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2020 Vol. 38, No. 7
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2020, 38(7): 1-12.
doi: 10.13205/j.hjgc.202007001
Abstract:
By the end of 2019, a total of 2913 urban wastewater treatment plants (WWTPs) in China had implemented the Grade I-A Discharge Standard in China's national standard GB 18918-2002, which accounted for 53.2% of the total WWTPs in China. The Grade I-A Standard has become the most widely implemented discharge standard for WWTPs in China. Based on the deep investigation of 204 WWTPs implementing the Grade I-A Standard of Taihu Basin in recent 6 years, in combination with whole process analysis of more than 100 WWTPs in China, this paper firstly evaluated the operational performance of WWTPs implementing the Grade I-A Standard. Results showed that total amount of pollutants reduction of WWTPs in Taihu Basin had been significantly increased due to the continuous increase of water inflow, and the continuous decrease of effluent concentration after the upgrading of Grade I-A Standard, positively contributing to the emission reduction of organic matter, nitrogen, phosphorus and the eutrophication control in Taihu Basin. Then the common problems in the operation process of WWTPs were summarized. Influent water quality, process design, selection and maintenance of equipment and facilities, as well as the performance control of functional bacterial group in activated sludge still had further improvement and optimization space. Meanwhile, targeted optimization operation measures were put forward. At last, key and difficult points and strategies in the new round of upgrading work were discussed. It is suggested that attention should be paid to improving the quality and efficiency of the wastewater collection system, and the quality and transmission efficiency of the pipe network. And the whole process analysis should be carried out before upgrading. Then the process optimization or engineering measures could be confirmed.
By the end of 2019, a total of 2913 urban wastewater treatment plants (WWTPs) in China had implemented the Grade I-A Discharge Standard in China's national standard GB 18918-2002, which accounted for 53.2% of the total WWTPs in China. The Grade I-A Standard has become the most widely implemented discharge standard for WWTPs in China. Based on the deep investigation of 204 WWTPs implementing the Grade I-A Standard of Taihu Basin in recent 6 years, in combination with whole process analysis of more than 100 WWTPs in China, this paper firstly evaluated the operational performance of WWTPs implementing the Grade I-A Standard. Results showed that total amount of pollutants reduction of WWTPs in Taihu Basin had been significantly increased due to the continuous increase of water inflow, and the continuous decrease of effluent concentration after the upgrading of Grade I-A Standard, positively contributing to the emission reduction of organic matter, nitrogen, phosphorus and the eutrophication control in Taihu Basin. Then the common problems in the operation process of WWTPs were summarized. Influent water quality, process design, selection and maintenance of equipment and facilities, as well as the performance control of functional bacterial group in activated sludge still had further improvement and optimization space. Meanwhile, targeted optimization operation measures were put forward. At last, key and difficult points and strategies in the new round of upgrading work were discussed. It is suggested that attention should be paid to improving the quality and efficiency of the wastewater collection system, and the quality and transmission efficiency of the pipe network. And the whole process analysis should be carried out before upgrading. Then the process optimization or engineering measures could be confirmed.
2020, 38(7): 13-18.
doi: 10.13205/j.hjgc.202007002
Abstract:
With the promulgation and implementation of Discharge Standard of Main Water Pollutants for Municipal Wastewater Treatment Plants & Key Industries of Taihu Area(DB 32/1072-2018) in June 2018, Jiangsu province launched a new round of upgrading of municipal wastewater treatment plants. Based on the urgent need of the upgrading, this paper put forward a set of new research programs, including a four-step research process:national sewage information system data statistical analysis, questionnaire & daily data analysis, on-site discussion and consultation, and on-site investigation of typical wastewater treatment plants, which was gradually progressive and mutually calibrated. The 83 municipal wastewater treatment plants to be submitted in Taihu area were taken as the research objects, in order to provide technical support for the new round of upgrading work of wastewater treatment plants in Taihu area, and the application of investigation scheme could identify the common and individual problems of wastewater treatment plants.
With the promulgation and implementation of Discharge Standard of Main Water Pollutants for Municipal Wastewater Treatment Plants & Key Industries of Taihu Area(DB 32/1072-2018) in June 2018, Jiangsu province launched a new round of upgrading of municipal wastewater treatment plants. Based on the urgent need of the upgrading, this paper put forward a set of new research programs, including a four-step research process:national sewage information system data statistical analysis, questionnaire & daily data analysis, on-site discussion and consultation, and on-site investigation of typical wastewater treatment plants, which was gradually progressive and mutually calibrated. The 83 municipal wastewater treatment plants to be submitted in Taihu area were taken as the research objects, in order to provide technical support for the new round of upgrading work of wastewater treatment plants in Taihu area, and the application of investigation scheme could identify the common and individual problems of wastewater treatment plants.
2020, 38(7): 25-31,99.
doi: 10.13205/j.hjgc.202007004
Abstract:
The structure and characteristics of expert system in the field of wastewater treatment, the technology and the research achievements in the application of expert system were reviewed. The acquisition and representation of knowledge, the establishment of rules and the combination with fault tree and other artificial intelligence technologies in the expert system were emphatically introduced, and the research status of the expert system in the three different stages including wastewater treatment process selection, operation control and fault diagnosis was analyzed in detail. On this basis, the problems to be solved and the direction of further research and development were put forward.
