A Cost Effective Environmentally Friendly Treatment of Municipal Wastewater Using ConstructedWetlands for Developing Countries

摘要

It is irony that the large amounts of money are spent in the construction of reservoirs and distribution systems to supply drinking water to cities and almost an equally large amount of money is needed to convey, treat and dispose of the used water, which many developing countries are not in a position to afford. In developing countries, use of conventional wastewater treatment systems, which involve construction of large treatment facilities, skilled supervision, power and maintenance, have become uneconomical in the long run, since most of these systems many times do not perform effectively. Further, in most of the cities, the stormwater and wastewater are conveyed in large open channels. The use of constructed wetlands seems to be a viable, cost effective treatment system under such situations. A pilot study carried out in a real world environment, by diverting pre-settled combined municipal wastewater into a constructed wetland showed that such system could be adopted in developing countries.rn This paper summarizes the results of the pilot constructed wetland in Warangal city in the State of Andhra Pradesh in India. This wetland was monitored for 12 months to understand the removal efficiencies of various pollutants in the municipal wastewater during different seasons in a year. This paper examines the potential of constructed wetlands for secondary municipal wastewater treatment especially in removing pollutants like BOD, COD, TSS, and nutrients like nitrates and phosphates etc. Since sufficient data pertaining to various seasons of the year are available, mathematical models to predict the behaviour of the system also are developed. A k-C* model, suggested by Kadlec (1996) also has been fitted for various parameters taking account the monthly data. The study shows that the system performs well and could be adopted as a viable alternative, which would be low in cost and at the same time environmentally and ecologically friendly, in upcoming cities in developing countries where sufficient land is cheaply available. It is to be noted that the successful performance of the pilot plant has motivated the city municipal authorities in Warangal to go in for a decentralized treatment wetland system for treating municipal wastewater in different parts of the city. Wetlands are widely regarded as the best low cost alternative eco-technology for treatment of municipal, industrial and agricultural effluents. Although developed countries have been using this technology, the use of these systems in treating wastewater has not been very popular in most tropical/ semi arid countries like India. The study reported in the present paper is the result of an attempt to use this technology to demonstrate to the authorities in charge of municipalities in less developed countries that the use of treatment wetland could be one of the most viable alternatives for municipal wastewater and stormwater management