H.M. The King's Royally Initiated LERD Project on Community Wastewater Treatment through Small Wetlands and Oxidation Pond in Phetchaburi, Thailand

The research on community wastewater treatment through small aquatic-planting and grass-filtration constructed wetland in cooperating with oxidation ponds is aimed to establish demonstration models for eliminating organic contaminants under nature-by-nature process, simple technology and less expenses. There have been 7 small wetlands on 100-m x 5-m x 0.75-m small vertical flow construction wetlands (VFCW), 7 small wetlands on 25-m x 5-m x 0.75-m small VFCW in cooperating with zero discharge, 2 experimental plots of planted mangrove forest and 5-consecutive oxidation ponds plus 3 herbivore fishes per square meter. For research operation, some municipal wastewater were pumped about 0.025-cms flow rate from Phetchaburi collected pond through 18.5-km HPDE pipe with separating receivers: firstly, to small grass and aquatic planted wetlands; secondly, to small constructed wetlands; thirdly, to the planted mangrove forest; and finally to the 5-consecutive ponds in descending order of 20 cm by beginning the depth of 2.6 m at the first pond (sedimentation pond) till 1.8 m at the last pond, In basic principles, an influent has to flow continuously at height of one-third depth below surface of oxidation pond on hydraulic retention time (HRT), then flowing over weir crest about 5 cm. The effluent of each oxidation pond was monthly sampled for analyzing the water quality in order to estimate the efficiency of wastewater treatment. In the same procedures, the effluent from small wetlands as grown by aquatic plants as well as zero discharge had to collect for water quality analysis. The results found the wastewater treatment efficiency above 60 percentages for COD, BOD, and TSS. The usable life of plants for maximum wastewater treatment efficiency were specified at 90 days and 45 days for aquatic plants (Typha angustifolia Linn. and Cyperus corymbosus Rottb.), respectively. It was noticed that small wetland and oxidation pond were suitable for community wastewater treatment and gained benefits from the wastewater treatment system.