Treatment Of Organic Wastewater In An Anaerobic Filter With Spherical Porous Carriers

For improving the processing efficiency of anaerobic filter,natural pumice,natural zeolite, plastic porous hollow ball and magnet blocks were adopted to make three different kinds of biocarriers including spherical pumice biocarrier,magnetic spherical pumice biocarrier and spherical zeolite biocarrier.These biocarriers were applied in an anaerobic filter for treating wastewater.The biofilm formation efficiencies and purification functions of biocarriers for domestic sewage and brewery wastewater were analyzed comparatively based on the adsorption properties of pumice.In addition,the bacteria and their adhesion condition onto biocarriers were identified by Scanning electron microscopy(SEM) and optical microscope.An iron-oxide coated pumice was developed and used to remove phosphorus from water for overcoming low removal efficiency of phosphorus by anaerobic filter.The main findings of the paper were as follows:(1) Natural pumice and zeolite can be applied as biocarriers in anaerobic filter since their porous surface could provide a well habitat environment to anaerobic microorganism.The experimental result showed that the removal rate of COD_Cr for magnetic spherical pumice biocarrier with 0～100mT was far lower than spherical pumice biocarrier in treating middle-high concentrated organic wastewater,which indicated that the magnetic field of 0～100 mT produced inhibition effects on anaerobic microorganism.(2) The results of adsorption experiments showed that both natural pumice and pumice in magnetic field were able to remove TP,NH₄⁺-N,COD_Cr from wastewater by adsorption.The magnetic field could increase the removal rates obviously.The removal rate of TP increased by 5.99 times when the magnetic intensity was 100～140mT.In the case of iron-oxide coated pumice, the maximum saturated adsorption capacity of phosphorus was 245mg/kg after 60 min of adsorption equilibrium time and the adsorbent particle size was 0.63～2.00mm.The removal rate of TP was 92.13%.Langmuir equation matched the isotherm adsorption feature well.(3) It is proved that the removal efficiency of magnetic spherical pumice biocarrier decreased rapidly in later stage of biofilm culturing experiment,after 69 days,the removal rate of COD_Cr decreased rapidly to about 30%,the removal rate of COD_Cr reached to above 70%by spherical pumice biocarrier.Seed sludge of biofilm culturing for spherical zeolite biocarrier came from excess sludge of spherical pumice biocarrier anaerobic.After 7 days,the removal rate of COD_Cr was above 80%,it was showed that the time of startup was shortened greatly compared to apply active sludge from urban wastewater treatment plant as seed sludge.(4) The treatment of domestic wastewater by anaerobic filters which filled with above three kinds of biocarriers was tested.It has revealed that the COD_Cr of effluent could meet the requirement for Class 2 of Discharge Standards of Pollutants for Municipal Wastewater Treatment Plant(GB 18918-2002),Sometimes it could reach the class 1B standard.The removal rate of TP,NH₄⁺-N,TN was low in all anaerobic filter.The treatment effect of magnetic spherical pumice biocarrier anaerobic was a little better than spherical pumice biocarrier anaerobic filter.(5) For treatment of brewery wastewater,the removal rate of COD_Cr was highest when Hydrological Retention Time(HRT) was 28h.The COD_Cr of effluent from spherical pumice biocarrier anaerobic and spherical zeolite biocarrier could reach pretreatment standard of Beer Industry Pollutants Emission Standard(GB19821-2005),and TP of effluent could reach the emission standard of GB19821-2005.(6) The SEM and optical microscope photos of the sludge show that the dominant species in anaerobic filters were bacillus and cocci,meanwhile these were a lot of high efficient methanogen which looked like Methanosarcina barkeri and Methanothrix soehngenii existed in anaerobic fitters.