A Study on the Use of Constructed Wetlands for Treatment of Municipal Wastewater During Summer and Rainy Seasons in a Semi Arid City in India

Abstract

The concept of using constructed wetland for treating municipal wastewater and stormwater has been gaining importance, especially in the past decade. These treatment wetland systems are engineered and managed ecological systems that use biological, physical and chemical processes for purifying the wastewater. Successful performance of constructed wetlands depends on ecological functions of the wetland vegetation that are based largely on interactions within plant communities. However, the processes by which plant populations enhance treatment performance are yet to be determined fully. In the present study, a pilot treatment wetland of the type free water surface flow (FWS) has been designed and constructed. This free surface flow artificial wetland is sand soil based, 21.5 m long, 5.5m wide and 1.8m deep with a water depth of 0.3, and has been constructed to treat the municipal wastewater. The average flow diverted to the treatment wetland is 5 m3 per day, with a detention period of 7 days. The objective of the study is to identify the design parameters and efficiency of treatment by diverting a part of the combined sewage from an open drain flowing through the historical city of Warangal, India. In addition the study also has the following objectives: To study the use of wetlands i) to improve the water quality ii) to study the processes involved in the purification of wastewater by wetland, and iii) to identify appropriate design criteria and suitable plant species. The treatment plant, with the locally available emergent macrophyte as the wetland vegetation (Typha Latifolia), is taken up for the study. The studies were conducted during the period April to December 2001, which included a summer and a rainy season. The daily temperature during this period varied from about 20 degrees C to about 43 degrees C. The work is continuing for the remaining season