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UDC 628.35:66.081.63
Stepanov S. V.
Calculation of membrane surface in membrane bioreactors
Summary
On the basis of the foreign publications analysis membrane bioreactors and membranes used in them are considered. In pressure units with a remote membrane assembly the specific flow through the membrane (at 20°C) is 80–200 l/(h∙m2) at 20–500 kPa transmembrane pressure; whereas in the units with submerged membranes – 8–30 l/(h∙m2) at 10–60 kPa vacuum. The specific power consumption in bioreactors with pressure membranes is within the limits of 1.5–4 kW·h/m3; with submerged membranes – 0.5–0.7 kW·h/m3. The results of analyzing the equipment market showed that submerged membrane elements and modules have been used in 97–99% biomembrane units. The comparison of submerged membranes shows that modules made of hollow fiber membranes have higher specific surface (300–600 m2/m3) compared to flat ones (50–150 m2/m3). Hollow fiber membranes are characterized by lower cost, higher resistance to fouling and backwashing. Flat membranes have higher mechanical toughness and can be more easily replaced. The operation of membrane batch bioreactors, the use of osmotic membrane bioreactor and nanofiltration processes in biomembrane technology are described. The technique of calculating submerged hollow fiber membrane surface with account of various allowed specific flows depending upon the durability of the design flows, time lost for backwashing and «relaxation», reflux from membrane backwashing is presented. At determining the number of the operating in parallel process lines one should take into account possible shutdown of one membrane tank for chemical washing or repair.
Key words
wastewater , biological treatment , transmembrane pressure , power consumption , membrane bioreactor , specific flow