The structure and characteristics of expert system in the field of wastewater treatment, the technology and the research achievements in the application of expert system were reviewed. The acquisition and representation of knowledge, the establishment of rules and the combination with fault tree and other artificial intelligence technologies in the expert system were emphatically introduced, and the research status of the expert system in the three different stages including wastewater treatment process selection, operation control and fault diagnosis was analyzed in detail. On this basis, the problems to be solved and the direction of further research and development were put forward.
2020, 38(7): 32-37,24.
doi: 10.13205/j.hjgc.202007005
Abstract:
The dissolved refractory organic compounds with high concentration and complex components in wastewater were the problems encountered by many urban wastewater treatment plants (WWTPs) which occupied a relatively higher proportion of industrial wastewater, in the new round of upgrading. In this paper, four typical wastewater treatment plants in Taihu Basin were taken as the research objects, and the removal efficiency of COD by hydrolysis acidification and various advanced wastewater treatment technologies were analyzed. The results showed that hydrolytic acidification technology could improve the biodegradability of wastewater to a certain extent, and the addition of fillers could improve the effect. Moreover, the removal efficiency of the two advanced treatment technologies, coagulation sedimentation and membrane filtration, was only about 30%~35%. Furthermore, the mineralization ability of the ozone oxidation technology for the partial refractory organics was poor, so this technology was influenced by the organics in the influent. The adsorption of organics by activated carbon was universal, and in this study, the efficiency of adsorption of dissolved refractory organics in wastewater by activated carbon at empty bed hydraulic retention time (HRT) of 10 minutes was studied. It was found the COD of the effluent was stable at less than 20 mg/L. Besides, the operation cost of activated carbon adsorption process was high, and the regeneration and disposal of activated carbon should be considered. Therefore, the selection of COD advanced treatment process should be based on the influent quality, full technical demonstration under the premise of feasibility of small-scale and pilot scale test, and comprehensive consideration of construction, operation, land occupation, elevation and other factors to select the suitable technology for upgrading.
The dissolved refractory organic compounds with high concentration and complex components in wastewater were the problems encountered by many urban wastewater treatment plants (WWTPs) which occupied a relatively higher proportion of industrial wastewater, in the new round of upgrading. In this paper, four typical wastewater treatment plants in Taihu Basin were taken as the research objects, and the removal efficiency of COD by hydrolysis acidification and various advanced wastewater treatment technologies were analyzed. The results showed that hydrolytic acidification technology could improve the biodegradability of wastewater to a certain extent, and the addition of fillers could improve the effect. Moreover, the removal efficiency of the two advanced treatment technologies, coagulation sedimentation and membrane filtration, was only about 30%~35%. Furthermore, the mineralization ability of the ozone oxidation technology for the partial refractory organics was poor, so this technology was influenced by the organics in the influent. The adsorption of organics by activated carbon was universal, and in this study, the efficiency of adsorption of dissolved refractory organics in wastewater by activated carbon at empty bed hydraulic retention time (HRT) of 10 minutes was studied. It was found the COD of the effluent was stable at less than 20 mg/L. Besides, the operation cost of activated carbon adsorption process was high, and the regeneration and disposal of activated carbon should be considered. Therefore, the selection of COD advanced treatment process should be based on the influent quality, full technical demonstration under the premise of feasibility of small-scale and pilot scale test, and comprehensive consideration of construction, operation, land occupation, elevation and other factors to select the suitable technology for upgrading.
2020, 38(7): 38-44.
doi: 10.13205/j.hjgc.202007006
Abstract:
During the regeneration of activated carbon by superheated steam method, a large amount of condensed wastewater containing refractory organics will be produced. In order to remove the refractory COD in the condensed wastewater, improve the biodegradability and facilitate the subsequent biodegradation, UV/ozone activated persulfate(UV/O3-Na2S2O8) oxidation system was used to treat the activated carbon regeneration condensate wastewater. The effects of ozone dosage, initial pH and Na2S2O8 dosage on the treatment efficiency of the organics were investigated. The changes in the treatment process of the condensate wastewater were investigated by means of infrared spectrum, UV-Vis spectrum and three-dimensional fluorescence. The results showed that when the dosage of ozone was 30 mg/L, pH was 9.0, and Na2S2O8 dosage was 0.4 g/L, the removal rate of COD and chroma(CN) was 82.1% and 86.3%, respectively. The biodegradability of condensed wastewater was improved, and the BOD5/COD value was increased from 0.17 to 0.46. It could be found from the characterization of dissolved organic matter(DOM) in condensed wastewater that humus and chromophore in DOM were oxidized continuously, and the aromatization degree was reduced. Tryptophan organics were effectively removed. The results showed that UV/O3-Na2S2O8 oxidation system could effectively remove the organics in the condensed wastewater.
During the regeneration of activated carbon by superheated steam method, a large amount of condensed wastewater containing refractory organics will be produced. In order to remove the refractory COD in the condensed wastewater, improve the biodegradability and facilitate the subsequent biodegradation, UV/ozone activated persulfate(UV/O3-Na2S2O8) oxidation system was used to treat the activated carbon regeneration condensate wastewater. The effects of ozone dosage, initial pH and Na2S2O8 dosage on the treatment efficiency of the organics were investigated. The changes in the treatment process of the condensate wastewater were investigated by means of infrared spectrum, UV-Vis spectrum and three-dimensional fluorescence. The results showed that when the dosage of ozone was 30 mg/L, pH was 9.0, and Na2S2O8 dosage was 0.4 g/L, the removal rate of COD and chroma(CN) was 82.1% and 86.3%, respectively. The biodegradability of condensed wastewater was improved, and the BOD5/COD value was increased from 0.17 to 0.46. It could be found from the characterization of dissolved organic matter(DOM) in condensed wastewater that humus and chromophore in DOM were oxidized continuously, and the aromatization degree was reduced. Tryptophan organics were effectively removed. The results showed that UV/O3-Na2S2O8 oxidation system could effectively remove the organics in the condensed wastewater.
