Energy-saving And Consumption-reducing Biological Nitrogen Removal Technology And New Model For Coking Wastewater

CW(Coking Wastewater)is a kind of typically toxic and harmful industrial wastewater with high concentration of ammonia.Nitrogen as the main pollutant in CW,it will cause serious damage to the environment if not treated properly.Compared with traditional BNR(Biological Nitrogen Removal)process,the CANON(Completely Autotrophic Nitrogen-removal Over Nitrite)process with patial nitrification and anaerobic ammonia oxidation as the core is one of the most economical and efficient methods for nitrogen removal of wastewater.However,the application of CANON in the treatment of CW is rarely reported.The main reason is that phenols and other toxic substances in CW can affect the activity of AOB(Ammonia Oxidizing Bacteria)and AnAOB(Anerobic Ammonium Oxidation Bacteria).In this paper,the BNR process of CW was taken as the research object.By comparing and analyzing the pollution removal efficiency and microbial community structure of the traditional AOO process and the sectional influent AOAO process in a coking plant,and studying the influence factor of CANON,based on the analysis of the shortcomings of the traditional BNR process and the feasibility of the CANON process of CW,a new energy-saving and consumption-reducing BNR model for CW was developed and its economic analysis was made.The main contents and conclusions are as follows:(1)Through comparative study on the treatment effect and microbial community structure of AOO and AOAO process,it was found that the full mixed continuous flow and anaerobic/aerobic uninterrupted alternating mode of operation was the main reason for the better nitrogen removal effect of AOAO process.When the average concentration of NH4+-N and TN in influent was 78.0 and 331.0 mg· L-1,respectively,the removal rate of TN by AOO was only 7.8%.The concentration of NH4+-N in AOAO effluent could meet the discharge standard,and TN was below 50 mg·L-1.The average concentration of COD in the effluent of the two processes was 410.3 and 318.6 mg ·L-1,respectively.The concentration of phenol,cyanide and heavy metals could meet the discharge standard.The results of 16S high-throughput sequencing showed that the microbial community structure of the two processes was quite different.The results of 16S high-throughput sequencing showed that most of the dominant bacteria in AOO process had stronger nitrification ability,while AOAO process adopted full mixed continuous flow and continuous anaerobic/aerobic operation mode,which made most of the dominant bacteria have stronger denitrification and decomposition ability of refractory organic compounds.(2)Phenol,a characteristic pollutant of coking wastewater,was selected for study.When the phenol concentration was less than 50 mg·L-1,the CANON-SBBR(Sequence Batch Biofilm Reactor for Completely Autotrophic Nitrogen removal Over Nitrite)could stabilize Nitrogen removal,and CANON process was feasible for coking wastewater treatment.In the short term,when the inhibitory concentration of phenol was 5,10,20,60 and 100 mg·L-1,the TN removal rate of CANON-SBBR decreased by 9.9%,49.7%,68.7%,76.8%and 94.8%,respectively.In the long-term test,the NRL(Nitrogen Removal Load)of the reactor decreased first and then recovered gradually under the condition of the same phenol concentration.When the phenol concentration rose to the maximum value of 40,50 mg·L-1,the system suffered a great impact,and the NRL dropped to 0.138 kgN·m-·d-1,then recovered to 0.413 kgN ·m-3·d-1 after 10 days.(3)By analyzing the shortcomings of traditional nitrogen removal process and the feasibility of CANON for CW,a new energy-saving and consumption-reducing BNR treatment model for CW based on non-evaporating ammonia pretreatment and CANON was proposed.Compared with AOO and AOAO process,this new model had considerable economic and environmental benefits.