In order to increase the applicability of photocatalysis in treating offshore produced water (OPW), an immobilized catalyst was introduced into the UV irradiation system and its performance on the degradation of organic compounds in OPW was evaluated. Naphthalene was selected as the target pollutant owing to its abundance in produced water and its chemical property as a typical polycyclic aromatic hydrocarbon. Aeroxide ® P25 nano-scale TiO 2 powder was immobilized on glass slides by a heat attachment method and its photocatalytic capacity was compared to that of the original powder in terms of naphthalene removal efficiency. The results of adsorption showed that the reduction of catalysts’ surface area by immobilization was similar to that by agglomeration. The photocatalytic reaction rate constants in the homogeneous and immobilized systems were 0.00219 min −1 and 0.00305 min −1 , respectively, indicating that the immobilized catalyst had a better performance in photo-oxidation. The fouling of catalyst surface during the irradiation process came from the deposition of insoluble particles, organic matters, and the scaling of calcium. In summary, the immobilization of catalysts was more resistant to the substrate effects of OPW, indicating a more promising alternative in treating OPW.
{"title":"Removal of naphthalene from offshore produced water through immobilized nano-TiO2 aided photo-oxidation","authors":"Bo Liu, Bing Chen, Kenneth Lee, Baiyu Zhang, Yinchen Ma, Liang Jing","doi":"10.2166/WQRJC.2016.027","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.027","url":null,"abstract":"In order to increase the applicability of photocatalysis in treating offshore produced water (OPW), an immobilized catalyst was introduced into the UV irradiation system and its performance on the degradation of organic compounds in OPW was evaluated. Naphthalene was selected as the target pollutant owing to its abundance in produced water and its chemical property as a typical polycyclic aromatic hydrocarbon. Aeroxide ® P25 nano-scale TiO 2 powder was immobilized on glass slides by a heat attachment method and its photocatalytic capacity was compared to that of the original powder in terms of naphthalene removal efficiency. The results of adsorption showed that the reduction of catalysts’ surface area by immobilization was similar to that by agglomeration. The photocatalytic reaction rate constants in the homogeneous and immobilized systems were 0.00219 min −1 and 0.00305 min −1 , respectively, indicating that the immobilized catalyst had a better performance in photo-oxidation. The fouling of catalyst surface during the irradiation process came from the deposition of insoluble particles, organic matters, and the scaling of calcium. In summary, the immobilization of catalysts was more resistant to the substrate effects of OPW, indicating a more promising alternative in treating OPW.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.027","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
H. Niu, Pu Li, Rujun Yang, Yongsheng Wu, Kenneth Lee
The proposed Energy East pipeline project has raised concerns about potential oil spills in Saint John, New Brunswick. While environmental conditions could pose challenges for using mechanical recovery methods if a spill occurs, chemical dispersant could be an alternative. However, the application of chemical dispersant in shallow water and costal zones remains an issue of debate. Furthermore, the effectiveness of chemical dispersant under different seasonal conditions is yet to be determined. This study attempts to describe a modelling effort to understand the probable distribution of petroleum hydrocarbons in Port Saint John following a hypothetical release of crude oil to which dispersant is applied during different seasons. A three-dimensional model was used to simulate the transport of oil with a release of 1,000 m3 of Arabian light crude in the summer and winter. A stochastic approach took into account the uncertainties of environmental inputs. The results were a significant reduction of oil ashore, and enhanced biodegradation with dispersant application. However, these effects were accompanied by an increase of oil in the sediment and water column, which is a concern. While the results are only conclusive for the selected scenarios of summer and winter, the method could be applied to other months and seasons to support more detailed analysis regarding dispersant application.
