Addressing the real cost of water in healthcare

Cost control without damaging the quality of patient care or the integrity of key services has always been at the heart of every hospital and NHS Trust.  Measures for controlling cost can be varied but typically include: 

• Reducing operating overheads, reducing OPEX 
• Effective procurement of new equipment or systems, to reduce CAPEX 
• The use of different funding mechanisms, for example equipment leasing or rental based on equipment usage 
• Value added, where additional services are bundled with an initial purchase to reduce the overall cost 

When it comes to normal hospital operating costs, although it is understandably the big-ticket items that get the most attention – staff, buildings, capital systems etc – there are often considerable opportunities to reduce the cost of what are generally considered everyday services. 

In particular, improvements in the way that water supply, treatment and reuse systems are designed and managed can offer significant and underexploited opportunities for cost savings. 

Although the cost of each cubic metre of mains water is relatively low in the UK, the huge volume used by the NHS across its estate makes it a major cost-centre, both nationally and within each hospital. 

Improving steam plant efficiency 
One area for potential savings for many hospital estates is by reducing the volume of water required by heating and steam generation plants.   

One of the key factors that can affect boiler efficiency, and thus the operating costs, are the level of total dissolved solids (TDS) or impurities in the feed and makeup water. These solids typically include inorganic salts such as calcium, magnesium, potassium, sodium, bicarbonates, chlorides and sulphates, plus organic matter. 

Dissolved solids will gradually precipitate and become increasingly concentrated as water is boiled and steam produced.  If this concentration reaches critical levels then there is a risk that contaminates will damage the steam and condensate systems, leading to corrosion and deposits on heat transfer surfaces.  In turn this increases energy consumption, the rate of blowdowns and maintenance costs.  

Typically, systems are managed to keep the level of dissolved solids below 3,000 or 3,500ppm.  In some parts of the UK, however, mains water supplies contain dissolved solids at levels of around 300ppm. Since solids are not evaporated as steam is generated, however, this level rises gradually during boiler operation. To keep dissolved solids at a safe level, a proportion of the water circulating in the system must be continually replaced. Beyond the additional raw water costs, the loss of hot water from the system also results in the loss of the energy used to heat it, as well as additional effluent treatment costs.  

Significantly, conventional pre-treatment systems, such as water softening, do not reduce total dissolved solids, but merely exchange calcium ions for an equivalent quantity of sodium.  

A more effective solution is to use a reverse osmosis (RO) pre-treatment system as part of the feedwater treatment process.  This will lead to a substantial reduction in water losses and an improvement in the boiler energy efficiency. 

Fig. 1 shows the potential impact of RO treatment on a steam plant producing just over 13,000 te/year, a size of plant often used in hospitals. Without pre-treatment, the plant consumes more than 11,000m3 of raw water per year.  

By introducing a RO pre-treatment system, annual raw water consumption is reduced by around 80% and energy consumption in the heating system is reduced by more than 355,000kwh.   Even with the additional cost of the new pre-treatment system, the change delivers annual savings of £12,117, rising to £16,311 if the concentrated reject water from the RO is treated and reused. 

Greywater reuse 
On site treatment using reverse osmosis technology creates other water re-use opportunities for hospitals. Many effluent streams contain low levels of contamination, for example water from swimming and hydrotherapy pools, water consumed during the regeneration of softening equipment, and water rejected from primary RO systems. The introduction of secondary RO treatment can bring this water to a suitable condition for reuse in cooling towers, as boiler feedwater or for toilet flushing, for example. 

A holistic approach 
The application RO pre and post treatment technologies are not the only measures available to healthcare organisations seeking to reduce water-related costs. Other important steps include the proper sizing of pumps, storage tanks and treatment equipment, the use of variable speed pump motors to better match energy consumption with demand, and a distribution system design that ensures the most appropriate grade of water is supplied for every application within a facility.