2020, 38(7): 45-50.
doi: 10.13205/j.hjgc.202007007
Abstract:
Comprehensive effect of carbon to nitrogen ratio (C/N), dissolved oxygen (DO) and temperature on phosphorus and nitrogen removal efficiency were identified using response surface methodology in a sequencing batch biofilm reactor (SBBR), aiming to develop high-standard urban sewage treatment technology based on the non-engineering measures. Total nitrogen (TN) and phosphate (PO43--P) removal rates were taken as the dependent variables, while C/N (A), DO (B) and temperature (C) were taken as independent variables. The Box-Benhnken (BBD) experimental design method and the quadratic polynomial model were applied. Results in response surface equations was illustrated as η(TN)=-70.76+7.58A+52.81B-0.36C+0.22AB-0.12AC+0.58BC-0.35A2-7.94B2+0.01C2, η(PO43--P)=-119.59+10.93A+72.91B+2.26C-1.50AB+0.05AC-0.13BC-0.33A2-6.86B2-0.07C2. Further analysis by ANOVA method proved that DO and temperature significantly affected both the phosphorus and the nitrogen removal rates whilst C/N had a remarkable effect on nitrogen removal efficiency. The impact degree of three parameters was DO, temperature and C/N, successively. The interaction of DO with temperature significantly affected the nitrogen removal rate. Moreover, PO43--P removal rate was obviously influenced by the interaction of C/N and DO. The quantifications of relation between operating parameters and system performance were achieved by the response equations, and the optimum working condition and efficiency of the model were verified by experiment, which could be used to guide the optimization of operating parameters in SBBR system for advanced phosphorus and nitrogen removal. The effluent NH4+-N, TN, PO43--P and COD concentration of the SBBR were 3.9, 5.0, 0.4, 40 mg/L respectively, under the condition of temperature of 23℃, C/N of 9.5 and DO of 4 mg/L, which reached the high standard treatment better than Grade I-A standard in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002).
Comprehensive effect of carbon to nitrogen ratio (C/N), dissolved oxygen (DO) and temperature on phosphorus and nitrogen removal efficiency were identified using response surface methodology in a sequencing batch biofilm reactor (SBBR), aiming to develop high-standard urban sewage treatment technology based on the non-engineering measures. Total nitrogen (TN) and phosphate (PO43--P) removal rates were taken as the dependent variables, while C/N (A), DO (B) and temperature (C) were taken as independent variables. The Box-Benhnken (BBD) experimental design method and the quadratic polynomial model were applied. Results in response surface equations was illustrated as η(TN)=-70.76+7.58A+52.81B-0.36C+0.22AB-0.12AC+0.58BC-0.35A2-7.94B2+0.01C2, η(PO43--P)=-119.59+10.93A+72.91B+2.26C-1.50AB+0.05AC-0.13BC-0.33A2-6.86B2-0.07C2. Further analysis by ANOVA method proved that DO and temperature significantly affected both the phosphorus and the nitrogen removal rates whilst C/N had a remarkable effect on nitrogen removal efficiency. The impact degree of three parameters was DO, temperature and C/N, successively. The interaction of DO with temperature significantly affected the nitrogen removal rate. Moreover, PO43--P removal rate was obviously influenced by the interaction of C/N and DO. The quantifications of relation between operating parameters and system performance were achieved by the response equations, and the optimum working condition and efficiency of the model were verified by experiment, which could be used to guide the optimization of operating parameters in SBBR system for advanced phosphorus and nitrogen removal. The effluent NH4+-N, TN, PO43--P and COD concentration of the SBBR were 3.9, 5.0, 0.4, 40 mg/L respectively, under the condition of temperature of 23℃, C/N of 9.5 and DO of 4 mg/L, which reached the high standard treatment better than Grade I-A standard in Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB 18918-2002).
2020, 38(7): 51-57.
doi: 10.13205/j.hjgc.202007008
Abstract:
N2O is a typical greenhouse gas, and contributes severely to global warming. The process for biological nitrogen removal from wastewater is considered as an important source of N2O emission. The present study investigated the characteristics and main source of N2O in a SBR system, with an anoxic-aerobic (A/O) running mode. The results showed that N2O emission occurred mainly during the aerobic phase in the A/O SBR system. The maximum N2O emission rate reached 2.02 μg/(min·g), and the cumulative N2O emission during the aerobic phase was 8.2 mg, then the nitrite accumulation concentrate was observed to get the highest value of 7.5 mg/L after 120-minite operation. On the basis of bacterial community analysis, the bacteria in the dominant DGGE bands were identified as Flavobacteria, some of which was found to be aerobic denitrifying bacteria. It was inferred that the accumulation of nitrite might inhibit the activity of nitrous oxide reductase (Nos) from aerobic denitrifying bacteria and lead to N2O emission. The accumulation of nitrite should be avoided or reduced in real biological wastewater treatment process.
