Constructed wetlands for effluent polishing of lagoons

Lagoon systems generally represent an effective wastewater treatment process for small communities in rural regions. However, sensitive receiving waters promote an increasing need for algal removal and effluent polishing; The study's main objective was to delineate a reed bed process feasible for upgrading lagoon systems; Results are given for two types of small constructed wetlands which have been investigated over a period of several years: The stress is upon the seasonal differences and the effect of dry or wet weather operation. Design, construction and maintenance of the wetlands are described. The reed beds produced high effluent qualities in terms of suspended solids, algae, COD and hygienic aspects. During summer about 50% of influent concentration of chlorophyll and about 60% of suspended matter could be filtered by a subsurface flown constructed wetland. Furthermore, a buffering of pH value and temperature could be observed after the passage of the wetlands. (C) 1998 Elsevier Science Ltd. All rights reserved.