Principle Of Process Salt Reduction In Industrial Wastewater Treatment Technology

Industrial wastewater has a large amount of production,and the state has put forward the requirement of"zero discharge"for some industries.There is a need for more coordination between water recycling and wastewater treatment.Desalination has gradually become a hot spot in the field of wastewater treatment and the focus of scholars from all walks of life.Most studies on desalination of wastewater focus on comparing the efficiency and performance differences of different desalination methods,such as seawater desalination process,membrane process,biological desalination tank and various combination processes.They only pay attention to the treatment effect and water recovery rate.Membrane process and other methods are facing the problems of high cost and pollution.No attention has been paid to the importance of salt reduction in wastewater treatment processes.High salt content,different electrolyte types and different salt complexes in wastewater all affect the final desalination cost,so the study of salt formation mechanism in wastewater is particularly important.Based on the above considerations,this study mainly investigates three aspects of wastewater treatment processes,including salt reduction caused by load reduction,formation and fate of salt in different denitrification pathways,and quantitative analysis of anaerobic ammonia oxidation salt reduction.Taking coking wastewater as an example,the research contents and results are as follows:?1?In view of the salt reduction caused by load reduction,based on the extraction of1000 mg/L COD from raw water by adsorption method,the effect of salt reduction was explored from two aspects of coagulation and biodegradation.The cost of extracting organic loads by adsorption method was elaborated.The amount and cost of coagulant saved in the coagulation process and alkali and phosphorus salts saved in the biological process were calculated and the energy-saving problem was studied.The salt reduction caused by organic mineralization was analyzed.At the same time,the economic value obtained from the energy conversion of organic matter was also investigated.It was found that it was reasonable and feasible to extract 1000 mg/L COD as a calculation dimension from the analysis of adsorption curve characteristics.The extracted COD is mainly volatile phenol.The cost of separation with activated carbon adsorption load is 1.5 CNY/m³.In the pretreatment represented by coagulation,1000 mg/L COD was extracted and 433.1 g/m³?single coagulant?was saved on average.The biodegradation process saves about 174.33 g/m³ alkali salt and 26.53 g/m³phosphorus salt,and saves about 1.2 kW·h/m³ energy consumption?taking OHO process as an example?.The total cost savings of coagulation and biological stage are 2.549 CNY/m³.The 1000 mg/L COD extracted was converted into electric energy and activated carbon into coke,resulting in 2.344 CNY/m³ profit and 1.01 CNY/m³ mass and energy conversion cost.Comprehensive economic analysis shows that the benefit is 2.383 CNY/m³.?2?Based on the analysis of salt fractal composition and influencing factors in different pathways of biological denitrification,the traditional three processes of nitrification and denitrification,short-cut nitrification and denitrification and anaerobic ammonia oxidation were compared from the aspects of electronic donor species/ratio,carbon source,dosage of alkali and phosphorus salts and hydraulic retention time?HRT?.The effect of salt reduction in different denitrification processes of simulated coking wastewater was discussed.The results showed that:?1?based on the target removal of 200 mg/L NO₂^--N/NO₃^--N in influent,the order of salt reduction ability of the three nitrogen removal pathways was anaerobic ammonia oxidation?41.97%?>short-cut denitrification?26.12%?>traditional denitrification?11.16%?;?2?under the optimal operating conditions?NO₂^--N/NH₄⁺-N=1.33,c?NaHCO₃?=100 mg/L,HRT=18 h?,the salt reduction rate,the degradation rates of NO₂^--N and NH₄⁺-N in anaerobic ammonia oxidation reached the optimum,which were 41.97%,100%and 99.38%respectively;?3?compared with single SCN^-or phenol,the combined use of SCN^-and phenol as electron donors had better denitrification and salt reduction performance;?4?when the electron donor ratio of SCN^-to phenol was 1:3 and HRT=38 h,the short-cut denitrification and traditional denitrification achieved the best treatment effects.The reduction rates of salt,NO₂^--N and SCN^-in short-cut denitrification were 26.12%,82.95%and 100%respectively.The reduction rates of salt,NO₃^--N and SCN^-in traditional denitrification were 11.16%,100%and 100%respectively.?3?On the basis of comparison of salt reduction by different denitrification routes,the correlation between theory and experiment was explored by taking the chemical equation measurement relationship of anaerobic ammonia oxidation as reference,conductivity as measurement index,and the data of denitrification and salt reduction by anaerobic ammonia oxidation under optimal conditions as theoretical data on the basis of material balance and metrological analysis.The results show that the linear equation of the concentration and conductivity of different substances is measured to form a database of metrological methods,which has good linearity and representativeness.Under the condition of chemical equation,the salt reduction rate of anaerobic ammonia oxidation process is 43.65%,while the theoretical salt reduction rate of material balance under the experimental condition is 41.67%,which is different with 41.97%of salt reduction of the actual experimental process,and the difference is 0.3%.Based on the conservation of materials,the theoretical and experiment results are very close and high consistent.The above results show that load separation can reduce the salt brought by organic mineralization,coagulants consumed during coagulation and nutrients needed in biological processes,thus achieving the goal of salt reduction in the process.The contribution of different denitrification processes to salt reduction is different because of the difference of reaction thermodynamics,carbon source and reaction metrology.The arrangement of reaction pathway and the mode of separation and re-reaction of electron donor and acceptor of compounds in wastewater are beneficial to salt reduction.The analysis of experimental process and theoretical measurement shows that salt reduction in anaerobic ammonia oxidation process can be theoretically analyzed by metrological method.Exploring different processes of wastewater treatment,including salt reduction by reducing load and salt reduction by different denitrification paths,has guiding significance in practical process selection.