Gabrielle String | Tufts University (original) (raw)
Papers by Gabrielle String
Journal of Water and Health, Jun 30, 2022
Bucket chlorination, where chlorine is dosed directly into water collection containers, is a poin... more Bucket chlorination, where chlorine is dosed directly into water collection containers, is a point-of-source water treatment intervention commonly implemented in cholera outbreaks. There is little previous data on chlorine efficacy against Vibrio cholerae in different waters and appropriate dosage regimes. We evaluated V. cholerae reduction and free chlorine residual (FCR) in waters with four turbidities (1/5/10/ 50 NTU), two total organic carbon (TOC) concentrations (0.4, 1 mg/L), and two dosing schemes (fixed-dose of 2 or 4 mg/L, variable-dose based on jar testing) treated with three chlorine types (HTH, NaOCl, NaDCC). We found that chlorine was efficacious at reducing V. cholerae by !2.75 to !3.63 log reduction value (LRV); variably dosed reactors were dosed higher, met !0.5 mg/L FCR at 30 min, and had higher LRVs (p¼0.024) than fixed doses; and low TOC reactors had more samples !0.2 mg/L FRC at 4 h (p¼0.007). Our results are conservative, as internationally recommended additives to create test water increased chlorine demand, highlighting the challenge of replicating field conditions in laboratory testing. Overall, we found that chlorine can efficaciously reduce V. cholerae; we recommend further research on appropriate chlorine demand for test waters; and we recommend establishing appropriate chlorine doses based on source water and taste/odor acceptability in bucket chlorination programs.
Journal Of Environmental Science And Health, Part A, Jul 3, 2022
Journal of Environmental Engineering, Nov 1, 2022
Environmental science, 2022
Results highlight that locally-manufactured ceramic water filters from different factories have h... more Results highlight that locally-manufactured ceramic water filters from different factories have high variability in V. cholerae removal efficacy, and silver disinfection is the most critical mechanism to remove V. cholerae from drinking water.
PLOS Water
Globally, cholera continues to cause morbidity and mortality, and the Global Task Force on Choler... more Globally, cholera continues to cause morbidity and mortality, and the Global Task Force on Cholera Control (GTFCC) works with countries affected by cholera to develop National Cholera Plans (NCPs). Water, sanitation, and hygiene (WASH) can prevent and/or control cholera. However, WASH program success varies, and is not necessarily replicable across contexts. Thus, guidance needs to be developed to assist countries in appropriately designing WASH programming in NCPs. The objective of this project was to develop guidelines for selecting context-specific WASH for cholera response. For that, a literature review of WASH interventions in cholera was completed, a Working Group was convened to collaboratively develop the guidelines, and we conducted key informant interviews (KII) with Working Group experts, representing international and national non-governmental organizations, donors, international organizations and health authorities. Inductive qualitative content analysis of KIIs was com...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Ultraviolet (UV) radiation systems, commonly used to disinfect surfaces, drinking water... more ABSTRACT. Ultraviolet (UV) radiation systems, commonly used to disinfect surfaces, drinking water, and air, stem from historical practice to use sunlight to disinfect household items after contagious illness. Currently, it is still recommended in viral outbreak contexts such as COVID-19, Ebola, and Marburg to expose soft surfaces to sunlight after washing with detergent or disinfecting with chlorine. However, sunlight that reaches the Earth’s surface is in the UVA/UVB wavelengths, whereas UV disinfection systems typically rely on biocidal UVC. Our goal was to fill the evidence gap on the efficacy of sunlight disinfection on surface materials common in low-resource healthcare settings by seeding four surfaces (stainless steel, nitrile, tarp, cloth) with three microorganisms (viral surrogate bacteriophages Phi6 and MS2 and Escherichia coli bacteria), with and without soil load, and exposing to three sunlight conditions (full sun, partial sun, cloudy). We conducted 144 tests in triplic...
Unprecedented global population displacement in recent years has increased the burden of waterbor... more Unprecedented global population displacement in recent years has increased the burden of waterborne illnesses in refugee and internally displaced person (IDP) settlements. Preventing outbreaks of waterborne diseases can be particularly challenging in urban-scale refugee and IDP settlements since recontamination commonly occurs post-distribution period. In this period users manually collect water from public tapstands, transport it to their dwellings where they store and use it over several hours. Unlike contexts where water is piped directly to the home, in urban-scale refugee and IDP settlements effective chlorination in these settlements requires that free residual chlorine (FRC) at tapstands be sufficient to ensure at least 0.2 mg/L of FRC throughout the period of storage and use, while remaining palatable to consumers. Thus, chlorination practice must account for both site-specific dynamics of chlorine decay as well as local attitudes towards chlorinated water taste and odor (T&...
