Experimental Water Distribution System Research Articles

Investigating alternative materials to EPDM for automatic taps in the context of Pseudomonas aeruginosa and biofilm control

Automatic taps use solenoid valves (SVs) which incorporate a rubber (typically EPDM) diaphragm to control water flow. Contaminated SVs can be reservoirs of opportunistic pathogens such as Pseudomonas aeruginosa; an important cause of healthcare-associated infection. To investigate the attachment and biofilm formation of P.aeruginosa on EPDM and relevant alternative rubbers to assess the impact on water hygiene in a laboratory model. Biofilm formation on EPDM, silicone and nitrile rubber coupons was investigated using a CDC biofilm reactor. SVs incorporating EPDM or nitrile rubber diaphragms were installed on to an experimental water distribution system (EWDS) and inoculated with P.aeruginosa. P.aeruginosa water levels were monitored for 12-weeks. SVs incorporating diaphragms (EPDM, silicone or silver ion-impregnated silicone rubber), pre-colonized with P.aeruginosa, were installed and the effect of flushing as a control measure was investigated. The concentration of P.aeruginosa in the water was assessed by culture and biofilm assessed by culture and microscopy. Bacterial attachment was significantly higher on nitrile (6.2×105 cfu/coupon) and silicone (5.4×105 cfu/coupon) rubber than on EPDM (2.9×105 cfu/coupon) (P<0.05, N=17). Results obtained invitro did not translate to the EWDS where, after 12-weeks in situ, there was no significant difference in P.aeruginosa water levels or biofilm levels. Flushing caused a superficial reduction in bacterial counts after <5min of stagnation. This study did not provide evidence to support replacement of EPDM with (currently available) alternative rubbers and indicated the first sample of water dispensed from a tap should be avoided for use in healthcare settings.

Contamination of hospital tap water: the survival and persistence of Pseudomonas aeruginosa on conventional and ‘antimicrobial’ outlet fittings

Pseudomonas aeruginosa infections have been linked to contaminated hospital taps, highlighting the potential for tap outlet fittings (OF) to harbour biofilm. P.aeruginosa may be transferred to OFs via contaminated cleaning cloths. Suggested interventions include flushing regimens and alternative OF designs. To investigate the transfer of P.aeruginosa from a contaminated cleaning cloth to conventional and 'antimicrobial/antibiofilm' OFs and to determine whether this contamination persists and/or leads to contamination of tap water. Microfibre cloths contaminated with P.aeruginosa (108cfu/mL) were used to wipe four different types of OF [one of conventional design (OF-A) and three marketed as 'antimicrobial' and/or 'antibiofilm' (OF- B, -C and -D)]. OFs were inserted into an experimental water distribution system for up to 24 h. Survival was assessed by culture. Single and multiple water samples were collected and cultured for P.aeruginosa. The median number of P.aeruginosa transferred from cloth to OF was 5.7×105cfu (OF-A), 1.9×106cfu (OF-B), 1.4×105cfu (OF-C) and 2.9×106cfu (OF-D). Numbers declined on all OFs during the 24 h period with log reductions ranging from 3.5 (OF-C) to 5.2 (OF-B; P>0.05). All water samples delivered immediately after OF contamination contained P.aeruginosa at ≥10cfu per 100 mL. Contamination of water delivered from OF-A persisted despite continued flushing. Water delivered from OF-B did not contain P.aeruginosa beyond the first flush. Contaminated cleaning cloths may transfer P.aeruginosa to OFs, leading to contamination of tap water. Although not removing the potential for contamination, 'antimicrobial/antibiofilm' OFs may prevent P.aeruginosa from continually contaminating water delivered from the outlet.

Biofilm formation in an experimental water distribution system: the contamination of non-touch sensor taps and the implication for healthcare

Hospital tap water is a recognised source of Pseudomonas aeruginosa. UK guidance documents recommend measures to control/minimise the risk of P. aeruginosa in augmented care units but these are based on limited scientific evidence. An experimental water distribution system was designed to investigate colonisation of hospital tap components. P. aeruginosa was injected into 27 individual tap ‘assemblies’. Taps were subsequently flushed twice daily and contamination levels monitored over two years. Tap assemblies were systematically dismantled and assessed microbiologically and the effect of removing potentially contaminated components was determined. P. aeruginosa was repeatedly recovered from the tap water at levels above the augmented care alert level. The organism was recovered from all dismantled solenoid valves with colonisation of the ethylene propylene diene monomer (EPDM) diaphragm confirmed by microscopy. Removing the solenoid valves reduced P. aeruginosa counts in the water to below detectable levels. This effect was immediate and sustained, implicating the solenoid diaphragm as the primary contamination source.

Showcasing a Smart Water Network Based on an Experimental Water Distribution System

Nowadays, modern utilities have installed a variety of measurement devices like pressure sensors, flow meters, noise loggers, water quality sensors for different intentions. In this paper we introduce an experimental water distribution system (EWDS-TUG) that serves as an example of implementing a smart water network solution. The used EWDS-TUG states a highly determined water supply system. Artificial customers are installed and can be controlled automatically by magnetic valves. We present how we collect sensor data and control magnetic valves installed, remotely via a web based control and communication solution, which is deeply integrated in the measurement workflow.

Experimental Setup to Examine Leakage Outflow in a Scaled Water Distribution Network

Abstract Leakages in water distribution systems are one of the most emerging topics in the field of water supply. Therefore, understanding leak hydraulics is of high interest. This paper outlines an experimental laboratory network. The main purpose of this experimental water distribution system is to gain knowledge and experience for two tasks. First, the verification of the hydraulic modeling approaches concerning leakage outflow. Second, the practically performance evaluation of algorithms for leakage localization developed at our institute. The chosen laboratory setup allows multiple leakages, flow measurements at every position as well as pressure measurements on defined locations.

Control of Coliform Growth in Drinking Water Distribution Systems

AbstractThe occurrence of coliforms in drinking water distribution systems may be explained by (i) inadequate water treatment, (ii) post‐treatment contamination, or (iii) coliform growth in the network. In order to confirm the third hypothesis, a 24 h‐starved dense suspension of Escherichia coli was injected into an experimental water distribution system. Results from this experiment clearly indicate that E. coli may find ecological conditions in drinking water distribution systems which will allow growth, particularly in the biofilm phase. Chlorination is an appropriate tool to limit coliform much more easily than the total heterotrophic bacterial biomass. However, in all cases, biofilm associated bacteria are more difficult to kill than suspended bacteria, because of chlorine consumption by the pipe material, and because of a diffusion‐limited reaction between chlorine and the biofilm.