Inhibition of biofilm formation on the surface of water storage containers using biosand zeolite silver-impregnated clay granular and silver impregnated porous pot filtration systems

Abstract

Development of biofilms occurring on the inner surface of storage vessels offers a suitable medium for the growth of microorganisms and consequently contributes to the deterioration of treated drinking water quality in homes. The aim of this study was to determine whether the two point-of-use technologies (biosand zeolite silver-impregnated clay granular (BSZ-SICG) filter and silver-impregnated porous pot (SIPP) filter) deployed in a rural community of South Africa could inhibit the formation of biofilm on the surface of plastic-based containers generally used by rural households for the storage of their drinking water. Culture-based methods and molecular techniques were used to detect the indicator bacteria (Total coliforms, faecal coliform, E. coli) and pathogenic bacteria (Salmonella spp., Shigella spp. and Vibrio cholerae) in intake water and on the surface of storage vessels containing treated water. Scanning electron microscopy was also used to visualize the development of biofilm. Results revealed that the surface water source used by the Makwane community was heavily contaminated and harboured unacceptably high counts of bacteria (heterotrophic plate count: 4.4–4.3 Log10 CFU/100mL, total coliforms: 2.2 Log10 CFU/100 mL—2.1 Log10 CFU/100 mL, faecal coliforms: 1.9 Log10 CFU/100 mL—1.8 Log10 CFU/100 mL, E. coli: 1.7 Log10 CFU/100 mL—1.6 Log10 CFU/100 mL, Salmonella spp.: 3 Log10 CFU/100 mL -8 CFU/100 mL; Shigella spp. and Vibrio cholerae had 1.0 Log10 CFU/100 mL and 0.8 Log10 CFU/100 mL respectively). Biofilm formation was apparent on the surface of the storage containers with untreated water within 24 h. The silver nanoparticles embedded in the clay of the filtration systems provided an effective barrier for the inhibition of biofilm formation on the surface of household water storage containers. Biofilm formation occurred on the surface of storage plastic vessels containing drinking water treated with the SIPP filter between 14 and 21 days, and on those containing drinking water treated with the BSZ-SICG filter between 3 and 14 days. The attachment of target bacteria on the surface of the coupons inoculated in storage containers ranged from (0.07 CFU/cm2–227.8 CFU/cm2). To effectively prevent the development of biofilms on the surface of container-stored water, which can lead to the recontamination of treated water, plastic storage containers should be washed within 14 days for water treated with the SIPP filter and within 3 days for water treated with the BSZ-SICG filter.

Co-Existence of Free-Living Amoebae and Potential Human Pathogenic Bacteria Isolated from Rural Household Water Storage Containers

“…Water quality deteriorates during household storage due to physical, chemical, and microbiological processes [ 2 , 3 , 4 , 5 , 6 ]. If the storage containers are not properly or regularly cleaned and hygiene behaviours are poor inside the household, a biofilm forms inside the container [ 7 , 8 , 9 ].…”

Occurrence of Escherichia coli and faecal coliforms in drinking water at source and household point-of-use in Rohingya camps, Bangladesh

“…The quality of water stored in households might provide the indicators of the level of secondary contamination by comparing the levels with that of the source water. Such a comparison would also be very important to model household transmission dynamics to understand pathogen flow pathways and to provide proper interventions [12–14]. In Cox’s Bazar, since the Rohingya population is living in a small and highly crowded area and since a huge number of people are using a single water point (on an average, 192 people are getting water from a single tubewell), it is difficult to testify water quality from every household.…”

Efficacy of locally-available cleaning methods in removing biofilms from taps and surfaces of household water storage containers

“…Additionally, fecal indicator bacteria presence was not associated with container type or opening, but was associated with storage time; no difference was found in water or biofilm gene copies after local cleaning (n = 2). Lastly, Budeli et al confirmed biofilm formation via scanning electron microscopy, in plastic storage container surfaces within 24 h of exposure to untreated water 33 . After filtration with silver nanoparticle containing ceramic filters, biofilm formation was visually apparent at 14-21 days or 3-14 days, depending on filter.…”