The University of Massachusetts Amherst
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An Inexpensive Incubator for Testing Microbial Water Contamination in the Field

Testing water for microbial contamination has long been the norm for evaluating the safety of water across the world, but in rural areas of underdeveloped countries the portable incubators currently on the market for this application are unavailable, expensive, or require reliable electricity. So what happens when our Engineers Without Borders’ volunteers need to test microbial contamination during their projects in Kenya and Ghana? Or what if the laboratory incubator breaks in a health office in rural Senegal? Or, even in upstate Maine, what can middle-school students do who are concerned about water quality in their wells at home?

To address this challenge, Professor Emily Kumpel of the Civil and Environmental Engineering Department is sponsoring an interdisciplinary senior design project for five Mechanical Engineering students to design a “DIY Portable Incubator for Testing Microbial Water Quality in Field Settings.” The deliverables of this ambitious project include a 3D CAD model with thermal analysis, a finite element method formulation for solving this particular engineering problem, and a functional prototype.

“Water quality test is performed by utilities, surveillance agencies, private citizens, and researchers all over the world,” says Kumpel. “However, while there are many ways to test for bacterial contamination, many require incubation at a constant temperature to produce reliable results that can inform water safety management. A DIY-style incubator made out of readily available parts that can work in a variety of settings would provide an important tool for making sure water is safe to drink, contributes to a larger movement around citizen science, and democratizes access to participate and be a part of scientific inquiry.”

Among other expertise, Kumpel studies water and sanitation in developing countries, global health and water, water quality monitoring, and sustainability of small community water supplies.

According to the senior design proposal, indicator organisms – including E. coli, fecal (or thermotolerant) coliform, and total coliform – are commonly used as a proxy for pathogens that can cause waterborne disease. “While these bacteria are not themselves necessarily pathogenic,” as the proposal explains, “their presence can indicate contamination from fecal sources that suggest may also contain pathogens.”

According to the proposal, a variety of methods exist to measure indicator organisms. “The easiest and cheapest are culture-based methods, where bacteria are given a favorable environment (including nutrients and warm temperatures) to grow, allowing us to observe their presence,” explains the proposal.

In this context, incubators represent one important tool in performing the best and most practical testing methods. However, in many situations in the field, including low-income countries and rural areas with poor transportation capabilities, testing must occur remotely. Therefore, incubators, which keep the bacteria and its media at warm temperatures, must be portable and able to function without reliable electricity. The proposal adds that portable incubators currently on the market that meet these requirements generally accommodate only methods from a single type of testing method, hold only a few samples, and are expensive.

As the proposal concludes, “There is a need for a more affordable incubator for water quality made of readily available materials in a variety of contexts that can provide the necessary temperature stabilization and keep the samples as undisturbed as possible.” To deal with these remote situations, incubators must maintain a specified temperature for 24-48 hours, control the humidity so as not to dry out the media, and withstand impacts and sudden loads when being moved in rough terrains.   

Kumpel would like her team to design and build an incubator that satisfies the following scope: it costs less than $150; it satisfies ASTM E1292-94 and UNICEF/MICS Water Quality Standards for incubators; it maintains an ambient air temperature for samples of 35-37C; it can accommodate a variety of testing methods for microbial water; it is fabricated from readily available material in key identified scenarios; it minimizes the need for reliable electricity input; it minimizes specialized components; and it comes with simplified directions for a variety of literacy levels and user ages.

As team leader Akshay Delity says about getting involved in this project: "My experiences in Dr. Kumpel's lab and the Engineers Without Borders Kenya Project have impressed upon me the importance of an incubator like this in the field of international development and water treatment. I'm lucky to be working with some diversely talented peers and know that we can produce an accessible incubator design for those without access to the same materials and education we have." (October 2018)