Research On The Performance Of The Advanced Dewatering Treatment Of Urban Excess Sludge By Electro-osmotic Progress

This paper studied the application of electro-osmotic dewatering(EOD)progress on the treatment of excess sludge after mechanical dehydration,which was weighted by the ending SMC,electric energy consumtion(EEC)and anode corrosion(AC).The influence of regular factors including initial thickness of the sludge cake,electric field intensity(EFI),pressure.The natures of the sludge itself demonstrated in this paper including its initial sludge moisture content-time(SMC),conductivity and initial pH of the sludge.Moreover,we have attempted to pretreat the sludge by the addition of K2Fe04,activated sodium persulfate(SPS),and Fenton reagent.It turned out that the thicker was the cake,the worse was the performance and the more of electric energy consumtion.When the initial thickness was 2.0cm,the EOD progress achieved the best performance with an ending SMC of 42.83%merely and its EEC and AC was 192.35(kW h)/tH,O and 12.32 kg/tH2O respectively.When the sludge cake was exposed to the vertical direct-current electric field,magnifying the EFI could improve the performance of EOD,reduce the EEC and AC.Result displayed that the EOD progress could get an ending SMC of 45.36%,when the EFI was 25V/cm.Then the EEC and AC was 357.42(kW·h)/tH20 and 14.96 kg/tH20 respectively.When the cake was extruded by a vertical force persistently,the cake could be dewatered quicky.But when the SMC was reduced to some extent,the help became weaker.When the initial was just 74.5%,the EOD progress obtained the best performance with a lowest SMC of 43.65%.The ending SMC reduced slightly with the increasing of initial SMC,when the sludge cake with a SMC lower than 74.5%.While the ending SMC increased prominently with the increasing of initial SMC,when the sludge cake with a SMC higher than 74.5%.A great conductivity had a slightly positive effect on the dewatering of the sludge,leading to the accumulation of heat in the cake quickly and largely.In the meantime,the magnifying of the sludge’s conductivity would result in the increasement of EEC and AC consequencely,and the larger was the sludge’s coductivity,the more of electric energy consumtion.When the sludge was pretreared by highly acidic environment or strong alkalis condition,the improvement of the EOD’s performance was not so obvious.Nevertheless,if it was pretreated by some mild acidic condition,the sludge could be dewatered fast and the ending SMC could be reduced to the largest extent.When the initial pH of the sludge was around 5,the ending SMC was reduced to 32.45%unbelievablely and the EEC and AC was only 201.67(kW·h)/tH2Oand 20.07 kg/tH20 respectively.That is,5 is the most effective initial pH.No matter the sludge was pretreated by K2Fe04,activated SPS or Fenton reagent,the performance of EOD progress would become better.And after it was pretreated by all of them,its VS S content and particle size was decreased,while Specific Surface Area(S.S.A)enlarged.When the dosage of Fe6+ was 50mg/gDS,K2Fe04 pretreatment achieved the best performance.However,addition of Fe6+resulted in the increasement of the alkalinity of the sludge and the outlet.Meanwhile,it leaded the the enlargement of the sludge’s conductivity and the increasement of EEC and AC at last.The optimal condition of activated SPS was a dosage of Fe2+18.8mg/gDS and a dosage of SPS 60mg/gDS with 15min stiring persistently.The ending SMC of the cake was only 35.19%after pretreated by activated SPS at the optimum.However,addition of activated SPS resulted in the decreasement of the sludge’s alkalinity.The optimal condition of Fenton was a dosage of Fe2+24mg/gDS and a dosage of H202162mg/gDS with 45min stiring persistently.The ending SMC of the cake was 43.87%after pretreated by Fenton reagent at the optimum.