Dissertation
Sensors, circuit riders, and community-managed passive in-line chlorinators: evidence for improved access to safely managed drinking water in rural Central America
University of Iowa
Doctor of Philosophy (PhD), University of Iowa
Autumn 2022
DOI: 10.25820/etd.006788
Abstract
2 billion people currently live without access to safely managed drinking water, leaving them at risk for contaminated water which can lead to waterborne disease. Sustainable Development Goal 6, target 6.1 targets reaching everyone in the world with safely managed drinking water, by 2030. But despite years of research, and billions of dollars in funding we are not on target to reach this goal. Accelerated progress must be made to redirect and sustain efforts for reaching this goal. One opportunity for the elevation of water supplies to provide safely managed drinking water is passive chlorination. Passive chlorinators are a form of simple, drinking water treatment which applies chlorine to an entire system at the community or institutional level. However, despite this clear potential there remains significant uncertainties in the scalability and performance of passive chlorinators for providing adequately chlorinated water. The purpose of this study was to evaluate community managed-passive chlorinators and several management paradigms, including external support and sensor-based monitoring to improve drinking water safety.
The first research objective was to evaluate baseline evidence for at scale implementation of passive chlorinators to provide safely managed drinking water. In this critical review, we first and foremost define passive chlorinators to set forth a standard for future researchers. We analyzed 27 chlorinators, evaluated across 27 peer reviewed articles, theses, and non-governmental organization reports. This chapter compiles and shares the most critical knowledge on passive chlorinators and presents practitioners and researchers with tools to select passive chlorination devices based on context and engineering specifications. We also evaluate the existing metrics used in evaluations on passive chlorinators and recommend a series of standardized metrics, to ensure future research on chlorinators is comparable. We also recommend critical research priorities for passive chlorination researchers, several of which are further explored in later chapters.
The second research objective was to determine the human and technical factors that affect passive chlorinator performance using a case study of rural communities in Honduras. For this chapter we analyzed nearly ten years’ worth of monitoring data of communities using passive chlorinators across Central America, collected by partner organization: EOS International. We demonstrate that the passive chlorinators used in these communities maintains adequate free chlorine residual, greater than the World Health Organization standard of 0.2 mg/L, in 77% of samples. This chapter is the longest evaluation time period for passive chlorinators, to date, indicating their potential for sustained effectiveness. For the remaining 23% of samples with low free chlorine residual, the leading cause of loss of chlorination was human errors associated with community water board management. Most frequently, community water board members forgot to replace chlorine tablets, or in some cases were opting not to replace chlorine tablets. EOS technicians provided regular monitoring and support visits during the evaluation period, and both shear number of monitoring visits and frequency of monitoring visits were positively correlated with free chlorine residual concentration at the community. But perhaps most critically, percentage of technical assistance visits made to communities were the most strongly correlated with improved free chlorine residual. We recommend EOS technicians optimize the amount of time they can spend on technical assistance for maximum improvement. These results highlight the maintenance and operations considerations necessary to implement passive chlorinators at scale.
Our third and final research objective was to develop a surrogate-sensor based approach for classifying low free chlorine residual and to evaluate use for maintenance alerts for passive chlorinators. To evaluate this objective, we implemented 5 pilot Sensor-Monitored Ambulance Response Telemetering (SMART) chlorinators in Nicaragua and Honduras. Each of which included oxidation reduction potential, pH and tank water level or flow sensors. These solar-powered, SMART chlorinators transmitted data using cellular connection alongside manually collected ground-truth measurements of free chlorine residual. We used SMART chlorinator data to develop a regression-based classification model for free chlorine residual, based on existing relationships. We designed our model to classify free chlorine residual using real-time, continuous oxidation reduction potential and pH measurements, as either above or below 0.5 mg/L. Across the four Honduras pilots our model had mixed performance, with accuracy scores ranging from 62-98%. For the community in which this model performed the best, we used our classification model to determine free chlorine residual uptime, or the proportion of time that community had adequate free chlorine residual. For the final objective of this chapter, we modeled several community or technician response scenarios in which classification of low free chlorine residual events would produce an alarm or alert. For our modeled scenarios we determined that surrogate-sensor based alerts could improve free chlorine residual uptime from between 45 and 55% to 62 and 99%. Though we recommend the continued development of additional models, particularly which require fewer sensors, for classification of free chlorine residual; our results demonstrate the first known use of sensors for monitoring passive chlorinators continuously. Sensor-based monitoring has significant potential for the improvement of maintenance and operations.
Together, this work provides evidence for the scalability of passive chlorinators to help the world meet Sustainable Development Goals Target 6.1 , safe drinking water for all. External support, for community organizations managing passive chlorinators is critical for their long-term sustainability. Our results show that external support providers need to optimize their efforts to ensure that routine monitoring is carried out, but not at the cost of technical assistance support visits. One way to optimize monitoring is through sensor-based free chlorine residual classification. Although, chlorine sensors are prohibitively expensive, we present evidence for surrogate measures used to classify low-chlorine events. Our results suggest that classification of low free chlorine residual events can be used to alert community members or technicians and improve delivery of safe drinking water. Ultimately the results presented within this dissertation indicate that passive chlorinators can improve drinking water safety and health outcomes, particularly if paired with external support for sustained management and operations and sensor-based monitoring.
Details
- Title: Subtitle
- Sensors, circuit riders, and community-managed passive in-line chlorinators: evidence for improved access to safely managed drinking water in rural Central America
- Creators
- Megan Lindmark
- Contributors
- Craig Just (Advisor)Kelly Baker (Committee Member)David Cwiertny (Committee Member)Jerald Schnoor (Committee Member)James Mihelcic (Committee Member)
- Resource Type
- Dissertation
- Degree Awarded
- Doctor of Philosophy (PhD), University of Iowa
- Degree in
- Civil and Environmental Engineering
- Date degree season
- Autumn 2022
- Publisher
- University of Iowa
- DOI
- 10.25820/etd.006788
- Number of pages
- xx, 194 pages
- Copyright
- Copyright 2022 Megan Lindmark
- Language
- English
- Description illustrations
- Illustrations, charts, graphs, tables
- Description bibliographic
- Includes bibliographical references.
- Public Abstract (ETD)
Nearly a quarter of the world’s population drinks water that may contain dangerous disease-causing bacteria. One of the primary ways we can remove bacteria from drinking water is through adding chlorine. Research is needed to determine how well devices that add chlorine (chlorinators) to drinking water can remove those dangerous bacteria, particularly in resource-constrained settings that need treatment most. In this work we compiled and reviewed research papers and reports on existing chlorination devices. We discovered that there are quite a few stumbling blocks which prevent our ability to install chlorinators globally. We created a list of recommendations for researchers who want to improve chlorinators. We also tested a chlorinator, which is already installed in 1800+ communities in Central America. Data collected by technicians servicing these systems revealed that these devices provide safe drinking water 77% of the time. Communities that were visited most frequently by technicians, who provide technical assistance, had some of the safest water. We also tested water quality sensors in four communities in Honduras, with those same chlorinators, to measure their performance. We propose a manner through which technicians view water quality information on their cell phone transmitted from sensors and then visit communities most in need of technical assistance. The information we have generated in this thesis will allow our partners in Central America to improve their technician assistance program. This work, and particularly our sensors and mathematical models can be improved upon and used by other organizations looking to provide safe drinking water.
- Academic Unit
- Civil and Environmental Engineering
- Record Identifier
- 9984362657902771
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