New Performance-Based Passive Septic Tank Underground Drainfield for Nutrient and Pathogen Removal Using Sorption Media

摘要

Removal of nutrients and pathogens in wastewater effluents is very important for the sustainability of thenaquatic ecosystem and environment. On-site sewage treatment and disposal systems commonly referred asnseptic systems are one of the major sources of nutrients and pathogens in groundwater systems. Drainfieldsnin septic tank systems are normally located in permeable, unsaturated natural soil or imported fill materialnso that wastewater can infiltrate and percolate through the underlying soil to the groundwater for finalndisposal. In the past, removal of nutrients in these conventional drainfields was too low to meet the waternquality requirements. This article presents a new passive underground drainfield of innovative design withnsoil amendments (sorption media) for nutrient and pathogen removal in a field-scaled septic tank system.nThis new system, which is filled with green sorption media consisting of recycled materials mixed withnnaturally occurring materials, was fully tested in both Phases I and II periods in late 2008 and early 2009,nrespectively. The new drainfield system with soil amendments was designed to furnish aerobic and anoxicnenvironments, which were fully demonstrated to support final nitrification and denitrification in our pilotnstudy. In this embodiment, the green sorption material mixture includes *68% fine sand, *25% tire crumbs,nand *7% sawdust by volume. Overall, >70.21% and 81.79% of total nitrogen and total phosphorus werenremoved, respectively. Removal efficiency of 5-day carbonaceous biochemical oxygen demand and ammonianwas also >80%. Removal efficiency of Escherichia coli was 99.93%. Such a new biofiltration systemnmay be integrated with any type of on-site sewage treatment and disposal systems to effectively removennutrients and pathogens. The technology will make a significant contribution to the development of sustainablenrural areas.