S.A. Trikannad
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Exploring electrochemical disinfection for decentralized drinking water production
From Laboratory Research to Field Application in Ghana
Decentralized drinking water production continues to face challenges in achieving acceptable standards for human consumption. This is mainly due to difficulty in developing treatments that can operate effectively in low-resource settings, either due to complications associated with providing the system in a decentralized context or overall unsatisfactory performance of the technology adopted. Electrochemical systems are emerging technologies within decentralized settings which provide many advantages to being adapted in resource-limited areas. This study focuses on understanding the mechanisms behind the electrochemical
disinfection for the treatment of surface water. Laboratory experiments were conducted to evaluate the performance of an RuO2/IrO2 and a Magneli-phase reactor for the disinfection of a bacteria species, Escherichia Coli, and a virus species, ΦX174. The two reactors are characterised in terms of distinct anodic properties and their performance is assessed by promoting different electrochemical reactions for the generation of various disinfectant agents within the electrochemical cell, with specific focus on the formation of chlorine and Reactive
Oxygen Species (ROS). Chlorine-based disinfection proved to be the primary agent in the removal of both pathogens; a 4 log removal for E. Coli was achieved at an energy use of 0.41 kWh/m3 for RuO2/IrO2 and of 0.31 kWh/m3 forMagneli, and a 5 log removal for ΦX174 was achieved at 2.88 kWh/m3 for RuO2/IrO2 and for 1.18 kWh/m3 for Magneli.
To further assess the viability for the treatment of surface waters in decentralized settings, the RuO2/IrO2 was also tested in a field setting in Ghana making use of different water types to compare the utility in using an electrochemical reactor to produce chlorine for disinfection as compared to traditional disinfection methods. Seawater, lagoon and river water were tested, achieving an energy use per gram of produced chlorine of 0.007, 0.046 and 0.066 kWh/gchlorine for a produced chlorine dose of 35 mg/L for seawater and 5 mg/L for the lagoon and river water. With these results, chlorine can be produced from river water at an equivalent dosage to traditional chlorine tablets, and at a cost that is 40 times lower. ...
disinfection for the treatment of surface water. Laboratory experiments were conducted to evaluate the performance of an RuO2/IrO2 and a Magneli-phase reactor for the disinfection of a bacteria species, Escherichia Coli, and a virus species, ΦX174. The two reactors are characterised in terms of distinct anodic properties and their performance is assessed by promoting different electrochemical reactions for the generation of various disinfectant agents within the electrochemical cell, with specific focus on the formation of chlorine and Reactive
Oxygen Species (ROS). Chlorine-based disinfection proved to be the primary agent in the removal of both pathogens; a 4 log removal for E. Coli was achieved at an energy use of 0.41 kWh/m3 for RuO2/IrO2 and of 0.31 kWh/m3 forMagneli, and a 5 log removal for ΦX174 was achieved at 2.88 kWh/m3 for RuO2/IrO2 and for 1.18 kWh/m3 for Magneli.
To further assess the viability for the treatment of surface waters in decentralized settings, the RuO2/IrO2 was also tested in a field setting in Ghana making use of different water types to compare the utility in using an electrochemical reactor to produce chlorine for disinfection as compared to traditional disinfection methods. Seawater, lagoon and river water were tested, achieving an energy use per gram of produced chlorine of 0.007, 0.046 and 0.066 kWh/gchlorine for a produced chlorine dose of 35 mg/L for seawater and 5 mg/L for the lagoon and river water. With these results, chlorine can be produced from river water at an equivalent dosage to traditional chlorine tablets, and at a cost that is 40 times lower. ...
Decentralized drinking water production continues to face challenges in achieving acceptable standards for human consumption. This is mainly due to difficulty in developing treatments that can operate effectively in low-resource settings, either due to complications associated with providing the system in a decentralized context or overall unsatisfactory performance of the technology adopted. Electrochemical systems are emerging technologies within decentralized settings which provide many advantages to being adapted in resource-limited areas. This study focuses on understanding the mechanisms behind the electrochemical
disinfection for the treatment of surface water. Laboratory experiments were conducted to evaluate the performance of an RuO2/IrO2 and a Magneli-phase reactor for the disinfection of a bacteria species, Escherichia Coli, and a virus species, ΦX174. The two reactors are characterised in terms of distinct anodic properties and their performance is assessed by promoting different electrochemical reactions for the generation of various disinfectant agents within the electrochemical cell, with specific focus on the formation of chlorine and Reactive
Oxygen Species (ROS). Chlorine-based disinfection proved to be the primary agent in the removal of both pathogens; a 4 log removal for E. Coli was achieved at an energy use of 0.41 kWh/m3 for RuO2/IrO2 and of 0.31 kWh/m3 forMagneli, and a 5 log removal for ΦX174 was achieved at 2.88 kWh/m3 for RuO2/IrO2 and for 1.18 kWh/m3 for Magneli.
