water pollutants, including pathogens, are removed from percolating drainfield effluents by microbial activity, soil filtration, and adsorption, preventing their entry into ground water. There is accumulating evidence, however, that water supplies in many areas of the United States are receiving increased pollution loads, and the source has frequently been traced to contaminated recharge waters. This paper reviews literature on both the conditions present where conventional disposal systems malfunction, and the mechanisms by which incompletely treated septic wastes may come into contact with various water resources. Current information regarding the function of a drainfield system and an examination of data from recent microbiological investigations on conditions necessary for the removal of enteric organisms from effluent waters is also included. Research needs are addressed with emphasis on problem areas which need further investigation in order to develop safe guidelines for determining the suitability of septic tank systems in relation to regional soil-water conditions.