| When the urban sewage treatment plant adopts the activated sludge method to treat sewage,it will generate a large amount of residual sludge.Due to its special floc gel structure and high hydrophilic characteristics,sludge dehydration performance is poor.After conventional chemical agent conditioning and mechanical dehydration,the sludge moisture content is still relatively high.Acid treatment and heat treatment are two cost-effective and easy-to-operate conditioning methods that can effectively crack the sludge flocs,release the combined water inside the sludge,and improve the degree of sludge dewatering.The separate conditioning of the two has limited improvement on the sludge dewatering performance,especially heat treatment only plays an active role at high temperatures.Domestic and foreign research on acid combined heat conditioning sludge is mainly concentrated in the high temperature stage,but there are some problems such as high requirements for equipment and high energy consumption.This paper mainly studies the effect of acid-heat combined conditioning method and acid and ferric sulfate combined with heat conditioning method at low temperature?less than 100°C?on sludge dewatering.The main research results of the experiment are as follows:?1?Separate acid and alkali to regulate sludge,and study the effect of acid and alkali on sludge dewatering performance at different pH.The results show that under acidic conditions,as the pH decreases,the sludge dewatering performance rises first and then decreases.The best pH is 3,After conditioning,the CST decreases from 130.2s of the original sludge to 88.2 s.The moisture content of the mud cake was reduced from 81.8%of the original sludge to 74.26%.Under alkaline conditions,the sludge dewatering performance continues to deteriorate with increasing pH.?2?Acid combined heat conditioning sludge,studied the effect of different pH,temperature and heating time on sludge dewatering performance.The experiment shows that the best conditioning conditions are:pH is 3,heating temperature 90°C,heating time 40 min.After conditioning,the CST is reduced to 45.2 s,and the moisture content of the mud cake is reduced to 64.86%.Too much acidity and too long heating time will cause the sludge dewatering performance to decline.?3?Fe2?SO4?3 combined with thermal conditioning sludge to study the effect of Fe2?SO4?3 dosage on sludge dewatering performance.The experimental results show that with the increase of the dosage of Fe2?SO4?3,the sludge dewatering performance will increase first and then decrease with or without heating.When the dosage is 136.4mg/g,the dehydration effect is the best.After Fe2?SO4?3 conditioning alone,the moisture content of CST and mud cake were 40.5 s and 67.99%respectively,which greatly improved the sludge dewatering rate,but the degree of dehydration was not high;after combined heat conditioning by Fe2?SO4?3,CST and mud The cake moisture content was as low as 20.4 s and 63.36%,respectively.?4?Combined thermal conditioning of sludge with acid and Fe2?SO4?3,the effects of different dosage of Fe2?SO4?3,heating temperature and heating time on the sludge dewatering performance were studied.On the basis of pH of 3,the best conditioning conditions were determined:Fe2?SO4?3 dosage 45.5 mg/g,temperature 70°C,heating time 40 min,after conditioning,CST and mud cake moisture content They are 28.2 s and 63.52%respectively.Considering the comprehensive dehydration effect and economic cost,it is considered that the combined heat conditioning method of acid and Fe2?SO4?3 is the best.Not only the dehydration effect is good,the required Fe2?SO4?3dose is small,but also the temperature requirement is reduced.?5?In this paper,by measuring the Zeta potential of sludge,the concentration of SCOD,protein and polysaccharide in the supernatant of sludge,SV and other indicators,a comprehensive analysis of the mechanism of each conditioning method affecting the sludge dewatering performance.The improvement of sludge dewatering performance by single acid conditioning is mainly through acid hydrolysis to crack the sludge flocs,reduce the internal water content of the sludge,increase the degree of sludge dehydration,and reduce the Zeta potential of the sludge by H+in the solution to promote sludge particles flocculation.The Fe2?SO4?3 conditioning alone mainly reduces the Zeta potential of the sludge through the high-valence positively charged electrolyte,causes the sludge flocs to aggregate,and improves the sludge dewatering performance.Acid-heat combined,Fe2?SO4?3 combined with heat,acid and Fe2?SO4?3 combined with heat conditioning can effectively crack the sludge floc and release more sludge through thermal hydrolysis or the combination of acid hydrolysis and thermal hydrolysis.The internal binding water increases the degree of sludge dehydration.On the other hand,under the condition that the sludge Zeta potential has been effectively reduced,increasing the temperature of the sludge accelerates the thermal movement of the particles and promotes the sludge to coagulate with each other into large flocs,which is significant improved sludge dewatering performance.Figure 37 table 4 reference 103... |
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