Microbial analysis of in situ biofilm formation in drinking water distribution systems: implications for monitoring and control of drinking water quality

Abstract

Biofilm formation in drinking water distribution systems (DWDS) is influenced by the source water, the supply infrastructure and the operation of the system. A holistic approach was used to advance knowledge on the development of mixed species biofilms in situ, by using biofilm sampling devices installed in chlorinated networks. Key physico-chemical parameters and conventional microbial indicators for drinking water quality were analysed. Biofilm coverage on pipes was evaluated by scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM). The microbial community structure, bacteria and fungi, of water and biofilms was assessed using pyrosequencing. Conventional wisdom leads to an expectation for less microbial diversity in groundwater supplied systems. However, the analysis of bulk water showed higher microbial diversity in groundwater site samples compared with the surface water site. Conversely, higher diversity and richness were detected in biofilms from the surface water site. The average biofilm coverage was similar among sites. Disinfection residual and other key variables were similar between the two sites, other than nitrates, alkalinity and the hydraulic conditions which were extremely low at the groundwater site. Thus, the unexpected result of an exceptionally low diversity with few dominant genera (Pseudomonas and Basidiobolus) in groundwater biofilm samples, despite the more diverse community in the bulk water, is attributed to the low-flow hydraulic conditions. This finding evidences that the local environmental conditions are shaping biofilm formation, composition and amount, and hence managing these is critical for the best operation of DWDS to safeguard water quality.Electronic supplementary materialThe online version of this article (doi:10.1007/s00253-015-7155-3) contains supplementary material, which is available to authorized users.

Diagnóstico del agua utilizada en las procesadoras de café del Municipio Caripe – Estado Monagas, Venezuela.// Diagnosis of the water used in coffee processors of the Caripe Municipality - Monagas State, Venezuela

“…Las bacterias fecales constituyen el principal indicador de riesgo patogénico dentro de los estándares microbiológicos para calidad de agua en la gran mayoría de los países (Sammon et al, 2010;Boubetra et al, 2011). Sin embargo, debido a que la presencia de Pseudomonas en el agua potable es un hecho bastante común (Nawrocki et al, 2010;Douterelo et al, 2013), muy recientemente se han sugerido como buenos indicadores de riesgo humano (Douterelo et al, 2016); siendo, además, una actualidad bien real que los nuevos enfoques y avances en procedimientos metodológicos han logrado evidenciar la proliferación de microorganismos, estructurados en comunidades bacterianas y fúngicas, cuya presencia han deteriorado la seguridad del vital líquido tanto en sus reservorios como en las redes de distribución que surten a los usuarios (Douterelo et al, 2016;Oliveira et al, 2016;Stauber et al, 2016).…”

“…Más recientemente Douterelo et al (2016), reportaron que las fuentes de agua potable constituyen el "semillero" de los microorganismos formadores de biopelículas por sus capacidades de incrementar resistencia a la desinfección (Soniago et al, 2011;Pereira et al, 2013). De esta manera, muchos patógenos logran sobrevivir durante los tratamientos de desinfección de los reservorios de agua desde donde, dependiendo de las condiciones hidráulicas establecidas para el caudal, viajan a través de los sistemas de acueducto y gran parte de ellos pueden llegar hasta los usuarios en niveles que son directamente proporcionales a la velocidad del flujo (Douterelo et al, 2013;Holinger et al, 2014).…”

Disinfection Processes

“…A holistic approach was used to advance knowledge on development of mixed species biofilms in situ, by using biofilm sampling devices installed in chlorinated networks (Douterelo et al, 2016). The microbial community structure, bacteria and fungi, of water and biofilms was assessed using pyrosequencing.…”

Dynamics of Biocorrosion in Copper Pipes under Actual Drinking Water Conditions

“…Water utilities invest time and money toward controlling the presence of undesirable microorganisms in drinking water systems [1]. The microbial contamination of a water distribution network begins with microbial attachment on a pipe surface [2,3], which then forms a mixed-species biofilm [4].…”

“…Copper pipes in the drinking water service are highly valued in domestic plumbing systems owing to their corrosion resistance [7,8] and antiseptic properties [9,10]. However, bacteria living in copper plumbing systems have reported [1,7,11,12]. Microorganism settlement can promote and enhance copper corrosion in pipes [2,3], causing a phenomenon known as microbiologically influenced corrosion (MIC) or biocorrosion [6,13].…”