Securing High Quality Drinking Water in Sensitive Facilities - Guidelines

Guidelines Securing High Quality Drinking Water in Sensitive Facilities

Preface The first three steps - prevention, monitoring and interven-tion - are prerequisites to secure top grade drinking water. The focus lies on preventive measures which will sustain- Certain water ingredients and unfavourable operating con- ably protect the investments made by the property opera- ditions may cause microbial contamination in drinking wa- tors. Safety risks must be reduced in particular in sensitive ter systems - an issue which often remains undetected un- facilities, i.e. facilities housing immunocompromised indi- til the entire system is impaired. Providing high quality viduals. drinking water in the last few meters to the consumer is a particular challenge in these facilities. After reading this brochure you will be familiar with • the control cycle comprising the four areas of a holistic approach to drinking water hygiene: Prevention, monitoring, intervention and risk assessment; • vital recommendations for planning, installing and operating drinking water systems providing top-grade drinking water in facilities such as: • School buildings, • Sports facilities, • Spas, • Apartment buildings, • Temporarily used residential buildings, Fig 1: • Palaces, castles, The assessment of energy e ciency calls for a holistic of the facility • Hotels, • Barracks, correctional facilities, • Old people’s homes, At the same time, a responsible use of energy is desired. As • Nursing homes, a result, facilities are heavily insulated and operated with • Hospitals, high energy efficiency if possible. A holistic assessment of • Negative examples and how to troubleshoot faults. the facility comprising both energy efficiency and drinking water hygiene, however, is only rarely conducted. Since they are increasingly faced with those two issues, especial- Note: ly Germany’s property operators are becoming more and Below recommendations are based on our ten-years’ prac- more aware of problems related to drinking water hygiene tical experience. They are not based on guidelines and and the risks involved when operating drinking water sys- standards as provided by trade associations, since they of- tems. ten lack important aspects, are dated and thus are no lon- ger state of the art. Just to name an example: the 3-litre In order to achieve long-term success, we need a system- rule calls for the taking of samples only with large volumes atic approach over the entire useful life of a drinking water of drinking water. Or too insensitive test methods used system. This approach is based on WHO’s “Water Safety during approval of materials which tone down test results Plan” and comprises the following four steps: and make selection more difficult. The following symbols indicate drinking water in hot water supply lines and cold water supply lines. 1. Prevention cold drinking water 2. Monitoring 3. Intervention hot drinking water 4. Risk Assessment 2

1. Prevention in the Drinking Water System To ensure high quality drinking water until the tapping point in the facility, drinking water distribution must be re- thought. While drinking water distribution was considered as maintenance-free until a few years ago, new installation concepts and preventive measures during operation are re- quired today. These measures preventively sustain drink- ing-water quality in the system, thus ensuring a high level of drinking water hygiene. The following approaches must be considered when planning, installing and using drinking water systems. Fig. 3 Cleaning and Disinfecting of Components Example of a facility and its domestic water inlet contaminated with Legionella, problematic dimensional o sets, backwash fi lter lacking a drain Source: Contaminated object, southern Germany, M. Lüscher Water exchange ≥ 1x/3d ≥ 1x/7d Dead-leg / end pipes and unused taps Unknown pipe distribution sections should be shut off and drained when not used. Additional shut-off valves should be installed at rarely used tapping points. Special attention Drinking should be paid to seasonal use (e.g. only in winter or in water summer). If the rooms are to be converted, taps must be Temperatures quality Flow Rate removed, drained or closed as needed. Pay special atten- < 25°C v (m/s) tion to the following risk factors: > 55°C pipe-∅ • Tapping points are not used over a period longer than three days • Branches in the distribution line of unknown use Fig. 2 The relationship between temperature, fl ow rate and water exchange is shown in this diagram in a simplifi ed form. • Remove sampling/drain valve piping Source: Thomas Kistemann: “For the long-term preservation of drinking water quality”, 2014 • Remove unused taps In recently built facilities and / or existing facilities we • Disconnect and drain terminal highly recommend to clean and disinfect the following flexible hoses components at regular intervals: • Remove unused hot water tanks • Domestic water meters, fine filters, ion exchangers, salt containers • Eliminate unassigned use of hot water taps • Taps, aerators, shower heads • Use dead space free valves and piping to eliminate contamination risks • Duschschläuche: nach Möglichkeit ersetzen • Remove pipe vents before circulation • Taps - flush thoroughly (at maximum flow rate) 3