N2O is a typical greenhouse gas, and contributes severely to global warming. The process for biological nitrogen removal from wastewater is considered as an important source of N2O emission. The present study investigated the characteristics and main source of N2O in a SBR system, with an anoxic-aerobic (A/O) running mode. The results showed that N2O emission occurred mainly during the aerobic phase in the A/O SBR system. The maximum N2O emission rate reached 2.02 μg/(min·g), and the cumulative N2O emission during the aerobic phase was 8.2 mg, then the nitrite accumulation concentrate was observed to get the highest value of 7.5 mg/L after 120-minite operation. On the basis of bacterial community analysis, the bacteria in the dominant DGGE bands were identified as Flavobacteria, some of which was found to be aerobic denitrifying bacteria. It was inferred that the accumulation of nitrite might inhibit the activity of nitrous oxide reductase (Nos) from aerobic denitrifying bacteria and lead to N2O emission. The accumulation of nitrite should be avoided or reduced in real biological wastewater treatment process.
2020, 38(7): 58-65.
doi: 10.13205/j.hjgc.202007009
Abstract:
With the new round upgrading of urban sewage treatment plants in key river basins across China, some sewage treatment plants reduced their total effluent (TP) emission limit from 0.5 mg/L to 0.3 mg/L, and even to 0.2 mg/L, which posed a new challenge for phosphorus removal in urban sewage treatment plants. In this paper, by investigating and analyzing 58 urban sewage treatment plants that implement the Grade I-A Discharge Standard in China's national standard GB 18918-2002, we discussed the main problems of phosphorus removal in the actual production and operation of sewage treatment plants and gave corresponding countermeasures for future high-standard TP emissions, in order to provide technical guidance for the operation and management of the sewage treatment plant. The survey results showed that the phosphorus release potential of each sewage treatment plant was in the range of 0.01~23.98 mg/(g·h), and the average phosphorus release potential was 2.77 mg/(g·h). The phosphorus release potential was generally weak; insufficient carbon source in the feedwater, high concentration of nitrate nitrogen in the anaerobic zone, and the inhibition of simultaneous chemical phosphorus removal were the main reasons for the poor biological phosphorus removal effect, and specific control measures were proposed accordingly. In addition, it was recommended that the sewage treatment plant determined the best phosphorus removal agents and appropriate dosage by static experiments according to the quality of the incoming water, so as to achieve more reasonable control of the chemical phosphorus removal process, thereby achieving the purpose of saving phosphorus removal agents consumption.
With the new round upgrading of urban sewage treatment plants in key river basins across China, some sewage treatment plants reduced their total effluent (TP) emission limit from 0.5 mg/L to 0.3 mg/L, and even to 0.2 mg/L, which posed a new challenge for phosphorus removal in urban sewage treatment plants. In this paper, by investigating and analyzing 58 urban sewage treatment plants that implement the Grade I-A Discharge Standard in China's national standard GB 18918-2002, we discussed the main problems of phosphorus removal in the actual production and operation of sewage treatment plants and gave corresponding countermeasures for future high-standard TP emissions, in order to provide technical guidance for the operation and management of the sewage treatment plant. The survey results showed that the phosphorus release potential of each sewage treatment plant was in the range of 0.01~23.98 mg/(g·h), and the average phosphorus release potential was 2.77 mg/(g·h). The phosphorus release potential was generally weak; insufficient carbon source in the feedwater, high concentration of nitrate nitrogen in the anaerobic zone, and the inhibition of simultaneous chemical phosphorus removal were the main reasons for the poor biological phosphorus removal effect, and specific control measures were proposed accordingly. In addition, it was recommended that the sewage treatment plant determined the best phosphorus removal agents and appropriate dosage by static experiments according to the quality of the incoming water, so as to achieve more reasonable control of the chemical phosphorus removal process, thereby achieving the purpose of saving phosphorus removal agents consumption.
2020, 38(7): 66-70,65.
doi: 10.13205/j.hjgc.202007010
Abstract:
In this paper, the secondary effluent of a municipal sewage treatment plant in Jiangsu Province was taken as the research object. Through the simulation test and the pilot test of coagulation+air flotation deep phosphorus removal, the deep phosphorus removal effect of air flotation process instead of filtration process was explored. The results showed that FeCl3 had the best phosphorus removal effect. When the molar ratio was 2.3, the TP of effluent could be reduced to 0.2 mg/L, and when the molar ratio was 7, the TP of effluent could be reduced to 0.05 mg/L; the process of air flotation had a strong dependence on PAM, so it was necessary to add PAM to ensure the effect of phosphorus removal and the stability of water quality up to standard. The concentration of PAM was 0.6 mg/L; when the reflux ratio was 20% and the dissolved gas pressure was about 0.6 MPa, the operation effect of the device was stable; through the analysis on the phosphorus components, it was found that the air floatation process had a good effect on the removal of suspended TP and phosphate, but no effect on the removal of non-coagulable phosphorus components.
In this paper, the secondary effluent of a municipal sewage treatment plant in Jiangsu Province was taken as the research object. Through the simulation test and the pilot test of coagulation+air flotation deep phosphorus removal, the deep phosphorus removal effect of air flotation process instead of filtration process was explored. The results showed that FeCl3 had the best phosphorus removal effect. When the molar ratio was 2.3, the TP of effluent could be reduced to 0.2 mg/L, and when the molar ratio was 7, the TP of effluent could be reduced to 0.05 mg/L; the process of air flotation had a strong dependence on PAM, so it was necessary to add PAM to ensure the effect of phosphorus removal and the stability of water quality up to standard. The concentration of PAM was 0.6 mg/L; when the reflux ratio was 20% and the dissolved gas pressure was about 0.6 MPa, the operation effect of the device was stable; through the analysis on the phosphorus components, it was found that the air floatation process had a good effect on the removal of suspended TP and phosphate, but no effect on the removal of non-coagulable phosphorus components.
