Research On The Technology Of Advanced Treatment Of Coking Wastewater

The composition of coking wastewater,which containing colour and a large number of organic pollutants which is difficult to biodegradation, is very complex. Hence, the pollution of the wastewater from coking industry has been the focus in the field of environmental and industrial sector. China is the largest producer of coke in the world and a large amount of coking wastewater discharge to the surrounding which cause serious pollution. With the further increasing of environmental protection management strength and the serious shortage of water resources, the discharge standard will be more stricter. So, the advanced treatment of coking wastewater becomes very urgent .Because the area of Shandong province lacks of water resource, the government and corporates pay much attention to environmental pollution.The subject is the branch of the project which is the research on regional wastewater and demonstration.In the paper, CODcr and chroma are the main evaluation indexs and controling optimum operation conditions. The advanced treatment study of coking wastewater was carried out by experiments of coagulation, oxidation and activated carbon adsorption. The three experimental processes of PAC coagulation—Fe²⁺/NaClO oxidation, PAC coagulation—activated carbon adsorption and Fe²⁺/NaClO oxidation—activated carbon adsorption were adopted respectively on the basis of single factor optimization. The economy and feasibility of the processes were analyseed. The methods of the preliminary experimental study and theoretical analysis for wastewater recycling and the advanced treatment of coking wastewater were done in this paper.Experimental results showed as following:1,Ferrous sulfate could remove more CODcr than the PAC and PFS and its CODcr removal rate was 42.1%.But the decolorization of the PAC was the best, which colour removal rate was 62.5% in the optimum coagulation conditions.2,Under the conditions of pH = 3.0, NaClO of 2mL/L, Fe²⁺ addition of 40mg/L, reaction time of 10min, temperature between 25℃～45℃, the results of the treatment from Fe²⁺/NaClO were the best and its CODcr and colour removal rate were 62.2% and 81.7% respectively. The result of CODcr was136mg/L and the result of colour was 64 time. The effluent could reach second class national discharge standard (GB8978—1996). The way of dosage addition of NaClO was the batching. This method could improve CODcr and color removal rate, but the dosage of addition is not frequent as much as possible. The reasonable way of addition should be based on the real situation of the project.By doing so,it is economical and viable.3,The treatment result of Fe²⁺/NaClO was better than the Fenton reagent under the same experimental conditions.4,Under the conditions of pH = 4.0, activated carbon dosage of 2g/L, adsorption time of 30min, temperature of 35℃,the effect of activated carbon adsorption was the best.5,The three experimental processes of PAC coagulation—Fe²⁺/NaClO oxidation, PAC coagulation—activated carbon adsorption and Fe²⁺/NaClO oxidation—activated carbon adsorption have been adopted respectively to treat the coking wastewater. The experimental result showed: three kinds of processes could achieve first class national discharge standard (GB8978—1996).The Fe²⁺/NaClO oxidation—activated carbon adsorption process was the best, which average removal rate of CODcr was 83.2% and the average removal rate of colour was 92.3%,and its cost of the treatment was 7.70 yuan per ton. The cost of the PAC coagulation—Fe²⁺/NaClO oxidation process was the least, only 1.58 yuan per ton.6,Analyzed three kinds of processes ,the process of PAC coagulation—Fe²⁺/NaClO oxidation was more feasible under the best operating conditions of pH=7.0, PAC dosage of 200mg/L, PAM dosage of 1.5mg / L; pH=3.0, NaClO dosage of 1.5mL/L, Fe²⁺ addition of 30mg/L, room temperature and oxidation of 10 minutes.