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CONCENTRATED AND HIGH-CONCENTRATED
SEWAGE PURIFICATION TECHNOLOGY
(patent No. 2159257; international application PCT/RU 098/00126)
These combined works (CW) can be applied for purification of the concentrated sewage produced by meat-packing plants, butter-and-cheese factories, sugar plants and tinned food factories, characterized by max. 1,000-5,000 mg/L BOD and up to 3,000 mg/L suspensions. The following purification chart is in this case recommended (see Fig. below):
1 - inlet chamber; 2 - fine mechanical purification grid; 3 - sand catcher; 4 - biocoagulator; CW1 - 1st purification stage works; CW2 - 2nd purification stage works; 5 - sand dewatering installation; 6 - sediment treating installation.
The primary sewage is driven to the fine mechanical purification grids of 2 mm spacing, where coarsely dispersed suspension is entrapped.
Then the sewage is cleaned of grits (sand, etc.) on the vertical sand catcher. The entrapped sand is driven by a sand pump to be further dewatered.
While in the biocoagulator, the suspended matters are caught, and some part of the dissolved organic compounds are removed due to flotation sorption and impurities coagulation by the excess active sludge driven here from the 2nd purification stage combined works. Besides, it is possible to discharge the 1st stage excess sludge to the biocoagulator. The biocoagulator purification effect reaches 25 - 30% BOD and 60 - 70% suspensions. After the biocoagulator, the sewage is driven to the 1st stage CW mixing chamber. There is also a possibility to partially discharge the primary sewage to the 2nd stage CW mixing chamber.
While in the CW mixing chamber, the sewage is mixed with the circulating sludge mixture coming here from the settling aeration tank. The mixture is taken from the mixing chamber by a circulator and then driven to the biofilter sprinkling system which consists of water-distribution chutes with drain connections and reflecting dusks. The falling fluid jets break on the disks thus sprinkling the biofilter feed. After the biofilter, the fluid is driven by assembly chutes to the air-spripping towers where the air is sucked in as a result of возникновения vortexes. The air-spripping towers distribute the air-and-water mixture around the aerotank inside. The shock of the air-and-water jet on the aerotank bottom and the movement of the gas-liquid flows provide efficient mixing the aerotank content. After the aeration zone the sludge mixture goes to the settling zone where it is split. Some part of the sludge forms flakes, then is packed and partially returned (through a slot) to the aeration zone. Another part of the sludge, together with the transit flow, is lifted making a suspended filter where too sorption, impurities oxidation and separate small sludge particles catching take place. The separated water gets to the collecting chutes and is driven to further treatment.
While in the 1st stage CW, the clarified sewage undergo incomplete biological purification (60 - 80% BOD; 70 - 90% impurities) at high loads upon the active biomass. Further on, there occurs complete biological purification at the 2nd stage CW at low loads upon the active sludge. The 2nd stage CW purification efficiency make up to 15 mg/L BOD and impurities. The excess sludge of high sorption power is driven to the biocoagulators to raise the effect of clarifying the primary sewage. The purification technology provides for supplying some part of the sewage, after the sand catcher and biocoagulator, directly to the 2nd stage CW, supplying the 1st stage excess sludge to the biocoagulators: this is done with the aim of making the purification control system flexible. The power consumption within this given flow chart makes 0.15 - 0.2 kWt/h/kg BOD.
Treatment plant of a meat-packing factory in the Dolgie Budy village of the Kursk Region
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