Research On Bio-drying Characteristics And Mechanism Of Sludge Electro-dewatering

Sludge treatment and disposal is an urgent problem in sewage treatment industry.In order to achieve the goals of reduction,stabilization,harmlessness and resource utilization of sludge,it is necessary to dewatering and drying the sludge.According to the current characteristics of high energy consumption of sludge drying,it was proposed that mechanical dewatered sludge was pretreated dewatering by electrical dewatering and then made the sludge further reduced by bio-drying.The influence factors on the process of electrical dewatering and the biological and chemical characteristics of sludge were investigated.The microbiological and kinetic mechanism of the bio-drying of electrical dewatered sludge was explored through the analysis of microbial community and the kinetic model of volatile solid degradation.The water and heat in the bio-drying of electrical dewatered sludge were calculated.This technical route provides an innovation,high efficiency,energy saving and environmental friendly new ideas for sludge treatment and disposal.With the water content(60.00%)of sludge as the target and the dewatering time and energy consumption as the evaluation indexes,the influencing factors of electrical dewatering process were optimized.The results showed that when selected P-100filter cloth,combined pressure,1000 g initial sludge and 20 V voltage to electrical dewatering,it cost 7.5 min and 0.065 k W?h energy consumption when the sludge moisture content was dewatered from 83.41%to 60.00%.This stage is the high-efficiency and low-consumption section of the process of sludge electrical dewatering.The electrical dewatering has a great influence on the characteristics of sludge.After electrical dewatering,the C/N value of sludge increased,the particle size increased,and the relative abundance of some aerobic microorganisms increased.This change is conducive to the bio-drying reaction of electrical dewatered sludge.The bio-drying of electrical dewatered sludge was studied.The direct bio-drying of the sludge after electrical dewatering was studied.It was showed that the water content of the sludge decreased from 53.28%to 42.17%during the drying process,and the accumulated water removal rate reached 41.49%,indicating that the electrical dewatered sludge direct bio-drying was feasible.Though investigating the influence of bio-drying factors,it was found that microbial inoculant could promote the drying effect.The combination of lower initial moisture content and smaller particle size is more suitable for bio-drying.The Sphingobacterium,which can decompose fatty acids and complex organic materials in the bio-drying,has always been the dominant genus in the bio-drying of electrical dewatered sludge.A new degradation model was proposed by studying the degradation kinetics of volatile solids in the bio-drying of electrical dewatered sludge,this model also contains the effects of temperature,moisture content,aeration rate,and can more suitable for the bio-drying of materials with lower volatile solid content.According to the water and heat balance,water evaporation in the bio-drying of electrical dewatered sludge is the main way to remove water.Metabolic water production accounted for 25.11%of the evaporated water,which was indicating that the biological action could degrade the water in the sludge cells,and then drying the sludge with the help of bio-heat production evaporation.The effect of different particle size and initial moisture content on the heat content was investigated,and the results showed that the maximum heat yield and the minimum Q_evap/Q_bio value in the reaction process occurred in the bio-drying group with small particle size(<3mm)and lower initial moisture content(38.69%).The synergistic effect of particle size and initial moisture content of sludge has a significant effect on the heat production of bio-drying.