SEWAGE TREATMENT SYSTEM

1,258,006. Sewage treatment system. ECODYNE CORP. 31 March, 1969 [1 April, 1968], No. 16813/69. Heading B1D. [Also in Division C1] Sewage sludge is precipitated in tank 15, by injecting a flocculant through junction 27 into the ingoing sewage, then flows through pipe 46 under gravity on to endless conveyor belt 56 of synthetic monofilament cloth, whereon gravity filtration occurs, the sludge being scraped off at 75 on to a similar belt 80, which conveys sludge under rollers 93 which squeeze remaining liquid through the belt successive pairs of rollers exerting progressively increasing pressures. Belts 56 and 80 have openings of 250 to 1410 microns diameter, and their drive rollers 61, 85 and upper rollers 93 are driven by belt 69 from motor 68. The belts 56, 80 are backwashed by filtrate passing through their upper and lower runs into troughs 70, 71, 99 and by water sprays 106, 107 of which 107 operates only intermittently. The flocculant may be a polyelectrolyte, other examples are given, and precipitation is aided by slowly rotating the arms of mixer 40. Central support roller 65 is raised above the plane of rollers 61, 62 to flex belt 56 and aid filtration. Sludge conveying plates 45, 76 are adjustable to vary flow. Three pairs of compression rollers are shown, but up to six pairs could be used. Sludge is removed from belt 80 by scraper 97. Clear liquid overflows from tank 15 at 36.