Xử lý nước thải bằng công nghệ sinh học, chương 1

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MBR (Membrane Brio-Reactor) can be broadly defined as systems integrating biological degradation of waste products with membrane filtration. Set up of MBR plant is mainly utilizing a bioreactor and membrane filtration as one unit process for wastewater treatment thereby replacing, and in some cases supplementing, the solids separation function of secondary clarification and effluent filtration, resulting the possibility to eliminate the secondary clarification and operate at higher MLSS concentration....

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Nội dung Text: Xử lý nước thải bằng công nghệ sinh học, chương 1

SYSTEM DESIGN & OPERATION MANUAL Membrane Bioreactor (MBR) System
Membrane Bioreacotr Operation & Maintenance Guideline MBR Introduction MBR (Membrane Brio-Reactor) can be broadly defined as systems integrating biological degradation of waste products with membrane filtration. Set up of MBR plant is mainly utilizing a bioreactor and membrane filtration as one unit process for wastewater treatment thereby replacing, and in some cases supplementing, the solids separation function of secondary clarification and effluent filtration, resulting the possibility to eliminate the secondary clarification and operate at higher MLSS concentration. In summary, the MBR system is the combination of traditional Actitived Sludge Treatment with the membrane technology. The design criteria of the system shall be base according to the traditional way of Activated Sludge Treatment principle. However, on top of that, the MBR modules are immersed and located in the air blow tank/ aeration basin (biological reactor tank), the clear water is pumped(sucked) out from the MBR modules. This shall possibly eliminate the needs of secondary clarifier. Advantages of the MBR: • Better control of biological activity • Effluent that is free of bacteria and pathogens • Smaller plant size • Biodegradation efficiency enhanced 10%~30% • Short Hydraulic Residence Time (HRT) & Long Sludge Residence Time (SRT) • Activated sludge increase by 2~3 times • No secondary settling and disinfecting tank required • Higher organic loading rates Typical Applications • Living wastewater treatment, medical water treatment and reuse (residential area, hotel etc.) • Food industry wastewater (bean factory, cake factory etc.) • Beverage industry wastewater • Agricultural waster • Waster water of pharmaceutical • Zoology toilet Working principle: • 3 pcs. of membrane modules are connected parallely through the header of the module to form a cassette (frame). It is then connected the suction side of a permeate pump, the membranes are subjected to a slight negative pressure (suction pressure). • In an “outside-in” process operation, water is drawn from the mixed liquor through the membrane module and into the capillary, further enhanced by suction effect of pump. From there, the treated water is drawn through the header and out through the discharge system.
• On a continuous basis, air diffusion at the bottom of the membrane modules, where it emerges as a coarse/ fine bubble stream. This air stream performs the triple role of process aeration, mixing of the biomass and membrane cleaning. • Also, with the continuous movement of air bubbles around and through the fibers, a lower concentration of biomass is maintained around the membranes and this, in turn, minimizes the potential for membrane fouling. • The membrane modules/ cassette are modular design and can be dismantled individually for manual cleaning as part of supplementary periodic maintenance. Specification - Model MBR-1000 • Material : Polypropylene • Type : Hollow Fiber • Capillary Thickness : 40 ~ 50 µm • Capillary Outer Diameter : 450 µm • Capillary Pore Diameter : 0.01 ~ 0.2 µm • 7.0 x 10-2 cm3/cm2 • S • cmHg Ventilation Rate : • Porosity : 40 ~ 50% • Lengthways strength : 120,000 kPa • 6 ~ 9 L/M2/H Designed flux : • 8 m2/module Area of membrane module : • Operating Pressure : -0.01 ~ -0.03 MPa • Abnormal Pressure : > -0.05 kpa • 1.0 ~ 1.2 m3/ day Flow-rate : Parameters of installation • Material of installation frame: UPVC or A3 steel with antirust • Connection pipe: PPR pipe, galvanize pipe or high strength tube • Space between MBR unites: 80-100mm • Space between installation frame and the wall of reactor: ≥400mm • Space between installation frames: ≥500mm Sizing • Treatment Flowrate, m3/hr = Tank Volume, m3 / HRT, hr • Module required = Treatment Flowrate, m3/day / (1 m3/day) Application Suggested HRT Sewerage treatment/ recycle 4 ~ 6 hr Wastewater treatment in food industry 10 ~ 20 hr Wastewater treatment in breed aquatics industry 10 ~ 20 hr Wastewater treatment in chemical industry 24 ~ 48 hr Suggested Influent Requirement/ Limitation Granular ≤ 50 µm Turbidity ≤ 20 NTU pH 1~14 Temperature 4~40ºC