Journal of Environmental Engineering
Journal of Environmental Science and Health, Part A
Journal of Water and Health
Bucket chlorination, where chlorine is dosed directly into water collection containers, is a poin... more Bucket chlorination, where chlorine is dosed directly into water collection containers, is a point-of-source water treatment intervention commonly implemented in cholera outbreaks. There is little previous data on chlorine efficacy against Vibrio cholerae in different waters and appropriate dosage regimes. We evaluated V. cholerae reduction and free chlorine residual (FCR) in waters with four turbidities (1/5/10/50 NTU), two total organic carbon (TOC) concentrations (0.4, 1 mg/L), and two dosing schemes (fixed-dose of 2 or 4 mg/L, variable-dose based on jar testing) treated with three chlorine types (HTH, NaOCl, NaDCC). We found that chlorine was efficacious at reducing V. cholerae by ≥2.75 to ≥3.63 log reduction value (LRV); variably dosed reactors were dosed higher, met ≥0.5 mg/L FCR at 30 min, and had higher LRVs (p=0.024) than fixed doses; and low TOC reactors had more samples ≥0.2 mg/L FRC at 4 h (p=0.007). Our results are conservative, as internationally recommended additives ...
Environmental Science: Water Research & Technology, 2022
Results highlight that locally-manufactured ceramic water filters from different factories have h... more Results highlight that locally-manufactured ceramic water filters from different factories have high variability in V. cholerae removal efficacy, and silver disinfection is the most critical mechanism to remove V. cholerae from drinking water.
Environmental Health Perspectives
Despite the promotion of Water Safety Plans (WSPs) as a comprehensive risk assessment and managem... more Despite the promotion of Water Safety Plans (WSPs) as a comprehensive risk assessment and management strategy for water delivery, there is a lack of documented outcomes and impacts from this approach, particularly for community-managed supplies. Through a mixed-methods protocol of household surveys, water quality testing of source and stored water samples, key informant interviews, and focus group discussions, this study looked at WSP implementation in four countries to ascertain lessons learnt from these programs. From 817 household surveys and 256 key informant discussions, it was determined that there was no clear evidence linking WSPs to improvements in water quality. However, interviews indicated improved capacity of local committees in understanding their water supply systems and in identifying key risks to the delivery of safe water. Additional outcomes of WSPs and challenges associated with their implementation are discussed.
While the number of international community development projects funded by agencies abroad has sk... more While the number of international community development projects funded by agencies abroad has skyrocketed, progress on sustainability and community acceptance has not maintained pace with the technical advances. The WASH Sustainability Charter was initiated in 2011, and seeks to address the issues of long-term sustainability of projects through a charter document. [1] The charter focuses on five areas of sustainability: strategy and planning, governance and accountability, service delivery support, financial management, reporting and knowledge- sharing. Our framework provides support in accomplishing these goals. This project proposes a new framework, see figures 1 and 2 below, for community education that complements technically- oriented international development projects. Our framework challenges the premise that technical implementation and construction should precede education and monitoring; and instead argues that properly designed target-based education modules can prepare ...
In DRC, the Healthy Villages and Schools (VEA) National Program consists of a community participa... more In DRC, the Healthy Villages and Schools (VEA) National Program consists of a community participatory process towards sustainable access to improved water services, hygiene and sanitation where villages and schools are certified “healthy” once they comply with 7 WASH specific norms. Through a mixed-methods survey of household questionnaires, water quality testing of source and stored water samples, mapping of water sources, and discussions with key informants, this study looked at VEA implementation in the Katana health zone, South Kivu province, to ascertain lessons learnt from the program. From 206 household surveys and 71 focus group discussions, it was determined that there are two primary barriers to effective water supply coverage: accessibility to a source within 30 minutes and delivery of water that conforms to WHO guidelines of <1 E. coli CFU/100mL. Additional demographic and WASH knowledge, attitudes, and practices outcomes as well as challenges associated with the VEA ...
