Dewatering of sewage sludge - by freeze-thaw treatment before adding flocculant

摘要

Dewatering of domestic sewage sludge by addn. of treating (esp. flocculating) agents followed by mechanical or dynamic dewatering is improved by cooling the sludge to >0 degree C (pref. -3 to -50 degrees C, esp. -5 to -20 degrees C) and then warming to >0 degree C before adding the treating agent. The freeze-thaw treatment greatly increases the solid content of the dewatered sludge. Prefd. flocculating agents are acylamide homo- and copolymers, esp. those contg. tert. amino or quat. ammonium gps. The flocculating agents are pref. added in an amt. of 50-200 g/m3. Primary sludge with a solids content of 6.2% was treated with 200 ppm of a polyacrylamide flocculant modified with 50% 2-methacryloylethyl-trimethylammonium chloride and then suction-filtered for 5 min. The prod. had a solids content of 26.6%. The same sludge was cooled to -5 degrees C, warmed to room temp. after 5 min., treated with 80 ppm of the same flocculant, and filtered. The prod. had a solids content of 38.4%.