Operating Vacuum Pressure -0.01 ~ -0.03 MPa Installation & Operation • 3 pcs. of membrane modules are connected parallely through the header of the module to form a cassette (frame). It is then connected the suction side of a permeate pump, the membranes are subjected to a slight negative pressure of -0.01 to -0.03 MPa (1.5 to 4.5 psi). (refer Diagram in “Module Assembly Arrangement”) • In an “outside-in” process operation, water is drawn from the mixed liquor through the membrane module and into the capillary, further enhanced by suction effect of pump. From there, the treated water is drawn through the header and out through the discharge system. • On a continuous basis, air is pumped towards the bottom header, where it emerges as a coarse/ fine bubble stream. This air stream performs the triple role of process aeration, mixing of the biomass and membrane cleaning. • Also, with the continuous movement of air bubbles around and through the fibers, a lower concentration of biomass is maintained around the membranes and this, in turn, minimizes the potential for membrane fouling. • The membrane modules/ cassette are modular design and can be dismantled individually for manual cleaning as part of supplementary periodic maintenance. Module & Spacing Dimension Membrane Individual Module Connected Membrane Cassette/ Frame MBR – SIDE VIEW
NOTE: Keep the distance between header-to-header closer (< 810mm) so that the MBR Membrane Module will not be stretched too stiff when installed while the air scouring/ scrubbing effect can be applied better on the membrane capillary. Module Assembly Arrangement (e.g. 75 pcs. MBR Module for capacity 75 TPD) MBR 3 modules = 1 5 Frames Total 5 Cassettes Module Frame = 1 Cassettes In Tank
System Component/ Facilities required: • Suction Pump @ capacity -0.01 ~ -0.03 MPa vacuum pressure/ 5~10 T/Hr suction rate. • Air Blower • Air diffuser facilities, diameter 215mm. • Control & sensing elements: Pressure Gauge, Vacuum Gauge, flow-meter, pH/ DO Meter. Diagram 1 – MBR Tank General Arrangement In the reactor tank, the MBR modules are fixed on a modular frame network. Below the MBR modules, there are these air-diffusers. The vacuum pump connect with the MBR modules. The MBR modules are submerged in the waste-water. Maintenance of MBR module MBR modules could have deterioration in flow-rate due to many reasons in the following: • In the system of waste-water treatment, the aerobic germs are easy to propagate in membrane because of the compatible temperature, oxygen and sedimentation. • Organic compound in imperfection treatment and inorganic ion cannot be treated accumulate on the external of membrane. • Activated sludge adheres to the external of membrane. • Concentration polarization comes into being pollution. In-service Air Scrubbing Cleaning However, this can be prevented in advance with aeration treatment with the membrane system submerged into the Aeration Tank. Aeration Tank with air-diffuser at the bottom will have the function of mixing, aeration and creating air-scouring effect on the MBR membrane that will prevent the accumulation of bio-mass on the membrane surface while scrubbed away the dirt/ sludge. At the same time, make the suction pump working intermediately. The suction pump shall be run for 4~5 minutes and stop for 1~2 minutes, effectively total 40~50 minutes in operation with intermediate stoppage of 10~20 minutes. This operation-&-stop
duration should be adjustable from job-to-job basis to suit the best operation condition. The vacuum pressure meter is used to keep monitoring the operation negative pressure in 100~250 kPa. On-line Auto Cleaning Operation It is suggested to have a PLC Control Panel to sense when the operation negative pressure is increasing and exceeds 50 kPa (adjustable parameter), MBR module need to be cleaned. The High & Low Pressure Switch will be activated and the PLC Control Panel will stop the Vacuum Pump to stop production of filtered water. Then, it will active the Flushing Pump and feeding the filtered water into the MBR modules in counter-current (reverse flow) to perform backward flushing process, with an adjustable duration of 20 sec. or more. The PLC Control Panel should be c/w manual over-ride button. Manual Cleaning Operation Alternatively, if the system is operated manual, user may clean in the following flow in order to make the membrane resumed adequately. 1. Dismantle and remove the MBR module from the installation frame. Rinse the surface of MBR module with clean water in order to wipe off the contamination on the surface of membrane such as the activated sludge. 2. Feed clean water into the membrane cassette for backwash flushing process until the discharge water is clear. 3. Immerse the MBR module in sodium hydroxide (NaOH) solution with 5% concentration for 2~3hours in order to remove the organic compound and the colloid material on the surface of membrane. 4. Then, immerse the MBR module in sodium hypochlorite (NaClO) solution with 0.5% concentration for ½ ~1 hour in order to disinfect the micro-organism on the surface of membrane. CAUTION: • During the cleaning operation above, the maintenance personnel must be extra careful in handling the MBR module to avoid breakage of the UF membrane! • Keep the distance between header-to-header closer (< 810mm) so that the MBR Membrane Module will not be stressed too stiff when installed while the air scouring/ scrubbing effect can be applied better on the membrane capillary. Contact us at: Hydro One Marketing Sdn. Bhd. 32, Jalan Bukit Rawang Putra 6, Taman Bukit Rawang Putra, 48000 Rawang, Selangor, Malaysia. (648758-P) Tel: +60-3-6092 0120 Fax: +60-3-6093 0305 E-Mail: enquiry@hydro1.com.my URL: www.hydro1.com.my