Two graduate students from Tufts University’s Mechanical Engineering Department spent the 2011-20... more Two graduate students from Tufts University’s Mechanical Engineering Department spent the 2011-2012 academic year working in an engineering classroom at Somerville High School to determine the possibilities of creating a more permanent outreach component to the graduate curriculum. Under the direction of the high school teacher, the students observed the classroom then organized their own projects and lesson plans to implement addressing a diverse topic range. Reflections of the first year of this partnership are varied but point to some key conclusions and possibilities for developing this into a permanent partnership and component of the graduate curriculum.
Objective The goal of this thesis is to determine the feasibility of a regenerative braking syste... more Objective The goal of this thesis is to determine the feasibility of a regenerative braking system (RBS) on a school bus and to subsequently develop and test a prototype system. Motivation It is proposed that a regenerative braking system be utilized on a school bus to improve fuel efficiency and reduce exposure of children to diesel particulates. The primary benefit of a RBS is a decrease in the amount of fuel used to drive the bus. The advantage of using less fuel is a decline in emissions. Previous studies conducted at Clarkson University have shown the level of exposure to tailpipe emissions that is experienced by children on a school bus. [1] The characteristic stages of driving a vehicle to its destination combine to create the vehicle's mission. First the car is started and then accelerated to speed. Acceleration of a vehicle is an extremely inefficient process; when a vehicle is accelerated, a large amount of fuel is consumed to increase the speed of the vehicle. After a...
Environmental science & technology, 2021
Ceramic filters for household water treatment can improve water quality and reduce diarrheal dise... more Ceramic filters for household water treatment can improve water quality and reduce diarrheal disease. Hydraulic performance is critical for quality control and user acceptability, and hydraulic models have previously been developed and tested with experimental full-scale filters. As filters are cumbersome, there is interest in using disks instead of filters in laboratory efficacy studies. To assess the validity of disk use, we collected experimental volume from three sets of full-scale frustum-shaped filters and matching disks with different burn-out material sieve sizes and firing temperatures. We compared the experimental and fitted data by calibrating hydraulic conductivities from filters and disks. Hydraulic conductivities increased with larger burn-out material and higher firing temperatures but were comparable between filters and disks (2.00-6.15 × 10-7m·s-1 and 2.69-6.32 × 10-7m·s-1, respectively). We found that previously described hydraulic models successfully predicted cum...
Journal of Water and Health, Jun 30, 2022
Bucket chlorination, where chlorine is dosed directly into water collection containers, is a poin... more Bucket chlorination, where chlorine is dosed directly into water collection containers, is a point-of-source water treatment intervention commonly implemented in cholera outbreaks. There is little previous data on chlorine efficacy against Vibrio cholerae in different waters and appropriate dosage regimes. We evaluated V. cholerae reduction and free chlorine residual (FCR) in waters with four turbidities (1/5/10/ 50 NTU), two total organic carbon (TOC) concentrations (0.4, 1 mg/L), and two dosing schemes (fixed-dose of 2 or 4 mg/L, variable-dose based on jar testing) treated with three chlorine types (HTH, NaOCl, NaDCC). We found that chlorine was efficacious at reducing V. cholerae by !2.75 to !3.63 log reduction value (LRV); variably dosed reactors were dosed higher, met !0.5 mg/L FCR at 30 min, and had higher LRVs (p¼0.024) than fixed doses; and low TOC reactors had more samples !0.2 mg/L FRC at 4 h (p¼0.007). Our results are conservative, as internationally recommended additives to create test water increased chlorine demand, highlighting the challenge of replicating field conditions in laboratory testing. Overall, we found that chlorine can efficaciously reduce V. cholerae; we recommend further research on appropriate chlorine demand for test waters; and we recommend establishing appropriate chlorine doses based on source water and taste/odor acceptability in bucket chlorination programs.
Journal Of Environmental Science And Health, Part A, Jul 3, 2022
Journal of Environmental Engineering, Nov 1, 2022
Environmental science, 2022
Results highlight that locally-manufactured ceramic water filters from different factories have h... more Results highlight that locally-manufactured ceramic water filters from different factories have high variability in V. cholerae removal efficacy, and silver disinfection is the most critical mechanism to remove V. cholerae from drinking water.
