Research On The Treatment Of The Sludge From Urban Sewage Disposal Plants By Cwao

It was puzzled that a large amount of sludge whose emission has already reached to 18 million tons/a produced by municipal sewage treatment plant, furrhermore, which will has increased by 10-15%. Therefor, it was very important significance to study an economic and reasonable sludge treatment method based on the principle of hazard-free, reducing quantity and reclamation. At the core of catalytic wet air oxidation technology (CWAO), this paper studied the treating and disposing scheme of municipal sludge systematically.Making the removal rate of CODCr as the target, the influence on sludge wet air oxidation efficiency of reaction temperature, time and oxygen partial pressure were investigated. It was found that the CODCr removal rate of sludge increased when the reaction temperature increased, or the reaction time prolonged, or the oxygen partial pressure of the reaction system rised. Reaction temperature:180℃, room temperature equivalent oxygen partial pressure:1.0MPa, reaction time:90min was found as the optimal technological conditions of sludge wet air oxidation treatment in which the sludge CODcr removal rate could achieve to 51.1%.Cu has been selected as primary catalytic element to prepare metal oxides catalyst by method of coprecipitation which respectively doped equimolar other elements such as Fe, Mn, Co, Ce, Zn, Ni, Al and Ag. The catalytic efficiency of each catalyst under the same reaction conditions of sludge catalytic wet air oxidation has been compared. It was found that Cu-Fe, Cu-Ni, and Cu-Co catalyst has obtained the highest catalytic efficiency in the initial, middle and terminal period of reaction as well as Cu-Ce catalyst had the characteristic of low leaching quantity of metalions.Technological conditions research of sludge catalytic wet air oxidation has been carry out withγ-Al2O3 supported catalyst which prepared by dipping equimolar elements of Cu, Fe, Co, Ni and Ce. It was found that the optimal technological conditions and catalyst preparation scheme of sludge catalytic wet air oxidation in the experimental system as follow, reaction temperature:180℃, stirring rate:400rpm, catalyst addition quantity:8.0g/L, room temperature equivalent oxygen partial pressure:1.0MPa, reaction time:90min, catalyst dipping concentration:4wt%, catalyst roasting temperature:500℃, catalyst roasting time:5h. Under the optimal technological conditions, the CODCr removal rate of sludge could achieve to 72.6% as well as Cu2+ leaching concentration reached 19.2mg/L while reaction ended.The moving-transiting rule of N ang P element in the sludge has been studied under the obtained optimal catalytic wet air oxidation technological conditions. It was found that a mojority of organic N and P has been inorganized and transferred to liquid-phase. The investigation of moving-transiting rule of organic-phase in the sludge while reaction lasted 30min has indicated that almost all organic matter in the sludge solid-phase transferred to liquid-phase or thoroughly mineralized, withal, dewatering property of sludge has been improved obviously. The volume of sludge have reduced by 80.3%,85.1% and 94.4% respectively by the solid-liquid separation technology of sedimentation, gravity filtration and vacuum filtration applied.