Disinfection Of Reclaimed Water In Urban Of Pilot Study

The reuse of sewage has become an important research field. Because of urban sewageincludes many pathogenic microorganisms which discharged by human and animal, so howto guarantee the healthy security of reclaimed water is much important, and disinfectionplay a key role in guarantee the safety for reclaimed water. Nowadays, chlorine is muchoften used in disinfection of reclaimed water, but chlorine could produce disinfectionby-products which are bad for the healthy of human. Therefor, in this test the disinfectiontechnology of secondary water tank which treated by UV and ozone micro-bubbles weremainly studied.In this test, the Gaobeidian secondary sedimentation tank effluent was taken as rawwater, Firstly, the secondary water from municipal wastewater treatment plant→GACenhanced sand filtration→UV disinfection and secondary effluent from municipalwastewater plant→UV disinfection ware taken as comparison test. The resultsshown that,after secondary effluent of wastewater treatment pretreated by GAC enhanced sand filtration,total coliform and fecal coliform inactivation rates increased by24.5%and23.3%,respectively; while the UV dose was13.2mJ/cm², the total coliform was less than100CFU/L; the fecal coliform were undetectable after UV disinfection. When the water treatedby the GAC enhanced sand filtration, the total coliform bacteria was less than100CFU/Lwhile the UV dose was13.2mJ/cm², and the total coliforms Photoreactivation also reducedsignificantly. The disinfection effect for reclaimed water is obviously. In order to ensure theeffluent accord with the GB18918-20021A standard in which the fecal coliform is less than1000CFU/L, UV dose for6mJ/cm2was necessary. From the study to kinetic of UVdisinfection reaction, particle concentration and the load of microbial both had the effect onkinetic reaction of UV disinfection, hereinto, the impact from particle concentration isbigger than load of microbial.The reclaimed water treated by secondary effluent of municipal→GAC enhanced sandfiltration→ozone mm-bubbles and secondary effluents of municipal→GAC sandfiltration→ozone micro-bubbles were taken as comparison tests. The results showed thatwhen the L/G between3.5and6.5, ozone dosage was25mg/L, the dissolved ozoneconcentration of micro-bubbles could reach4.6mg/L, and the dissolution rate of micro-bubbles increased by2.5times more than bubble aeration. When bubble aeration wasreplaced by micro-bubbles in the ozone dosage was8mg/L, the maximum removal rate ofColor, UV254, TOC and COD_Mnincreased by32%,9%,5%and6%，respectively. Underthe same ozone dosage, the total coliforms of micro-bubbles effluent were less than3CFU/L,faecal coliforms were not detected, but the total coliforms of bubble aeration effluent couldreach35CFU/L, and faecal coliforms could reach6CFU/L.In the ozone oxidation test, the relativity between COD_Mnand TOC was also discussed.The test results showed that the correlation was much well. In addition, through the costassessment of ozone micro-bubbles disinfection, the maintenance cost of the wholeequipment of the ozone micro-bubbles was around0.11RMB/t.