2020, 38(7): 71-74,121.
doi: 10.13205/j.hjgc.202007011
Abstract:
Taking the secondary sludge of municipal sewage treatment plant as the research object and using thermal alkali treatment process to treat the sludge, this study investigated the optimal treatment condition and analyzed the guiding function of static experiment to dynamic experiment. The results showed that for the static experiment of thermal alkali treating sludge, it had the optimal initial pH of 13, temperature of 30℃, and time of 10 h. Under the optimum conditions, the dissolution rate of COD was 61.53%, and the concentration of protein and polysaccharide in aqueous medium were 761.73, 649.85 mg/L respectively; the optimum reaction time of dynamic experiment was 10 h, and under the optimum conditions, the COD dissolution rate was 75.77%, the concentration of the protein and polysaccharide were 1024.70, 842.34 mg/L, which were higher than the results of static experiment. The results showed that the static experiment of sludge had practical guidance to the dynamic experiment, and thermal-alkaline method had a good application prospect.
Taking the secondary sludge of municipal sewage treatment plant as the research object and using thermal alkali treatment process to treat the sludge, this study investigated the optimal treatment condition and analyzed the guiding function of static experiment to dynamic experiment. The results showed that for the static experiment of thermal alkali treating sludge, it had the optimal initial pH of 13, temperature of 30℃, and time of 10 h. Under the optimum conditions, the dissolution rate of COD was 61.53%, and the concentration of protein and polysaccharide in aqueous medium were 761.73, 649.85 mg/L respectively; the optimum reaction time of dynamic experiment was 10 h, and under the optimum conditions, the COD dissolution rate was 75.77%, the concentration of the protein and polysaccharide were 1024.70, 842.34 mg/L, which were higher than the results of static experiment. The results showed that the static experiment of sludge had practical guidance to the dynamic experiment, and thermal-alkaline method had a good application prospect.
2020, 38(7): 75-80.
doi: 10.13205/j.hjgc.202007012
Abstract:
At present, many urban wastewater treatment plants are facing the problems of low concentration and imbalance of influent pollutants. However, there are few reports on the source and quantitative analysis of leakage. In order to quantitatively analyze the influence of river water (groundwater), rainwater and pollutant degradation in pipeline on the reduction of wastewater pollutants' concentration, wastewater source of the target wastewater treatment plant was analyzed by the method of water balance trigonometry, conbined with analysis of wastewater in typical sites and the S-P degradation model. The results showed that historical water volume data combined with rainfall analysis indicated that the actual amount of primary sewage in the influent of the WWTP was only about 60.0%, and the remaining 40.0% was groundwater and river water infiltration or rainwater infiltration. The pipe network of residential quarters and municipal drainage pipe network were the main leakage sources in the sunny days, and their contribution to the reduction of inflow concentration were 20.2% and 26.4%, respectively. In addition, the pipe network of residential quarters was the main leakage source, which contributed 39.5% to the decrease of the influent concentration under 25 mm rainfall events. Therefore, attention should be paid to the completeness of residential quarters' pipe network in the process of improving the quality and efficiency of wastewater treatment.
At present, many urban wastewater treatment plants are facing the problems of low concentration and imbalance of influent pollutants. However, there are few reports on the source and quantitative analysis of leakage. In order to quantitatively analyze the influence of river water (groundwater), rainwater and pollutant degradation in pipeline on the reduction of wastewater pollutants' concentration, wastewater source of the target wastewater treatment plant was analyzed by the method of water balance trigonometry, conbined with analysis of wastewater in typical sites and the S-P degradation model. The results showed that historical water volume data combined with rainfall analysis indicated that the actual amount of primary sewage in the influent of the WWTP was only about 60.0%, and the remaining 40.0% was groundwater and river water infiltration or rainwater infiltration. The pipe network of residential quarters and municipal drainage pipe network were the main leakage sources in the sunny days, and their contribution to the reduction of inflow concentration were 20.2% and 26.4%, respectively. In addition, the pipe network of residential quarters was the main leakage source, which contributed 39.5% to the decrease of the influent concentration under 25 mm rainfall events. Therefore, attention should be paid to the completeness of residential quarters' pipe network in the process of improving the quality and efficiency of wastewater treatment.
APPLICATION OF BIOLOGICAL CARBON IN DEEP PURIFICATION OF TAIL WATER OF URBAN SEWAGE TREATMENT PLANTS
2020, 38(7): 81-87.
doi: 10.13205/j.hjgc.202007013
Abstract:
To study the deep purification technology of tail water of urban sewage treatment plant, the biological carbon made from the waste of agricultural and forestry straw biomass power generation, was used as the filler to investigate the treatment effect of tail water of urban sewage treatment plant. Miseq high-throughput sequencing technology was also applied to study the microbial community structures of suspended packing in the moving bed biofilm reactor (MBBR) and biological carbon filler. The results showed that biological carbon could deeply purify the tail water, and the average removal rate of NH4+-N, TN, COD and TP was higher than that of effluent from sedimentation tank by 0.9%, 19.0%, 7.1% and 10.5%. The microbial species richness and diversity of biological carbon filler were higher than those in MBBR, and denitrification related bacteria in the microbial community was dominant species(24.2%). In addition, phosphorus accumulating bacteria (4.6%), and nitrifying bacteria (1.3%) related genera were detected in the biofilm samples. The results suggested that biological carbon filler was conducive for the enrichment and growth of functional bacteria like nitrogen and phosphorus removal bacteria and played a key role in wastewater treatment. This study could provide a scientific basis and parameters for biological carbon in engineering application.
