Research On Sludge Water Treatment In Waterworks In Wuhan

The two primary sourses of waste from water treatment processes are sludge from the settling tank, resulting from chemical coagulation, and wash water from backwashing filters. These discharges are highly variable in composition, containing concentrated materials removed from the raw water and chemicals added in the treament process. Historically, the method of waste disposal was to discharge to a water course added no new impurities,but merely returned material that had originally been present in the water. This argument is not now considered valid, since water quality is degraded to the extent that a portion of the water is withdrawn and chemicals used in processing introduce new pollutants. This thesis has reviewed the benefit of Water-Treatment-Plant (WTP) wastes disposal, its history and state-of-the-art in China and other countries. The experiment is made of jar test and spot test phases. During the course of the jar test phase,the study was conducted on the sludge thickening properties and some facters that affect the sludge thickening in waterworks. According to the concentration tank design theories, a model concentration tank was designed and made by fruit of the jar test. The spot test phase is divided into two steps: middle test on concentration tank and research on pilot sludge drying field. In middle test on concenrtration tank, different burthens of flux were chosen, the suspended solid in supernatant and the solid content in the sludge after thickening are inspected during the course of persistent working state in order to validate the design parameter, Besides this, the test by means of treating by polyacrylamide before the sludge enters the thickening tank and adding different inclined boards were conducted. Then based on the results of the field experiment of pilot sand drying bed, the performance of sand drying beds for waterworks sludge dewatering in Wuhan was researched, and some problems existed in the present design methods for sand drying beds were studied. The performance for sludge treated by polyacrylamide was also researched. After making analysis we can make conclusions as follows:. The sludge in Baihezui Water Plant belonged to river sludge containing much mineral, have good thickening properties and dewaterablity with less specific resistance; Thickening and dewatering properties of sludge will be amlierated by means of being treated by cation polyacrylamide or anion polyacrylamide, the effect of cation polyacrylamide is better, the turbidity of supernatant of the former is also lower,but cost of cation polyacrylamide is higher;The result of experiment and anlysis indicates that using the concentration tank design theories to design concenration tank was feasible; Space between the inclined boards exert great influence on the thickening capability of the concentration tank, the burthen of the concentration tank with the space of 6.7cm is 30 per-cent higher than that of 12cm; the burthen of the concentration tank with adding polyacrylamide will be improved more than 50 percent than without. The turbidity of supernatant will hoik rapidly even if polyacrylamide is added largely while solid content in influent sludge is more than 1.5 percent; The suspended solid of leachate through the drying sand bed is very low and is always less than criterion of drainage. During the studying time, phenomena that sludge choke the filter bed or penetrate through the filter bed never happens; While sludge is treated by polyacrylamide, course of air dehydration is accelerated obviously and the cycle of air dehydration is curtailed about ten days, the burthen of the drying bed is aggrandized distinctly.