PLOS Water
Globally, cholera continues to cause morbidity and mortality, and the Global Task Force on Choler... more Globally, cholera continues to cause morbidity and mortality, and the Global Task Force on Cholera Control (GTFCC) works with countries affected by cholera to develop National Cholera Plans (NCPs). Water, sanitation, and hygiene (WASH) can prevent and/or control cholera. However, WASH program success varies, and is not necessarily replicable across contexts. Thus, guidance needs to be developed to assist countries in appropriately designing WASH programming in NCPs. The objective of this project was to develop guidelines for selecting context-specific WASH for cholera response. For that, a literature review of WASH interventions in cholera was completed, a Working Group was convened to collaboratively develop the guidelines, and we conducted key informant interviews (KII) with Working Group experts, representing international and national non-governmental organizations, donors, international organizations and health authorities. Inductive qualitative content analysis of KIIs was com...
The American Journal of Tropical Medicine and Hygiene
ABSTRACT. Ultraviolet (UV) radiation systems, commonly used to disinfect surfaces, drinking water... more ABSTRACT. Ultraviolet (UV) radiation systems, commonly used to disinfect surfaces, drinking water, and air, stem from historical practice to use sunlight to disinfect household items after contagious illness. Currently, it is still recommended in viral outbreak contexts such as COVID-19, Ebola, and Marburg to expose soft surfaces to sunlight after washing with detergent or disinfecting with chlorine. However, sunlight that reaches the Earth’s surface is in the UVA/UVB wavelengths, whereas UV disinfection systems typically rely on biocidal UVC. Our goal was to fill the evidence gap on the efficacy of sunlight disinfection on surface materials common in low-resource healthcare settings by seeding four surfaces (stainless steel, nitrile, tarp, cloth) with three microorganisms (viral surrogate bacteriophages Phi6 and MS2 and Escherichia coli bacteria), with and without soil load, and exposing to three sunlight conditions (full sun, partial sun, cloudy). We conducted 144 tests in triplic...
Unprecedented global population displacement in recent years has increased the burden of waterbor... more Unprecedented global population displacement in recent years has increased the burden of waterborne illnesses in refugee and internally displaced person (IDP) settlements. Preventing outbreaks of waterborne diseases can be particularly challenging in urban-scale refugee and IDP settlements since recontamination commonly occurs post-distribution period. In this period users manually collect water from public tapstands, transport it to their dwellings where they store and use it over several hours. Unlike contexts where water is piped directly to the home, in urban-scale refugee and IDP settlements effective chlorination in these settlements requires that free residual chlorine (FRC) at tapstands be sufficient to ensure at least 0.2 mg/L of FRC throughout the period of storage and use, while remaining palatable to consumers. Thus, chlorination practice must account for both site-specific dynamics of chlorine decay as well as local attitudes towards chlorinated water taste and odor (T&...
Journal of Environmental Engineering
Journal of Environmental Science and Health, Part A
Journal of Water and Health
Bucket chlorination, where chlorine is dosed directly into water collection containers, is a poin... more Bucket chlorination, where chlorine is dosed directly into water collection containers, is a point-of-source water treatment intervention commonly implemented in cholera outbreaks. There is little previous data on chlorine efficacy against Vibrio cholerae in different waters and appropriate dosage regimes. We evaluated V. cholerae reduction and free chlorine residual (FCR) in waters with four turbidities (1/5/10/50 NTU), two total organic carbon (TOC) concentrations (0.4, 1 mg/L), and two dosing schemes (fixed-dose of 2 or 4 mg/L, variable-dose based on jar testing) treated with three chlorine types (HTH, NaOCl, NaDCC). We found that chlorine was efficacious at reducing V. cholerae by ≥2.75 to ≥3.63 log reduction value (LRV); variably dosed reactors were dosed higher, met ≥0.5 mg/L FCR at 30 min, and had higher LRVs (p=0.024) than fixed doses; and low TOC reactors had more samples ≥0.2 mg/L FRC at 4 h (p=0.007). Our results are conservative, as internationally recommended additives ...
Environmental Science: Water Research & Technology, 2022
Results highlight that locally-manufactured ceramic water filters from different factories have h... more Results highlight that locally-manufactured ceramic water filters from different factories have high variability in V. cholerae removal efficacy, and silver disinfection is the most critical mechanism to remove V. cholerae from drinking water.
