Study On Treatment Of Waste Incineration Leachate Membrane Concentrate By Combined Process Of Chemical Precipitation-VUV/O₃-Membrane Distillation

Waste Incineration Leachate Membrane Concentrate（Incineration Leachate Membrane Concentrate,ILMC）contains lots of salt(such as Na⁺,K⁺,Ca²⁺and Mg²⁺)and refractory biodegradable organic pollutants,and the electrical conductivity is as high as 30-80 m S/cm.Thus,typical high-salt organic wastewater needs to be effectively treated.In this study,the chemical precipitation-VUV/O₃-membrane distillation combined process was used for advanced treatment,and the efficiency and influencing factors of ILMC in the chemical precipitation-VUV/O₃process,Ca²⁺and Mg²⁺removal mechanism,the changed characteristics and degradation mechanism of organic matter,and the influences on membrane distillation were studied.In addition,combined with computational fluid dynamics（Computational Fluid Dynamics,CFD）technology and the desalination performance and membrane flux of ILMC treated by membrane distillation were systematically explored.The study revealed the flux decay law,membrane fouling type and control strategy,temperature and concentration polarization.The research concluded theoretical support for the resource application of ILMC.In order to eliminate the inorganic scaling problem on the membrane surface,the chemical precipitation method was used to remove Ca²⁺and Mg²⁺in ILMC,and the influencing factors and removal mechanism were studied.The results showed that:when p H=12.3 and PAM dosage=3mg/L,>99%Ca²⁺and Mg²⁺in ILMC were removed by the formation of calcite and brucite,and the floc sedimentation effect was better;The total number of DOM obtained increased,in which the removal and generation of macromolecular organic matters with carbon number>35 and highly unsaturated substances with DBE>25 were obvious,and the compounds in other regions changed less.On the basis of eliminating the inorganic scaling problem on the membrane surface,the VUV/O₃process was used to treat the remaining organic matter in ILMC after chemical precipitation,and the influencing factors and degradation mechanism were studied.The results showed that:VUV radiation and appropriate solution alkalinity could increase the·OH concentration in the VUV/O₃process;When p H=11.5-12,O₃dosage=50 mg/min,88.1%COD removal and 100%humus removal were achieved;the combined action of O₃and·OH degrades organic compounds（1-4 k Da）with high aromaticity and high conjugation into simple aliphatic products（<1 k Da）;the order of DOM oxidation by VUV/O₃was humic-like acid>fulvic-like acid>protein-like substances;from the molecular level,after VUV/O₃treatment,the total amount and complexity of DOM were greatly reduced,and it was mainly shifted to substances with high H/C value,low O/C value,and simpler molecular composition;CHO compounds（39.75%）and CHON compounds（35.87%）accounted for a larger proportion in the DOM after the reaction.In this paper,the membrane flux(V_m^ave),water quality and membrane fouling of ILMC in the membrane distillation process were studied,and the velocity field,temperature field and concentration field in the process of membrane distillation processing ILMC were simulated by CFD technology.The results showed that:the inorganic scaling（Ca CO₃and Mg₅（CO₃）₄（OH）₂·4H₂O）on the membrane surface was eliminated by the chemical precipitation process,the concentration factor（Concentration Factor,CF）of ILMC treated by the membrane distillation process was increased from 0.5 times to 12.5times,after the VUV/O₃process further reduced the organic pollution（such as humus scaling）of membrane surface,the CF was increased to 19.5 times;the membrane distillation process can efficiently retain inorganic salts and other substances（>99.99%）,and the obtained distillate meets the water standard of the circulating cooling system in the plant;the effects of temperature and concentration polarization during membrane distillation treatment of ILMC were gradually enhanced along the fluid flow direction;moreover,increasing the temperature difference will increased V_m^ave,but also increased the degree of concentration polarization and the risk of mineral fouling;increasing the feed concentration will reduce V_m^aveand concentration polarization,but it had relatively little effect on temperature polarization;increasing the feed flow will increase V_m^ave,at the same time,the temperature polarization effect of the membrane surface was significantly reduced.