Grantee Research Project Results
Final Report: "Smart" Turbidimeters for Remote Monitoring of Water Quality
EPA Grant Number: SU835517Title: "Smart" Turbidimeters for Remote Monitoring of Water Quality
Investigators: Weber-Shirk, Monroe , Krolick, Alex , Saltzman, Jonah
Institution: Cornell University , The Johns Hopkins University
EPA Project Officer: Packard, Benjamin H
Phase: I
Project Period: August 15, 2013 through August 14, 2014
Project Amount: $14,527
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2013) RFA Text | Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Safe and Sustainable Water Resources , P3 Awards , Sustainable and Healthy Communities
Objective:
Timely monitoring of drinking water treatment is a crucial engineering and public health challenge. Commercial models of one of the most important tools of drinking water monitoring – a turbidimeter, which measures by proxy the amount of dirt suspended in water – cost upwards of $750, effectively placing this important tool beyond the budgets of countless poor communities. Pricing poor people out of the water monitoring market endangers the sustainability of global drinking water infrastructure development efforts. Our project directly addresses the need for affordable turbidity monitoring tools that are well-suited to low-resource and developing regions of the world.
The unaided eye can distinguish cloudy water from clear water, but even visibly clear samples of water can have dangerous quantities of pathogens. Commonly a chemical or physical disinfectant (such as chlorine, or ultraviolet light) is applied to water during treatment, to inactivate pathogens so the water may be safely consumed. However, natural water sources typically contain suspended sediments (such as clay, silt, organic matter) which can interfere with drinking water disinfection by reducing chemical disinfectants in redox reactions (or by reflecting UV light) and by providing micro-refuges in which pathogens can be shielded from disinfecting light or chemicals. It is crucial that suspended sediments be removed during to the best practicable extent during drinking water treatment, and that suspended sediment levels are taken into consideration when selecting disinfectant dosage levels.
Engineers measure suspended sediment levels indirectly, by measuring the turbidity, or “cloudiness,” of water caused by suspended sediments; the device for this is known as a turbidimeter. The modern commercial turbidimeter is a complex piece of equipment that costs several hundred dollars, largely because it is designed to be an extremely accurate, general-purpose laboratory tool.
Without access to affordable turbidimeters, low-resource communities around the world are unable to proactively assess the microbial risk of their drinking water; microbes must be cultured at significant time and expense, whereas turbidity can be assessed in seconds and at negligible cost per measurement (once the equipment is purchased). An affordable, open-source turbidimeter designed specifically for water quality monitoring would broaden access to the principal quality-assurance procedure in the drinking water treatment sector and remove a major roadblock to the sustainability of programs that seek to expand global access to treated drinking water.
Prior to the start of Phase I, Chris Kelley at Johns Hopkins University developed the OpenSourceWater SMS network (data portal online at Wash 4 All Exit ), to provide water treatment plant operators a way to broadcast turbidity and other water quality data to the internet from any cell phone. Our task in Phase I included the following objectives:
- Develop a low-cost ($100) turbidimeter for automated continuous sampling of groundwater and surface water;
- Develop the means to integrate this low-cost turbidimeter with the OpenSourceWater data transmission network, to ensure that water treatment technicians in rural areas can communicate treatment plant performance data to trained water treatment engineers both locally and internationally;
- Develop the means for trained water treatment engineers to evaluate data broadcast via the OpenSourceWater system, and offer technical advice if requested.
Design criteria for the low-cost turbidimeter included:
- Turbidimeter costs less than $100 (for a production model);
- Reads samples with an accuracy of 0.05 NTU in the sample range 0-5 NTU, and with an accuracy of 0.2 NTU in the range of 5-20 NTU;
- Reads samples with an accuracy of 5% in the range 20-1000 NTU;
- Can be operated manually, or in automated mode for continuous sampling;
- Transmits data to an Android phone, via USB connection or Bluetooth;
- Is powered by one 9-volt battery (or equivalent widely-available power supply);
- Can collect samples automatically every 15 minutes for one month without needing new batteries;
- Can handle color correction in the typical range of color expected from turbid surface water.
