| The main way to deal with municipal solid waste was sanitary landfill,which produced landfill leachate.In this paper,the landfill leachate produced by a household garbage landfill site is taken as the research object,COD removal rate as the main index,through the analysis of water quality and the comparison of the existing treatment process,the method of treatment of landfill leachate by coagulation combined with advanced oxidation technology is proposed.This study mainly includes the following aspects:?1?Experimental study on treatment of initial landfill leachate by coagulation method.PAC and PFS was selected as the coagulant,the order of addition is PAC before PFS addition,the ratio of m?PAC?:m?PFS?3:1,the dosage of coagulant and PAM 1451.80 mg/L and 3mg/L respectively,reaction pH=5.The stirring speed was 200 r/min for 2 minutes?min?,and the stirring speed was 50 r/min for 20 min.After the reaction,the stirring was allowed to rest for 30 min.Under these conditions,the removal rate of the COD 60.14%,and the content of COD decreased from 2903.76 mg/L to 1157.58 mg/L.?2?The treatment of initial landfill leachate with Hydrodynamic Cavitation?HC?under inlet pressure of 0.4 MPa.In the experiments,the influence of operating parameters such as orifice opening rate???,the arrangement of orifice and reaction time on chemical oxygen demand?COD?and BOD5?biochemical oxygen demand?/COD removal in leachate was studied,and the energy efficiency was evaluated.The results show that under the above conditions,the removal rate for COD of orifice plate with annular arrangement orifice was better than that of orifice plate with radiation arrangement orifice.And the orifice plate with an orifice opening rate???of 0.0439 had the best effectiveness.The COD removal rate was22.63%when the optimal operation time was 60 min.The biodegradability of water was obviously improved,and the BOD5/COD was increased by 57.27%.The energy efficiency evaluation also showed that the energy efficiency of the orifice plate with?=0.0439 was the highest,which was 8.24×10-3 mg COD/J.?3?Treatment of landfill leachate by ClO2 alone after coagulation.The effects of ClO2dosage and reaction pH on the treatment were investigated.The results showed that ClO2greatly increased COD in leachate,this suggested that ClO2 could only destroy organic matter but not mineralize it.In the process of ClO2 treatment of landfill leachate,in the range of pH=4-8,the change range of COD was the same.When pH=4,the increase range of COD was the largest,53.44%.When ClO2 dosage reached 400 mg/L,COD increased by 71.72%,and COD hardly changed after further increasing ClO2 dosage.?4?Experiment of landfill leachate treated by HC/ClO2 after coagulation.On the basis of HC,the effects of ClO2 dosage and reaction pH on the treatment effect were investigated.The results show that the best operating conditions for HC/ClO2 were:pH=5,the initial concentration of ClO2 was 25 mg/L,and the maximum COD removal could be achieved after the reaction for 120 min at the inlet pressure of 0.4 MPa.After HC/ClO2 treatment,the content of COD decreased from 1157.58 mg/L to 476.69 mg/L,and the removal rate reached58.82%.?5?Free radical verification experiment.The phthalic acid was used as the·OH capture agent,the capture products were analyzed by fluorescence spectrophotometry.The results showed that both HC and HC/ClO2 could produce·OH,and the capture·OH of HC/ClO2system was much higher than that of HC process alone.At the same time,Rh B was used as a pollutant model,the addition of trichloromethane which was O2·-scavenger and tert-butanol was ClO·scavenger were all reduced the removal efficiency of on Rh B traed by HC/ClO2,indicating that HC/ClO2 system could produce O2·-and ClO·. |
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