The removal of ammonia and phosphorus from an artificial wastewater was studied in two lab-scale reed beds.During batch and continuous operations,it was found that ammonia was removed from the wastewater via a two-ste...The removal of ammonia and phosphorus from an artificial wastewater was studied in two lab-scale reed beds.During batch and continuous operations,it was found that ammonia was removed from the wastewater via a two-step process,sorption inside bed matrices followed by nitrification into nitrite and nitrate.Rapid decrease in the concentration of ammonia in the artificial wastewater was observed during the batch operation,whereas during the continuous operation,which lasted for 39 days,the percentage removal of ammonia decreased gradually with time before stabilizing at around 20%.The efficiency of phosphorus removal exhausted rapidly during the continuous operation,from 39% on the first day of operation to virtually zero after only 5 days.The results suggest that sorption(which may include ion exchange,adsorption,and biomass assimilation) serves as an initial step to remove ammonia and phosphorus from the wastewater,prior to any microbial transformations.展开更多
In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed...In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed only a slight temperature variation, from an influent average of 26.3°C to an effluent of 24.7°C. Electrical conductivity decreased from 1331 mS/cm to 974.5 mS/cm post-primary treatment, with suspended solids (SS) dramatically reduced from 718.9 mg/L to 5.7 mg/L in the final effluent. Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) saw a notable decrease, from initial levels of 655.6 mg/L and 1240 mg/L to 2.3 mg/L and 71.3 mg/L, respectively. Nitrogenous compounds (N-TN) and phosphates () also decreased significantly, indicating the system’s nutrient removal capacity. Microbiological analysis revealed a reduction in fecal coliforms from 7.5 Ulog/100ml to 1.8 Ulog/100ml and a complete elimination of helminth eggs. The presence of Phragmites and Typha was instrumental in enhancing these reductions. The system’s compliance with the Senegalese standards for disposal into natural environments, WHO recommendations for unrestricted water reuse in irrigation, and the European legislation for water reuse was established. The effluent quality met the stringent criteria for various classes of agricultural reuse, illustrating the system’s potential for sustainable water management. This wetland model presents a robust solution for water-stressed regions, ensuring environmental protection while supporting agricultural needs. The study calls for ongoing research to further refine the system for optimal, reliable wastewater treatment and water resource sustainability.展开更多
Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances parti...Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances partition strongly to organic particulate matter. In order to evaluate this premise, the study investigated the organic matter, pesticides and PCBs content in wastewater and in soil within the reed beds, in their entry, middle, and exit-part areas in a full-scale operating subsurface-flow （SSW） constructed wetland （CW） in Poland. It is found that chlorinated pesticides such as 2,4＇dichlorodiphenyltrichloroethane （2,4＇DDT）, 4,4＇dichlorodiphenyldichloroethylene （4,4＇DDE）, hexachlorobenzene （HCB）, as well as PCBs in the wastewater. In the entry-part area of reed beds, nearly all of the pesticides and PCBs content in the wastewater had been removed by soil. The level of contamination by these compounds declined with increasing distance from the point of discharge of the wastewaters into the reed beds, as well as downwards through the soil profile from the surface into the deeper layers. Vertical distributions of pesticides and PCBs content were proportional to the organic carbon content in the soil. It is therefore concluded that reed beds act as a trap for pesticides and PCBs, and thus can provide a very effective mechanism for their removal from wastewater.展开更多
The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed,and a mathematical model was established to quantify the removal of each pollutant,based on its main ...The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed,and a mathematical model was established to quantify the removal of each pollutant,based on its main removal mechanisms.Subsurface horizontal flow wetlands were treated as a series of continuous stirred-tank reactors(CSTRs).Kinetic models for the removal of biochemical oxygen demand,chemical oxygen demand,ammonia,total nitrogen and faecal coliforms were established by combining Monod or first-order kinetics with CSTR assumptions.These tentative models account for a wide range of factors that affect wetland performance,but the models have not been proven by experiment data.Depending on the derivation of various coefficients in the models and verification by actual performance data,this study may provide a starting point for an integrated pollutant removal model to be developed,and experimentally verified,thereby making a step forward from the current greenbox'approach of wetland design.展开更多
文摘The removal of ammonia and phosphorus from an artificial wastewater was studied in two lab-scale reed beds.During batch and continuous operations,it was found that ammonia was removed from the wastewater via a two-step process,sorption inside bed matrices followed by nitrification into nitrite and nitrate.Rapid decrease in the concentration of ammonia in the artificial wastewater was observed during the batch operation,whereas during the continuous operation,which lasted for 39 days,the percentage removal of ammonia decreased gradually with time before stabilizing at around 20%.The efficiency of phosphorus removal exhausted rapidly during the continuous operation,from 39% on the first day of operation to virtually zero after only 5 days.The results suggest that sorption(which may include ion exchange,adsorption,and biomass assimilation) serves as an initial step to remove ammonia and phosphorus from the wastewater,prior to any microbial transformations.
