A Simple Off-Grid Incubator for Microbiological Water Quality Analysis

Abstract

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.

Water quality assessment and evaluation of human health risk of drinking water from source to point of use at Thulamela municipality, Limpopo Province

“…Colilert media was added to 100 mL sample and mixed until dissolved completely. The solution was poured into an IDEXX Quanti-Tray/2000 and sealed using the Quanti-Tray sealer 26 . The samples were incubated at 35 °C for 24 h. Trays were scanned using a fluorescent UV lamp to count fluorescent wells positive for E. coli concentration and counted with the most probable number (MPN) table provided by the manufacturer 27 .…”

MicroMI: A portable microbiological mobile incubator that uses inexpensive lithium power banks for field microbiology

“…Current innovative incubator designs have made use of heated foam ice boxes [3] or food chiller boxes [1] powered by a 12 V car battery or similar flexible power supplies. Such designs have made use of widely available and inexpensive temperature control modules, coupled to resistive heater panels and fans [11] .…”

Rapid qPCR-Based Water Quality Monitoring in New York State Recreational Waters

“…Crucially, the long incubation period and reliable electricity source required by these methods limits their feasibility for routine, rapid, on-site monitoring. Although research has been done to eliminate the need for electricity by using homemade incubators, these systems are not widely used (Bernardes et al, 2020). In recent years, new culture-based methods have been developed including TECTA (Bramburger et al, 2015) and Compartment Bag Tests (CBTs; Brooks et al, 2017;Wang et al, 2017).…”