To study the deep purification technology of tail water of urban sewage treatment plant, the biological carbon made from the waste of agricultural and forestry straw biomass power generation, was used as the filler to investigate the treatment effect of tail water of urban sewage treatment plant. Miseq high-throughput sequencing technology was also applied to study the microbial community structures of suspended packing in the moving bed biofilm reactor (MBBR) and biological carbon filler. The results showed that biological carbon could deeply purify the tail water, and the average removal rate of NH4+-N, TN, COD and TP was higher than that of effluent from sedimentation tank by 0.9%, 19.0%, 7.1% and 10.5%. The microbial species richness and diversity of biological carbon filler were higher than those in MBBR, and denitrification related bacteria in the microbial community was dominant species(24.2%). In addition, phosphorus accumulating bacteria (4.6%), and nitrifying bacteria (1.3%) related genera were detected in the biofilm samples. The results suggested that biological carbon filler was conducive for the enrichment and growth of functional bacteria like nitrogen and phosphorus removal bacteria and played a key role in wastewater treatment. This study could provide a scientific basis and parameters for biological carbon in engineering application.
2020, 38(7): 88-92,18.
doi: 10.13205/j.hjgc.202007014
Abstract:
The removal of dissolved refractory organic compounds can be strengthened by ozone oxidation and ozone catalytic oxidation process used as advanced treatment unit in urban sewage treatment plants. In order to explore the selectivity of ozone oxidation and the stability of removal of COD by ozone-catalyzed oxidation, the effects of ozone oxidation under different inlet water quality conditions, the treated effluents biodegradability and NH3-N were evaluated via ozone oxidation laboratory-scale and pilot-scale test. The results showed that the effect of ozone oxidation on the removal of COD from different influents was quite different. The treatment effect of wastewater with large amount of saturated organic acids was poor. The effluents BOD5 and NH3-N didn't increase after ozone oxidation treatment. The effect of ozone catalytic oxidation to remove COD was related to the degree of adsorption saturation of the catalyst. Therefore, it was recommended to conduct a laboratory-scale experiment to clarify the removal effect on COD before designing the ozone oxidation and ozone-catalytic oxidation process of urban sewage treatment plants. The laboratory-scale experiment of ozone catalytic oxidation needed to be performed for more than 90 days or until the ozone catalyst reaches adsorption saturation state. It was not recommended to add biological filters or aerated biological filters after the ozone oxidation process.
The removal of dissolved refractory organic compounds can be strengthened by ozone oxidation and ozone catalytic oxidation process used as advanced treatment unit in urban sewage treatment plants. In order to explore the selectivity of ozone oxidation and the stability of removal of COD by ozone-catalyzed oxidation, the effects of ozone oxidation under different inlet water quality conditions, the treated effluents biodegradability and NH3-N were evaluated via ozone oxidation laboratory-scale and pilot-scale test. The results showed that the effect of ozone oxidation on the removal of COD from different influents was quite different. The treatment effect of wastewater with large amount of saturated organic acids was poor. The effluents BOD5 and NH3-N didn't increase after ozone oxidation treatment. The effect of ozone catalytic oxidation to remove COD was related to the degree of adsorption saturation of the catalyst. Therefore, it was recommended to conduct a laboratory-scale experiment to clarify the removal effect on COD before designing the ozone oxidation and ozone-catalytic oxidation process of urban sewage treatment plants. The laboratory-scale experiment of ozone catalytic oxidation needed to be performed for more than 90 days or until the ozone catalyst reaches adsorption saturation state. It was not recommended to add biological filters or aerated biological filters after the ozone oxidation process.
2020, 38(7): 93-99.
doi: 10.13205/j.hjgc.202007015
Abstract:
The method for performance evaluation and simulation of wastewater treatment plants to support process retrofitting was introduced in this study, with a case study to illustrate the analysis procedure. By historical data tracking and monitoring campaign along the process, tempo spatial variation of the pollutants was understood for estimating the performance of each functional zone in the process. By assessing the biological activity of activated sludge, the reaction rate and potential of nitrification, denitrification and phosphorus release were acquired and analyzed. Moreover, process modeling and scenario analysis were applied to quantify the key factors of removal efficiency of the process. As a result, suggestions on the upgrade design and operation optimization were proposed after the analysis, proving the feasibility of the integral method to assist the process retrofitting.
The method for performance evaluation and simulation of wastewater treatment plants to support process retrofitting was introduced in this study, with a case study to illustrate the analysis procedure. By historical data tracking and monitoring campaign along the process, tempo spatial variation of the pollutants was understood for estimating the performance of each functional zone in the process. By assessing the biological activity of activated sludge, the reaction rate and potential of nitrification, denitrification and phosphorus release were acquired and analyzed. Moreover, process modeling and scenario analysis were applied to quantify the key factors of removal efficiency of the process. As a result, suggestions on the upgrade design and operation optimization were proposed after the analysis, proving the feasibility of the integral method to assist the process retrofitting.
