Improvements in Soil Absorption Trench Design

Improperly functioning soil absorption systems are often cited as sources of groundwater contamination. Clogging of the infiltration surfaces and uneven distribution of wastewater along the length of the trench are believed to be a primary reason for poor treatment. A new soil absorption system design, the capillary seepage trench (CST), is similar to conventional systems except that an impermeable liner is placed at the bottom of the trench. The liner prevents direct percolation and causes the wastewater to move upwardly and horizontally by capillary action before percolating downwards. Preliminary experiments comparing the CST to conventional soil absorption system designs were conducted. Removal of organic matter in the CST was found to be significantly better than in the conventional system. Possible reasons for superior treatment of the CST compared with the conventional system include: increased residence time in the aerobic soil zone and a more even distribution of wastewater along the trench.