Applied Research And Safety Analysis Of Reusing Filter Backwashing Water Directly

In the production of a large number of drinking water,the water plant can not avoid the discharge of part of the wastewater,this part of wastewater in the traditional process is not taken seriously,generally take a direct way to enter the drainage network.These wastewater mainly comes from the coagulation sedimentation and filtration unit in the water treatment plant,these two parts of the wastewater accounted for 4% to 7%,for the water plants,which daily output several hundred thousand tons or even millions of tons,this part of the wastewater is already great.And with more and more attention in China's water resources and water environment,the treatment of the wastewater has been widespread concern.In order to solve the above problems,the wastewater began to be used in the water plant,which not only solve the problem of water shortage,but also reduce the emissions.while eliminating a large number of pollutants in the sewage water environment and the impact of land,So for the disposal of wastewater production provides an important social and economic benefits.Removing adverse effects in the water environment and land,and providing important social benefits and economic benefits for the disposal of wastewater as the same time.In this paper,the DE water plant in Guangdong Province was used as the object of study,and the effect of backwashing wastewater reuse on water quality was studied by small experiment.Short-cycle production test and long-cycle production test were carried out to monitor the influence of reflux on effluent quality index of each process unit.In addition,the introduction of biological testing techniques,the proposed biosafety evaluation testing system,the main research results and conclusions are as follows:In the wastewater producting by the water plant,the sludge is more polluted than the filter backwash water,and the composition is more complicated.The total amount of solid particles in the front of the sedimentation tank is more.The static sedimentation experiment found that the front end of the sludge to achieve a longer time,but after 30 minutes to achieve mud separation.Most of the metal elements in the sedimentation process to be removed,mainly due to the flocculation of metal elements on the adsorption,so the placental water content of metal elements higher,and appear along the pool length from the front and then gradually less trend,the front end higher.And backwash water content decreased over time,and maintained at 5NTU.Backwash metal of raw water indicators exceed dozens of times,so in direct reuse should focus on the concentration of metal ions in question.Through the backwash water backflow test experiments,found in the range of 20% reflux ratio as the backwash water recycling ratio increases,water turbidity decreased after the sinking.In CODMn indicators,when the Recycle ratio is less than 6%,the water significantly decreased when the reflux ratio between 6%~10%,slowly increasing trend.When the reflux ratio is less than 6%,no significant increase of the total water bacteria,but after he exceeded this proportion,began to increase.For Al,Fe,Mn,Cd several metal elements in some reflux ratio does not sink in water after preconcentration,but will be removed more effectively.In the actual production,the reflow process will not have an impact on SS,ammonia nitrogen,DOC and other indicators,by t-test,we know that,in addition to SS index return these water quality objectives have not changed significantly.But on the solid particle content have strengthened such as turbidity removal effect.Long-period surveillance backwash flow back to turbidity,NH3-N,CODMn had no obvious impact,sink water and filtered water outlet are well below the limit requirements of national standards.Biological safety evaluation,bacteria were detected found the recycling process does not increase the total number of colonies of filtered water,filtered but will to a certain extent,an increase in water,Escherichia coli and fecal streptococci levels,other bacteria was found,this is mainly due to the reflux is relatively small,so less impact.Luminescent bacteria toxicity test and suggested that the reuse of wastewater and fish acute toxicity test acute toxicity risks associated with not,mercuric chloride equivalent is less than 0.02mg/L,zebra fish and no abnormal deaths and cases.SOS/umu genetic toxicity tests show that,backwash recycling will increase direct genotoxicity in filtered water,but also indirect genotoxic substances removed.The carcinogenic risk is less than 10-5,so at a safe level.Through the study of Backwashing wastewater in some reflux ratio of security under the condition of no significant effect on water quality,in line with national drinking water standards.