The occurence of health-related water quality indicator bacteria associated with contaminant build-up in various types of domestic storage containers

Abstract

This study assessed the occurrence of health-related microbiological indicator bacteria as well as of indicators of bio£ilm that might form inside various rypes of drinking-water storage contamers ill a domestic environment. The susceptibiliry of different container rypes to environmental contamination (dust, £lies, ants etc) as well as the formation of contaminant build-up were also compared in order to identify the container rype least likely to support bio£ilm formation. Previous studies have indicated that the way water is stored and used at home has often led to deterioration of its microbiological qualiry to a point where it posed a risk to consumer health. This appears to be a result of contaminant build-up (i.e. "bio£ilm" formation) in storage containers because of poor container hygiene and handling of containerised water by individuals. The results of this study indicated contaminant build-up formation in various rypes of containers, which contributed to the deterioration of water qualiry. Container water qualiry was assessed before and after dislodging bio£ilm in the containers. A significant increase was found in the indicators of contaminant build-up (turbidiry and heterotrophic bacteria) after the samples of mixed suspenslOn were analysed. The level of turbidiry and heterotrophic bacteria supported the assumption of contaminant build-up in all the rypes of drinking water storage containers. High counts of total coliforms, Escherithia toli and Clostridium per[ringens were also observed after dislodging the contamination build-up. This showed a strong association between these indicators and those of contaminant build-up. It was therefore evident that bio£ilm did form as organic or inorganic surface deposits as well as microorganisms contributing significantly to the potential presence of pathogenic microorganisms in the container water. The health-related qualiry of water did not comply with the values and limits proposed by various guidelines used for the study. The level of contamination was found to be much higher ill containers \vith maxunum environmental contamination (uncovered I unrinsed) than in the containers with minimum environmental contamination (covered I rinsed), as had been expected. This contamination might have resulted from dusts and other environmental pollutants of the containerised water. Higher levels of microbial contamination and decreased water qualiry were associated with widemouthed storage containers (e.g. bucket-rype containers) that are inadequately protected (uncovered or poorly covered). The water in the uncovered containers generally appeared to be subjected to contamination from the outside environment (such as dusts, £lies etc). Floating bacteria and inorganic particulate matter that might be introduced into the water probably attached to the inner surfaces of the containers and formed the contaminant build-up, thereby causing deterioration of water quality. Higher levels of indicators of organic pollution (total coliform bacteria) were found in the plastic than in the metal containers. Polyethylene (from the plastic material) has been described in a number of studies as hydrophobic material, enhancing bacterial attachment and growth. The container type least prone to contaminant build-up was determined by using the "after" data sets (worst scenario data sets). The quality of water in the screw-top containers differed significandy ~ower indicator counts) from that of the water in the bucket-type plastic and metal containers. The screw-top containers were found to be the container types least prone to promoting build up of contaminants. Their smaller mouth-tops minimised contamination and therefore they appeared to be more suitable for use. It was evident that improving household water collection and storage is one option for achieving a beneficial health effect. Household water collection and storage deserve due consideration in the prioritization and implementation of water, sanitation and hygiene measures for use at household, community and regional levels.