2020, 38(7): 100-108.
doi: 10.13205/j.hjgc.202007016
Abstract:
Denitrification is one of the important processes of wastewater treatment plant (WWTP). The carbon source, reflux ratio, DO and agitation method are all important factors affecting the denitrification. Fifty-eight WWTPs in Taihu Lake Basin were evaluated for upgrading operation, and the law of water quality fluctuation, process design and equipments were investigated and analyzed to explore the impact of different conditions on the denitrification rate of activated sludge, so as to provide basic data for the operation and management of high standard WWTPs in the future. The results showed that the denitrification rate was in the range of 0~5.18 mg NO3--N/(g VSS·h), among which the average denitrification rate was 1.40 mg NO3--N/(g VSS·h). The main reason for the low denitrification rate was the low concentration of carbon source in the influent. Among them, the type and location of the added carbon source had greater impact on nitrification and denitrification. It could also enhance the denitrification performance of sludge through adding appropriate carbon source and sufficient stirring conditions. When adding easily degradable carbon source in the influent of each WWTP and maintaining a relatively low concentration of carbon source in the influent, the denitrification potential was found to be 1.16~20.80 mg NO3--N/g VSS·h at a high agitation rate, which indicated that improving the quality of influent water and creating better denitrification conditions were conducive to the improvement of the overall denitrification level. Setting proper internal reflux ratio could effectively enhance the biological denitrification performance, however, high dissolved oxygen in internal reflux had greater effect on denitrification, and reducing the reflux dissolved oxygen could effectively promote the NO3--N removal.
Denitrification is one of the important processes of wastewater treatment plant (WWTP). The carbon source, reflux ratio, DO and agitation method are all important factors affecting the denitrification. Fifty-eight WWTPs in Taihu Lake Basin were evaluated for upgrading operation, and the law of water quality fluctuation, process design and equipments were investigated and analyzed to explore the impact of different conditions on the denitrification rate of activated sludge, so as to provide basic data for the operation and management of high standard WWTPs in the future. The results showed that the denitrification rate was in the range of 0~5.18 mg NO3--N/(g VSS·h), among which the average denitrification rate was 1.40 mg NO3--N/(g VSS·h). The main reason for the low denitrification rate was the low concentration of carbon source in the influent. Among them, the type and location of the added carbon source had greater impact on nitrification and denitrification. It could also enhance the denitrification performance of sludge through adding appropriate carbon source and sufficient stirring conditions. When adding easily degradable carbon source in the influent of each WWTP and maintaining a relatively low concentration of carbon source in the influent, the denitrification potential was found to be 1.16~20.80 mg NO3--N/g VSS·h at a high agitation rate, which indicated that improving the quality of influent water and creating better denitrification conditions were conducive to the improvement of the overall denitrification level. Setting proper internal reflux ratio could effectively enhance the biological denitrification performance, however, high dissolved oxygen in internal reflux had greater effect on denitrification, and reducing the reflux dissolved oxygen could effectively promote the NO3--N removal.
2020, 38(7): 109-115.
doi: 10.13205/j.hjgc.202007017
Abstract:
The Futian Sewage Treatment Plant (STP) is the first semi-underground STP in China,with a design capacity of 4×105 m3/d, and the covering land as the second floor was planned to build as a municipal park. This STP effluent complied with the first A standard of Discharge Standard of Pollutants for Urban Sewage Treatment Plants (GB 18918-2002). The moisture content of sludge cake was reduced to 50%. This paper introduced the wastewater treatment process selection, design features, and application of innovating technologies. Due to the higher concentration influent SS, heavy nitrogen removal, and high requirements of sludge treatment, the treatment processes included rectangular primary sedimentation tank for the pretreatment process, multi-influent, multi-stage enhanced denitrification and improved A2/O biological tank, rectangular secondary sedimentation tank, fiber rotary filter and ultraviolet disinfection. The sludge treatment process finally employed the combination of mechanical concentration + plate and frame deep dehydration. After the project completed, the production operation was stable, and the water quality of effluent was better than the design standard.
The Futian Sewage Treatment Plant (STP) is the first semi-underground STP in China,with a design capacity of 4×105 m3/d, and the covering land as the second floor was planned to build as a municipal park. This STP effluent complied with the first A standard of Discharge Standard of Pollutants for Urban Sewage Treatment Plants (GB 18918-2002). The moisture content of sludge cake was reduced to 50%. This paper introduced the wastewater treatment process selection, design features, and application of innovating technologies. Due to the higher concentration influent SS, heavy nitrogen removal, and high requirements of sludge treatment, the treatment processes included rectangular primary sedimentation tank for the pretreatment process, multi-influent, multi-stage enhanced denitrification and improved A2/O biological tank, rectangular secondary sedimentation tank, fiber rotary filter and ultraviolet disinfection. The sludge treatment process finally employed the combination of mechanical concentration + plate and frame deep dehydration. After the project completed, the production operation was stable, and the water quality of effluent was better than the design standard.
2020, 38(7): 116-121.
doi: 10.13205/j.hjgc.202007018
Abstract:
Grit chamber is an important equipment of pretreatment unit in wastewater treatment plant. In recent years, vortex-type grit chamber had been widely used in municipal wastewater treatment plant, however the inorganic particles yield was poor in practical operation. This article focused on the the poor operation effect and low inorganic particles yield in a vortex-type grit chamber from wastewater treatment plant. Specific measures including changing to a spiral curved blade, reducing the speed of the blade, and adjusting the distance between the blade and the bottom were proposed. After the modification, continuous testing was conducted on the vortex-type grit chamber of the plant, and it was found that the SS removal rate was significantly improved from 1.86% to 21.38%, with an average sand output of 51 kg/d. Meanwhile, the interception effect of COD was improved, which was conducive to reduce the carbon source addition into the subsequent biological tanks. Compared to the original chamber, the TN removal rate kept at a level of 0.9%, but TP removal rate was increased from 0.44% to 0.99%. In general, the vortex-type grit chamber was more stable and the inorganic particles yield was enhanced after the modification.
