Plant for purifying sewage, more particularly refinery and chemical sewage

摘要

A plant for chemical and/or biological purification of refinery or chemical works sewage, comprises a number of treatment basins 2, 9 having circulating and oxygenating devices 3, 10 and a number of clarifying basins 6, 11 associated with the treatment basins, combined to form a compact structure subdivided into groups each comprising at least one treatment basin and at least one clarifying basin and arranged to enable sewage to flow through the groups in parallel or in sequence as required, a treatment basin of each group having closable connections to conduits for feeding activated or flaky sludge selectively to chosen basins of the group. Raw sewage from which solids have been removed mechanically enters the plant at 1 together with flocculants at 4 and is circulated PICT:1094963/C1/1 and oxygenated in basin 2 for chemical purification, syphoned to clarifying basin 6 where the clarified liquor spills over into channel 7 and passes via channels 8 to circulating and oxygenating basins 9 for biological purification with activated sludge, and then passes into clarifying basin 11 where the treated sewage leaves via line 14. Activated sludge settling in basins 11 passes into sludge concentration shafts 15, where the concentrated sludge passes via line 16, 17, pump 18 and line 20 to a concentrator (not shown), or possibly via line 32 back to channel 24. The cloudy water accumulating in shafts 15 flows through lines 21 to sump 22 and is pumped via screw 23 to channel 24 leading to basins 9, to give a closed activated sludge circuit. The flaky sludge from basin 6 goes to sump 25 where screw 26 returns the cloudy water through channel 27 to basin 2, and the sludge goes through lines 28, 29, pump 30 and line 20 to a concentrator, or possibly via line 33 to channel 27 and basin 2. Stop elements 34, 35, 36, enable activated sludge from line 16 to be introduced via pump 30 and line 33 to basin 2, or flaky sludge from line 28 to be introduced via pump 18 and line 32 to basins 9, so that a combined chemical and biological treatment, or a single chemical or biological treatment can be given in all parts of the plant.