Membrane Bioreactor (mbr) as an Advanced Wastewater Treatment Technology
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| Faecal coliform, Cryptosporidium, and Giardia even in processes that use MF
membranes due to a dynamic film layer over the membrane that reduces the effective filtration pore size [267]. In addition, the clarity of the effluent pro- duced by the MBR process is consistently below 0.1 nephelometric turbidity units (NTU), which is comparable to drinking water standards. This low tur- bidity can result in an effluent highly amenable to final disinfection using ultraviolet light. Membrane filtration followed by ultra-violet (UV) treatment results in a highly disinfected effluent. MBR systems do not require any more significant operational attention, in each case much less than CAS process. A process control of an MBR system is reduced to monitoring the MLSS concentration, occasional adjustments of the chemical feed rates, and scheduling membrane recovery cleaning. Therefore, MBR is a much better solution for the small plants where CAS is non-feasible due to its requirement for constant attention and monitoring. On the other side, the cost of oxygen demand is superior in MBR. Energy consumption of MBR comes from power requirements for pumping feed wa- ter, recycling retentate, permeate suction (occasionally) and aeration [268]. The two MBR configurations have substantial differences in terms of aeration. In the side-stream configuration, aeration is supplied by fine bubble aerators that are highly efficient for supplying oxygen to the biomass. In submerged MBRs, the aeration mode is turbulent and cross-flow is generated, which scours the membrane surface and provides oxygen to the biomass. Aeration cost in the latter-mentioned configuration represents around 90% of the total costs, whereas in side-stream MBR, only ∼20% derives from it [269]. However, energy consumption of the side-stream system is usually two orders of mag- nitude higher than that of submerged systems. These low costs of submerged MBRs are associated with low fluxes, which in turn increase capital costs and 90 J. Radjenovi´c et al. footprints. Also, packing density influences the final cost of MBR: low packing densities of membrane modules mean that higher specific area of membrane is required to produce the same flux, which increases the energy requirements. There are certain drawbacks for wider implementation of MBR technology. MBR is widely viewed as being a state-of-the-art technology but is also some- times seen as high-risk and prohibitively costly compared to CAS and other more established technologies. MBRs were historically perceived as suitable only for small-scale plants with high operator skill requirements, and the key operating expenditure parameters such as membrane life unknown [4]. Many of these drawbacks are no longer true. Perhaps the biggest challenge to companies active in the market is to persuade decision-makers of the capabil- ity of MBRs and what benefits they will undoubtedly bring to the customer. In the past, there were an insufficient number of full-scale MBR treatment plants to convince decision-makers of the reliability of this advanced treat- ment. Presently, there are a number of examples of successful implementation of MBRs across the range of applications, and there is certainly less reason to be suspicious of this technology. tải về 0.95 Mb. Chia sẻ với bạn bè của bạn:
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