To further assess the viability for the treatment of surface waters in decentralized settings, the RuO2/IrO2 was also tested in a field setting in Ghana making use of different water types to compare the utility in using an electrochemical reactor to produce chlorine for disinfection as compared to traditional disinfection methods. Seawater, lagoon and river water were tested, achieving an energy use per gram of produced chlorine of 0.007, 0.046 and 0.066 kWh/gchlorine for a produced chlorine dose of 35 mg/L for seawater and 5 mg/L for the lagoon and river water. With these results, chlorine can be produced from river water at an equivalent dosage to traditional chlorine tablets, and at a cost that is 40 times lower.
disinfection for the treatment of surface water. Laboratory experiments were conducted to evaluate the performance of an RuO2/IrO2 and a Magneli-phase reactor for the disinfection of a bacteria species, Escherichia Coli, and a virus species, ΦX174. The two reactors are characterised in terms of distinct anodic properties and their performance is assessed by promoting different electrochemical reactions for the generation of various disinfectant agents within the electrochemical cell, with specific focus on the formation of chlorine and Reactive
Oxygen Species (ROS). Chlorine-based disinfection proved to be the primary agent in the removal of both pathogens; a 4 log removal for E. Coli was achieved at an energy use of 0.41 kWh/m3 for RuO2/IrO2 and of 0.31 kWh/m3 forMagneli, and a 5 log removal for ΦX174 was achieved at 2.88 kWh/m3 for RuO2/IrO2 and for 1.18 kWh/m3 for Magneli.
To further assess the viability for the treatment of surface waters in decentralized settings, the RuO2/IrO2 was also tested in a field setting in Ghana making use of different water types to compare the utility in using an electrochemical reactor to produce chlorine for disinfection as compared to traditional disinfection methods. Seawater, lagoon and river water were tested, achieving an energy use per gram of produced chlorine of 0.007, 0.046 and 0.066 kWh/gchlorine for a produced chlorine dose of 35 mg/L for seawater and 5 mg/L for the lagoon and river water. With these results, chlorine can be produced from river water at an equivalent dosage to traditional chlorine tablets, and at a cost that is 40 times lower.
Slow sand filters (SSFs) are essential for ensuring microbial quality and biological stability of drinking water in the Netherlands. However, gaps exist in understanding of removal processes of dissolved organic carbon (DOC) and ammonium and the effects of grain size, loading rate, and backwashing on removal in SSFs.
Four lab-scale SSF columns filled with fine (0.4-0.6 mm) and coarse (0.85-1.25 mm) sand were constructed and operated in two phases with a total of 165 days. In phase I, SSFs operated at a flow rate of 0.5 m/h to investigate the influence of grain size. After stabilization, higher loading rate of 2 m/h and backwashing procedure (20% expansion for 5 min) was applied during the phase II experiment. Various physicochemical and biological parameters, including DOC, ammnoium, phosphate, and ATP were analyzed in water along the filter depth. Additionally, biomass development on sand was quantified suing ATP measurement.
Results showed the stable SSF operation after 90-100 days, removing 100% of dosed 1.5 mg/L of DOC and 1.0 mg/L of ammonium. Compared with fine sand, coarse sand had similar removal performance but better backwashing effectiveness and lower clogging risk. Increased loading rate led to faster microbial growth, reducing operational lifespan, and poor removal performance. Backwashing showed minimal impact on DOC and ammonium removal capacity and microbial activity, which were recovered after backwashing within 7-14 days, indicating the potential for backwashing to prolong SSF’s operational lifespan.
This research investigated the DOC and ammnoium removal processes and the influence of grain size, loading rate, and backwashing on filter performance. Providing insights for optimized SSF design and operation. Future studies could delve into mechanisms using isotope analysis or metagenomics, along with more comprehensive sand sample analysis.
...
Four lab-scale SSF columns filled with fine (0.4-0.6 mm) and coarse (0.85-1.25 mm) sand were constructed and operated in two phases with a total of 165 days. In phase I, SSFs operated at a flow rate of 0.5 m/h to investigate the influence of grain size. After stabilization, higher loading rate of 2 m/h and backwashing procedure (20% expansion for 5 min) was applied during the phase II experiment. Various physicochemical and biological parameters, including DOC, ammnoium, phosphate, and ATP were analyzed in water along the filter depth. Additionally, biomass development on sand was quantified suing ATP measurement.
Results showed the stable SSF operation after 90-100 days, removing 100% of dosed 1.5 mg/L of DOC and 1.0 mg/L of ammonium. Compared with fine sand, coarse sand had similar removal performance but better backwashing effectiveness and lower clogging risk. Increased loading rate led to faster microbial growth, reducing operational lifespan, and poor removal performance. Backwashing showed minimal impact on DOC and ammonium removal capacity and microbial activity, which were recovered after backwashing within 7-14 days, indicating the potential for backwashing to prolong SSF’s operational lifespan.
