Urban Water Body Restoration in Semiarid Areas Using Treated Sewage: Challenges and Emerging Trends

Alterations in the water quality of various lakes due to human interventions over the past three decades have been well documented in Bangalore and various management efforts have been initiated to bring these water bodies to their former pristine condition. However, most of restoration techniques undertook was short-sighted and long-term perspectives were inadequate. Today, out of 262 major lakes of Bangalore, only 34 are in good condition. This is mostly due to hydromorphological changes in drainage basins and catchment area, obstruction in interlinking of water bodies, and unregulated sewage and effluent entry. Several restoration models have been tried in different lakes (Ulsoor, Hebbal, and Jakkur Lakes in Bangalore) yet problems of malodor, algal bloom, weed infestations, lake bed drying, and fish kill have recurred. After assessing shortcomings of each model, a novel restoration process is proposed for Puttenhalli Lake, North Bangalore where dry weather inflow will be raw sewage. Here along with conventional physical modifications to suit a bird preserver, a passive treatment system within the lake is proposed, which will assimilate and stabilize the nutrients in sewage water and maintain the adequate water level by compensating for evaporation and seepage losses while keeping water quality clean.