Pilot Plant Research On Advanced Treatment And Re-utilization Of The Wastewater From Coking Plant

Based on the deeply analysis of property and constituents of sewage which derived from Wuhan Pingmei Wugang Unite Coking Co. Ltd, the circulating cooling sewage was determined to be purified by Coagulation - Sand filter treatment and Ultra-Filtration - Reverse Osmosis (UF-RO) process. Meanwhile, coking biochemical effluent was treated by Coagulation - Sand filter - Active carbon method and UF - RO treatment. In addition, the total amount of the predetermined water were calculated, the membrane material and the pump were selected. Two technical process aforementioned were merged into the pilot-plan perfectly by using overstep pipe. According to the continuous operation of device, the UF- RO trement's effects on these two sewage were investigated, and then some operating process parameters were analysed and optimized, as well as the economical feasibility of treatment.The indication of results could be stated as follow: as regards the coagulation effect of circulating cooling sewage, poly ferric sulfate (PFS) was superior to poly aluminium chloride (PAC); Quartz sand as a filter material used in mechanical filtration devices could meet the requirements of UF pre-filtration. If the property of sewage was better (lower concentrations of Ca2+and Mg2+), it can be directly reused after the treatment of mechanical filtration and Ultra-Filtration (UF) ; On the contrary, it needs further Reverse Osmosis (RO) treatment if the property of sewage was worse(higher concentrations of Ca2+and Mg2+), and its total hardness exceeds the required values of circulating cooling sewage on this condition. After the treatment of UF, effluent's indicator such as turbidity, sludge density index (SDI) conformed to requirements of the influent of RO process. RO system is not only running steadily, but also eliminated various ions effectively in wastewater (such as COD <12.5mg / L, Cl-<1.5mg / L, Ca2+ = 0mg / L, Mg2+ = 1.3mg / L, hardness = 5.4mg / L, conductivity = 11.5μS/cm etc.). Moreover, the rate of desalination is more than 98% , and the characters of effluent is very stable.The sewage could be reused without the treatment of RO if the property of sewage was better (lower concentrations of Ca2+and Mg2+), and the cost is only 0.48 yuan / t. Provided more than 50% of sewage didn't dispense with the process of RO, the cost could be around 1.04 yuan / t. The bigger propotion of effulent RO treated, the more money it consumed. If the whole sewage was isolated by both UF and RO, the operation expense could be mounted to 1.34 yuan/ t.As to coking biochemical effluent, if it was decontaminated only by Coagulation - Sand Filter - Activated Carbon Adsorption Process, SDI> 3, Turbidity> 1NTU, which still fall short of the requirements of RO's influent. By means of consecutive operation, membranes of both UF and RO are seriously contaminated. For this reason, the coking biochemical effluent must be resorted to even more efficacious ways (such as Fenton's reagent Oxidation, increasing the height of Activated Carbon Adsorption column, etc.), so that dual-membrane could be applied to cleanse wastewater without being stained by residual organics and suspended paticles, but that will aggrandize operational costs.