| Filtration rate and pretreatment is one of the important parameters affecting filtration efficiency in drinking water treatment system,pre-ozonation and pre-chlorination are the two most commonly used chemical pre-oxidation methods,which are widely used,flexible to adjust and have good universality.However,there is still a lack of in-depth research and unified conclusion on the impact of filtration rate and pretreatment on the filter performance.In this paper,by means of water plant investigation,operation data analysis,pilot-scale test and production test,the filtration rate and operation condition of the filters were evaluated and diagnosed,the optimal operation and treatment effect of water plants in regions with different typical raw water quality were investigated,the treatment effect of pre-oxidation enhanced filtration on water pollution during seasonal drainage period in southern China was investigated,the difference of pre-ozonation and pre-chlorination for performance enhancement of filtration was explored.The results show that the average filter rate difference within±0.5 m·h-1,probably three filter filter rate is roughly uniform and close to the design value,which can avoid the water quality change caused by the volatile filter rate,in addition,through the continuous monitoring found that filter rate fluctuation affected significantly by raw water flow changes,the correlation coefficient is 0.796,Bilateral test value P was 0.000,the survey results showed that raw water in different places suffered from different pollution,presenting different water quality characteristics,such as high algae,high organic matter,high turbidity,etc.Pre-oxidation with conventional process can effectively treat the above water pollution,improve the water purification efficiency of conventional process,so as to ensure the water quality,the analysis of historical data shows that the pre-oxidation enhanced filtration process can effectively deal with the deterioration of raw water quality in the seasonal drainage period,and the filtered water can be controlled within the internal control standard of 0.3 NTU to guarantee the quality of finished water.Although pre-ozonation and pre-chlorination has enhanced filtration performance,but the pre-ozonation and pre-chlorination on the strengthening of the filter effects are different,the biomass of filter surface layer with pre-ozonation is pre-chlorination’s 5～6 times,pre-ozonation can provide both oxygen and nutrients to the formation and growth of biofilm in the top layers of sand filter,which is one of the main reasons for the rapid increase of water head loss when pre-ozonation is applied.After the 2.0 mg/L prechlorination,there is still 0.35 mg/L residual chlorine in the water,which will restrain the growth of filter biofilmin sand filter,which in turn would solve the problem of excessive head loss increase caused by excessive biofilm growth in the filter.Pre-chlorination with polyaluminium chloride have more excellent performance in filtration process than with ferric chloride,the turbidity of the water before filter and after filter is lower than ferric chloride about 0.1 NTU,the total head loss and surface loss ratio of filter with polyaluminium chloride are lower than using ferric chloride about 10%.The analysis and discussion in this aspect has positive theoretical and practical significance for the operation management optimization and upgrading of pre-oxidation and filter process. |
