Chapter 12 - Membrane reactors

Abstract

Wastewater is a type of polluted water which results from different human mediated and natural activities. Municipal and industrial wastewater include various types of pollutants like xenobiotic compounds, recalcitrant compounds, persistent organic pollutants, radioactive substances, heavy metals and pathogens. Different types of treatment membrane bioreactor (MBR) involves combination of activated microbial sludge and membrane which is nowadays widely used over conventional activated sludge (CAS) process due more advantages. The main advantage of membrane use in wastewater treatment is ease of removal of pathogens and solid liquid separation by ultrafiltration and microfiltration. Thus it eliminates secondary clarifier which is used in conventional method. Another benefit of MBR is controlled operating mechanism of wastewater treatment. By controlling various parameters like solid retention time, hydraulic retention time, flocs size, membrane type, food/microbes ratio, aeration, transmembrane pressure, pore size, chemical oxygen demand/ nitrogen ratio, mixed liquor suspended solids, optimum degradation of pollutants, and less membrane fouling can be achieved. MBRs are of mainly two types. External MBR include side stream and internal type including immersed or submerged one. Extractive MBR is useful for elimination of particular type of waste or toxic material. Batch, continuous stirred tank, and immobilized cells or enzymes are other types of MBR. Membranes can be made up of ceramic or polymeric material and are available with flatsheet, hollow fiber, or tubular type configuration. Different microbial communities of bacteria, algae, protozoa, and extremophiles are present in MBR for wastewater treatment. MBR can decrease pollutants 30%–50% more than CAS treatment. Treated water can be further used for agricultural purpose, for irrigation, for cooling in industries, livestock watering, and for recreational of water supply. Thus MBR is an efficient method that can be used for the recycling of wastewater.