INTRODUCTION

Bangalore has been experiencing rapid urbanisation evident from the concentrated growth of core region and sprawl at outskirts. Temporal land use analyses show 584% growth in built-up area during the last four decades with the decline of vegetation by 66% and water bodies by 74% [1]. Analyses of the temporal data reveals an increase in urban built up area of 342.83% (during 1973 to 1992), 129.56% (during 1992 to 1999), 106.7% (1999 to 2002), 114.51% (2002 to 2006) and 126.19% from 2006 to 2010.

The city is located on a ridge and the natural water courses along the three directions are Vrishabhavathi, Koramangala-Challaghatta (K&C) and Hebbal-Nagavara valley systems. These water courses are today being used for the transport and disposal of the city’s sewage. Most of the sewage and wastewater generated is discharged directly into these storm water drains that ultimately link to water bodies. The shortfall or lack of sewage treatment facilities has contaminated the majority of water bodies [2].

The city generates around 3000-4000 t/d of USW and organic component constituent >70% [3,4,5]. The existing solid waste treatment system in the city is not very effective resulting in large scale disposal of biodegradable organic waste at open dump sites. Waste generated in the city has increased significantly and most wastes are being openly dumped at about 60 known dumping sites and many unrecorded sites [4,6]. Open dumping has become a common practice of waste disposal. It generally occurs near accessible public and private open land, fallow agricultural land, road sides, at the foot of hilly regions and near water bodies or open sewer channels [7,8]. It mainly consists of household waste and in some cases construction debris.

Biodegradation of organic wastes in open dumps through the breaking down of simple compounds by aerobic and anaerobic microorganisms releases gas and leachate. The leachate accumulates at the bottom of the dumpsite and starts percolating through soil as rain water infiltrates through the piled waste.  Leachate generated from these open dumps consists of inorganic ions, organic constituents apart from trace metals, etc. Generated leachate quantum and characteristics is dependent on the age and composition of waste and quantum of rain [9]. Thus, improper management of solid waste is a serious environmental concern as it contaminates groundwater, surface water and soil.

Household waste with both inorganic and organic constituents is heterogeneous in nature and requires longer degradation time leading to a longer period of contact of leachate with soil or water bodies. The sustained dumping of wastes without any treatment, leads to the contamination of groundwater resources [10,11]. The impact of leachate generated from solid waste has been studied in recent years [12,13,14,15,16,17,18]. Solid wastes are also dumped near or into the water channels or drainage channels which causes clogging of drains due to non-degradable inorganic wastes. Lack of appropriate treatment facilities for treating wastes (solid and liquid) has contaminated surface water resources. This is evident from higher instances of disease vectors and occurrence of water borne diseases, profuse growth of invasive water weeds, which necessitates regular monitoring of water quality for public health and environment.

The present communication assesses the implication of mismanagement of organic fractions of waste (solid and liquid) on the other natural resources. The study involves spatial analyses of water quality in and around i) water bodies receiving untreated or partially treated sewage and ii) in the region proximate to unauthorized dumps of solid waste.