(Micro)Biological Sediment Formation in a Non-Chlorinated Drinking Water Distribution System

Abstract

Sediment formation in drinking water distribution systems can lead to brown water at customer taps. Previous studies have shown that sediment formation is closely linked with (micro)biological processes in the distribution system, however the mechanism is not fully understood. Most available studies on discoloration or sediment formation mechanism are based on modeling, pilot-scale experiments, or low frequency data collected during pipe flushing. In this study, long-term sediment development in a large-scale drinking water distribution system was studied at one location over 11 years and at several locations along a known water trajectory during one year. Particulate material was collected at several locations using built-in and mobile filters that were connected to transport and distribution pipes in a semi-continuous manner. The volume of the collected material varied seasonally and the highest volumes were collected in the summer season. The material followed similar variations as temperature, invertebrates biomass and concentration of Aeromonas. The results showed that particulate matter of the sediment at downstream distribution locations was not released by the treatment works but instead forms along the distribution network, with increasing particle/floc size, biomass and Fe and Mn content. The large crustacean, Asellus, contributed to material production through feces excretion and formation of detritus by degradation of exoskeletons of dead animals. Detailed chemical characterization of the collected material showed the presence of proteins, calcium carbonate and iron precipitates. A similar sediment composition in a reference distribution system where customer complaints about brown water are experienced less frequently suggests that the sediment formation mechanism is the same but that water quality of the treatment effluent impacts the extent of material formation and growth of invertebrates. Overall, the results indicate that sediment formation in the distribution system is the result of complex combinations of (micro)biological and bio-chemical processes, including aggregation of particles with organic and inorganic matter, microbial growth on particles and biofilm, biomineralization, and growth of invertebrates. The determining factors to limit sediment formation, however, could not be identified. Further research is required to focus on the impact of treatment on shaping the distribution system ecosystem.

Identifying Eukaryotes and Factors Influencing Their Biogeography in Drinking Water Metagenomes

“…In fact, the presence of both single and multicellular eukaryotes and the identified positive diversity and richness correlations support the presence of a complex food web within DWDSs where eukaryotes could be both predators of prokaryotes and viruses , but also be prey of other eukaryotes or hosts of other taxa . As a result, besides direct management strategies affecting all microorganisms and viruses in DWDS (e.g., disinfection), management strategies targeting specific taxa could indirectly affect other potentially detrimental taxa, such as opportunistic pathogens, or impact unrelated operational issues, such as water discoloration …”

“…135 As a result, besides direct management strategies affecting all microorganisms and viruses in DWDS (e.g., disinfection), management strategies targeting specific taxa could indirectly affect other potentially detrimental taxa, such as opportunistic pathogens, 112 or impact unrelated operational issues, such as water discoloration. 10 A better understanding of the ecological role of eukaryotes in DWDSs provided by both experimental and bioinformatic advancements deepens our understanding of current microbiological management strategies in DWDSs (e.g., disinfection and nutrient starvation). Such information could be used to not only limit the presence of unwanted microorganisms (e.g., Cavallaro and collaborators 112 ) but also to devise new ecologically informed microbiological management plans, improving both water treatment and distribution (e.g., Derlon and collaborators 113 ).…”

“…9 In addition, eukaryotes have been linked to operational issues, such as the increased presence of sediments within DWDSs and consumer complaints. 10 For these reasons, these microorganisms should not be ignored during DWDS management but, instead, should be included in the design of ecologically-informed management practices. Leveraging knowledge of the microbial ecology of the drinking water microbiome could enable strategies to engineer drinking water microbiomes to address current operational issues and guarantee safe water at the consumers' taps.…”

“…These studies, employing targeted approaches (e.g., internal transcribed spacerITS, 18S rRNA) and traditional culture-based methods, showed that variations in the eukaryotic community in drinking water systems are associated with water quality characteristics (e.g., organic carbon, nutrients), source water type, and disinfection strategies. , The presence of eukaryotes in drinking water systems has been shown to affect other microorganisms, for example, by shielding opportunistic pathogens from disinfection and altering biofilm properties through grazing and colonization . In addition, eukaryotes have been linked to operational issues, such as the increased presence of sediments within DWDSs and consumer complaints . For these reasons, these microorganisms should not be ignored during DWDS management but, instead, should be included in the design of ecologically-informed management practices.…”

Exploring the metabolic potential ofAeromonasto utilise the carbohydrate polymer chitin

“…Aeromonads are frequently found in the sediments and loose deposits of drinking water distribution systems (1, 4, 5, 37-40). These deposits contain a variety of organic and inorganic suspended solids, and harbor microscopic fungi, as well as small and larger invertebrates, such as A. aquaticus (41-44). These organisms are known to produce biopolymers, including chitin, which can serve as a source of carbon and nitrogen for microbes.…”