Mechanism And Application Of Anammox Driven By Carbon Source Management In A-O/H/O Process For Coking Wastewater Treatment

The main sources of nitrogen compounds in wastewater include natural activities and human industrial activities.Although nitrogenous compounds are beneficial to humans as nutrients,excessive eutrophication interferes with the balance of the ecosystem.In this regard,it is essential to find efficient and energy-saving ways to remove pollutants.However,the selection and stability of the treatment process are affected by the multivalent and multiform composition of the components in the wastewater.Coking wastewater is a typical representative of industrial wastewater,currently,A/A/O process is generally selected for the coking wastewater treatment,which simply follows for domestic sewage treatment process,makes it difficult to achieve the economic and stability goals of synergistic removal of total nitrogen and other pollutants from coking wastewater.In response to the weaknesses of the A/A/O process,which could not cater for new technology principles such as anaerobic ammonia oxidation for nitrogen removal,unstable pollutant removal efficiency and high energy consumption.Based on the properties of coking wastewater solution,it is necessary to develop a new treatment process to achieve energy and cost savings in the selection and matching of nitrogen removal paths with simultaneous removal of other pollutants.Taking coking wastewater as a case study,this research analyzes the morphological and structural distribution of the characteristic components and concentrations of wastewater,as well as the correlation between indicators is discussed.The migration and transformation of typical carbon and nitrogen-containing compounds in the process is examined to clarify how the wastewater components influence the choice of functional reactions in the process units and the optimization of carbon source utilization and denitrification pathways.With A-O/H/O process as the platform,the function of each unit reactor was explored.The mechanism of carbon source management in unit A based on the principle of adsorption was investigated,meanwhile,the water quality changes and risk transfer brought by this process were analyzed.Aiming at the low C/N ratio of coking wastewater after carbon source recovery contributes to the construction of a synergistic energy-efficient denitrification pathway of partial nitrification（PN）-anaerobic ammonia oxidation（Anammox）process,the selective inhibition strategy and mechanism for achieving nitrite accumulation in the O1 reactor were studied.The feasibility of Anammox process for coking wastewater treatment and its microbial behaviour were also verified in the H-unit.Then,the engineering application of mainstream Anammox process in conjunction with other key pollutants in the A-O/H/O process was examined,and a model was developed to assess the effect of operating conditions on the stability and performance of the mainstream Anammox process.Finally,based on the configuration of A-O/H/O process,the material balance and energy consumption calculation of potential multiple denitrification modes in the process were analyzed,as well as the advantages and development potential of A-O/H/O process compared with A/A/O process were discussed.The main findings obtained are described as follows:（1）The statistical indicators of coking wastewater（such as COD,BOD,etc.）,organic and inorganic pollutant composition,concentration distribution and its correlation analysis show that the quality of coking wastewater has not only the pollution attribute of toxicity inhibition but also the resource attribute of added value.For example,phenol accounts for more than 60%of the total organic matter in the wastewater,as well as tar,ammonium and thiocyanate,etc.,which could be the potential energy substance.The distribution of total nitrogen in wastewater typically shows that ammonium only contributes 30%to 40%.To achieve effective nitrogen removal,a normalization process involving complete nitrification and partial denitrification must be employed,followed by complete denitrification to ensure water quality stability.Anaerobic unit（A）pre-treatment process is susceptible to toxicity inhibition and difficult to play a role,while aerobic unit（O1）pre-treatment process is able to remove toxicity inhibition and release ammonium,allowing the O/H/O biological process to demonstrate a highly efficient combination of carbon and total nitrogen removal.The highly editable material flow pattern and microbial function of O/H/O biological process,make it able to cope with various wastewater quality.Given the treatment goal of energy and cost reduction,the carbon source management of the evolving A-O/H/O process could further reduce energy consumption and cater to the Anammox operation requirements.It can be seen that the combination of material component planning and element valence/morphology regulation in wastewater solution properties could support the innovation of complex wastewater treatment processes.