Study On Novel Bio-denitrification Technology Of Coking Wastewater

Coking wastewater comes from the high-temperature carbonization of coal, Purification of coal gas and the process of refining chemical products. It’s shown from MRI-chromatogram that there are dozens of inorganic and hundreds of organic compounds in the wastewater. The inorganic ones are mostly nitrogen, thiocyanate, sulfide, cyanide, etc. And the organic ones include mainly single-ring or polycyclic aromatic compounds, heterocyclic compounds with N, S, or O, etc.A/O and A2/O are widely adopted for coking wastewater treatment at present. The biochemical reaction in the processes is traditional nitrification and denitrification. Ammonia nitrogen is oxidized to nitrite (NO2-) and nitrate (NO3-) by the action of aerobiotic nitrobacteria. Then NO3-and NO2-are transformed into N2, which can emit to the air, by the action of anaerobic denitrifying bacteria with the consumption of organic carbon resource. The processes have such problems as high rang of nitrate solution refluence, external carbon resource requirement because of low C/N ratio, long flow, and high capital investment and running cost.It was studied to treat coking wastewater with new process of Partial-nitrosation Anaerobic Ammonium Oxidation. The process is a novel new biological denitrogenation technology as ammonia nitrogen reacts with nitrite to denitrogen directly by the action of anaerobic ammonium oxidation bacteria in wastewater. The coking wastewater for studying in laboratory was from Chemical Plant of Anshan Iron and Steel Group. The Industrial trial was fulfilled at sewage disposal plant of Dandong Wantong Coking Limited Company. The influential factors of Partial-nitritacation-Anaerobic Ammonium Oxidation Process in the treatment of coking wastewater were investigated in the laboratory. The optimal conditions for the nitrous nitrification were obtained as following:temperature about35℃, pH value about from8.1to8.3, hydraulic residence time about16h, sludge residence time about from 15d to60d. While the optimal conditions of anaerobic ammonium oxidation bioreactory were achieved as following:NH4+/NO2-ratio about from1.7to2.2, pH value about8.0, temperature about35℃. Operation conditions and results of every processing step were studied on industrial trial. Reliability and consistence of the laboratory test and industrial were testified. The process for coking wastewater treatment showed several advantages such as high denitrification rate, without external carbon resource, low capital investment and running cost. The effluent is up to Ⅰ-class criteria specified in Integrated Wastewater Discharge Standard (GB8978—1996) and suitable for quenching coke.Biodiversity research was on the level of molecules. The sludge samples were analyzed by PCR-DGGE technique. Viz DNA samples were abstracted by the phenol-chloroform-isoamyl alcohol extraction method, and then16SrDNA gene fragment of the samples was amplified by PCR, and the proliferating products were were seprated by Denaturing Gradient Gel Electrophoresis (DGGE), at last the Sequence analysis results showed the change laws of target bacterial flora and the degradation laws of pollutants in different stages.Based on the research of nitrosification rate and ammonia oxidation rate in variety of reaction conditions such as biomass, substrate concentration and so on, some correlative kinetic models were established. The models parameters can be used quantificationally for direction of engineering design and operation.