Treatment Of Domestic Wastewater By Combined Processes Of Coagulation Cloth Media Filtration-biofilter

In recent years, although the overall wastewater treatment efficiency of our countryis high, the wastewater treatment and collecting efficiency of small town is low. Smalltowns have the characteristics of low economic development level and small water flow.The conventional nitrogen removal treatment facilities do not fit into small townsbecause of large covering area. In order to treat wastewater in an effective, energysaving and low consumption manner, this article established a combined coagulationcloth media filtration-anaerobic filter/trickling filter system.Primary settling tank in conventional wastewater treatment process was replacedby coagulation cloth media filtration system to remove SS, part of organic pollutantsand TP, the effluent of coagulation cloth media filtration system then entered a biofilterwhich consisted of anoxic-aerobic filter to mainly remove dissolved organic compoundsand nitrogen. The aerobic filter obtained oxygen by natural ventilation without aeration,which could save a lot of energy. In this paper we studied the treatment efficiency ofsmall towns sewage by coagulation cloth media filtration-anaerobic filter/trickling filtersystem, witch included the construction and optimal operation parameters of coagulationcloth media system, the start of biofilter, the treatment efficiency of pollutants especiallyDOM, the DO distribution through the biofiter, the property of biofilm and sludgeduring the stable operation of the combined process.In the coagulation cloth media filtration system, supernatant fluid of acid solublefly ash was selected as flocculating agent with400nylon mesh as filter cloth material.When the system was adapted in the treatment of actual domestic wastewater,50%CODCr and81%TP was removed at the condition of pH=7,1mL/L flocculating agentand30L/h constant flow rate. After50min, filtration pressure reached2KPa andbackwash was needed.The startup of aerobic trickling tank took30days and more than70%COD wasremoved with more than2mg/L dissolved oxygen in on-way outlets and3~7m3/m2hydraulic loading. The trickling tank could effectively remove ammonia. However,when the hydraulic loading increased to6~7m3/m2·d, ammonia removal rate decreased.TN removal rate was highest when nitrated liquid reflux ratio was160%.The on-way dry weight of biofilm, content of polysaccharide and protein decreasedwith the drop of the height of trickling tank. When the height was0-30cm, high dryweight of biofilm, content of polysaccharide and protein could be obtained, whichincreased with hydraulic loading,The DOM of domestic wastewater of small towns consists of hydrotropicsubstance HPI and hydrophobic organic acids HPO-A, which contain vast amount ofhumic acid fluorescence peak, fulvic acid fluorescence peak, microbial leachatefluorescence peak and aromaticity protein fluorescence peak. Among them, microbial leachate fluorescent substance and aromaticity protein fluorescence are the primaryfluorescence substances in DOM of domestic wastewater of small towns. Thecoagulation cloth media filtration system could effectively remove hydrophobicsubstance while microbial trickling filter system could effectively remove aromaticsubstances.The excess sludge of the system was primary chemistry sludge with sludgeproduction of0.105~0.21kg/m3,97~98%of water content. The production of chemistrysludge far exceeded the sludge produced by trcilking tank. The content of residue TNwas23g/kg, TP was43g/kg, organic compound was320g/kg, aluminium salt was13.2g/kg, ferric salt was7.3g/kg.