{"title":"Effects of chemical dispersant and seasonal conditions on the fate of spilled oil – modelling of a hypothetical spill near Saint John, NB","authors":"H. Niu, Pu Li, Rujun Yang, Yongsheng Wu, Kenneth Lee","doi":"10.2166/WQRJC.2015.018","DOIUrl":"https://doi.org/10.2166/WQRJC.2015.018","url":null,"abstract":"The proposed Energy East pipeline project has raised concerns about potential oil spills in Saint John, New Brunswick. While environmental conditions could pose challenges for using mechanical recovery methods if a spill occurs, chemical dispersant could be an alternative. However, the application of chemical dispersant in shallow water and costal zones remains an issue of debate. Furthermore, the effectiveness of chemical dispersant under different seasonal conditions is yet to be determined. This study attempts to describe a modelling effort to understand the probable distribution of petroleum hydrocarbons in Port Saint John following a hypothetical release of crude oil to which dispersant is applied during different seasons. A three-dimensional model was used to simulate the transport of oil with a release of 1,000 m3 of Arabian light crude in the summer and winter. A stochastic approach took into account the uncertainties of environmental inputs. The results were a significant reduction of oil ashore, and enhanced biodegradation with dispersant application. However, these effects were accompanied by an increase of oil in the sediment and water column, which is a concern. While the results are only conclusive for the selected scenarios of summer and winter, the method could be applied to other months and seasons to support more detailed analysis regarding dispersant application.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2015.018","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67982028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper presents the outcomes of a study on the water quality of Dubai Creek which aimed to assess its eutrophication status. Field water quality data from stations along the creek collected in 2012 and 2013 were used. Ordinary least squares (OLS) and spatial autocorrelation analyses were used as part of geographic information system (GIS)-based exploratory regression analysis to study the relationship between chlorophyll- a and nutrients, specifically total nitrogen and phosphate. Multiple logistic regression analysis was used to study the vulnerability of the creek to eutrophication. Results showed unique trends of spatiotemporal variability of chlorophyll- a and nutrients. OLS modeling showed high correlation between field and modeled chlorophyll- a values between Al Garhoud Bridge and Sanctuary stations, located about 2 km upstream and downstream of the Sewage Treatment Plant (STP) Outfall station. Furthermore, results showed the lower half of the creek was more vulnerable to eutrophication than the upper, which was believed to be due to the location of the STP station, poor flushing, shallow water depth, and irregular circulation patterns in the creek. Accordingly, this study recommends development of a mitigation plan in order to control the levels of nutrients in the creek.
{"title":"A GIS-based spatiotemporal study of the variability of water quality in the Dubai Creek, UAE","authors":"Tarig Ali, M. Mortula, S. Atabay, Ehsan Navadeh","doi":"10.2166/WQRJC.2015.020","DOIUrl":"https://doi.org/10.2166/WQRJC.2015.020","url":null,"abstract":"This paper presents the outcomes of a study on the water quality of Dubai Creek which aimed to assess its eutrophication status. Field water quality data from stations along the creek collected in 2012 and 2013 were used. Ordinary least squares (OLS) and spatial autocorrelation analyses were used as part of geographic information system (GIS)-based exploratory regression analysis to study the relationship between chlorophyll- a and nutrients, specifically total nitrogen and phosphate. Multiple logistic regression analysis was used to study the vulnerability of the creek to eutrophication. Results showed unique trends of spatiotemporal variability of chlorophyll- a and nutrients. OLS modeling showed high correlation between field and modeled chlorophyll- a values between Al Garhoud Bridge and Sanctuary stations, located about 2 km upstream and downstream of the Sewage Treatment Plant (STP) Outfall station. Furthermore, results showed the lower half of the creek was more vulnerable to eutrophication than the upper, which was believed to be due to the location of the STP station, poor flushing, shallow water depth, and irregular circulation patterns in the creek. Accordingly, this study recommends development of a mitigation plan in order to control the levels of nutrients in the creek.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-08-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2015.020","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67982101","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A decentralized full-scale sequencing batch reactor (SBR) system for treating wastewater was operated to assess their feasibility and the response of bacterial population dynamic and nutrient removal performance. The reactor was operated under low dissolved oxygen (DO) concentration (0.3–0.7 mgL−1) and an average applied organic load of 0.5 g COD L−1 d−1 (COD: chemical oxygen demand). Removal efficiencies were higher than 70% for both soluble chemical oxygen demand and ammonium, with average effluent concentration of 51 ± 15 mg COD L−1 and 16.0 mg NH4+ L−1. The mixed liquor volatile suspended solids/total suspended solids ratio was 0.9, and the average food/microorganism ratio was 0.3 g COD g VSS−1 d−1 (VSS: volatile suspended solids). The active biomass was composed of 94.9% heterotrophic and 5.1% autotrophic organisms. The most frequently identified were chemoorganoheterotrophic organisms affiliated with Bacteroidetes and Firmicutes, some of them with the capacity to denitrify and grow under low DO concentration. Temperature and sludge withdrawal were important factors in determining nitrification and phosphorus removal rates. The SBR was viable for domestic wastewater treatment and showed that the microbial community greatly influenced its performance. This work can also provide valuable insights into further applications in systems operated under low DO condition.