文摘In Saint-Louis, Senegal, a constructed wetland with horizontal flow reed beds (FHa and FHb) has demonstrated significant efficacy in treating municipal wastewater. Analyzing various treatment stages, the system showed only a slight temperature variation, from an influent average of 26.3°C to an effluent of 24.7°C. Electrical conductivity decreased from 1331 mS/cm to 974.5 mS/cm post-primary treatment, with suspended solids (SS) dramatically reduced from 718.9 mg/L to 5.7 mg/L in the final effluent. Biochemical oxygen demand (BOD5) and chemical oxygen demand (COD) saw a notable decrease, from initial levels of 655.6 mg/L and 1240 mg/L to 2.3 mg/L and 71.3 mg/L, respectively. Nitrogenous compounds (N-TN) and phosphates () also decreased significantly, indicating the system’s nutrient removal capacity. Microbiological analysis revealed a reduction in fecal coliforms from 7.5 Ulog/100ml to 1.8 Ulog/100ml and a complete elimination of helminth eggs. The presence of Phragmites and Typha was instrumental in enhancing these reductions. The system’s compliance with the Senegalese standards for disposal into natural environments, WHO recommendations for unrestricted water reuse in irrigation, and the European legislation for water reuse was established. The effluent quality met the stringent criteria for various classes of agricultural reuse, illustrating the system’s potential for sustainable water management. This wetland model presents a robust solution for water-stressed regions, ensuring environmental protection while supporting agricultural needs. The study calls for ongoing research to further refine the system for optimal, reliable wastewater treatment and water resource sustainability.
文摘Constructed wetlands containing reed beds are believed to facilitate the removal from water of various toxic substances, such as polychlorinated biphenyls （PCBs）, pesticides and herbicides, as these substances partition strongly to organic particulate matter. In order to evaluate this premise, the study investigated the organic matter, pesticides and PCBs content in wastewater and in soil within the reed beds, in their entry, middle, and exit-part areas in a full-scale operating subsurface-flow （SSW） constructed wetland （CW） in Poland. It is found that chlorinated pesticides such as 2,4＇dichlorodiphenyltrichloroethane （2,4＇DDT）, 4,4＇dichlorodiphenyldichloroethylene （4,4＇DDE）, hexachlorobenzene （HCB）, as well as PCBs in the wastewater. In the entry-part area of reed beds, nearly all of the pesticides and PCBs content in the wastewater had been removed by soil. The level of contamination by these compounds declined with increasing distance from the point of discharge of the wastewaters into the reed beds, as well as downwards through the soil profile from the surface into the deeper layers. Vertical distributions of pesticides and PCBs content were proportional to the organic carbon content in the soil. It is therefore concluded that reed beds act as a trap for pesticides and PCBs, and thus can provide a very effective mechanism for their removal from wastewater.
文摘The main removal mechanisms for the degradations of seven pollutants in wastewater treatment wetlands were analysed,and a mathematical model was established to quantify the removal of each pollutant,based on its main removal mechanisms.Subsurface horizontal flow wetlands were treated as a series of continuous stirred-tank reactors(CSTRs).Kinetic models for the removal of biochemical oxygen demand,chemical oxygen demand,ammonia,total nitrogen and faecal coliforms were established by combining Monod or first-order kinetics with CSTR assumptions.These tentative models account for a wide range of factors that affect wetland performance,but the models have not been proven by experiment data.Depending on the derivation of various coefficients in the models and verification by actual performance data,this study may provide a starting point for an integrated pollutant removal model to be developed,and experimentally verified,thereby making a step forward from the current greenbox'approach of wetland design.
