Advanced Treatment Of Landfill Leachate Effluent By Hydration Reaction

Source reduction is a critical approach to decrease leachate concentration discharged from landfill. Permeable Reactive Barrier (PRB) has been proven to be an effective on site way for the removal of the leakaged leachate, while the components of PRB is the key factors for the efficiency of the pollutant removal.The cement is one of the promising and predominated materials used in PRB through the hydration reaction. In this work, the different types of cements,ie.portland cement,aluminate cement and compound cement, were applied for the advanced treatment of landfill leachate from MBR, and the reaction conditions,such as dosage of cement,the value of initial pH, reaction time and stirring rate,were optimized by the measure of the eluate in terms of COD, TOC, SUVA254,TN,TP;The mechanism of pollutant removal was studied using GC-MS,IR, XRF and SEM,etc, of which the model was established. The results in detail were as follows: (1) Hydration reaction could be one of the promising ways for the advanced leachate treatment, and Portland cement could be applied,with the optimum dosage, the value of initial pH,the reaction time and the stirring rate of 50 g/L,8.3(which was the pH of raw landfill leachate), 24 h, and 200 rpm, respectively. The corresponding removal rate of COD, TOC and SUVA254 were 55.6%, 62.1% and 68.8%, respectively. Portland cement is more effective in the removal of the refractory organic pollutants with the ultraviolet range of 200-400 nm, such as aromatic organic, double bond of organic matter. As for aluminate cement, the optimum conditions under the test conditions were as follows: cement dosage of 50g/L, pH of 10, reaction time of 15 h, the stirring rate of 300 rpm, and the corresponding average removal rate of COD, TOC and SUVA254 were 45.6%, 52%, 65.8%, respectively.(2) The combined cement of aluminate cement and Portland cement at the ratio of 1:10 are more effective in the pollutant removal in leachate, and the corresponding removal rate of COD, TOC and SUVA254 were 47.1%, 56.9%, 64.4%, respectively, under the optimum conditions of the dosage of 50 g/L, pH of 8.3 (which was the pH of raw landfill leachate), reaction time of 24 h, and the stirring rate of 200 rpm.(3) The removal rate of TN and Cl- from landfill leachate was as low as below 10%, while that of SO42- was more effective, with the removal rate more than 70%. It was also found that portland cement were more efficency for the SO42- removal, compared to the compound cement and aluminate cement.(4) The hydration reaction preferred to remove benzene, alcohols and organic matters with double bonds in leachate, instead of the Saturated hydrocarbons, such as alkanes, which both contribute to COD concentration in leachate effluent after biological treatment. Hydration reaction model was also preminially developed based on the test conditions, and the pollutant in leachate could be mainly removed by the accumulated of hydration products, such as Ca(OH)2, C-S-H, using the adsorption, complexioned with Ca2+ and coated within the complexion.