Bioremediation of aquatic pollutants using mat forming cyanobacteria

Abstract

High-rate oxidation pond (syn. High-rate algal pond ) represents a phytoplankton-based secondary newlinemethod of wastewater treatment which can appreciably alleviate BOD of wastewater. This method can, at newlinethe same time, also strip eutrophication-triggering nutrients from wastewater provided algal biomass is newlinesatisfactorily harvested, which is incidentally a serious constraint with this already well established newlinewastewater treatment technology. Phytoplankton biomass from a high-rate pond can be harvested using newlinealum; however, the harvested biomass would have plenty of this toxic chemical thereby making the newlinebiomass unfit for commercial application. In this context, self immobilized cyanobacteria and algae seem to newlinehave tremendous potential as these biomass types are easy to handle and can be easily removed after use in newlinewastewater treatment. Guided by this idea, the present study explores the feasibility of using cyanobacterial newlinemats for bioremediation of wastewaters. Cyanobacterial mats are virtually ubiquitous and easily grow in newlinelaboratory as well as under outdoor conditions. After extensive survey of the area around Varanasi, four newlinecyanobacterial mats were selected; three of them are dominated by species of Phormidium namely P. newlinelaminosum (mat # 1), P. fragile (mat # 2) and P. molle (mat # 3), and the fourth has Oscillatoria rubescense newline(mat # 4) as the dominant organism. Although initial experiments on nutrient removal are based on all the newlineselected mats, the data concerning metal removal and bioremediation of real wastewater are based on Mat # newline3, dominated by Phormidium molle, was employed. This mat was found to be free of any algal or newlinecyanobacterial contaminant. Moreover, it could very well grow attached to polyester mesh and never grew newlineoutside the polyester mesh disc. So it was easy to harvest and handle. An effort has been made to test the newlinepotential of these mats in stripping nutrients, especially nitrogen and phosphorus, toxic metals and newlinemalachite green, a commonly used dye.