INTRODUCTION

Unplanned rapid urbanisation in Bangalore has led to the increase in population resulting in the lack of basic amenities and adequate infrastructure. Quantum of wastewater generated has been estimated as ~40 billion litres each day (CPCB Report) and less than 30% undergoes partial treatment before being let into receiving waters. Most of the developing cities do not have an infrastructure for municipal water supply and sewerage. Bangalore possesses few functional wastewater treatment plants (WWTP’s), and some below the installed capacity. However sewage networks have severe shortcomings and are often inadequate to transfer sewage to these treatment units. This result in treatment of a small fraction of the total sewage generated. The major chunk of sewage bypasses these networks and flows across storm water drains and ultimately reaches the surface water bodies. The close proximity of the sewage flow paths to human settlements results in health and hygiene problems. Furthermore stagnation of sewage leaches contaminating ground water resources.
The wastewaters are rich in nutrients to grow oleaginous algae that can be used for producing biofuel as algal bio-diesel. 

Bangalore city has grown spatially 10 times (69 to 741 sq.kms) since independence. The present population density of Bangalore is ~8822 persons/sq. km. The wastewater generated in the city is about 1500 MLD (million litres per day). Partially treated or untreated sewage enters the lakes of the city enriching them with nutrients and resulting in obnoxious algal blooms. Bangalore receives water from river Cauvery, situated 90 km away further south of Bangalore. The state spends about 75 MW electricity every day to supply water to Bangalore. Drinking water in the city has become a serous concern. The suggestion of Cauvery management committee of providing 9000 Cusec water daily to Tamil Nadu from KR Sagara Dam, Mysore has added miseries and panic among local residents in Bangalore. Reuse of wastewater through suitable and efficient decentralised algal wastewater treatment options seems viable, cost effective and environment friendly option to meet the growing demand of water. Cultivation of algae in wastewaters and harvest regularly ensures proper resource utilisation and rejuvenate water bodies.

Bangalore has a dependable supply of sewage throughout the year. The large volume of sewage provides great potentials if proper treatment and water management issues are carried out optimally. The wastewater can be treated efficiently and economically, which reduces reliance on the freshwater need. Treated wastewaters can be reused for non-portable domestic, industrial and agricultural use. Resource demand analyses for algal biofuel production highlight the need for sustainable wastewater treatment together with production of algal biofuel. This strategy would promote generation of biofuel with sustainable biological nutrient removal (Chanakya et al., 2012). Adopted wastewater treatment technologies in the city only remove C (carbon) and solids, leaving behind the nutrients. Conjunction of these treatment plants with HDAP (high detention algal ponds) would aid in the nutrient removal and sustained biofuel generation. Despite many benefits of using wastewater for algal biomass production, it is unknown whether there is sufficient land or wastewater available for large-scale fuel production. The use of wastewater for algal production is to be near WWTP’s.  Availability of wastewater effluent and land within short distances from WWTP’s would help in biofuel production. There have been significantly higher numbers of studies on growth of algae under a wide variety of wastewater environments (Ip et al., 1982; Konig et al., 1987; Wrigly and Toerien, 1990). Most of these studies have focussed on efficient algal sp. in pure cultures for the treatment of sewage and artificial wastewaters (Ruiz-Marin et al., 2010). These studies have primarily looked at evaluating the potential of algae for removing N and P, and in some instances metals and other minerals from wastewater. The present study investigates the viability of wastewater algae in treatment of urban wastewaters and generation of algal biofuel through its integration to existing treatment plants in the city.

The main objective of this analysis is to devise a sustainable nutrient (C, N and P) capture mechanism for the city wastewaters and to investigate the feasibility of producing algae lipids (biofuel) in urban localities. The study was conducted for the city of Bangalore, and the nutrient dynamics studies were performed in the two big lakes of the city because of its higher detention and high algal productivities. The average algal productivity and lipid content were determined from laboratory based studies at Aquatic ecology laboratory, Centre for Ecological Sciences, IISc, Bangalore campus with the similar wastewater algal consortia. The algal lipid content and productivities were examined to create realistic baseline values to estimate the city’s biofuel production potential from algal scums in surface waters. This study provides the geospatial analysis of wastewater treatment plant locations and investigations of land availability near the plants for integration of HDAP to existing treatment technologies.