Applied Research On The Two-stage Filter Process In Advanced Urban Wastewater Treatment

The State Environmental Protection Administration stated that urban sewage dischange plant shall subject to the implementation of the fist level A standard of the " Pollutant Discharging Standard of Urban Sewage Disposal Plant "(GB18918-2002). In this case, it’s a necessity to add an advanced sewage disposal System.Based on the experiment of effluent from secondary tank passing through homogeneous quartz sand and combet fiber material series connection combination filter (two-stage filter), the effect of the two-stage filter is studied, and then the feasibity of the two-stage fitter’s application to the advanced urban sewage dischange is discussed.based on the experiment of effluent from secondary tank pass through homogeneous quartz sand and comet fiber filter material series connection combination filter (two-stage filter), the effect of the two-stage filter is researched and also the feasibility of the two-stage filter’s application to the advanced urban sewage dischange is discussed in this paper.According to the experimental results analysis, we can confirm basic parameters such as, the filter layer’s thickness, the particle diameter of quartz sand filter material, leakage of SS, etc. Study shows that the layer thickness of two-stage filter should be600mm, homogeneous quartz sand particle diameter should be0.71mm to2.0mm, leakage SS should be controlled below5mg/L;We take an experiment with the sewage of Secondary Setting Tank as filter raw water through the two-stage filter, the initial speeds respectively are12m/h,14m/h,16m/h,18m/h,20m/h, to study the impact on removal rate of SS in sewage by different initial filter tates, and removal effect of the two-stage filter on other water quality indexes. It showed that the faster the initial filter speed, the lower the removal effect on SS and other water quality indexes, when at he best filtration rate of16m/h, the SS removal rate is more than90percent, the removal rate of CODcr, NH3-N, TN and TP are28.9%,21.2%,24.6%and21.2%respectively.Piezometer tube changes can reflect the changes in head loss during filtration.Through the analysis of head loss of piezometer tube,head losses of homogeneous quartz sand filter column and comet type fiber filter column are92.6cm and57.7cm respectively.Compared with the traditional filter, head loss value is smaller.According to the study of filtration performance curve of the two-stage filter and the comparison with filtration performance curves of comet-style fiber filter,homogeneous quartz sand filter and fiber ball filter, we can analyze the filter features of the two-stage filter through the analysis of filtration performance curves.Backwash is an indispensable phase for filter, after many times research, we have got the most suitable type of back flushing method for homogeneous quartz sand and the comet-style fiber filter material, homogeneous quartz sand filter material joint air and water backwash is divided into three stages, the comet fiber filter material air and water backwash is divided into five stages. By analyzing and comparing experimental effectiveness of backwash under the condition of different gas intensity and water intensity,we can determine the most suitable water intensity and gas intensity of two-stage filter backwash, to get the backwash parameters.This study shows that the two-stage filter has the advantage of good filter effects, huge water production capacity and large interception capacity, small head water loss, backwash thoroughly, etc. It is feasible to applicate the two-stage filter to the advanced sewage disposal, the two-stage filter research has developed a new combination of reliable filtration process for advanced sewage disposal.