For dehydration of rainfall of sewage and excess active silt nepreryvnodeystvuyushchy, osaditelny horizontal centrifuges with shnekovy unloading of a deposit are most effective. Advantage of these centrifuges - high efficiency at low specific power consumption and weight. Shortcomings - low degree of a condensation of a deposit, and also fast wear of the screw and a rotor.
When using such method for dehydration of excess active silt microbic biomass can be condensed by 305 times. Such degree of a condensation should be considered good at rather simple hardware registration of process of pressure head flotation. However losses of microbic biomass with the clarified silt water at a condensation of active silt pressure head flotation in certain cases rather big.
Researches showed that one of effective methods of preliminary consolidation of active silt is also electroflotation. Degree of a condensation of active silt electroflotation makes 3-5 at initial concentration of 0,6-1,0% absolutely of solids, and energy consumption makes about 1-2 kW. h on 1 m3 of initial suspension. Current density has the greatest impact on process of electroflotation.
Highly effective method of a condensation of rainfall of sewage and excess active silt is centrifugation. Advantages of a way - simplicity, profitability and low humidity of the condensed product; a shortcoming - big ablation of a firm phase with the clarified liquid (fugaty) that results in need of an additional stage of cleaning of a fugat, for example separation.
Tests of the electrofloatation device of the offered design on a number of productions showed its high efficiency at sewage treatment. As a lack of electrofloatation devices of a similar design it is necessary to consider that they cannot be applied to clarification of the suspensions containing grubodispersny impurity.
The applied schemes of cleaning have to provide the maximum use of the cleared waters in the main technological processes and their minimum dumping in open reservoirs. At widespread introduction of reverse systems there are additional reserves on reduction of a consumption of fresh water and reduction of dumping in open reservoirs. At widespread introduction of reverse systems there are additional reserves on reduction of a consumption of fresh water and reduction of dumping of sewage in reservoirs (improvement of technological processes, increase of efficiency of cleaning waste in. Sewage is pure if their assignment in water objects does not lead to violation of standards of quality of water in a controlled alignment or point of water use.
As the concentrated silt suspension has high viscosity, before its drying it is expedient to warm up previously. If biomass is used further as feed additive, thermal treatment is necessary.
It should be noted that at coagulation of impurity in volume of water and at contact with granular loading the optimum dose will be various as kinetic conditions of coagulation on a surface of the filtering material it is much better, than in volume of water.
Rather wide circulation was gained by pressure head flotation for consolidation of excess active silt. Its essence is in water saturation by air with considerable supersaturation by it that is provided with creation of excessive pressure for some time. At pressure decrease to the atmospheric the smallest vials of air which float the particles of impurity containing in water start being allocated.
Choice of optimum technological schemes of water purification - rather complex challenge that is caused by primary variety of the impurity which are in water and great demands made of quality of water purification. At a choice of a way of purification of impurity consider not only their structure in sewage, but also requirements with which have to satisfy the cleared waters: when dumping in a reservoir - MPD (maximum permissible dumpings) and maximum concentration limit (maximum permissible concentration, and when using of the cleared sewage in production - those requirements which are necessary for implementation of concrete technological processes.