| With the continuous improvement of urban residents’ living standards and the increasing proportion of social industry industrialization,sewage discharge from sewage treatment plants increases,while sludge production increases.According to statistics,the annual discharge of sludge in China is about 22 million tons(moisture content calculated according to 80%),and the amount of sludge in China is about 10%～15% growth rate every year.At the same time,China has a large number of abandoned crop straw resources,the output of about 700 million tons per year,but due to the lack of appropriate treatment measures,can not reach the effective use of straw.At present,the main disposal methods of straw in China are incineration and stacking,which is obviously uneconomical and unreasonable for the disposal of a large number of crop waste straw.In north China,the winter temperature is low,especially the water temperature of sewage treatment plant can not reach the appropriate temperature in winter,which affects the effluent quality and the water quality treatment effect is poor.However,the water source heat pump,gas boiler,biomass boiler and other commonly used water source heat pump are affected by high heat source consumption and high environmental protection requirements.Therefore,it is of great significance to seek economical,energy and efficient heat generation system and way for wastewater extraction and improvement of effluent water quality under low temperature conditions.In this study,sludge cultivation and domestication were firstly carried out by controlling pH value,dissolved oxygen and other influencing factors.Then on the basis of sludge cultivation and acclimation,aerobic composting of sludge and straw was carried out by adjusting the ratio of sludge and straw,and the variation rules of volume,moisture content and C/N ratio parameters in the aerobic composting process were studied.The optimal ratio of sludge and straw was determined based on the highest temperature that the heat generation system could reach.Finally,the influencing factors and measures of temperature control of the heat generation system were studied.Main conclusions:(1)Temperature,pH value and dissolved oxygen are important factors affecting the effect of sludge cultivation and domestication.In the process of sludge cultivation and domestication,the real-time monitoring and regulation of these factors is the key to ensure the good effect of cultivation and domestication.In this experiment,the biochemical tank temperature was 16℃～18℃,the pH value was 7.6～8.5,the dissolved oxygen concentration was 1～2mg/L in the early stage,and 3～5mg/L in the later stage.Finally,good mature sludge floc was obtained.(2)Through the calculation and analysis of the heat generation model of the heat generation system,the heat of the heat generation system is positively correlated with the C/N ratio and water content of the system.In the range of 20:1-30:1 C/N ratio,the higher the C/N ratio,the higher the heat of the system.In the range of water content of 50%～65%,the higher the water content of the system,the higher the heat of the system.Taking the maximum temperature that can be reached by the heat generation system as the judging standard,the best ratio of heat generation system operation is sludge and straw mass ratio of 1:1.5,under this ratio,the maximum temperature of heat generation system temperature can reach more than 50℃.(3)Based on the analysis of the factors affecting the temperature of the heat generation system,the pH value of the reactor is stable in the neutral or slightly alkaline range of 7.0 ～8.5 on the basis of the ratio of sludge to straw 1:1.5,moisture content is 65%,and C/N=25 is the optimal initial operating conditions of the heat generation system. |
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