The efficiency of removing suspended solids from biologically treated effluent by microscreening in disc filters

Summary

The article covers the results of studying the separation of suspended solids from biologically treated effluent and separation of mixed liquor from aeration tanks by microscreening method. The specialists of R&D Centre of «Mosvodokanal» JSC performed pilot testing of microscreening technology. The tests were carried out in a pilot plant designed on the basis of DynaDisc filter (Nordic Water Products AB, Sweden). The surface of filtration area was 2.8 m2. The tests were carried out at the Kur’ianovskie Wastewater Treatment Facilities in Moscow. In the course of studies it was shown that disc microscreening provided for effluent polishing with reducing suspended solids to 4 mg/l when using 18 µm sieve mesh and to 3 mg/l when using 10 µm sieve mesh. The concentration of suspended solids in backwash water is 0.5–1.4 g/l; backwash water flow rate does not exceed 1.2% of the installation capacity. Addition of Praestol 650 flocculant allows improving filtrate quality to 1 and 0.5 mg/l, respectively. The quality of filtrate during separation of mixed liquor from aeration tanks in DynaDisc filter with 50, 30 and 18 µm sieve mesh is, respectively, 140, 60 and 45 mg/l; suspended solids in backwash water – 30–70 g/l, backwash water flow rate – 6–8%. In the course of tests the optimal filter operational performance in effluent polishing and separating mixed liquor from aeration tanks by microscreening was determined.

Key words

wastewater treatment , flocculant , dragged particles , mixed liquor separation , microscreening , disc filter