| Sediment is related to the nutrient circulation of river and lake ecosystems.The formation process is full of various physical chemistry and biological reactions.It is usually located at the bottom of rivers and lakes.It contains rich organic matter and nutrients,mostly gray-black.For the ecological management of rivers and lakes,the first consideration is the ecological dredging and treatment of the sediment.The dredged sediment has a high water content and is rich in nutrients.It is randomly stacked to occupy a large amount of land and pollute the environment.Therefore,the most important thing for river and lake sediment is to dehydrate and control the release of pollutants,so as to reduce its accumulation volume and environmental impact.In this regard,this article has carried out the following aspects of research around the river sediment:Calcium-based Polyferric Sulfate(CaPFS)strengthens electroosmosis dehydration,and explores and optimizes the amount of CaPFS added,electrode voltage,mud cake thickness and standing time.The results show that under constant piezoelectric infiltration,as the amount of CaPFS added increases,the moisture content of the mud cake decreases first and then increases.When the amount of CaPFS added is 0.5gFe/kg·DS,the dehydration efficiency reaches a maximum of34.9%.The sediment rate is 68%,and the moisture content of the final mud cake is57.88%.Measurement and analysis of mud cake organic matter,pH value,electrical conductivity,sludge particle size and temperature found that the amount of CaPFS added had no significant effect on the content of organic matter;the conductivity of the extracted water and the osmotic dehydration efficiency had similar trends;mud cake temperature Increasing the reduction of its viscosity is conducive to the progress of electroosmosis dehydration,but it will also increase the energy consumption of dehydration accordingly.Properly increasing the electrode voltage can improve the dewatering effect and reduce the moisture content of the mud cake,but too high voltage also results in a decrease in dehydration efficiency and an increase in energy consumption.At 20 V,the electroosmotic dehydration efficiency is 43.16%,the energy consumption is 0.10 kWh/kgfiltrate,and for a sediment with a moisture content of 68%,its moisture content can be reduced to 54.76%.Increasing the thickness of the mud cake can appropriately increase the dewatering effect,but the energy consumption for dewatering has increased.When the thickness of the mud cake is 3.75 cm,the dehydration efficiency reaches a maximum of 45.62%,and the final moisture content of the mud cake is 53.62%.After adding CaPFS,the standing time becomes longer,and the electroosmotic dehydration efficiency increases first and then decreases,but the energy consumption for dehydration decreases first and then increases.When the standing time is 10 hours,the final moisture content of the mud cake is reduced to 49.90%,and the dehydration efficiency is 40.85%.Considering the dehydration efficiency and energy consumption,the appropriate parameters of CaPFS to assist in electroosmosis dehydration are:CaPFS dosage 0.5 gFe/kg·DS,electrode voltage 20 V,mud cake thickness 3.75 cm,and standing reaction time 10 h.CaPFS enhances the effect of phosphorus fixation:When the amount of CaPFS is 0-0.5gFe/kg·DS,the phosphorus retained in the sediment to the cake is increased from 65%to 83%.Decreasing the pH of the sediment is beneficial to the fixation of phosphorus,and it is found that the relationship between the amount of iron in CaPFS and the loss to remove phosphorus in the water:LP=0.011+0.058*exp(-39*Fe),R~2=1.00.According to this,the amount of CaPFS added can be determined according to the phosphorus concentration pre-controlled in the water body,so that the removed water can reach the corresponding water body control standard.Effect and economic analysis of phosphorus dehydration and sedimentation in sediment:when CaPFS is added at 0.5gFe/kg·DS,voltage is 20 V,mud cake thickness is 3.75cm,and standing time is 10h,the moisture content of layered mud cake after dehydration is tested,Analysis of pH,conductivity,and phosphorus content.turn out:(1)The final moisture content of the upper layer,middle layer and lower layer of mud cake increases sequentially;(2)From bottom to top,the pH of the mud cake changes from weakly acidic to weakly alkaline;(3)Electricity distribution law:upper mud cake>lower mud cake>middle mud cake;(4)Phosphorous fixing efficiency:middle layer(49.33%)>upper layer(40.32%)>lower layer(36.73%).According to the analysis,an electrolytic reaction occurs near the electrode plate,the anode generates H~+and the cathode generates OH-,and the middle part has the highest conductivity due to H~+and OH~-.Driven by an electric field,the phosphorus element gradually moves from the cathode to the anode,so the total phosphorus content of the sludge near the anode and the middle layer is higher than that of the cathode. |
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