Research On Electro-osmosis Dewatering For Sludge Reduction Technology

With the gradual improvement of urban sewage treatment rate and the increasing in the number of new sewage treatment plants, the amount of sludge produced by various types of wastewater treatment facilities are also gradually increasing. Every year, China’s urban emission of wet sludge (with the moisture content of about 80%) is estimated to have reach 30 million tons. At the same time, the speeding up of urbanization makes the receiving farmland into urban areas. Sludge treatment and disposal problems begin to appear in some big cities, and spread to medium-size cities and small cities. The sludge reduction has become an issue of urgent and it is one of the hot studies of scientific research personnel.In the sludge reduction, how to reduce the moisture content of sludge is the key to solve the problem of sludge treatment. According to the state regulations, when the sludge is used for landfill or land utilization, the moisture content of sludge must be reduced to below 60%. Therefore, we need a cost-effective depth of dewatering technology to make the moisture content of sludge to achieve the state standard.In this paper, we use the sludge which is dewatered by mechanical dewatering for the research and use the electro-osmosis dewatering technology for the depth sludge dewatering experiment. Effect of different experimental conditions, as well as using different kinds of cloth and electrode materials to the electro-osmosis dewatering and energy consumption are studied. And the characteristics of the sludge cake after electro-osmosis dewatering are studied in this paper. In addition, the influence of conductivity and pH on dewatering effect and energy consumption is evaluated by adding the inorganic salt solutions, washing by the deionized water and adding different concentrations of acid and alkali solutions. The experimental results show that:The optimal operating conditions for the electro-osmosis dewatering of sewage sludge in the experiment are determined to be the mechanical pressure of 61 kPa, the voltage of 30V, and the sludge thickness of 1.0cm. We choose 300 mesh nylon cloths and compared with the use of stainless steel plate electrodes, the coated titanium electrodes have better anti-corrosion and dewatering efficiencies.After the electro-osmosis dewatering, the moisture content, pH, and conductivity of the sludge cake will have some changes. With adding inorganic salt solutions to the sludge, the final moisture content of sludge has decreased as the increasing of the conductivity. However, the energy consumption has increased. Then decreasing the sludge conductivity by deionized water washing has little impact on the final moisture of sludge. But the energy consumption has decreased. In addition, under acid condition, the effect of electro-osmosis dewatering is slightly better than the alkaline condition.