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A Simple Off-Grid Incubator for Microbiological Water Quality Analysis

Inter-American Institute for Cooperation on Agriculture, Brasilia, DF 71600-530, Brazil
Núcleo de Estudos Amazônicos, Universidade de Brasilia, Brasilia, DF 70910-900, Brazil
Department of Civil Engineering, University of Victoria, Victoria, BC V8P 5C2, Canada
Author to whom correspondence should be addressed.
Water 2020, 12(1), 240;
Received: 14 November 2019 / Revised: 20 December 2019 / Accepted: 11 January 2020 / Published: 15 January 2020
(This article belongs to the Section Water and Wastewater Treatment)
There is a need for accessible and low-cost microbiological water quality testing in contexts where diarrheal illness is a major public health concern. In most cases, the quantification of Escherichia coli and other microbial indicators by conventional culture methods requires an incubation step for processed samples at specific temperatures for bacterial growth over a prescribed time. However, incubators can be the most expensive equipment required for such microbial analyses, limiting the number and scope of water quality testing available in low-resource contexts. In this study, a low-cost incubator was developed using a locally available expanded polystyrene (EPS) foam cooler, with two water bottles filled with hot water to heat incubator to a target of 35 °C. The EPS incubator performance was validated by processing 150 water samples in duplicates using the Colilert Quanti-tray/2000 system, incubated in either the EPS incubator or a standard laboratory incubator set at 35 °C. Statistically significant correlations of results indicated that the quantification of E. coli was comparable between both methods. Risk categorizations from standard and EPS incubation results agreed for 141 of 150 (94%) samples, with zero false negatives. In addition to being reasonably mobile the EPS incubator would reduce the cost of such water quality testing, thus potentially increasing the scope of water quality testing coverage. View Full-Text
Keywords: Escherichia coli; fecal indicator bacteria; incubation; microbiological drinking water quality; testing Escherichia coli; fecal indicator bacteria; incubation; microbiological drinking water quality; testing
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Bernardes, C.; Bernardes, R.; Zimmer, C.; Dorea, C.C. A Simple Off-Grid Incubator for Microbiological Water Quality Analysis. Water 2020, 12, 240.

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