WRRCTR No.131 Leachate Quality from Lysimeters Treating Domestic Sewage

Abstract

A study was undertaken to determine the treatability of raw domestic wastes using waste water treatment lysimeters. A pilot treatment unit was constructed that included four waste water treatment lysimeters, each utilizing a different Hawaiian soil. The soils included two silty clays of the Wahiawa and Lahaina series, a silty loam of the Tantalus series, and a beach sand of the Jaucas series. The use of graded rocks or gravel was incorporated in all of the soil series with the exception of the Wahiawa series. The Wahiawa and Lahaina soil lysimeters employed a top surface application scheme while the Tantalus and Jaucas lysimeters utilized a lateral flow scheme. Two residential cottages served as the domestic waste water source and produced flows ranging from 3.15 to 5.04 X 10^6 m^3/s (72-115 gpd). In general, the Tantalus and Jaucas series attained relatively higher removal efficiencies than the Wahiawa and Lahaina series. However, in all of the soil series, only moderate constituent removals were observed particularly for dissolved solids, organics, ammonia nitrogen, and bacteria. The only constituents which showed high removals were suspended solids and phosphorus. The primary factor for the low overall removals was probably overloading of the lysimeters inasmuch as both the hydraulic and constituent loadings (especially organics, solids, nitrogen, and bacteria) proved to be excessive. Soil clogging was also evident to some extent in all of the soil series.