Study On The Characteristics Of Sludge Electro-dewatering And Quaternary Ammonium Surfactants Enhanced The Sludge Electro-dewatering

In this study,the relationship between moisture content and conductivity,dewatering rate and current or voltage were discussed through electro-dewatering experiments of sludge.The kinetic equations of electro-dewatering process under constant voltage were derived based on the conclusions obtained from the experiments and the theoretical analysis,then the mathematical expressions of moisture content changing with dewatering time were obtained,and finally the accuracy of equations were verified by the experimental results.The effects of quaternary ammonium surfactants dosages on the electro-dewatering capacity and energy consumption were analized,and then the mechanism for quaternary ammonium surfactants enhancing sludge electro-dewatering were also investigated.The main experimental conclusions are as follows:?1?Under constant current,the decline rate of moisture content increases first and then remains stable,the decline rate of moisture content keeps decaying in the operating mode of constant voltage.No matter in what kind of operating mode,dewateing rate is strongly correlated with current,constant current can maintain a constant dewateing rate.Although the change of process parameters significantly affects the electro-dewatering kinetics,but the variation of sludge conductivity with moisture content is not affected.?2?The mathematical expressions of current and dewatering rate,moisture content and dewatering time were derived,which were verified by the results of electro-dewatering with two different sludge.The results show that during the transitional period,the slow increase in dewatering rate and the rapid decrease in conductivity are related to the strong migration of ion,when the migration was completed,the dewatering rate is proportional to the current,the experimental results of the current and dewatering rate are in good agree with the derived equation?R²>0.79?.The fitted curves of the equations of sludge moisture content and dewatering time in stage II are basically consistent with the experimental results?R²=0.99?,which proves the effectiveness of the proposed equations.?3?Compared with the untreated sludge,when 0.6%and 0.8%TMAB were added,the average dewatering rate of sludge were improved by 7.8%and 18.2%,and the final moisture content of sludge was 59.3%and 57.7%,lower than 63.5%of the untreated sludge.For sludge treated with 0.6%and 0.8%DTAB,the average dewatering rates were increased by 21.9%and 31.2%compared with the untreated sludge,and the final moisture content of treated sludge were 56.9%and 52.2%respectively,below than 63.5%of untreated sludge.When the dosages of TMAB are 0.6%and 0.8%,the dewatering time to obtain the target moisture content?60%?were 858 s and 772 s,respectively,and the target dewatering time for 0.6%and0.8%DTAB conditioned sludge were 745 s and 581 s,while the moisture content of untreated sludge cannot be reduced to below 60%before the end of dewatering process.Economically and energetically,0.6%DTAB performed best,as it can achieve the second shortest target dewatering time?745 s?,second lowest final moisture content?56.9%?,smallest target energy consumption(5.0 k Wh/kg _DS)and most important of all,the lowest f?cost?(0.26k W·h²·kg _Dose/kg_DS³).This work also shows the DTAB are more effective in promoting sludge electro-dewatering and reducing cost,due to its superior solubilization and bridging effect.