Research Of Ultrasound On Activated Carbon Regeneration In Coking Wastewater

Activated carbon, as an excellent adsorbent, has been widely used in wastewater treatment because of its well-developed pore structure, large surface area and other characteristics. In advanced treatment of sewage in coking plants, the combination of powdered activated carbon (PAC) and UF membrane process is often adopted as pre-treatment to decrease the COD concentration of the sewage and reduce the difficulty of the subsequent treatment processes. Due to the high cost of PAC, regeneration of PAC is an effective way to lower the overall cost of the treatment. Ultrasound technology was adopted for PAC regeneration in this research. The research studied the optimum conditions for PAC regeneration and the changes of PAC and organic matter during the regeneration. The main results are as follows:(1)Using ultrasonic for PAC regeneration was practicable. The results showed that under the condition of33kHz ultrasound,200W power, pH=7and the mass ratio of carbon to water were1/15, the PAC regeneration efficiency could reach69.39%after20minutes of ultrasound operation. When using treated wastewater from coking plants as regeneration fluid, the regeneration efficiency of PAC could reach to6.56%under the optimum condition. But the regeneration efficiency could be increased to36.23%when the proportion between treated wastewater and tap water is1:3. The wastewater could be used as regeneration fluid with tap water to reduce cost and save running water.(2) The B/C of regeneration fluid increased from0.03to0.33after regeneration. It was showed that after regeneration the wastewater could be transported to biochemical process of the plant. Besides, the organics could be degraded by ultrasonic during PAC regeneration process. The B/C of the effluent from secondary biochemical treatment increased to0.31after being treated by ultrasonic under the optimum condition for240min. The biodegradability of wastewater became better after regeneration.(3)The research also studied the changes of particle size of activated carbon, surface area, exterior appearance, adsorption of iodine and methylene blue during the regeneration. After9months’adsorption-regeneration circulation the exterior appearance, adsorption of iodine and methylene blue of the PAC decreased37.57%,29.77%and57.88%, respectively. The PAC could not remove the COD and became muddy. So the PAC should be replaced regularly in a practical application.(4)The water during the adsorption-regeneration process was separated by UF equipment for analyzing changes of organic matter under the function of ultrasonic. The result showed that the organic matter lower than5kDa could be removed best by PAC.83.20%of the organic matter lower than5kDa could be removed by unused PAC and74.00%by regenerated PAC. The result also showed that the organic matter lower than5kDa and between30kDa to10kDa could be cumulated into the PAC during the regeneration.