This research investigated the DOC and ammnoium removal processes and the influence of grain size, loading rate, and backwashing on filter performance. Providing insights for optimized SSF design and operation. Future studies could delve into mechanisms using isotope analysis or metagenomics, along with more comprehensive sand sample analysis.
...
Slow sand filters (SSFs) are essential for ensuring microbial quality and biological stability of drinking water in the Netherlands. However, gaps exist in understanding of removal processes of dissolved organic carbon (DOC) and ammonium and the effects of grain size, loading rate, and backwashing on removal in SSFs.
Four lab-scale SSF columns filled with fine (0.4-0.6 mm) and coarse (0.85-1.25 mm) sand were constructed and operated in two phases with a total of 165 days. In phase I, SSFs operated at a flow rate of 0.5 m/h to investigate the influence of grain size. After stabilization, higher loading rate of 2 m/h and backwashing procedure (20% expansion for 5 min) was applied during the phase II experiment. Various physicochemical and biological parameters, including DOC, ammnoium, phosphate, and ATP were analyzed in water along the filter depth. Additionally, biomass development on sand was quantified suing ATP measurement.
Results showed the stable SSF operation after 90-100 days, removing 100% of dosed 1.5 mg/L of DOC and 1.0 mg/L of ammonium. Compared with fine sand, coarse sand had similar removal performance but better backwashing effectiveness and lower clogging risk. Increased loading rate led to faster microbial growth, reducing operational lifespan, and poor removal performance. Backwashing showed minimal impact on DOC and ammonium removal capacity and microbial activity, which were recovered after backwashing within 7-14 days, indicating the potential for backwashing to prolong SSF’s operational lifespan.
This research investigated the DOC and ammnoium removal processes and the influence of grain size, loading rate, and backwashing on filter performance. Providing insights for optimized SSF design and operation. Future studies could delve into mechanisms using isotope analysis or metagenomics, along with more comprehensive sand sample analysis.
Four lab-scale SSF columns filled with fine (0.4-0.6 mm) and coarse (0.85-1.25 mm) sand were constructed and operated in two phases with a total of 165 days. In phase I, SSFs operated at a flow rate of 0.5 m/h to investigate the influence of grain size. After stabilization, higher loading rate of 2 m/h and backwashing procedure (20% expansion for 5 min) was applied during the phase II experiment. Various physicochemical and biological parameters, including DOC, ammnoium, phosphate, and ATP were analyzed in water along the filter depth. Additionally, biomass development on sand was quantified suing ATP measurement.
Results showed the stable SSF operation after 90-100 days, removing 100% of dosed 1.5 mg/L of DOC and 1.0 mg/L of ammonium. Compared with fine sand, coarse sand had similar removal performance but better backwashing effectiveness and lower clogging risk. Increased loading rate led to faster microbial growth, reducing operational lifespan, and poor removal performance. Backwashing showed minimal impact on DOC and ammonium removal capacity and microbial activity, which were recovered after backwashing within 7-14 days, indicating the potential for backwashing to prolong SSF’s operational lifespan.
This research investigated the DOC and ammnoium removal processes and the influence of grain size, loading rate, and backwashing on filter performance. Providing insights for optimized SSF design and operation. Future studies could delve into mechanisms using isotope analysis or metagenomics, along with more comprehensive sand sample analysis.
Though slow sand filtration is one of the oldest and effective means of drinking water treatment, the mechanisms contributing to bacteria and viruses removal are not well understood. The lack of understanding of actual removal potential and different mechanisms occurring in the filter bed has limited the development of new filter design and operation. This research aims at assessing the bacteria and viruses removal capability of filter material in different depths from the top 40 cm of full-scale slow sand filter (SSF) operated for 436 days. In addition, the focus is to identify the key removal mechanisms that aid bacteria and viruses removal in the schmutzdecke.
The results show that three depths: 0-5, 5-20 and 20-35 cm contribute to E. coli removal of 0.55, 1.3 and 1.04 logs, PhiX174 removal of 0, 0.30 and 0.14 logs. The log reduction value of E. coli and PhiX174 is rather similar in different layers, even though the schmutzdecke is considered to be the critical component for E. coli removal. It indicated that the deeper layers are also important in a well-established SSF. No removal of PhiX174 was observed in 0-5 cm with a thick biofilm, which indicates that the thickness of a certain level would impact the performance of virus removal.
