ABSTRACT
INTRODUCTION The municipal sewage-the runoff from the houses (domestic sewage) and that of factories and roads being the major source of organic material, a point source of pollution-is discharged directly into different lotic and lentic ecosystems in many developing countries. This malpractice is the unavailability of proper sewage treatment facilities and/or inadequately maintained treatment facilities and sewage systems in most cases, which cause major environmental problems, particularly cultural eutrophication, emanating a foul odour, and leading to the occurrence and spread of various waterborne diseases (Mason, 1961; Reddy & Vijaykumar, 2004). In the Indian subcontinent, there are several cases of discharge of the municipal sewage from different towns and cities into various water bodies like the Ganges, Yamuna and Gomati, Godavari rivers, and the Dal Lake in Kashmir, upper and lower lakes in Bhopal, Powai Lake in Mumbai, Husainsagar Lake in Hyderabad, Ooty Lake in Udhagamandalam, and Pallikarani marsh in Chennai, which grossly pollute these aquatic bodies, in the process, perturbing their water quality characteristics, causing algal blooms, severely depleting the dissolved oxygen, increasing the Biochemical Oxygen Demand (BOD) and rendering the water unfit for any use. Therefore, these water bodies need to be depolluted or prevented from further pollution by stopping the direct inflow of the sewage, which will help in the restoration of these polluted ecosystems. It has been reported that construction of a sewage treatment plant (STP) reduced such nutrient loading of Lake Suwa in Japan (Okino and Kato, 1987; Okino, 1990). Some of the water bodies in Europe were restored to their non-polluted states by diverting and preventing the inflow of allochthonous organic matter, as was the case in Lake Vesijari in Finland (Horppila and Kairesed, 1992). Meeder et al., (1997) reported containment (physical barriers) to prevent exposure of creatures living at ground level to the underlying hazardous waste, and can also be achieved using vertical or horizontal in-ground barriers to prevent the horizontal migration of the contaminants. However, in developing countries like India, very few attempts have been made to prevent the direct inflow of allochthonous organic matter into the aquatic bodies and enough information is not available on such aspects, and on the success stories of their restoration. The present chapter reports a long-term monitoring study on the effects of prevention of direct inflow of municipal raw sewage in ameliorating some of the water quality characteristics of the surfacewater, by constructing a physical barrier in the form of the necklace road on the west side of the eutrophic Husainsagar Lake located in the centre of the twin cities of Hyderabad and Secunderabad, the state capital of Andhra Pradesh (India).
