The efficiency of a low-cost hydrogen sulphide (H2S) kit as an early warning test for assessing microbial rainwater quality and its correlation with standard indicators microorganisms

Abstract

Testing microbial quality of the harvested rainwater remains a challenge in many countries. The H2S test kit is a low-cost microbiological field-based test which can be used in areas where water testing facilities are limited. This study compares its efficiency with the standard indicators microorganisms in the detection of faecal contamination of rainwater in South Africa. A total of 88 rainwater samples were collected from various tanks in the Eastern Cape, South Africa over three months in 2016. The collected samples were analysed for faecal bacterial contamination using the H2S test kit, Colilert-18/Quanti-tray®/2000 and the membrane filtration technique for faecal coliforms (MFT). The correspondence rate of the H2S test kit with MFT was 88 %, while for the Colilert® it was 76 %. The H2S test kit confirmed faecal contamination when concentrations of standards indicators microorganisms were 5 most-probable number of cells/100 cm3 or higher. Overall, the best correspondence of the H2S test kit with Colilert® was observed at E. coli concentrations above 50 most-probable number of cells/100 cm3. Results of the H2S test kit correlated better with MTF, while the medium used has strongly influenced the enumeration of faecal contamination. Results point to strong effect of media used and revealed the need to calibrate the correspondence between the standard indicator microorganisms and the H2S test kit under local conditions for specific settings.

Citizen science based monitoring of microbial water quality at a single household level in a South African local municipality during the COVID19 lockdown

“…The microbial water quality monitoring was based on the use of the H2S test kit and a cell-phone App. All consumables were purchased from the same suppliers and the H2S test kits were prepared using the general methodology of Luyt et al (2011) and Malema et al (2019). Those activities had been carried out in a microbiological laboratory in the Faculty of Pharmacy of Rhodes University, Makana Local Municipality before the lockdown began.…”

“…Angala et al 2019;Nqowana 2019). It is assumed in further text of this study that there is similarity in the monitoring performance of the H2S test kit and the standard indicator mcroorganisms in the detection of faecal contamination in the Makana municipal drinking water and the rainwater in the Eastern Cape Province of South Africa (Malema et al 2019). The author reports the results of a one-location monitoring of microbial water quality just before and during the strictest phase of the COVID19 nationwide lockdown in South Africa.…”

“…The H2S test kit is a viable tool to perform testing for faecal contamination of drinking water in areas where formal laboratory access is logistically a challenge (Luyt et al 2011;Tandlich et al 2014;Malema et al 2019). The correspondence rates, along with the rates false positive and false negative results, in the analysis of rainwater was recently published on by Malema et al (2019). Use of the kit in citizen science monitoring was also conducted previously (e.g.…”

“…Neal (2020) stated that a re-alignment of the priorities and functioning of the water sector, as well as uses of water in general, are a must. Parts of South Africa have been experiencing water quality problems since at least 2011 (Luyt et al 2011;Tandlich et al 2014;Malema et al 2019) and drought since at least 2015 (Monyela 2017). Previous studies by the author and his collaborators indicate that municipal potable/drinking water has suffered from faecal contamination in Makana Local Municipality in the Eastern Cape Province of South Africa (Luyt et al 2011).…”

“…The author has worked and collaborated with other researchers over the past decade on the development, usage and benchmarking of the H2S test kit against standard indicator microorganism test for microbial water quality (Luyt et al 2011;Tandlich et al 2014;Malema et al 2019). The H2S test kit is a viable tool to perform testing for faecal contamination of drinking water in areas where formal laboratory access is logistically a challenge (Luyt et al 2011;Tandlich et al 2014;Malema et al 2019). The correspondence rates, along with the rates false positive and false negative results, in the analysis of rainwater was recently published on by Malema et al (2019).…”