Summary/Accomplishments (Outputs/Outcomes):
Throughout Phase I, the team at Cornell University worked informally with the Phase II team at Johns Hopkins University. Together, the teams developed and tested a handheld turbidimeter that can be built for approximately $25. This bare-bones turbidimeter has a sample port into which the operator must manually load a glass cuvette into which a water sample has been gathered. The bare-bones turbidimeter uses an infrared LED to shine light through the sample of water, and a TSL230R light intensity-to-frequency sensor to detect light scattered by suspended solids. At turbidity levels generally considered unsafe for human consumption (> 1.0 NTU), the device performs on par with commercial turbidimeters that cost 30+ times as much. The laboratory test work has been summarized in a manuscript with an extensive Supplementary Materials section (containing full construction and programming details) which has been accepted for publication in the open-access journal Sensors.
Initial investigations suggested that the best way to achieve Objective 2 (broadcast of data from rural and developing areas) was to include a Bluetooth module in the turbidimeter, which would relay data to an Android smartphone that would in turn pass data on to the OpenSourceWater network. However, we found several affordable GSM modem units (essentially, the communication guts of a cell phone) which could be incorporated directly into the turbidimeter. This yielded a significant cost savings at $90 for a GSM modem versus $175 for a Bluetooth module ($15) + Arduino-capable phone ($160), and also reduced theft risk -- Android phones have immediate resale value, whereas GSM modems individually are not useful to the average person. Thus by achieving Objective 2 we reduced the cost for a turbidimeter with wireless access to $115, putting us within reach of Objective 1. The wirelessenabled handheld turbidimeter can store up to 24 turbidity readings, initiate communication with the local cellphone network, and communicate data in specially formatted SMS messages. To reduce the cost of data transmission, the device will encode numeric data into a base-64 alphanumeric representation that will allow more data to be fit into each SMS message.
Production models of the bare-bones handheld turbidimeter are currently being field-tested in rural Nicaragua. The teams next focused on producing an in-line turbidimeter in which the light source and sensor are housed in an immersible probe to allow for automated and continuous turbidity monitoring of a moving channel of water. The design challenge is comparable to that of the handheld turbidimeter, except that it is more challenging to eliminate the effect of background light (which can distort sensor readings). Several prototypes have been completed to date, and performance is improving with each design iteration. We anticipate that performance of the in-line turbidimeter will soon match that of the handheld model.
To complete Objective 3, we developed a monitoring and evaluation “data loop” in cooperation with the Honduran water and sanitation NGO Agua Para El Pueblo (APP). APP has built several gravityflow water treatment plants designed by the Agua Clara program at Cornell University (which is headed by faculty advisor Dr. Monroe Weber-Shirk); operators at these treatment plants use the OpenSourceWater network to relay data to the web from their cell phones. We worked with Drew Hart of APP to develop a mechanism on the OpenSourceWater monitoring page (http:\monitor.wash4all.org) to enable one-click downloads of monthly treatment plant data summaries. APP staff review these summaries and write up brief reports offering specific advice for individual treatment plants and operators. These reports are then sent back to the water treatment operators and to the heads of the community water boards which own the plants, thus closing the communication loop. The use of this data loop and the easy remote oversight that it provides to AguaClara engineers at Cornell University have already led to insights and minor design modifications to improve the performance of the APPbuilt water treatment plants.
Conclusions:
Our research into low-cost turbidimeter design has yielded major cost reductions over current commercial models and has provided – to our knowledge – the most complete description yet of how to affordably conduct turbidity monitoring in rural and low-resource areas. The core purpose of Objective 1 has been met, and Objectives 2 and 3 have been amply met.
Journal Articles on this Report : 1 Displayed | Download in RIS Format
Other project views: | All 1 publications | 1 publications in selected types | All 1 journal articles |
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Type | Citation | ||
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Kelley CD, Krolick A, Brunner L, Burklund A, Kahn D, Ball WP, Weber-Shirk M. An affordable open-source turbidimeter. Sensors 2014;14(4):7142-7155. |
SU835517 (Final) |
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Supplemental Keywords:
turbidity, water quality monitoring, open-source, low-cost technology, sustainable development;Relevant Websites:
Wash 4 All ExitP3 Phase II:
Smart Turbidimeters for Remote Monitoring of Water QualityThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.