To determine mechanisms, filter material from 0-5 cm was operated under three conditions: active, inactive, and ignited condition. The results show E. coli removal of 0.68, 0.74, and 0.43 logs, PhiX174 removal of 0, 0, and 0.28 logs for active, inhibited, and ignited sand, respectively. Contrary to previous studies, no function of microbial mechanisms is observed for E. coli removal. That key mechanism might change with the different maturity levels of SSFs might be a possible reason. In addition, this may ascribe to incomplete microbial active inhibition. On the other hand, despite evidence that virus removal enhances with filter maturation, schmutzdecke did not improve PhiX174 removal. Poor virus removal may be attributed to higher interstitial velocity along with higher shearing forces caused by abundant biofilm within the schmutzdecke.
...
The results show that three depths: 0-5, 5-20 and 20-35 cm contribute to E. coli removal of 0.55, 1.3 and 1.04 logs, PhiX174 removal of 0, 0.30 and 0.14 logs. The log reduction value of E. coli and PhiX174 is rather similar in different layers, even though the schmutzdecke is considered to be the critical component for E. coli removal. It indicated that the deeper layers are also important in a well-established SSF. No removal of PhiX174 was observed in 0-5 cm with a thick biofilm, which indicates that the thickness of a certain level would impact the performance of virus removal.
To determine mechanisms, filter material from 0-5 cm was operated under three conditions: active, inactive, and ignited condition. The results show E. coli removal of 0.68, 0.74, and 0.43 logs, PhiX174 removal of 0, 0, and 0.28 logs for active, inhibited, and ignited sand, respectively. Contrary to previous studies, no function of microbial mechanisms is observed for E. coli removal. That key mechanism might change with the different maturity levels of SSFs might be a possible reason. In addition, this may ascribe to incomplete microbial active inhibition. On the other hand, despite evidence that virus removal enhances with filter maturation, schmutzdecke did not improve PhiX174 removal. Poor virus removal may be attributed to higher interstitial velocity along with higher shearing forces caused by abundant biofilm within the schmutzdecke.
...
Though slow sand filtration is one of the oldest and effective means of drinking water treatment, the mechanisms contributing to bacteria and viruses removal are not well understood. The lack of understanding of actual removal potential and different mechanisms occurring in the filter bed has limited the development of new filter design and operation. This research aims at assessing the bacteria and viruses removal capability of filter material in different depths from the top 40 cm of full-scale slow sand filter (SSF) operated for 436 days. In addition, the focus is to identify the key removal mechanisms that aid bacteria and viruses removal in the schmutzdecke.
The results show that three depths: 0-5, 5-20 and 20-35 cm contribute to E. coli removal of 0.55, 1.3 and 1.04 logs, PhiX174 removal of 0, 0.30 and 0.14 logs. The log reduction value of E. coli and PhiX174 is rather similar in different layers, even though the schmutzdecke is considered to be the critical component for E. coli removal. It indicated that the deeper layers are also important in a well-established SSF. No removal of PhiX174 was observed in 0-5 cm with a thick biofilm, which indicates that the thickness of a certain level would impact the performance of virus removal.
To determine mechanisms, filter material from 0-5 cm was operated under three conditions: active, inactive, and ignited condition. The results show E. coli removal of 0.68, 0.74, and 0.43 logs, PhiX174 removal of 0, 0, and 0.28 logs for active, inhibited, and ignited sand, respectively. Contrary to previous studies, no function of microbial mechanisms is observed for E. coli removal. That key mechanism might change with the different maturity levels of SSFs might be a possible reason. In addition, this may ascribe to incomplete microbial active inhibition. On the other hand, despite evidence that virus removal enhances with filter maturation, schmutzdecke did not improve PhiX174 removal. Poor virus removal may be attributed to higher interstitial velocity along with higher shearing forces caused by abundant biofilm within the schmutzdecke.
The results show that three depths: 0-5, 5-20 and 20-35 cm contribute to E. coli removal of 0.55, 1.3 and 1.04 logs, PhiX174 removal of 0, 0.30 and 0.14 logs. The log reduction value of E. coli and PhiX174 is rather similar in different layers, even though the schmutzdecke is considered to be the critical component for E. coli removal. It indicated that the deeper layers are also important in a well-established SSF. No removal of PhiX174 was observed in 0-5 cm with a thick biofilm, which indicates that the thickness of a certain level would impact the performance of virus removal.
To determine mechanisms, filter material from 0-5 cm was operated under three conditions: active, inactive, and ignited condition. The results show E. coli removal of 0.68, 0.74, and 0.43 logs, PhiX174 removal of 0, 0, and 0.28 logs for active, inhibited, and ignited sand, respectively. Contrary to previous studies, no function of microbial mechanisms is observed for E. coli removal. That key mechanism might change with the different maturity levels of SSFs might be a possible reason. In addition, this may ascribe to incomplete microbial active inhibition. On the other hand, despite evidence that virus removal enhances with filter maturation, schmutzdecke did not improve PhiX174 removal. Poor virus removal may be attributed to higher interstitial velocity along with higher shearing forces caused by abundant biofilm within the schmutzdecke.