Environmental Health Perspectives
Despite the promotion of Water Safety Plans (WSPs) as a comprehensive risk assessment and managem... more Despite the promotion of Water Safety Plans (WSPs) as a comprehensive risk assessment and management strategy for water delivery, there is a lack of documented outcomes and impacts from this approach, particularly for community-managed supplies. Through a mixed-methods protocol of household surveys, water quality testing of source and stored water samples, key informant interviews, and focus group discussions, this study looked at WSP implementation in four countries to ascertain lessons learnt from these programs. From 817 household surveys and 256 key informant discussions, it was determined that there was no clear evidence linking WSPs to improvements in water quality. However, interviews indicated improved capacity of local committees in understanding their water supply systems and in identifying key risks to the delivery of safe water. Additional outcomes of WSPs and challenges associated with their implementation are discussed.
While the number of international community development projects funded by agencies abroad has sk... more While the number of international community development projects funded by agencies abroad has skyrocketed, progress on sustainability and community acceptance has not maintained pace with the technical advances. The WASH Sustainability Charter was initiated in 2011, and seeks to address the issues of long-term sustainability of projects through a charter document. [1] The charter focuses on five areas of sustainability: strategy and planning, governance and accountability, service delivery support, financial management, reporting and knowledge- sharing. Our framework provides support in accomplishing these goals. This project proposes a new framework, see figures 1 and 2 below, for community education that complements technically- oriented international development projects. Our framework challenges the premise that technical implementation and construction should precede education and monitoring; and instead argues that properly designed target-based education modules can prepare ...
In DRC, the Healthy Villages and Schools (VEA) National Program consists of a community participa... more In DRC, the Healthy Villages and Schools (VEA) National Program consists of a community participatory process towards sustainable access to improved water services, hygiene and sanitation where villages and schools are certified “healthy” once they comply with 7 WASH specific norms. Through a mixed-methods survey of household questionnaires, water quality testing of source and stored water samples, mapping of water sources, and discussions with key informants, this study looked at VEA implementation in the Katana health zone, South Kivu province, to ascertain lessons learnt from the program. From 206 household surveys and 71 focus group discussions, it was determined that there are two primary barriers to effective water supply coverage: accessibility to a source within 30 minutes and delivery of water that conforms to WHO guidelines of <1 E. coli CFU/100mL. Additional demographic and WASH knowledge, attitudes, and practices outcomes as well as challenges associated with the VEA ...
Two graduate students from Tufts University’s Mechanical Engineering Department spent the 2011-20... more Two graduate students from Tufts University’s Mechanical Engineering Department spent the 2011-2012 academic year working in an engineering classroom at Somerville High School to determine the possibilities of creating a more permanent outreach component to the graduate curriculum. Under the direction of the high school teacher, the students observed the classroom then organized their own projects and lesson plans to implement addressing a diverse topic range. Reflections of the first year of this partnership are varied but point to some key conclusions and possibilities for developing this into a permanent partnership and component of the graduate curriculum.
Objective The goal of this thesis is to determine the feasibility of a regenerative braking syste... more Objective The goal of this thesis is to determine the feasibility of a regenerative braking system (RBS) on a school bus and to subsequently develop and test a prototype system. Motivation It is proposed that a regenerative braking system be utilized on a school bus to improve fuel efficiency and reduce exposure of children to diesel particulates. The primary benefit of a RBS is a decrease in the amount of fuel used to drive the bus. The advantage of using less fuel is a decline in emissions. Previous studies conducted at Clarkson University have shown the level of exposure to tailpipe emissions that is experienced by children on a school bus. [1] The characteristic stages of driving a vehicle to its destination combine to create the vehicle's mission. First the car is started and then accelerated to speed. Acceleration of a vehicle is an extremely inefficient process; when a vehicle is accelerated, a large amount of fuel is consumed to increase the speed of the vehicle. After a...
Environmental science & technology, 2021
Ceramic filters for household water treatment can improve water quality and reduce diarrheal dise... more Ceramic filters for household water treatment can improve water quality and reduce diarrheal disease. Hydraulic performance is critical for quality control and user acceptability, and hydraulic models have previously been developed and tested with experimental full-scale filters. As filters are cumbersome, there is interest in using disks instead of filters in laboratory efficacy studies. To assess the validity of disk use, we collected experimental volume from three sets of full-scale frustum-shaped filters and matching disks with different burn-out material sieve sizes and firing temperatures. We compared the experimental and fitted data by calibrating hydraulic conductivities from filters and disks. Hydraulic conductivities increased with larger burn-out material and higher firing temperatures but were comparable between filters and disks (2.00-6.15 × 10-7m·s-1 and 2.69-6.32 × 10-7m·s-1, respectively). We found that previously described hydraulic models successfully predicted cum...