HIGH-PERFORMANCE AND N-REMOVABLE AND P-REMOVABLE ON-SITE DOMESTIC WASTE-WATER TREATMENT SYSTEM BY MULTI-SOIL-LAYERING METHOD

Multi-Soil-Layering (MSL) method was applied to make appropriate, but high performance and N & P-removable, on-site domestic waste water treatment system. The MSL soil unit is composed from soil layer mixed with 10-25% of metal iron and pelletized jute. The MSL units were piled in a brick pattern at 5cm vertical and 10cm horizontal distance, which were surrounded by layers of Zeolite. Air can be supplied through porous pipes installed at adequate depths of the MSL system. The systems were tested using model houses. The waste waters, which were pretreated by septic tank to the level of SS 29-75, BOD 42-116, COD 32-56, T-N 29-86, and T-P 6-11 mg.l-1 respectively, could be treated at the rate of 100-850 1.m-2.d-1 without significant clogging. The mean concentrations of treated waters were SS 15, BOD 8.7, COD 11, T-N 6.8, and T-P 0.86 mg.l-1 respectively. Zeolite layers and brick pattern prevent clogging. Metal iron and jute pellets were effective to remove Phosphate and Nitrate. Intensive aeration assists decomposition of BOD, COD, and SS as well as nitrification, but decreases denitrification and phosphate fixation. The degree of purification could be controlled by setting adequate aeration.