（2）Based on the resource properties of high organic concentration of coking wastewater have been identified,the dual physicochemical adsorption technology was adopted to carry out carbon source separation management for coking wastewater treatment,that is,adsorption of the biological effluent followed by adsorption of the high concentration raw wastewater.The adsorption capacity of powdered activated carbon（PAC）increased from 50-120 mg COD/g PAC to 800-1200 mg COD/g PAC,achieving an energy matter transfer of 144,555k J/m³.GC-MS analysis showed that biological effluent PAC adsorption was effective for refractory organic matter,and raw coking wastewater adsorption was effective for phenol.And the new idea of dual physicochemical based on adsorption realized the improvement of economic equivalent of adsorbent.Therefore,the lower of C/N ratio and reducing of toxic substances by changing the properties of wastewater solution,which creates the water quality and environmental conditions of Anammox process for the subsequent biological treatment process.（3）The change in C/N ratio resulting from the dual physicochemical contributes to an energy efficient PN-Anammox pathway.The combined regulation of organic loading（OLR）and dissolved oxygen（DO）in fluidized bed reactor achieved selective inhibition of toxic substances by nitrifying bacteria,controlled in the nitritation phase,with a nitrite accumulation rate（NAR）greater than 80.5%,where Nitrosomonas spp.were the main ammonium oxidizing bacteria（AOB）（0.1-0.3%）.The dynamic model demonstrates that thiocyanide（SCN^-）in wastewater is the main substrates and inhibitors of nitrite oxidizing bacteria（NOB）(IC_50-NOB=40.01 mg/L,IC_50-AOB=308.12 mg/L),and the mathematical model verified that nitritation could be achieved when the OLR is controlled in the range of 0.80 to1.35 kg/（m³·d）.This discovery solves the bottleneck in the stoichiometric control of nitrite in the Anammox process.（4）The feasibility of Anammox in unit H for the denitrification of coking wastewater was demonstrated in A-O/H/O process with a controlled nitritation process.The Anammox process was successfully implemented in a fluidized bed combined reactor with an influent OLR of 0.30 kg COD/（m³·d）,achieving a total nitrogen removal of 87.1%±3.0%and nitrogen removal rate of 0.37 kg/（m³·d）.In the reactor,Candidatus Brocadia（0.15%）and Do K59（2.54%）were the dominant bacterial groups of Anammox.The secretion of extracellular polymer（EPS）（EPS=200.79 mg/g-VSS）from the Anammox sludge is effective in protecting the sludge activity and structure in response to the changes in the wastewater influent components during the long-term operation process.The concentration and type weighting of organic matter in wastewater is the key factor affecting the Anammox activity.Residual organic matter in aerobic unit（O1）does not affect the Anammox reaction（specific anammox activity is 3.73 mg N/（g VSS·h））,and SCN^-(IC₅₀=590.10 mg/L)does not produce irreversible inhibition of Anammox activity.This facilitation and inhibition mechanism provides new perspectives for industrial wastewater to achieve the mainstream Anammox process.（5）Based on the above findings,the mainstream PN-Anammox denitrification process synergistic key pollutant removal was verified on the constructed A-O/H/O process platform,and the removal rates of COD and TN reached 93.2%and 94.7%respectively.Combined with the dual-physicochemical principal technology（A unit）,the final 14 national control indicators in external drainage could reach the stable standard.The configuration of the A-O/H/O process determines that the microorganisms in each unit of the system perform their own unique functions,with carbon removal and nitritation（Ottowia,Limnobacter,Thiobacillus）in unit O1,anaerobic ammonia oxidation（Candidatus＿Anammoximicrobium）in unit H and complete nitrification（Nitrospira）in unit O2.AM-ASM3 model predicted that the hydraulic retention time（HRT）and DO variation in O1 unit were significant contributors to the stability of mainstream Anammox process.The A-O/H/O principle suggests a variety of potential denitrification pathways,which are optimized according to material flow and energy allocation of wastewater solutions of varying characteristics.On the basis of carbon source management,the A-O/H/O process could reduce sludge production and oxygen consumption by 57.8%to 77.7%and 66.7%to 74.0%compared to the O/H/O process,which exhibits lower oxygen consumption,electron donor consumption,alkali consumption and sludge production requirements for the same TN removal target.It is proved that A-O/H/O process is a new wastewater treatment process which could realize resource utilization,energy and cost saving,high efficiency and stability of nitrogen and carbon removal with synergistic removal of other pollutants.In summary,we believe that the A-O/H/O process proposed based on the properties of the wastewater solution could better respond to the changes in the wastewater treatment object and realize the optimization of labor and division of bacterial community in time and space scales on the basis of carbon source management,electron donor acceptor separation,multi-chemical reaction coordination and biological function regulation.It has enriched the technological theory of wastewater treatment in terms of multi-objective,multi-functional and multi-conditions.