采用分散式全尺寸序批式反应器(SBR)处理废水，对其可行性、细菌种群动态响应及营养物去除性能进行了评价。反应器在低溶解氧(DO)浓度(0.3-0.7 mg / L−1)和平均施加有机负荷0.5 g COD L−1 d−1 (COD:化学需氧量)下运行。出水COD浓度为51±15 mg L−1,NH4+ L−1平均浓度为16.0 mg，对可溶性化学需氧量和铵的去除率均高于70%。混合液挥发性悬浮固体/总悬浮固体比为0.9，食品/微生物平均比为0.3 g COD g VSS−1 d−1 (VSS:挥发性悬浮固体)。活性生物量由94.9%的异养生物和5.1%的自养生物组成。最常见的是与拟杆菌门和厚壁菌门有关的化学有机异养生物，其中一些具有反硝化和在低DO浓度下生长的能力。温度和污泥提取量是决定硝化和除磷率的重要因素。SBR处理生活污水是可行的，并表明微生物群落对其性能有很大影响。这项工作还可以为在低DO条件下运行的系统的进一步应用提供有价值的见解。
{"title":"Investigation of full-scale step-fed SBR under low dissolved oxygen: performance and microbial community response","authors":"Heloísa Fernandes, R. Antônio, R. Costa","doi":"10.2166/WQRJC.2016.042","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.042","url":null,"abstract":"A decentralized full-scale sequencing batch reactor (SBR) system for treating wastewater was operated to assess their feasibility and the response of bacterial population dynamic and nutrient removal performance. The reactor was operated under low dissolved oxygen (DO) concentration (0.3–0.7 mgL−1) and an average applied organic load of 0.5 g COD L−1 d−1 (COD: chemical oxygen demand). Removal efficiencies were higher than 70% for both soluble chemical oxygen demand and ammonium, with average effluent concentration of 51 ± 15 mg COD L−1 and 16.0 mg NH4+ L−1. The mixed liquor volatile suspended solids/total suspended solids ratio was 0.9, and the average food/microorganism ratio was 0.3 g COD g VSS−1 d−1 (VSS: volatile suspended solids). The active biomass was composed of 94.9% heterotrophic and 5.1% autotrophic organisms. The most frequently identified were chemoorganoheterotrophic organisms affiliated with Bacteroidetes and Firmicutes, some of them with the capacity to denitrify and grow under low DO concentration. Temperature and sludge withdrawal were important factors in determining nitrification and phosphorus removal rates. The SBR was viable for domestic wastewater treatment and showed that the microbial community greatly influenced its performance. This work can also provide valuable insights into further applications in systems operated under low DO condition.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.042","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983411","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
D. A. Waterman, S. Walker, Bingjie Xu, R. Narbaitz
Currently, there is no standard bench-scale dead-end ultrafiltration (UF) testing system. The aim of the present study was to design and build a bench-scale hollow fiber UF system to assess the impact of operational parameters on membrane performance and fouling. A bench-scale hollow fiber UF system was built to operate at a constant flux (±2% of the set-point flux) and included automated backwash cycles. The development of the bench-scale system showed that it is very difficult to maintain a constant flux during the first minute of the filtration cycles, that digital flow meters are problematic, and that the volume of the backwash waste lines should be minimized. The system was evaluated with Ottawa River water, which has a relatively high hydrophobic natural organic matter content and is typical of Northern Canadian waters. The testing using different permeate fluxes, filtration cycle duration and backwash cycle duration showed that this system mimics the performance of larger systems and may be used to assess the impact of operating conditions on membrane fouling and alternative pretreatment options. Modeling the first, middle, and last filtration cycles of the six runs using single and dual blocking mechanisms yielded inconsistent results regarding the controlling fouling mechanisms.
