Biofilms in Drinking Water Distribution System: A Major Challenge for Sustainable and Safe Drinking Water

Article By - Dr. Neha Panjiar , Ph.D. (Applied Microbiology)

Since India gained its independence from the United Kingdom in 1947, there has been a continuous and significant improvement in the nation’s water supply. ?In 2015, 88% of the total population had access to at least basic water. However, according to a report by UNICEF, less than 50% of the population in India has access to safely managed drinking water (improved water supply located on-premises, available when needed and free of contamination), which is one of the major challenges for India. Approximately 1 billion people worldwide do not have access to sufficient safe drinking water, a major roadblock for socioeconomic development and a healthy ecosystem.

A drinking water distribution system (DWDS) with kilometers of pipelines plays a pivotal role in the accessibility of safe drinking water to the household. SUEZ has mapped 6,000 kilometers of distribution network in India by geographic information system (GIS). Maintenance of water quality in these DWDS is one of the drinking water providers’ major concerns. Drinking water in the distribution system is not sterile, as the water may contain microbes that survive the treatment process or enter the distribution system through the pipe network.

Biofilms are ubiquitous in a DWDS, affecting the microbiological quality of drinking water. These are a complex accumulation of microbes, organic and inorganic material bound together by microbially produced extracellular organic polymer matrix (EPS) attached to the inner surface of the distribution system, either in patches or in the form of continuous layer. Biofilms constitute a reservoir of primary and opportunistic pathogens like Salmonella, Shigella, Pseudomonas, Legionella, etc., which are responsible for waterborne diseases. It is estimated that 45% of all deaths are accounted to contaminated drinking water in developing countries. According to a report by UNICEF, it is estimated that waterborne diseases have an economic burden of USD $600 million a year, in India.

Biofilms’ presence in DWDS are responsible for a vast array of quality and operational problems like contamination of drinking water with increased CFU count; harbouring of hygienically relevant organisms like bacteria, virus, fungi and protozoa; increased tolerance against biocides; increased oxidizing disinfectant demand; reduction of dissolved oxygen; red or black water problems due to iron or sulphate-reducing bacteria; taste change and presence of malodors; hydraulic pressure drop by surface roughness; microbially influenced corrosion (MIC); and reduced material life.

Biofilms are relatively difficult to remove from a DWDS. It is essential to improve the current control strategy of using chlorine as a disinfectant. One crucial requirement is developing more effective novel alternatives to remove the already established biofilm community. The progress in green chemistry, the use of engineered nanostructures and high-throughput screening methods for the assessment of large numbers of chemicals with disinfectant activity, will certainly provide new and efficient biofilm disruption methodology.