Temperatures in the hot and cold water Temperatures in the drinking water distribution must not be in the range of 25 to 45 °C, since this temperature range promotes microbial growth. In addition, the drinking water distribution concept should ensure that prolonged periods of stagnation neither occur in the hot water nor the cold water lines. Furthermore, please note: • The cold and hot water system requires a thorough (complete) insulation. • The regulation of the hot water circulation system must ensure a uniform heat distribution. • At elevated cold water temperatures, we recommend a cold water circulation or at least a suitable flushing device. Fig. 4 Unsuitable sampling valves and fl exible hose used to fi ll the heating (not allowed), insulation of middle pipe is missing • Monitor the temperatures in the cold and hot Source: Contaminated facility, southern Germany water, preferably on-line. This ensures a high level of safety for the property operator. Sampling points • Flush each cold water line at least every 3 For testing drinking water quality, suitable sampling points days or have it flushed automatically with the should be determined together with the planners. The fol- help of flush valves. lowing points should be considered: • Exchange the hot water volume of the tank Determine sampling points in both the hot as well as in the every day, so that periods of stagnation in the cold drinking water lines critical temperature range between 25 and 50 °C can be kept short. The temperature in the tank • Determine the sampling points in the cold should never fall below 50 °C.. water distribution according to the distribution concept. • Adjust the dimensions to the current needs of the user to ensure flow rates of at least • Pay special attention to rarely use tapping 0.1 m / s at any time. points and their distribution (washbasin in the utility room, shower for the caretaker, garden tap in facilities without garden etc.). • Install additional sampling valves in rooms with sensitive use (kitchens, operating theatres, etc.). Use angle sampling valves with wash basins to facilitate sampling without using the wash basin faucets. Sampling water quality at single-handle mixing valves has proven problematic, since the grease in the mixing valve may lead to severe microbial contamination. The disinfection of a mixing valve would only be possible after it has been disas- sembled and cleaned beforehand. 4

Sampling points (minimum level) exploratory assessment additional sampling points as further assessment measuring point Fig. 5 Fig. 7 Sampling points in the property, with the sampling points marked in blue Lime and rust deposits form an ideal basis for bacterial growth. being statutory, however, often insu cient; the cold water at the domestic Source: Watercryst GmbH, Kematen water inlet and the tapping points ought to be sampled as well. Source: based on DVGW Bulletin 551 Hard drinking water Dosing water to prevent corrosion In regions with moderately hard to hard water allow for In many existing facilities, drinking water distribution lime scale protection since calcium promotes microbial lines are made of galvanized steel. The water is often growth and lime deposits serve as an optimal habitat for dosed with sulphate or phosphate to prevent corrosion. bacteria (small dead spaces). Hence, we recommend using Whenever possible, keep this dosage low, as it promotes an approved descaling device. the growth of bacteria. • Ion exchangers should be used only in cold utility rooms which are maintained on Hygiene flushing schedule a yearly basis. The easiest method to ensure high quality drinking water is • Ion exchangers should be used only in the regular flushing of all taps. It is advisable to draw up a check-list for each room with all the relevant taps. Make • We recommend using a descaling device sure that the volume of drinking water is exchanged every in case of high water hardness and high 3 days. conductivity. It is advisable to air pulse flush the hot and cold water dis- tribution once a year as a precautionary measure. Duct T = 22-28 °C T = T = TV= K R 10°C 55°C 60°C Fig. 6 Fig. 8 Duct cross-section with hot water circulation and stagnant cold water that Dosing a 50-year-old galvanized distribution neglecting that a phosphate heats up to duct temperature after 4-5 hours. dosage breeds bacteria downright. Source: Technical Report; Focussing on contamination risks in cold drinking Source: Dosing in a contaminated object, southern Germany, M. Lüscher water, M. Lüscher 2014 5

