Study on water purification ability and permeability of different filter materials in LID-type ditch

Abstract

In rural areas of China, sewage is often discharged to ditch directly without any treatment. We propose a new type of ditch based on Low Impact Development (LID) strategy by replacing bed soil in rural ditch with mixed filter material of approximately 30cm in thickness. This new type of ditch is so-called LID-type ditch having the function of storage, penetration, purification and drainage. Four basic materials, red loam, sand, gravel and zeolite, are used to create 3 types of mixed filter materials by evenly mixing these basic materials with different mass ratios. Their saturated permeability coefficients and water purification ability are measured and compared. Results indicate that all 3 types of mixed filter materials are suitable to apply to LID-type ditch, and the all outflows meet the water quality standard for farmland irrigation. The best mixed filter material is type 1 with 50% of red loam, 30% of sand, 10% of gravel, and 10% of zeolite, it has removal rate for TP as high as 81.31% and average removal rate of 47.09% for TP, TN, NH3-N, COD, BOD5.