{"title":"Bench-scale study of ultrafiltration membranes for evaluating membrane performance in surface water treatment","authors":"D. A. Waterman, S. Walker, Bingjie Xu, R. Narbaitz","doi":"10.2166/WQRJC.2016.039","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.039","url":null,"abstract":"Currently, there is no standard bench-scale dead-end ultrafiltration (UF) testing system. The aim of the present study was to design and build a bench-scale hollow fiber UF system to assess the impact of operational parameters on membrane performance and fouling. A bench-scale hollow fiber UF system was built to operate at a constant flux (±2% of the set-point flux) and included automated backwash cycles. The development of the bench-scale system showed that it is very difficult to maintain a constant flux during the first minute of the filtration cycles, that digital flow meters are problematic, and that the volume of the backwash waste lines should be minimized. The system was evaluated with Ottawa River water, which has a relatively high hydrophobic natural organic matter content and is typical of Northern Canadian waters. The testing using different permeate fluxes, filtration cycle duration and backwash cycle duration showed that this system mimics the performance of larger systems and may be used to assess the impact of operating conditions on membrane fouling and alternative pretreatment options. Modeling the first, middle, and last filtration cycles of the six runs using single and dual blocking mechanisms yielded inconsistent results regarding the controlling fouling mechanisms.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.039","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Stocker, J. Rodriguez-Valentin, Y. Pachepsky, D. Shelton
Evaluation of microbial water quality is commonly based on monitoring populations of fecal indicator organisms (FIO) such as E. coli (EC) and enterococci. The occurrence of elevated FIO concentrations in surface waters after storm events is well documented and has been attributed to runoff and sediment resuspension. The reasons for FIO concentration variation under baseflow conditions are less clear. The objective of this study was to quantify the variability of EC and enterococci in two small streams running through agricultural land use areas. FIO concentrations were measured at upstream and downstream locations under baseflow conditions. Concentrations were not significantly different along cross-sections of the streams. Diurnal concentration trends were observed at each of the sampling locations. Significant differences in concentrations between upstream and downstream locations were noted for both creeks during baseflow periods when no runoff or sediment resuspension occurred. A hypothetical explanation is that indicator organisms are released from sediments during baseflow conditions due to the effect of groundwater influx into streams or due to the motility of indicator organisms. If confirmed, this hypothesis may affect our understanding of the role of sediments in the microbial quality of surface waters.
