Bacterial invasion potential in water is determined by nutrient availability and the indigenous community

In drinking water (DW) and the distribution systems, bacterial growth and biofilm formation have to be controlled both for limiting taste or odour development and preventing clogging or biocorrosion problems. After a contamination with undesired bacteria, factors like nutrient availability and temperature will influence the survival of these invaders. Understanding the conditions enabling invaders to proliferate is essential for a holistic approach towards microbial risk assessment in DW. Pseudomonas putida was used as a model invader because this easy-growing bacterium can use a wide range of substrates. Invasion experiments in oligo- to eutrophic waters showed the requirement of both a carbon and phosphate source for survival of P.putida in DW. Addition of C, N and P enabled P.putida to grow in DW from 5.80x10(4) to 1.84x10(8)cellsmL(-1) and survive for at least 12days. However, in surface water with similar nutrient concentrations, P.putida did not survive, indicating the concomitant importance of the present indigenous microbial community of the specific water sample. Either extensive carbon or phosphate limitation can be used in water treatment design in order to obtain a DW which is not susceptible for unwanted bacterial growth

Occurrence of transparent exopolymer particles (TEP) in drinking water systems

Numerous membrane fouling studies have been conducted to predict and prevent membrane fouling. It was only recently that a new parameter, TEP, was introduced in this research. The deposition of TEP on reverse osmosis (RO) membranes has already been imaged, correlations between ultrafiltration (UF) fouling and TEP concentrations have been reported. Furthermore, TEP deposition takes place in an early stage of aquatic biofilm formation, making TEP one of the accused in search for biofilm initiation factors. After literature reporting about TEP in marine, surface and wastewater, this is the very first research focusing on TEP through in drinking water. Every single treatment step in three completely different drinking water production plants was scored on TEP removal. It could be concluded that TEP concentrations were very dependent of the raw water source but in none of the installations, TEP was able to reach the final drinking water in significant concentrations. The combination of coagulation and sand filtration proved efficient in strongly reducing TEP levels, while the combination of UF and RO could provide a total TEP removal

Occurrence of transparent exopolymer particles (TEP) through drinking water treatment plants

Numerous membrane fouling studies have been conducted to predict and prevent membrane fouling. It was only recently that a new parameter, TEP, was introduced in this research. The deposition of TEP on reverse osmosis (RO) membranes has already been imaged, correlations between ultrafiltration (UF) fouling and TEP concentrations have been reported. Furthermore, TEP deposition takes place in an early stage of biofilms formation, making TEP one of the accused in search for biofilm initiation factors. After literature reporting about TEP in marine, surface and wastewater, this is the first research focusing on TEP through in drinking water. Each treatment step in three completely different drinking water production plants was evaluated on TEP removal and it could be concluded that a limited restfraction or no TEP could reach the drinking water. Coagulation + sand filtration proved efficient in strongly reducing TEP levels, UF + RO can provide a total TEP removal

Growth and flow cytometric monitoring of bacteria in drinking water

Bacteria are omnipresent, also in our drinking water. This is unavoidable but should not be a reason to worry. It is better to understand them, to be able to control and predict their behavior. In a first section of this research, fundamental factors affecting bacterial presence in drinking water were studied. Transparent exopolymer particles were monitored as a possible biofilm promoter, but their importance in Flemish drinking waters appeared to be limited. In addition, the factors governing growth or survival of intruding bacteria in drinking water were studied. It appeared that next to the available nutrients, the present indigenous microbial community was crucial. Routine monitoring of bacteria in drinking water asks for performant tools. Therefore, the second section optimized the use of flow cytometry as a high-throughput monitoring tool and it was shown that bacterial analysis could be done fast and precise. A third and final section was conducted in close collaboration with drinking water industry and searched for additional applications for flow cytometry, deviating from routine monitoring. The tool was successfully applied for providing fast information during rinsing of major supply pipes and for a quick screening of bacterial growth in a local drinking water network

Bacterial exchange in household washing machines

Household washing machines (WMs) launder soiled clothes and textiles, but do not sterilize them. We investigated the microbial exchange occurring in five household WMs. Samples from a new cotton T-shirt were laundered together with a normal laundry load. Analyses were performed on the influent water and the ingoing cotton samples, as well as the greywater and the washed cotton samples. The number of living bacteria was generally not lower in the WM effluent water as compared to the influent water. The laundering process caused a microbial exchange of influent water bacteria, skin-, and clothes related bacteria and biofilm-related bacteria in the WM. A variety of biofilm-producing bacteria were enriched in the effluent after laundering, although their presence in the cotton sample was low. Nearly all bacterial genera detected on the initial cotton sample were still present in the washed cotton samples. A selection for typical skin- and clothes related microbial species occurred in the cotton samples after laundering. Accordingly, malodour-causing microbial species might be further distributed to other clothes. The bacteria on the ingoing textiles contributed for a large part to the microbiome found in the textiles after laundering

Germ-free sea bass Dicentrarchus labrax larval model : a valuable tool in the study of host-microbe interactions

A thorough understanding of host-microbe interactions is crucial for more efficient disease management in the marine larviculture industry. As demonstrated in terrestrial animal research, gnotobiotic systems (involving animals cultured in germ-free conditions or inoculated with known microorganisms) are excellent tools to extend our understanding of the mechanisms involved in host-microbe interactions and allow the evaluation of new treatments for diseases. In this study, we introduce a germ-free European sea bass Dicentrarchus labrax larval model, independent of the continuous addition of antimicrobial agents. This model has an experimental set-up that allows addition of live feed to the larvae without compromising the germ-free status. This model will facilitate and render aquaculture research more effective in terms of mitigation fish larval diseases

Flow cytometric examination of bacterial growth in a local drinking water network

Bacterial growth in drinking water networks can result in health-based implications, affect network hydrology and induce customer complaints. In this study, cultivation-based methods were compared to flow cytometric methods for the study of growth in a local drinking water network. Comparison of flow cytometric cell concentrations indicated growth in several samples, while further data analysis with fingerprinting algorithms showed the different origin of this growth; low similarity between samples with elevated cell counts indicated that growth occurred mainly in the sampled household plumbing installations instead of centrally in the water network. Fast obtained flow cytometric data made this thorough analysis possible, while cultivation-based methods were yielding too scarce information. Flow cytometry showed to be more rapid, complete, and accurate than cultivation-based methods for a network growth study. It is proposed as a future useful tool for the fast detection of microbial point contaminations in drinking water networks

Sulfur-based denitrification treating regeneration water from ion exchange at high performance and low cost

Autotrophic denitrification with sulfur is an underexplored alternative to heterotrophic denitrification to remove nitrate from wastewater poor in organics. The application on ion exchange regeneration water (19.4-32.1 mS cm(-1)) is novel. Three fixed bed reactors were tested at 15 degrees C for > 4 months, inoculated with activated sludge from sewage treatment. All were fast in start-up (< 10 days) with high performance (94 +/- 2% removal efficiency). pH control with NaOH rendered higher nitrate removal rates than limestone addition to the bed (211 +/- 13 vs. 102 +/- 13 mg N L-1 d(-1)), related to higher pH (6.64 vs. 6.24) and sulfur surface area. Bacterial communities were strongly enriched in Sulfurimonas (63-67%) and Thiobacillus (24-26%). In an economic comparison, sulfur-based denitrification ((sic)5.3 kg(-1) N) was 15% cheaper than methanol-based denitrification ((sic)6.22 kg(-1) N) and both treatments were opex dominated (85.9 vs. 86.5%). Overall, the technological and economic feasibility should boost further implementation of sulfurotrophic denitrification