TREATMENT OF RAW MUNICIPAL WASTEWATER USING ALGAE AND ALGAE SLUDGE INOCULUM WITH SPECIAL EMPHASIS ON TREATMENT PERFORMANCE IMPROVEMENT

Abstract

The discharge of inadequately treated municipal wastewater in various waterbodies is a major cause of environmental pollution in urban areas of developing countries. The effluents from municipal wastewater treatment plants (WWTPs) are heavily charged with nutrients (nitrogen and phosphorus) causing eutrophication and resulting in ecosystem disruption. Last few decades, researchers have been focusing on developing technologies towards consolidating microalgal-bacterial consortia, which exhibit numerous advantages related to efficiency of removal of nutrients and organic carbon due to cooperative interactions between microalgae and bacteria. Microalgae-bacteria consortia are emerged as a promising candidate for remediating municipal wastewater by reducing nutrients, organic carbon and pathogens and likewise produces valuable biomass from municipal wastewater. In this study, a mixed algal culture, collected from Saharanpur UASB polishing pond, enriched using BG 11 media was used. The mixed algal culture can grow in between 16–40℃. Preliminary studies conducted using autoclaved raw wastewater collected from IIT, Roorkee SBR plant showed that the mixed algal culture showed enhanced nutrients removal. This mixed algal culture was later used for primary effluent treatment under 12h light and 12h dark study under two illuminations: high light (~380 µmol/m2/sec) and low light (~100 µmol/m2/sec). Before inoculating the primary effluent, the algal culture was grown in a nutrient depleted BG 11 media (without N and P) either for 3 days (low starvation condition) or for 7 days (high starvation condition). Hence, this study investigated the effects of light intensity and starvation conditions on the treatment performance. This mixed algal species showed around 80–90% COD removal, and 35–91% TN removals and 63 -82% P removals. Algal inoculum starved for 7 days showed enhanced N and P uptake compared to the algal inoculum starved for 3 days. Removal efficiency of COD, TN -N and TP – P were within 60 – 100% for 7 days starvation condition. COD removals were higher for algal inoculum starved for 3 days compared to one starved for 7 days. Removals of other species of N and P were higher in the algal inoculum starved for 7 days than that in algal inoculum starved for 3 days.