{"title":"Spatial and temporal variation of fecal indicator organisms in two creeks in Beltsville, Maryland","authors":"M. Stocker, J. Rodriguez-Valentin, Y. Pachepsky, D. Shelton","doi":"10.2166/WQRJC.2016.044","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.044","url":null,"abstract":"Evaluation of microbial water quality is commonly based on monitoring populations of fecal indicator organisms (FIO) such as E. coli (EC) and enterococci. The occurrence of elevated FIO concentrations in surface waters after storm events is well documented and has been attributed to runoff and sediment resuspension. The reasons for FIO concentration variation under baseflow conditions are less clear. The objective of this study was to quantify the variability of EC and enterococci in two small streams running through agricultural land use areas. FIO concentrations were measured at upstream and downstream locations under baseflow conditions. Concentrations were not significantly different along cross-sections of the streams. Diurnal concentration trends were observed at each of the sampling locations. Significant differences in concentrations between upstream and downstream locations were noted for both creeks during baseflow periods when no runoff or sediment resuspension occurred. A hypothetical explanation is that indicator organisms are released from sediments during baseflow conditions due to the effect of groundwater influx into streams or due to the motility of indicator organisms. If confirmed, this hypothesis may affect our understanding of the role of sediments in the microbial quality of surface waters.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.044","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qinhong Cai, Baiyu Zhang, Bing Chen, Tong-chuan Cao, Z. Lv
Biosurfactants have been considered as superior alternatives to currently used surfactants as they are generally more biodegradable, less toxic, and better at enhancing biodegradation. However, the application of biosurfactants is limited by the availability of economic biosurfactants and the corresponding producers that can work effectively. Hyperproducers generated by metabolic engineering of biosurfactant producers are highly desired to overcome this obstacle. A Rhodococcus erythropolis SB-1A strain was isolated from offshore oily water samples. One of its mutants derived by random mutagenesis with ultraviolet radiation, producing high levels of biosurfactants, was selected by the oil spreading technique. The mutant produces biosurfactants with critical micelle dilutions approximately four times those of the parent strain. The results obtained with thin layer chromatography indicated the produced biosurfactant remained unchanged between the mutant and the parent strain. In addition, the produced biosurfactants were recovered with solvent extraction and applied as the oil spill response agents. Based on the baffled flask test (BFT) results, the dispersion efficiency of the biosurfactants produced by the mutant is higher than that induced by the parent strain. When compared with Corexit dispersants, it was found that the produced biosurfactants performed better than Corexit 9527 and were comparable with Corexit 9500.
{"title":"Biosurfactant produced by a Rhodococcus erythropolis mutant as an oil spill response agent","authors":"Qinhong Cai, Baiyu Zhang, Bing Chen, Tong-chuan Cao, Z. Lv","doi":"10.2166/WQRJC.2016.025","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.025","url":null,"abstract":"Biosurfactants have been considered as superior alternatives to currently used surfactants as they are generally more biodegradable, less toxic, and better at enhancing biodegradation. However, the application of biosurfactants is limited by the availability of economic biosurfactants and the corresponding producers that can work effectively. Hyperproducers generated by metabolic engineering of biosurfactant producers are highly desired to overcome this obstacle. A Rhodococcus erythropolis SB-1A strain was isolated from offshore oily water samples. One of its mutants derived by random mutagenesis with ultraviolet radiation, producing high levels of biosurfactants, was selected by the oil spreading technique. The mutant produces biosurfactants with critical micelle dilutions approximately four times those of the parent strain. The results obtained with thin layer chromatography indicated the produced biosurfactant remained unchanged between the mutant and the parent strain. In addition, the produced biosurfactants were recovered with solvent extraction and applied as the oil spill response agents. Based on the baffled flask test (BFT) results, the dispersion efficiency of the biosurfactants produced by the mutant is higher than that induced by the parent strain. When compared with Corexit dispersants, it was found that the produced biosurfactants performed better than Corexit 9527 and were comparable with Corexit 9500.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.025","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67982423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
O. C. Alfaro, A. M. Domínguez, F. Rigas, Myriam Solís-López, R. Ramírez-Zamora
We used an experimental design to determine the best coagulation–flocculation mechanism and the optimal operating conditions for the maximum removal of the natural organic matter fractions (hydrophobic acid (HPOA) and hydrophilic neutral (HPIN)), which are the main factors responsible for irreversible membrane fouling and the generation of disinfection by-products (DBPs). Charge neutralization and sweep mechanisms (SM) were studied using the jar test experiment, and synthetic waters prepared with different hydrophobic/hydrophilic (HPO/HPI) weight ratios by adding model compounds, to represent the dissolved organic matter (DOM) fractions. Significant influence factors were identified for both coagulation mechanisms. The SM was the best one for DOM removal independent of the HPO/HPI weight ratio. The SM removed HPOA and HPIN fractions with efficiencies of 87.5–90.5% and 73.6–89.8%, respectively. The dissolved organic carbon (DOC) values of all met the recommendation proposed by the United States Environmental Protection Agency (2 mg total organic carbon (TOC)/L or 1.8 mg DOC/L) for DBPs (<100 μg/L). Furthermore, all effluents met the DOC and silt density index recommended values by membrane suppliers (<3 mg DOC/L and <5%/min, respectively) to minimize fouling potential and to extend the membrane life.
