Contamination potential of biofilms in water distribution systems

Abstract

Biofilms are ubiquitous in drinking water systems, either in the form of thin and patchy colonies or as surface-covering multiple layers. In biofilters they are used for the elimination of biologically degradable substances. However, they occur in other sites, e.g., on the walls of containers and pipes, on sediment and on suspended particles. They can rise problems by contamination of the water phase by detaching biofilm organisms. Biofilms provide a possible habitat for hygienically relevant microbes in which they can persist and even multiply. Here they are protected against disinfectants, in particular if located in corrosion products, sediments or ingested by protozoa which feed on biofilm cells. Biofilms are related to the occurrence of “black water” and malodours. They are involved in the corrosion of metals, mineral materials and synthetic polymers. The limiting factor for biofilm growth is usually the availability of nutrients, mainly provided either by biodegradable substances leaching from materials or from by the water phase. The extent of biofilm growth and of the occurrence of hygienically relevant organisms is still unknown and to be investigated. However, latest research indicates that such organisms do not multiply in large numbers in drinking water biofilms; it is possible that drinking water biofilms can inhibit the propagation of invading pathogens.

Physico-Chemical Properties and Microbiological Quality of Borehole Water in Four Crowded Areas of Benin City, Nigeria, During Rainfalls

“…The most predominant bacteria isolated from borehole water in this study were Pseudomonas aeruginosa (62, 38%) and Escherichia coli (53, 32.3%); P. aeruginosa is an important opportunistic biofilm -forming pathogen associated with contaminated domestic plumbing systems (34)(35)(36). This explains the presence of P. aeruginosa in borehole water samples.…”

Dynamics of drinking water biofilm in flow/non-flow conditions

“…In a drinking water distribution system where the volume/surface area ratio is 5 cm, Flemming et al (2002) estimated that 95% of the overall biomass is attached to pipe walls, while only 5% is in the water phase. Therefore, the development of bacteria in biofilms is highly relevant for water quality since it may directly affect cell density in the bulk water phase through detachment phenomena (van der Wende et al, 1989), which depend on a variety of factors such as hydrodynamic patterns and surface materials.…”

Safety Assessment of Transgenic Organisms, Volume 4

“…Once formed, this microbial ecosystem can persist, remain viable and become a continuous reservoir for bacterial contaminants, from which particles can break off and disperse through the water system. The potential for biofilm growth by Acinetobacter in water distribution systems and for promotion of coagrregation of other bacteria was explored (Chaves-Simões et al, 2008;Menaia and Mesquita, 2004;Flemming et al, 2002;Hallam et al, 2001). …”