Membrane Bioreactor (mbr) as an Advanced Wastewater Treatment Technology
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sorbed ≤ 0.1L sol, out , (6) where L sorbed is the load of the compound sorbed onto sludge (g m –3 WW, treated ), and L sol, out is the soluble load in the effluent (g m –3 WW, treated ). In the same study, biodegradability of pharmaceuticals was estimated in MBR and CAS sludge. Transformation rate constants were similar in two types of sludge for most of the compounds. However, in some cases they differed quite a lot, like for gemfibrozil and fenofibric acid, where k biol in MBR was ten times smaller than for CAS sludge, and also MBR degrada- tion of piracetam and bezafibrate was conducted at a significantly higher rate (Fig. 17). 76 J. Radjenovi´c et al. Fig. 17 Kinetic degradation constants of pharmaceuticals observed in sludge from nutrient-removing municipal WWTPs: the average of CAS and MBR batch experiments is indicated. The error bars indicate the 95% confidence interval. The lines at K biol 0.1 and 10 L g –1 SS d –1 indicate limits for less than 20% and more than 90% removal expected from nutrient-removing municipal wastewater treatment. The faded columns indicate values from which experimental resolution allows only identifying an upper limit for K biol (upper error bar) (adopted from Joss et al. [150]) Knowledge about the removal of trace organic compounds by MBR is very limited. There have been several investigations conducted on the efficiency of WWTPs in removing PhACs from wastewater and its comparison with ad- vanced MBR treatment [106, 137, 146, 150, 151, 153–155, 177]. For most of the investigated PhACs, MBR effluent concentrations were usually significantly lower than in the effluent of a conventional treatment. They are removed from wastewater during membrane treatment by sorption, degradation, or a com- bination of both. Better removal of readily biodegradable micropollutants in the MBR could be due to smaller flock size of sludge, which enhances mass transfer by diffusion and therefore increases the elimination. Considering the Membrane Bioreactor (MBR) as an Advanced Wastewater Treatment Technology 77 composition of sludge originating from a membrane bioreactor (specialized microorganisms, large portion of active biomass in suspended solids) im- proved removal is to be expected. In general, no relationship has been found so far between the structures of micropollutants and their removal during wastewater treatments. Urbanization and constant population growth is likely to keep increasing the quantity of wastewater discharged to WWTPs. Also, considering fast de- velopment of pharmaceutical industry and general aging of population, it can be assumed that PhACs will be more consumed and with a more di- verse array, with development of new compounds that have unknown fate and effects on the environment. At the same time, the demand for clean water increases as well. Therefore, new technologies for wastewater treatment like MBR will have increasing interest. Although the efficiency of MBR as a barrier for micropollutants such as PhACs is still not clear, it seems to be a promising mean for their removal. tải về 0.95 Mb. Chia sẻ với bạn bè của bạn:
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