Grit chamber is an important equipment of pretreatment unit in wastewater treatment plant. In recent years, vortex-type grit chamber had been widely used in municipal wastewater treatment plant, however the inorganic particles yield was poor in practical operation. This article focused on the the poor operation effect and low inorganic particles yield in a vortex-type grit chamber from wastewater treatment plant. Specific measures including changing to a spiral curved blade, reducing the speed of the blade, and adjusting the distance between the blade and the bottom were proposed. After the modification, continuous testing was conducted on the vortex-type grit chamber of the plant, and it was found that the SS removal rate was significantly improved from 1.86% to 21.38%, with an average sand output of 51 kg/d. Meanwhile, the interception effect of COD was improved, which was conducive to reduce the carbon source addition into the subsequent biological tanks. Compared to the original chamber, the TN removal rate kept at a level of 0.9%, but TP removal rate was increased from 0.44% to 0.99%. In general, the vortex-type grit chamber was more stable and the inorganic particles yield was enhanced after the modification.
2020, 38(7): 122-126.
doi: 10.13205/j.hjgc.202007019
Abstract:
The dewaterability of waste activated sludge was improved by sodium periodate and anionic polyacrylamide (APAM) conjunction. Sludge dewaterability was determined by specific resistance to filtration and the sludge moisture content, and the contents of protein and polysaccharide in extracellular polymers substances (EPS), as well as zeta potential and particle size of the sludge were also determined. The result indicated that 88 mg/g DS (dry sludge) sodium periodate and 2 mg/g DS APAM could effectively improve sludge dewaterability under pH of 8, and specific resistance to filtration and the sludge moisture content decreased to 4.82×1012 m/kg and 69.67%, respectively. After the oxidation of sodium periodate, the zeta potential of sludge increased, protein content of soluble extracellular polymeric substances increased. Fluorescence spectroscopy showed that humic acid in soluble extracellular polymeric substances was oxidized, and the particle size of sludge decreased. The combined conditioner can effectively improve sludge dewaterability and facilitate the subsequent sludge treatment and disposal.
The dewaterability of waste activated sludge was improved by sodium periodate and anionic polyacrylamide (APAM) conjunction. Sludge dewaterability was determined by specific resistance to filtration and the sludge moisture content, and the contents of protein and polysaccharide in extracellular polymers substances (EPS), as well as zeta potential and particle size of the sludge were also determined. The result indicated that 88 mg/g DS (dry sludge) sodium periodate and 2 mg/g DS APAM could effectively improve sludge dewaterability under pH of 8, and specific resistance to filtration and the sludge moisture content decreased to 4.82×1012 m/kg and 69.67%, respectively. After the oxidation of sodium periodate, the zeta potential of sludge increased, protein content of soluble extracellular polymeric substances increased. Fluorescence spectroscopy showed that humic acid in soluble extracellular polymeric substances was oxidized, and the particle size of sludge decreased. The combined conditioner can effectively improve sludge dewaterability and facilitate the subsequent sludge treatment and disposal.
2020, 38(7): 127-131.
doi: 10.13205/j.hjgc.202007020
Abstract:
The reasons and characteristics of clogging corundum aerators from a waste water treatment plant were investigated, and the components of acid pickling from corundum aerators were studied. It was of great significance to the stable operation of the aeration system in the sewage treatment plant. The results showed that the effective operation time of the new and old aerator was only 160 days, far lower than 840 days of the new aerator. It showed that the aerator was easy to block and needed to be cleaned and maintained in time. Microorganism had little effect on the clogging of corundum aerators, but an indicator effect on judging the blockage state of the corundum aerator. The corundum aerator blockage was related to the content of organic and inorganic matters, and had a positive correlation with the total iron content. Acid cleaning could improve the performance of corundum aerator. Pickling with 15% hydrochloric acid solution for 20 minutes could restore the oxygen mass transfer coefficient of corundum aeration head from about 0.5 min-1 to about 0.7 min-1 after scraping mud, which was close to the oxygen mass transfer coefficient of the new aeration head and indicated good pickling performance.
The reasons and characteristics of clogging corundum aerators from a waste water treatment plant were investigated, and the components of acid pickling from corundum aerators were studied. It was of great significance to the stable operation of the aeration system in the sewage treatment plant. The results showed that the effective operation time of the new and old aerator was only 160 days, far lower than 840 days of the new aerator. It showed that the aerator was easy to block and needed to be cleaned and maintained in time. Microorganism had little effect on the clogging of corundum aerators, but an indicator effect on judging the blockage state of the corundum aerator. The corundum aerator blockage was related to the content of organic and inorganic matters, and had a positive correlation with the total iron content. Acid cleaning could improve the performance of corundum aerator. Pickling with 15% hydrochloric acid solution for 20 minutes could restore the oxygen mass transfer coefficient of corundum aeration head from about 0.5 min-1 to about 0.7 min-1 after scraping mud, which was close to the oxygen mass transfer coefficient of the new aeration head and indicated good pickling performance.