{"title":"Optimization of the coagulation–flocculation process for the removal of natural organic matter fractions present in drinking water sources","authors":"O. C. Alfaro, A. M. Domínguez, F. Rigas, Myriam Solís-López, R. Ramírez-Zamora","doi":"10.2166/WQRJC.2016.041","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.041","url":null,"abstract":"We used an experimental design to determine the best coagulation–flocculation mechanism and the optimal operating conditions for the maximum removal of the natural organic matter fractions (hydrophobic acid (HPOA) and hydrophilic neutral (HPIN)), which are the main factors responsible for irreversible membrane fouling and the generation of disinfection by-products (DBPs). Charge neutralization and sweep mechanisms (SM) were studied using the jar test experiment, and synthetic waters prepared with different hydrophobic/hydrophilic (HPO/HPI) weight ratios by adding model compounds, to represent the dissolved organic matter (DOM) fractions. Significant influence factors were identified for both coagulation mechanisms. The SM was the best one for DOM removal independent of the HPO/HPI weight ratio. The SM removed HPOA and HPIN fractions with efficiencies of 87.5–90.5% and 73.6–89.8%, respectively. The dissolved organic carbon (DOC) values of all met the recommendation proposed by the United States Environmental Protection Agency (2 mg total organic carbon (TOC)/L or 1.8 mg DOC/L) for DBPs (<100 μg/L). Furthermore, all effluents met the DOC and silt density index recommended values by membrane suppliers (<3 mg DOC/L and <5%/min, respectively) to minimize fouling potential and to extend the membrane life.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.041","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983293","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
F. Guesmi, Islem Louati, Chiraz Hannachi, B. Hamrouni
The main purpose of this work was to determine adsorption characteristics of fluoride, nitrate and sulfate ions on the AFN membrane. The sorption isotherms for ![Graphic][1] , ![Graphic][2] and ![Graphic][3] ions on the AFN membrane were investigated in the range of 0.05–1 mol.L–1 at 298 K. The suitability of the Langmuir, Dubinin–Astakhov (D-A) and Redlich–Peterson adsorption models to the equilibrium data was investigated. The sorption parameters of the studied models were determined by non-linear regression and discussed. Equilibrium data obtained in this study were found to best fit the Langmuir isotherm. The ΔG° values deduced from the Langmuir isotherm suggest that the affinity order of the AFN membrane for the studied anions is: ![Graphic][4] . In order to improve their selectivity towards monovalent ions, the AFN membrane was modified by adsorption of polyethyleneimine on its surface. Adsorption parameters values of the studied models were determined for the modified AFN membrane. The D-A model provides the best fit to the experimental points. In fact, removal of fluoride and nitrate ions by adsorption on the modified AFN membrane was more effective than the adsorption on the unmodified one. Desorption of fluoride from the modified AFN membrane by nitrate and sulfate ions was investigated. [1]: /embed/inline-graphic-1.gif [2]: /embed/inline-graphic-2.gif [3]: /embed/inline-graphic-3.gif [4]: /embed/inline-graphic-4.gif
{"title":"Comparison of adsorption models for the removal of fluorides, nitrates and sulfates by adsorption onto AFN membrane","authors":"F. Guesmi, Islem Louati, Chiraz Hannachi, B. Hamrouni","doi":"10.2166/WQRJC.2016.031","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.031","url":null,"abstract":"The main purpose of this work was to determine adsorption characteristics of fluoride, nitrate and sulfate ions on the AFN membrane. The sorption isotherms for ![Graphic][1] , ![Graphic][2] and ![Graphic][3] ions on the AFN membrane were investigated in the range of 0.05–1 mol.L–1 at 298 K. The suitability of the Langmuir, Dubinin–Astakhov (D-A) and Redlich–Peterson adsorption models to the equilibrium data was investigated. The sorption parameters of the studied models were determined by non-linear regression and discussed. Equilibrium data obtained in this study were found to best fit the Langmuir isotherm. The ΔG° values deduced from the Langmuir isotherm suggest that the affinity order of the AFN membrane for the studied anions is: ![Graphic][4] . In order to improve their selectivity towards monovalent ions, the AFN membrane was modified by adsorption of polyethyleneimine on its surface. Adsorption parameters values of the studied models were determined for the modified AFN membrane. The D-A model provides the best fit to the experimental points. In fact, removal of fluoride and nitrate ions by adsorption on the modified AFN membrane was more effective than the adsorption on the unmodified one. Desorption of fluoride from the modified AFN membrane by nitrate and sulfate ions was investigated.