Treatment of sewage water by using microalgae coupled with membrane bioreactor (MBR) system

Abstract

“Microalgae in combination with membrane technology is an emerging process to combat the ever increasing pollution in the water bodies (rivers, lakes and sea) along with CO2 sequestration in a eco-friendly way without using the chemicals. As a microalga cultivates under four different conditions (photoautotrophic, heterotrophic, mixotrophic and photohetrotrophic), it can uptake nutrients, organic compounds, inorganic carbon (in the form of CO2)in the presence of bacteria and uses natural sunlight as a energy source for their growth. In short, microalgae are versatile unicellular species which not only prevents the eutrophication of the water bodies but also helps to increase the dissolved oxygen concentration thereby, helping the aquatic habitat to flourish in a natural way. As, microalgae were generally dispersed and suspended in the water, its harvesting is one of the bottleneck issue of the microalgal industries to grow forits mass production for various applications like fertilizers, biofuel, animal feed etc. Recently membrane technology shows sustainable solution for the harvesting of microalgae from water. Membrane filtration in combination with microalgal treatment for sewage water not only reduces the water footprints but also reduce the energy requirement as it does not require extensive oxygen like the conventional sewage water treatment plants. Therefore, microalgae in combination with membrane technology will be the futuristic technology for the treatment of sewage water. Conventional sewage water treatment plant required huge amount of air for aeration which is costly and also space required for plant is very large. The main objective of this dissertation is to (1) Screen and isolate microalgae from its natural habitat having potential to remove nutrients from sewage water.(2) Sewage water treatment using starved isolated microalgae species for the efficient removal of nutrients (TN and TP) (3)Optimization of process parameters for improving growth rate of microalgae and effective removal of nutrients.(4) Study the kinetics of nutrients uptake from the sewage water by immobilizing microalgae as well as to make effort for the reduction in the residence time. (5) Harvesting of microalgal biomass by applying membrane technology using different types of membranes. (6) Study the effects of various operational parameters such as Tran-membrane pressure (TMP), fluxes and membranes physicochemical properties parameters to get higher fluxes with maximum biomass recovery. (7) Economical analysis of the whole process for the treatment of sewage water using microalgae in combination with membrane technology for a small village. The microalgae-membrane based technology has a huge potential for the treatment of sewage as well as industrial wastewater in the near future. However, efficient design of photo-bioreactors or raceway pond using artificial radiation or solar radiation is essential. The commercial viability for the treatment of sewage water/industrial wastewater using microalgae-membrane based process will be depend upon the efficiency of microalgae for uptake of nutrients, design of photo-bioreactor for growth of microalgae and its harvesting using suitable membrane technology.”