A method of treating raw sludge in sewage systems

摘要

1,009,707. Filtering and pressing settled sludge. LEJE & THURNE A.B. July 23, 1962 [Nov. 30, 1961], No. 28190/62. Heading B1D. Collected sedimented sludge 4 from sewage is withdrawn by a pipe 5 and mixed with, e.g., sulphuric acid at 6 to adjust the pH to the isoelectric point of its protein content. It is then mixed with wood pulp or cellulose fibres and passed through a flat or rotary screen at 14, filtrate passing back at 15 to the tank 1. The screened sludge-pulp mixture is then dewatered by compression, e.g. by a rotary screw press, at 17, and the final product is burned on a grate 22. The resulting ash is collected at 30. Where a rotary screen is provided at 14, it may be as described in Specification 710,741, the filtering layer in that case being paper waste in suspension.