The Effects of Aeration Units on Water Quality in Upper Lake, Bhopal, India

Abstract

The freshwater bodies around the world are becoming polluted due to sewage, agricultural effluent, domestic and industrial waste. The water body selected for this study is Upper Lake of Bhopal, the state capital of Madhya Pradesh, India. The upper lake is one of the important sources of potable water supply for the Bhopal city. The lake receives a large amount of domestic wastes, sewage, agricultural and industrial effluents, hence it is grossly polluted. It has a floating fountain type of aeration unit, which is very useful in improving the lake's water quality by aerating the water at varying depths. The authors examined physicochemical parameters like pH, dissolved oxygen, biochemical oxygen demand, and chemical oxygen demand to ascertain the effectiveness of the aeration unit. Introduction Water resources in India have reached a point of crisis due to unplanned urbanization and industrialization (Singh, Pathak, & Singh, 2002). Urban water bodies receiving external pressure from human settlements adversely affect nearby aquatic ecosystems. Urbanization has direct negative impacts on water bodies (Khan, Bhatnagar, & Saxena, 1988). To study the effectiveness of artificial aeration units, the water body selected for the study is Upper Lake of Bhopal city. Upper Lake that possesses floating fountains has been chosen as sampling stations. The Upper Lake of Bhopal is a small man-made reservoir as per the definition and classification by Welch (1948). The quality of water in Lower Lake has deteriorated to a greater extent than that in the Upper Lake (Pani & Mishra, 2000). Organic enrichment of the lake through floral offerings, idol immersion, and decomposition of aquatic weeds are also the significant causes of its eutrophication. The aeration units had been installed under Bhoj Wetland Project. An artificial aeration unit is an effective supporting device for supplement of oxygen (Rusan, 1971). Floating fountains are mechanical devices to facilitate pumping of the lower level anoxic/low oxygenated water to expose them to the atmosphere. These devices, apart from beautification, are effective in improvement of water quality of the lake by oxygenating it through aeration. Experimental Work The study area selected was Upper Lake located in the Bhopal city, the state capital of Madhya Pradesh, India (latitude 23 0 12'-23 0 16'N and longitude 77 0 18'-77 0 23'E). The Upper Lake has an area of 31 km 2 and a catchment area of 361 km 2. The Upper Lake has a partial urban component in its catchment on the eastern end while the remainder is rural. The topography of the lake indicates that the basin is natural, as northern and southern sides of the lake are hilly while the western end has flat contours and forms the agricultural land. Sampling Two different sampling stations with floating fountain aeration units were selected. Water samples were collected from both stations at different distances (i.e. 0m, 10m, 20m) and time intervals. Sampling was done six hours prior to the functioning of the units, then during the functioning, and finally six hours after the functioning of the units. The water samples were collected in sterile glass bottles such that their necks were below the water surface so as to avoid the inclusion of atmospheric oxygen. Sampling and physicochemical investigation was carried out according to standard methods (American Public Health Association, 1985). pH: T he pH of the samples was determined using digital pH meter. Dissolved oxygen: Dissolved oxygen was fixed instantly on the spot and analyzed immediately as per the Wrinkler's method with Azide modification (De, 2002). Biochemical oxygen demand (BOD) : BOD was determined as per standard method (De,2002). Chemical oxygen demand (COD): COD was determined by potassium dichromate open reflux method. Results and Discussion pH: pH ranged from 7.2-7. …