Research On Application Of Aluminum-Containing Wastes In Wastewater Polishment And Sediment Remediation

Focusing on the massive dumping of aluminum sludge and waste slag generated in the water treatment plant and aluminum factory,this paper mainly discussed the feasibility of using the above aluminum-containing wastes in sewage polishment and sludge remediation.Firstly,the paper studied the optimal method to adopt these two aluminum-containing wastes to prepare the phosphorus-removing fillers after pretreatment.Based on this,the adsorption characteristics and mechanism of the fillers and the selection of desorbent were explored.Then,the prepared filler was packed in a column reactor to remove phosphorus in the simulated effluent of a constructed wetland.Later,the paper used aluminum sludge as an in-situ remediation agent for endogenous pollution in lakes,and explored its effect on overlying water,interstitial water and sediment,by which the control effect of aluminum sludge on the endogenous pollution of sediment was evaluated.The above research can not only reduce the environmental pollution caused by the stacking of aluminum-containing wastes,but also reduce resource waste and achieve the goal of“using waste to treat waste”.The main results and conclusions obtained in this study are as follows:?1?The fillers made of aluminum slag and aluminum sludge had good characteristics to adsorpt phosphorus.The optimal method to prepare the filler is as follows:0.5M hydrochloric acid was used as a solvent to mix with the waste residue of the aluminum plant at a ratio of mass to volume of 1g:30mL for 12h and collected the supernatant.Then the aluminum sludge,cement and the supernatant acquired were put into a granulator with a mass-to-volume ratio of 3g:2g:1mL to make fillers.Finally,the filler was maintained with proper humidity.?2?The adsorption test shows that the adsorption process of PO₄^3--P in solution with the filler can be described with a quasi-second-order kinetic adsorption model,and the adsorption rate was controlled by chemical adsorption.The adsorption characteristics of the filler to the phosphorus-containing solution can be described by the Langmuir isotherm adsorption model,and the adsorption type of the filler was chemical adsorption.The saturated adsorption capacity of the filler for phosphorus obtained by this model is 28.99mg/g according to calculation,which was close to 28.55mg/g acquired with measurement.?3?The continuous adsorption test of 110d showed that the concentration of PO₄^3--P can be reduced from 2mg/L to below 0.5mg/L when the simulated wetland effluent passed through the columnar adsorption reactor with hydraulic retention time of 60min and 30min.In addition,the adsorption column can also remove NO₃^--N and COD in the wastewater to a certain extent during the phosphorus adsorption process.Moreover,the effluent hardly contained heavy metals such as Cu,Zn,Ni and Cd,except that Pb concentration in the effluent was 0.025mg/L,which were lower than the specified value required in“Emission Standard for Pollutants for Urban Sewage Treatment Plants GB18918-2002”.Therefore,the filler can be used as a superior adsorbent for phosphorus removal without the potential danger of heavy metal pollution.?4?The combination of“0.02M citric acid+0.3M sulfuric acid”was used as the desorbent for the saturated adsorbent in the phosphorus adsorption column.After re-adsorb the desorbed filler for three cycles,the adsorption effect of the filler was decreased from the initial value of 28.27mg/g to 25.00mg/g.Meanwhile the mass loss was increased from 4.3%to 18.7%during this process.Therefore,the filler prepared with the aluminum-containing wastes not only can be used for phosphorus removal,but can be regenerated and reused.?5?The test results of aluminum sludge repairing sediments showed that the addition of aluminum sludge can significantly reduce the phosphorus concentration in the overlying water and interstitial water,where the greater the dosage used,the lower the phosphorus concentration was.There was no significant difference in the phosphorus concentration of the overlying water between one-time dosing and multi-dosing under the same total dosage.The addition of aluminum sludge can convert the unstable and easily released NH₄Cl-P and BD-P in the sediment to the stable and uneasily released NaOH-rP and HCl-P content,which had little effect on the content of residual phosphorus Res-P.Therefore,the addition of aluminum sludge can make the phosphorus form in the sediment more stable and can achieve the purpose of phosphorus-lock.?6?The dosage and method of aluminum sludge had no significant effect on the DO,pH,turbidity of the overlying water and ORP of the sediment,but it would increase the concentration of sCOD and NH₄⁺-N in the overlying water.It has been determined that the release potential of ammonia nitrogen in aluminum sludge was 0.065mg/g.Moreover,compared with the control group,the average sCOD in the overlying water of the test with 3%mass fraction of aluminum sludge was increased by 38.14%at the end of the 120-day experiment.Therefore,the addition of aluminum sludge has the potential to increase the concentration of ammonia nitrogen and sCOD in the overlying water.