Calculation of low-capacity plants with membrane filtration for biological wastewater treatment

Summary

The calculation of standard series of plants for biological treatment of wastewater is set. The plants include a fermentation settling tank and a membrane bioreactor. The method has been approbated for calculating the plants with a capacity less than 500 m³/day. It was determined that increasing the activated sludge dosage from 3 to 5 g/l provided for 1.5 reduction of the size of the treatment facilities; at that increasing the activated sludge dosage more than 3-fold (more than 8 g/l was inexpedient. The size of the plants for 3 and 5 g/l activated sludge dosages with account of 25% volume increase (with correction for reliability) is given. The use of the suggested process flow scheme provides for increasing the efficiency of wastewater treatment. The effluent quality parameters approach the maximum permissible sanitary-hygienic regulations for the discharge into fishery water bodies. At that the use of chemicals for nutrients removal is not foreseen. The use of membrane filtration provides for equalizing and enhancing biological processes by means of possible increase of activated sludge concentration, and also for reducing the size of the plant, increasing the efficiency of wastewater treatment by means of enhanced removal of suspended solids.

Key words

wastewater , biological treatment , nitrification , denitrification , membrane filtration , dephosphorization

Comparative evaluation of the methods of phosphorus removal from wastewater

Summary

The evaluation of the methods of eliminating phosphorus, a most important nutrient that is a limiting element in water body eutrophication, from wastewater is presented. Biological, physical, chemical and combined methods are considered that differ from each other in the method of implementation, construction and operating expenditures. The biological method is based on phosphorus removal through its utilization in biomass synthesis in the biological system. Physical and chemical methods suppose mandatory application of chemicals used for free phosphate-ion binding to low soluble ortho-phosphate. Combined methods suppose dephosphorization at the biological treatment stage with subsequent inclusion of phosphate-ions into crystals at the physical and chemical treatment stage. The examples of practical implementation of the methods are presented; process flow schemes are considered; the process parameters of the treatment facilities are pointed out where the process of phosphorus removal is taking place; the data on the process efficiency is provided; the advantages and drawbacks of the applied methods are reported. The experience of adjustment works is described together with the results of experimental selection of chemicals for phosphorus binding and determination of the optimal point of their addition carried out by the authors in the laboratory, during pilot and full-scale studies.

Key words

filter , nitrification , bioreactor , reagent , aeration tank , denitrification , nutrient , wastewater , crystal , dephosphorization , effluent polishing , sludge growth