A Pilot Study On Recirculating Filtration For Municipal Wastewater Treatment

Wastewater treatment is to a very large extent a matter of particle separation. This is a result of the fact that most of the pollutants in wastewater exist on particulate or colloidal form or are transformed to this form in the course of the treatment process. Seeking one kind of highly effective technology to remove the particulate pollutant at the same time, also may remove the partial dissolve pollutant, not only may greatly reduce the processing flow, moreover can reduce the operating cost, has the extremely vital significance to the developing country or the area. The technics of recirculating filtration aerated out of the filter, has offered a new idea for solving this problem. While recirculating filter has shorter process, lower cost, better pollutant-holding capability, once handle may be able to reach the requirement to discharge. The pilot study that filling was expanded-perlite took actual municipal sewage as marriage partner in Xi'an, lasting for 235 days, The research content was focused on the following parts: performance of contaminants removal, influence factors of operation performance, periodic changing of operation performance and backwash characteristic.The results of operation data showed that recirculating filter attained stability in 12 days in the start-up period. While the flow rate was 1 m/h and recirculation ratio was 5, the recirculating filter got the best operation performance, TCOD, SCOD and SS of the inflow were 489.0mg/L, 177.4mg/L and 304.2mg/L, outflow were 82.2, 65.0 and 40.7mg/L and average removal ratios of TCOD, SCOD and SS were 82.7%, 62.1% and 86.9%.While influent loading varied from 3 to 8kgCOD/(m~3·d), the COD of outflow fluctuated from 40 to 170mg/L. The influence of influent loading on operation performance of recirculating filter can be got over by adjusting recirculation ratio. Removal effect of SS was bad with high hydraulic loading. While the recirculation ratio were 3, 5 and 7, removal ratios of SS were 90.6%, 86.9% and 76.3%. The operation performance of recirculating filter varied periodically in response to backwash, and the periods was 24h.