Water and air working together: Turbulently, yet controlled Air bubbles of a precisely The area to be cleaned is revealed Deposits are removed smoothly predetermined size are on on the boundary surfaces of air and e ciently. their way. and water. Fig. 9 Air pulse fl ushing: Flushing with air-water mixture and its e ect Source: Hamnann air pulse fl ushing 2 Monitoring Test series with new test technologies such as the flow cytom- etry (https://en.wikipedia.org/wiki/Flow_cytometry) also of Drinking Water Quality show that bacterial cells are over 90 per cent active in fresh drinking water supplied from the utilities and still cannot be The various factors impairing drinking water quality can be detected with the cultivation method. This method, however, reduced to a minimum when preventive measures are used is still considered the gold standard by all approved laborato- which help eliminate some of the negative factors ries offering microbiological analysis. As of today, we know (stagnation, critical temperatures, water exchange). It is that bacterial cells may have a third state of life (viable but quite difficult to forecast the quality of drinking water non-culturable = VBNC). Bacteria assume this VBNC state supplied at the domestic water inlet since it is subject to when conditions for growth become unfavourable. If drinking fluctuations. That is why monitoring the drinking water water conditions change in terms of nutrients, oxygen, and quality is essential already before commissioning the temperature, bacteria may rapidly grow within hours.. drinking water system and during the operation of the facility. While in many places the chemical composition of drinking water will change little over longer periods of time, there are large seasonal fluctuations with regard to the bacterial cell counts already noticeable at the domestic water inlet. By far, the statutory tests for Legionella cannot ensure drinking water quality, since the time intervals of Microbiological Analyses of Water twelve or more months are set too much apart. Research Centre EAWAG Facility assessments of recent years show that 95% of all bacteria deposit on the surface of drinking water pipes thus 7 % forming a biofilm (research project of H.C. Flemming 2008). It has become evident that cavities and niches are preferably colonized by bacteria. These include: • Cavities rich of nutrients from grease and rubber Intact gaskets that are not flushed with water 93 % Permeabilized • Grease chambers in fittings • Membranes of solenoid valves (tie rods with water Samples = 69 enclosed) STDEV : T 4.82 % inw • Purge sectors in backwashable filters Fig. 10: The test series in drinking water applying fl ow cytometry shows that 93 per cent of the bacteria are active. Source: St.Kötzsch, Flow Cytometry of Water Samples, 2014 6

Hence, we recommend the following measures when moni- • When testing for Legionella do not only test toring drinking water quality: for Legionella pneumophila SG1, but also for all other serogroups. • Monitor drinking water temperatures at various locations in the drinking water • When testing for Legionella in cold drinking distribution; measure both hot and cold water also test for Pseudomonas aeruginosa, drinking water. because this bacterium may cause serious problems in sensitive areas (infestation of • Monitor drinking water quality and test for wounds). all bacteria cells at different tapping points and at regular intervals (at least twice a year). • Test for Legionella also at cold water taps and additionally at the domestic water inlet. Circulation Temperature Profi le at AG Stadelbach Valve 1 Valve 2 Valve 3 Valve 4 Valve 5 Valve 6 Valve 7 Valve 8 Valve 9 Fig. 11 Temperature profi le over a day, recorded with the LegioTherm system Source: Temperature monitoring in a nursing home, north-western Switzerland 7

3 Intervention Thermal Disinfection with Hot Water Removal of Before you carry out a thermal disinfection in the hot water Contaminations distribution, hydraulically calibrate all lines in normal op- eration. The temperature difference between the tank out- let and the longest circulation line must not exceed <10 °C. High bacterial counts or a high number of pathogens evi- The DVGW even calls for a temperature spread as low as denced through tests of the drinking water are often due to only 5 °C. Furthermore, check the tank volume and the the neglection of preventive measures frequently aggra- state of the heater required for the increase in tempera- vated by use “other than the intended use” over longer pe- ture. Carry out the thermal disinfection between 01:00 and riods, which is to say that water has not been tapped for 04:00 a.m. when water is usually not tapped. We recom- months or even years. Particularly in existing facilities, mend to hot water flush each line individually in series to preventive measures must be taken at least for the base- keep the warming up of the duct as low as possible. If you ment distribution and the risers before taking intervention flush the system with hot water at 75 °C for an extended measures. The number of interventions should be kept as period, the cold drinking water will heat up within a few low as possible and should only be seen as a last resort to hours to reach the critical temperature zone, which in turn ensure top-grade drinking water. In any case, it is impor- will trigger a counter-productive effect - namely microbio- tant to pay particular attention to a holistic assessment of logical growth in cold water. the drinking water system. Below we would like to recom- mend two types of interventions that have proven success- ful in practice. Duct T = 22-28 °C TK= TR= TV= 10°C 55°C 60°C Fig. 12 The cold water will heat up to 25 °C within a few hours. Source: Thesis, Cold Water Circulation, A. Meinero 8

