Study On The Treatment Of Coke Wastewater With Iron/Carbon/Fenton-biological Combination Processing

Coke wastewater contains a large amount of pollutants with high concentration, toxic,high chromaticity and poor biochemical performance. It is difficult to use conventional biochemistry or physicochemistry methods to treat coke wastewater to meet the standard of treatment. Consequently, developing other steady and high-efficiency methods is the most important aim in the field of development of treatment technology of coke wastewater.In this study, considering the properties of coke wastewater, Fe/C-Fenton coupling technique was used as the pretreatment technology, aiming to dispose refractory organism, reduce toxicity and enhance the biodegradability. After the pretreatment combination process of O/A/O was chosen as the follow-up biochemical treatment system. Influencing factors in treating process, optimization of operation condition of pretreatment reactor and combination biotechnology and methods of enhancing biodegradability of wastewater were investigated. Based on the result of this research, pretreatment of Fe/C-Fenton and biological combination technology of O/A/O were used and adjusted in a wastewater treatment project treating coke wastewater, and the stablity and effect of this system in the project were considered.The research concludes that:optimum operating condition of the pretreatment reactor is that pH in the range of 3.0-3.5,1.4mL/L of H2O2, Fe/C of 1.5(v/v),3.5mg/L of PAM,30min reacting time and no aerating; optimum operating condition of the system of biochemistry treatment is that influent pH at 7.5-8.5, keeping temperature in the range of 25-35℃,40h of HRT in contact oxidation stage with DO 4.0-5.Omg/L,25h of HRT in anoxic stage with DO<0.5mg/L,25h of HRT in secondary aeration stage with DO 3.0-4.0mg/L and the recycle flow rate of the nitrified effluent of 300%. Under the optimum operating condition, in the pretreatment stage above 35% of COD,45% of volatile phenol and 70% of colority could removal and the value of B/C increase from 0.22 to above 0.45 which could satisfy the requirement of O/A/O treatment. Because of the reliable and stable treatment results and favorable effluent quality achieved in pretreatment, a high-efficiency biodegradation, stable treatment results and strong impact resistance on loading could be obtained. The specific effluent quality of contact oxidation tank and secondary clarifier are respectively as follows: contact oxidation tank:COD<600mg/L, ammonia nitrogen<120mg/L, chromaticity<170, volatile phenol<10mg/L, cyanide<0.5mg/L and oils<5mg/L; secondary clarifier: COD<100mg/L, BOD5<20mg/L, NH4+-N<15mg/L, volatile phenol<0.5mg/L, cyanide<0.5mg/L, oils<5.0mg/L and chromaticity<50.The practice running result of project shows that using combination biochemistry technology of Fe/C-Fenton and O/A/O to treat coke wastewater the effluent quality could up to the Class A of Integrated Wastewater Discharge Standard(GB8978-1996), which proof that it is feasible to use the combination biochemistry technology in coke wastewater treatment.