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Membrane Processes For Waste Water Treatment By: Rohit Chaurasia 3rd B. Tech. Civil Engineering 71/08 Contents 1. 2. 3. 4. 5. 6. 7. Introduction Stages in waste water treatment Conventional waste water treatment techniques Processes and equipments Membrane bioreactor processes Advantages and Disadvantages of MBR Conclusions Introduction Wastewater treatment is the process of taking wastewater and making it suitable for discharge back into the environment. Wastewater can be formed by a variety of activities. Using advanced technology it is now possible to re-use sewage effluent for drinking water. Stages in waste water treatment PRIMARY SECONDARY TERTIARY CONVENTIONAL WASTE WATER TREATMENT TECHNIQUES Physical/Chemical Treatment Systems Physical Process • The water is pumped into large tanks where matter settles or sinks, just like in a biological treatment system. • aided by the addition of flocculants and dissolved air. Chemical Process • Chemical processes include added chemicals to precipitate dissolved materials. Biological Treatment System Biological treatment systems use bacteria and other biological matter to break down waste. wastewater is screened to eliminate easily removed objects the wastewater is taken to a primary settling basin where matter can float or sink in the tank The remaining water is then sent to the secondary treatment tank PROCESSES AND EQUIPMENTS Screening Removal System Grit Removal System Clarification Filtration Sludge Dewatering Solar Drying of Sludge MEMBRANE BIOREACTOR PROCESSES Introduction to MBR Membrane bioreactor(MBR) technology combines the use of biological processes and membrane technology to treat wastewater and provide organic and suspended solids removal. Produces a tertiary standard effluent of 5: 5: 5 BOD: Suspended Solids: Ammonia. Contains an ultra-filter or micro-filter membrane unit. It can be operated in either an AEROBIC or ANAEROBIC mode, increasing the spectrum of chemicals suitable for biological treatment. Membrane Technology These processes differ depending on the type of substance to be removed. Membrane types can be broadly placed into four categories as shown ahead: Micro Filtration Filtration by particle size. Removes e.g. colloidal silica, oil emulsion, Collidocillus staphylococcus. Used for wastewater treatment. Membrane size: 0.1 - 10 μm. Ultra Filtration Selectively filters only molecules of a specified size and weight. Removes various viruses. Used for sterilization, clarification, wastewater treatment. Membrane size 1 - 0.01 μm. Nanofiltration Used for partial desalination. Removes e.g. sucrose, egg albumin. Used for blood osmosis, blood fitration, water purification. Membrane size: 10 - 0.001 μm. Reverse Osmosis A filtration process used for complete desalination. Used for blood osmosis, blood filtration, water purification. Membrane size: 10 - 0.001 μm Electro dialysis This is a process in which electrically charged membranes are used to separate ions from water solutions by the effect of a difference of electric potential. May have up to 400 cationic and anionic membranes. Convenient for very high concentrations (between 0.5 and 1 gram per litre) Membrane materials Some of the polymers most frequently used as materials for membranes are: ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Polycarbonate. Polyvinylidene-flouride. Polytetrafluoroethylene. Polypropylene. Polyamide. Cellulose-esters. Polysulfone. Polyetherimide. Membrane Processes Cross Flow Filtration Dead End Filtration ADVANTAGES AND DISADVANTAGES OF MBR Advantages Cost-effective - low life-cycle costs. Difficult contaminants degraded. High-quality effluent produced. Recovery of high-value products. Recovery of energy. Increase of productivity. Improvement of quality. Creation of new products. Easy to expand the system. Disadvantages The disadvantages include: The problem of FOULING. Membrane malfunctioning. Conclusions Study of the effluent quality produced by conventional secondary treatment processes reveals that such treatment methods do not remove many pollutants. The advantages of MBR show that it is the best option economically, socially, environmentally and sustainably. Can achieve cost effective wastewater regulatory compliance.