Additionally, flush each tap at 70 °C for three minutes when carrying out a thermal disinfection with hot water. After you 1. Analyse the drinking water quality (chemically have informed the consumers accordingly, the cleaning staff and microbiologically) will be able to support you in doing so in many facilities. 2. Determine the types of wetted materials 3. Determine the hydraulic conditions of cold and hot water Chemical Disinfection of 4. Detect critical operating conditions and Drinking Water Systems connections of the system 5. Determine existing water treatment devices Microbial contamination in drinking water systems are at the domestic water inlet usually detected during the periodic sampling and affect 6. Make sure that the drinking water system is only a part of the installation. If further tests are carried “used as intended” (no stagnation for more out, the bacterial count might be low, however, the con- than 3 days) tamination may spread over the entire drinking water dis- tribution. That is why, an intervention is not only necessary for the hot, but also for the cold water, since the microbial contamination is passed on from the cold into the hot wa- ter. Only if you clean the system prior to the chemical disinfec- tion, you will achieve the desired long-term effect. As disin- When carrying out a chemical disinfection, appropriate fectant we recommend using the electro-activated disin- preventive measures, such as a hydraulic calibration of the fectant Hycleen Des 30. Long-term tests of GF JRG over lines and periodic flushing, must be taken to protect the more than five years have shown that an electro-activated entire drinking water distribution. We recommend drawing disinfectant with a proportion of sodium hypochlorite can up a hygiene schedule prescribing periodic samplings. be used for all materials used in the drinking water system. When using GF JRG products to dose water according to Before planning a chemical disinfection, make sure the fol- the German Drinking Water Ordinance, there will be no lowing points are considered. Your chemical disinfection lifetime limitations of the materials used in the drinking will only be successful if you observe below guidelines. water system - a fact property operators will clearly benefit from. We know from experience that the system should be air pulse flushed to clean it before you carry out a chemical disinfection. 9

4 Risk Assessment The risk assessment of the drinking water system is of par-ticular importance with large facilities, as drinking water to Secure quality may fluctuate due to various reasons. Property op- erators are constantly improving this risk assessment and Drinking Water Quality have developed emergency scenarios in case of impaired and an Optimum drinking water quality supplied at the domestic water inlet. The disinfection system Hycleen Des 30 is an optimal solu- Energy E ciency tion. A simple schematic shows the property operator how to The measures taken in the three steps prevention, moni- secure high quality drinking water in four steps. toring and intervention are prerequisites to secure top grade drinking water until the tapping points in the facili- ties. Facility conversions or adjustments made by the utility companies, however, may require a reassessment of the measures taken from time to time. This is also true, since energy and water prices are rising and operating costs are gaining in importance. The risk assessment combines and analyses all relevant parameters. Microbiological analyses and detected tem- perature values are examined to determine how frequently temperatures have reached the critical ranges. See an ex- ample in the illustration below. Microbiological TWK Analyses Microbiological TWW Analyses Temperature in cold water Temperature in hot water kitchen never once a month always Critical temperature range 10 Contamination potential low favoured high

Prevention • Hydraulics of the entire system • Limescale protection if necessary • Periodic cold water flush 01 Risik Assessment 04 02 Monitoring • Assessment of drinking • Temperature monitoring water quality on the • Drinking water sampling basis of various indicators 03 Intervention • Thermal disinfection • Chemical disinfection The advantages of this control cycle: • A drinking water system can be operated efficiently in terms of hygiene. • It shows where energy costs can be reduced. • Such a holistic approach to drinking water quality and thermal energy will gain in importance for property operators in future. 11

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