Reading guidance：In all sludge disposal technologies, anaerobic digestion technology with energy recovery and processing the sludge stability, sludge less amounts of advantages, and gradually become one of the major te

     In all sludge disposal technologies, anaerobic digestion technology with energy recovery and processing the sludge stability, sludge less amounts of advantages, and gradually become one of the major technique of residual sludge treatment and energy utilization. But traditional sludge anaerobic digestion are slower, anaerobic fermentation cycle is long, sludge processing efficiency is very low, limiting the wide application of anaerobic digestion technology.
    It is proved by relevant researches that the hydrolysis reaction of sludge cell wall in the main limiting step of anaerobic digestion rate of sludge. Because of the presence of most of the organic matters in the sludge in the microbial cells and cell wall of microbial cells is a stable semi rigid structure and belongs to biology to inert material degradation, hydrolysis is difficult, resulting in sludge anaerobic digestion process takes a long time. In order to improve the performance of anaerobic digestion, the domestic and foreign scholars for residual sludge pre processing efficiency method and conducted extensive research. Its ultimate goal is to for subsequent sludge disposal and utilization of process optimization of the premise.
    It is thermal disposal technologies which are successfully applied in relevant projects. But, thermal disposal requires high operation temperature and pressure. It also requires high running and management level. Therefore, it is difficult to apply thermal disposal technology widely in china. Ultrasonic due to the relatively low energy consumption and processing time is short without introducing may cause secondary pollution to the material, has received extensive attention. Scholars through reduce the operating conditions of the heat treatment, using a simple thermal treatment on sludge floc structure improvement and inspect heat treatment alone, alone of ultrasonic treatment and thermal and ultrasonic combined pre treatment on sludge broken cells and subsequent anaerobic digestion effect.
 1. Influence to anaerobic digestion gas amount caused by pretreatment
    Thermal hydrolysis treatment in the process of high temperature and high pressure can make sludge cell wall breaking, so that cells in most of the colloid substances dissolved, macro molecular organic matter is broken down. At the same time, the cell bound water is released;
   During ultrasonic pretreatment process, certain intensity of ultrasound radiation liquid will produce cavitation phenomenon and the sludge cells to break, two pre processing method can make sludge cell material was released, can be used in the process of anaerobic digestion of organic matter quantity increased, so as to improve the gas production of sludge anaerobic digestion.
   After analysis, we find that pretreatment will produce different effect for different sludge. For sludge whose solid content is about 3%, the influence caused by pretreatment to anaerobic digestion gas production efficiency can be presented as following sequence: pyrohydrolysis, ultrasonic pretreatment and combination disposal of these two methods; for sludge whose solid content is about 5%, the sequence is presented as following: ultrasonic pretreatment, pyrohydrolysis and combination of these two methods. the reason why different effects are got is caused by ultrasonic functional mechanism. Ultrasonic pretreatment, ultrasonic radiation from the object is sludge system of liquid phase, solid containing rate for 5% of the sludge system, liquid content less sludge flow difference, ultrasonic effect was not very good diffusion, making treatment effect is reduced.
 2. Influence caused by temperature to anaerobic digestion
  Generally, temperature mainly affects growth rate and metabolic rate of microbes. Then, gas production amount is affected. Foreign countries always adopt pyrohydrolysis (after disposal, the temperature is 38 to 42 degree centigrade). Digestion effect is pretty good. Under a same pretreatment condition, whether we can get same or better effect with 35 degree centigrade, which should be tested by real projects.
   Different temperature under anaerobic bio-gasification of different, is due to the microbial growth needs suitable temperature, temperature will not only affect the anaerobic microbial growth rate, but also affect the rate of microbial degradation of organic matter. Therefore the degradation of suitable temperature can ensure the efficiency of anaerobic digestion. Pretreatment and temperature is changing the two factors of anaerobic digestion period. The increase of pretreatment and raising the temperature to the sludge in the anaerobic digestion process faster organic matter decomposition, shorten the reaction time of anaerobic digestion. Shorten the cycle of anaerobic digestion test, the influence of the temperature effect greater than pretreatment.
   In summary, by increasing pre treatment can improve the anaerobic digestion of sludge gas production performance. Reasonable high temperature can make the anaerobic digestion of sludge gas production has been greatly improved. Reasonable increasing temperature and pretreatment can increase anaerobic digestion bio gas production and shorten the sludge anaerobic digestion period. On the effect of anaerobic digestion to produce gas pretreatment effect was greater than that of temperature. And for the anaerobic digestion time effect of temperature effect greater than pretreatment.
 
 

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