| With the increase of the disposal of sludge volume by municipal sewage treatment plants,the sewage treatment problem is quite severe.How to achieve efficient dewaterability becomes an important topic as well as a hot research task at home and abroad.This thesis,which was based on H2O2 lysis and flocculation conditioning technology,aims to develop more effective technology of sludge dehydration after investigating the effects of the combination on dewaterability.Based on the hydrogen peroxide chemical lysis technique,the current study investigated the effects of different kinds of flocculants in combination with hydrogen peroxide to improve the sludge dewatering performance.By comparing the effect and cost of the chemicals,aluminum sulfate was decided as the optimizing flocculant in combination with hydrogen peroxide.The optimal sequence of combination was that the hydrogen peroxide should be added before the aluminum sulfate.A single-factor experiment was conducted to examine the impact of every influence factor on sludge dewatering performance.And an orthogonal experiment was conducted to further determine the sequence of each factor which effects the sludge dewaterability is pH>dosage of Al2(SO3)4>dosage of H2O2>oxidized time of H2O2.The optimal condition parameters for combination were determined as follows:initial pH was 3,hydrogen peroxide dosing was 2ml/L(AR H2O2 volume/sludge volume),conditioning time was 60 minutes,and aluminum sulfate dosing was 0.2 g/g.This study also explored the impact of filtrate recycling to original sludge(moisture content 80%)on dewaterability.Results found that the dewaterability could be improved significantly under the optimum conditions,and the moisture content of sludge cake as well as the specific resistance of sludge reduced 12.28%and 64.92%respectively.Besides,the problem that the pH of filtrate was low when sludge was treated with combination of hydrogen peroxide and aluminum sulfate was solved,and the dosage of acid and the chemical cost were reduced as well.To further analyze the mechanism of the combination of hydrogen peroxide and aluminum sulfate,this study also explored the effect of Zeta potential,the flocculate structure in sludge,and the composition of the EPS on sludge dewaterability.It was demonstrated that there's link between dewaterability and Zeta potential.Both H2O2 and Al2(SO4)3 could decrease the Zeta potential of the sludge particles.When combined,the average of |?| was 1.17mv.The ? potential of the sludge particles declined,thus improving the sludge dewatering performance.With proper quantity,aluminum sulfate could promote the flocculation of sludge particles and improve the dewaterability.Whereas excessive aluminum sulfate made the sludge particles to bring a positive charge,making the sludge flocculation capacity and the dewaterability of sludge worse.The average value of fractal dimension(D2)of sludge flocs increased from 1.25 to 1.55,which indicated that the sludge dewatering performance was related to the sludge floc structure.The more dense the sludge floc was,the smaller the sludge particle clearance was,the better the settleability of sludge and the dewatering rate of sludge was.After co-conditioning of H2O2 and Al2(SO4)3,the contents of EPS and LB-EPS in sludge reduced considerably,and the ratio of LB-EPS/TB-EPS reduced as well.The contents of LB-EPS was related to the flocculation capability of sludge,the ratio of LB-EPS/TB-EPS was also related to the degree of sludge dewatering,thus can prove that the reduction of the contents of LB-EPS and the ratio of LB-EPS/TB-EPS was beneficial to enhance sludge dewaterability. |
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