New water system for
Weinviertel district clinic
In early April 2009, agreement was reached for a new water system for the Weinviertel district clinic in Mistelbach. Their own spring water is treated in the hospital’s central water installation to produce potable and non-potable feed water for steam boilers and pure water for medical applications. In all aspects of water treatment advanced, state-of-the-art membrane filtration systems are used as the main processing technology modules.
It had become essential to upgrade the water system, as the existing plant was outdated and the water had also become extremely aggressive as a result of treatment using acid regenerated ion exchangers, causing extensive corrosion damage to the hospital’s entire supply network.
Renovation was carried out during ‘business as usual’ at the hospital
This new build presented a major challenge for both planning and physical implementation, as the renovation works had to take place without disrupting the hospital’s operational continuity. The operator had set a maximum buffer time for the supply of drinking water at 12 hours. The technical planner therefore developed a design whereby the central unit of the new spring water treatment system, the nanofiltration plant, would have three completely prefabricated, standalone turnkey lines, each providing a third of the total power. The plants were housed in containers and placed on the flat roof of the water plant to provide a temporary piping system for the hospital. Once the old plant was demolished and the new machine halls were renovated, the new facilities were moved to their final installation location in three sections. The reduction to a third of total system performance immediately following the supply changeover was offset by using the water stored in the drinking water reservoir for a maximum period of 12 hours. In addition, as far as was technically possible, other process modules were delivered prefabricated in portable units to reduce the overall construction time.
Modular drinking water treatment
Spring and well water has a very high mineralisation of around 900 mg/l with total alkaline earths (total hardness) of 5.5 mmol/l (30.9° dH). The proportion of carbonate ions in the alkaline earths (carbonate hardness) is 4.2 mmol/l (23.5° dH), which makes the value for the non-carbonate ions in the alkaline earths (non-carbonate hardness) 1.3 mmol/l (7.4° dH). The water must be treated owing to the high content of iron (0.8 mg/l) and manganese (0.23 mg/l), and water softening is also necessary to protect equipment and pipework from extensive calcification (scale), particularly in hot water areas. Besides causing sectional constriction and poor energy transfer, these deposits are perfect breeding grounds for dangerous microorganisms such as Legionella.
The new drinking water treatment plant comprises the following process modules:
Removal of iron and manganese, using ozone as the oxidation medium
Activated carbon filtration stages for protecting the membrane module downstream
Membrane filtration stages with nanofiltration modules for selective reduction of total salt content, hardness and associated ions, e.g. chloride and sulphate, that are linked with corrosion
Separation of permeate from the membrane plant with iron- and manganese-free water.
Optimised pH value, using carbon dioxide degassing towers
Addition of chlorine dioxide for downstream disinfection of the drinking water
Dosing of an appropriate drinking water mineral substance to reduce any pipe corrosion that may have already started
Consumption-regulated pumping station to supply the hospital water network from the drinking water reservoir
The fully automated plant, with a total capacity of 30m³/h, has in-built redundancy to prevent total failure of the drinking water supply in the event of component damage.
Pure water for the medical section
Production of pure water is achieved with a further phase of drinking water treatment using ion exchange and reverse osmosis. Following activated carbon filtration, the water is fully softened in an ion exchange process. It is then desalinated in a two-stage reverse osmosis system until it reaches a residual salt content of up to <5 µS/cm; this value is reduced even further in a downstream blending stage. A consumption-regulated pumping station pumps the water from the pure water tank through a UV disinfection stage and heat exchanger into the pure water pipe system. The detoxified water concentrate resulting from the drinking water nanofiltration is used again as a cooling medium. Owing to the special structure of the pure water network, point-of-use sterile filters are used for critical applications. The fully automatic system, with a total output of 1.5 m³/h, has in-built redundancy (2 x 100%) and is connected to the hospital’s own emergency power system, guaranteeing a continuous supply of pure water.
Hygiene was a particular focus in terms of the planning and commissioning of the drinking water and pure water systems, involving:
There was a particular emphasis on compliance with drinking water regulations TWV (BGBl II-304/2001), ÖNORM B 2531-1 (2004) and VDI 6023 (2006). The new water plant therefore also has its own CIP (clean in place) system.
Steam boiler feed water for high- and low-pressure steam systems.
Low-salt boiler feed water is also generated from the drinking water. A partial flow is extracted from the existing softening system for the laundry, desalinated in a reverse osmosis system and stored in a tank. By means of a pumping station, and subject to demand, the low-salt water is pumped to the boiler feed water reservoir. Here, the required conditioning agents are metered proportionally. The fully-automated RO system, with a total output of 3.5m³/h, is located in the boiler room.
The central control system in the control room communicates with the system modules and the hospital’s control system via Profibus, and automatic valves are controlled via an ASI bus.
Niederösterreich Region, NÖ Landeskliniken-Holding, Landesklinikum Weinviertel-Mistelbach
TGA General Planning:
Technical Office: SAN.*C.O.*WENT/Scheiblingkirchen
BWT Austria GmbH/Mondsee, Buildings and Industry Technology
Hr. Jürgen Heiser, Construction Management: Hr. Alfred Schindler
Straka GmbH/Laa an der Thaya
2-level RO System for producing
pure water 2 x 1,5 m3/h
Filters that remove iron and manganese
3 x 13,3m3
Nanofiltration 3 x 10m3/h