\u0000\u0000 [1]: /embed/inline-graphic-1.gif\u0000 [2]: /embed/inline-graphic-2.gif\u0000 [3]: /embed/inline-graphic-3.gif\u0000 [4]: /embed/inline-graphic-4.gif","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.031","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983186","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Hamouda, W. B. Anderson, M. I. Dyke, I. Douglas, S. McFadyen, P. Huck
While traditional application of quantitative microbial risk assessment (QMRA) models usually stops at analyzing the microbial risk under typical operating conditions, this paper proposes the use of scenario-based risk assessment to predict the impact of potential challenges on the expected risk. This study used a QMRA model developed by Health Canada to compare 14 scenarios created to assess the increase in risk due to potential treatment failures and unexpected variations in water quality and operating parameters of a water treatment plant. Under regular operating conditions, the annual risk of illness was found to be substantially lower than the acceptable limit. Scenario-based QMRA was shown to be useful in demonstrating which hypothetical treatment failures would be the most critical, resulting in an increased risk of illness. The analysis demonstrated that scenarios incorporating considerable failure in treatment processes resulted in risk levels surpassing the acceptable limit. This reiterates the importance of robust treatment processes and the multi-barrier approach voiced in drinking water safety studies. Knowing the probability of failure, and the risk involved, allows designers and operators to make effective plans for response to treatment failures and/or recovery actions involving potential exposures. This ensures the appropriate allocation of financial and human resources.
{"title":"Scenario-based quantitative microbial risk assessment to evaluate the robustness of a drinking water treatment plant","authors":"M. Hamouda, W. B. Anderson, M. I. Dyke, I. Douglas, S. McFadyen, P. Huck","doi":"10.2166/WQRJC.2016.034","DOIUrl":"https://doi.org/10.2166/WQRJC.2016.034","url":null,"abstract":"While traditional application of quantitative microbial risk assessment (QMRA) models usually stops at analyzing the microbial risk under typical operating conditions, this paper proposes the use of scenario-based risk assessment to predict the impact of potential challenges on the expected risk. This study used a QMRA model developed by Health Canada to compare 14 scenarios created to assess the increase in risk due to potential treatment failures and unexpected variations in water quality and operating parameters of a water treatment plant. Under regular operating conditions, the annual risk of illness was found to be substantially lower than the acceptable limit. Scenario-based QMRA was shown to be useful in demonstrating which hypothetical treatment failures would be the most critical, resulting in an increased risk of illness. The analysis demonstrated that scenarios incorporating considerable failure in treatment processes resulted in risk levels surpassing the acceptable limit. This reiterates the importance of robust treatment processes and the multi-barrier approach voiced in drinking water safety studies. Knowing the probability of failure, and the risk involved, allows designers and operators to make effective plans for response to treatment failures and/or recovery actions involving potential exposures. This ensures the appropriate allocation of financial and human resources.","PeriodicalId":54407,"journal":{"name":"Water Quality Research Journal of Canada","volume":null,"pages":null},"PeriodicalIF":2.0,"publicationDate":"2016-05-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.2166/WQRJC.2016.034","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67983221","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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