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BACKGROUND:
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- Since the beginning of 20th century, activated sludge process has been used as biological treatment for industrial and municipal wastewater treatment and reuse purpose.
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- Biological processes are designed to accumulate microorganism which oxidize organic and mineral pollutants and the efficiency depends on the biomass concentration in the reactor and specific conversion rate of the microorganism.
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- After 100 years, there were only marginal improvements to conventional activated sludge processes. In recent years, membrane bioreactor (MBR) emerges as an economical alternative for reliability, compactness and excellent treated water.
•DEFINITION:
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MBR is a combination of two basic processes – biological degradation and membrane separation – into a single process where suspended solids and microorganisms responsible for biodegradation are separated from the treated water by membrane filtration unit.
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The influent enters the bioreactor, where it is brought into contact with the biomass. The mixture is pumped from the bioreactor and filtered through the membrane. The permeate is discharged from the system while the entire biomass is returned to the bioreactor. Excess sludge is pumped out in order to maintain a constant sludge age and the membrane is regularly cleaned by backwashing with occasional chemical washing.
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The entire biomass is confined within the system, providing both perfect control of the residence time for the microorganism in the reactor (sludge age) and the disinfection of the effluent.
Advantages Over Other Biological Processes:
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Capable of simultaneously biologically treating and disinfecting the effluent;
- Complete separation between the HRT (hydraulic retention time) and the suspended SRT (solids retention time) provides optimum control of biological reactions and greater reliability and flexibility in use;
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Ability to absorb variations and fluctuations in the hydraulic and organic load to the systems;
- Complete control of the sludge age is important to allow the development of slow-growing microorganisms such as nitrifying bacteria;
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Process intensification through high biomass concentrations:
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Reduce sludge production compared to other aerobic processes;
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Ability to treat high strength wastes;
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Smaller footprint with no clarifier or significantly smaller aeration tank.
CONVENTIONAL ACTIVATED SLUDGE PROCESS |
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MEMBRANE BIOREACTOR PROCESS |
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MBR PILOT PLANT WITH SMALLEST FOOTPRINT AT BEDOK SEWERAGE SINGAPORE TRIALS |
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ULTRA-FLO® MEMBRANE BIOREACTOR
- Compact design with small footprint
- Low system and operating cost
- Highly efficient energy utilization
- Complete solids removal
- Removal of combined COD, solids and nutrients in a single unit
- High loading rate capability
- Low/zero sludge production
- No problems with sludge bulking
- Operate at low DO (oxygen demand)
- Rapid startup
- Modular/retrofit
Advantages Over Immerse System
- No fine bubble diffuser maintenance
- Easier to clean membranes chemically without upsetting the biological process in the tanks
- No unnecessary movement, hence less stress on hollow fibers during filtration process
- Ability to control environment around the membrane modules better
- Higher flux with smaller footprint using less membrane surface area
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