Study On The Treatment Of Landfill Leachate By Physics Chemical Process

As we all know the gross of garbage grew fast with the development of economy, and the sanitary landfill was considered to be the favorable process on treating lots of waste in our country, so it is necessary to study the landfill leachate treatment craft. Through introducing the characteristic of leachate and some disposal technologies, we can know adsorption, membrane technology, chemical oxidation and biotreatment were widely used to removing organic matter in the landfill leachate treatment, meanwhile the main problems in the leachate treatment process at present and the development tendency in the future were indicated. Adopting the single tehchnology to deal with the leachate was hardly to reach the standard. Hence, it is of great significance to study on the pre-treatment technologies, we adopted physical-chemical multi- stage as the pretreatment craft in the research. The main aim was to looking for a high efficacy and low cost pre-treatment process, which was able to alleviate the high load of leachate in the following biological treatment process. NH3-N, COD, TP, Color and BOD₅ were considered as the detection index during influent and effluent in the research, technology about denitrogenation had compared too. In the paper, Microwave, Fenton, NaClO, KMnO₄, H₂O₂ and Na2HPO₄·12H2O, MgCl2·6H2O were choosen to deal with the leachate. Via controling pH, oxidant dosage and reaction time, we had foud the favorable experiment condition. The economic efficency evaluation was also done in the paper.The single factor experiment results showed that while the microwave power was 700W, irradiation time was 10min, COD, NH3-N, TP and Color removal rate in the leachate could reach 37.66%, 96.14%, 40.00% and 80.00%, the ratio of BOD₅/COD increased from 0.16 to 0.43 under single microwave process. The efficiency of chemical agent was ordered on organic degradation ability, it was Fenton>NaClO>MgNH4PO₄>KMnO₄>H₂O₂, and COD removal rate could reach 63.62%, 59.53%, 56.87%, 46.34%, 21.60%, respectively. Microwave process and the principle of ammonia phosphate magnesium precipitation have high efficiency in ammonia nitrogen removal.Comprehensive each experiment results, we had choosen Fenton, NaClO, KMnO₄, H₂O₂ to combine Microwave process for further studying. The effects of leachate treatments under microwave-oxidation process were investigated in the most favorable condition. Compared to these without microwave-pretreatment, NH3-N removal rate increased evidence under microwave-oxidation process, and it has saved some oxidant dosage, while pH=5, reaction temperature T=50℃, added NaClO 24mL·L^-1 into the leachate, the removal efficiency of COD, NH3-N, TP and Color under microwave-NaClO process was 98.63%, 99.67%, 97.25% and 98.00%, respectively, BOD₅/COD has risen to 0.8. The efficiency was microwave-NaClO>microwave-Fenton>microwave-KMnO₄>microwave-H₂O₂. The removal efficiency of microwave-H₂O₂ process is lowest of the microwave-oxidant, while pH=3, reaction temperature T=50℃, added H₂O₂ 9mL·L^-1 into the leachate, COD, NH3-N, TP and Color removal efficiency under microwave-H₂O₂ process was 69.23%, 99.30%, 91.50% and 97.00%, respectively, BOD₅/COD has reached to 0.7. Reasons for the efficiency of microwave-Fenton process lower than that of Microwave-NaClO process were discussed, it relies on the change of oxidation relative to coagulation on increased less apparent molecular weight organic in the leachate after irradiated by microwave, and the change of pH also makes some effects. Research on kinetics suggests that the process of microwave induced oxidant to deal with the high concentration landfill leachate accords with the first-order or second-order reaction rule. The cost of leachate treatment by Microwave-Fenton process was 4.5 yuan/m3, it was lowest of the microwave-oxidant processes.The introduction of MW-pretreatment in microwave combined oxidant process, macro–molecular substances has degradated into micro-molecular substances in leachate after irradiated by MW, making use of the“thermal effect”and“non-thermal effect”of MW, it has enhanced the biochemistry ability of the leachate, and it has also enhanced the following oxidizing reaction efficiency; Na2HPO₄·12H2O and MgCl2·6H2O followed the principle of ammonia phosphate magnesium precipitation by phosphate and magnesium. Ammonia was wiped off in the formed of MgNH4PO₄, at the same time some organic matters were wiped off through complexation-flocculation.