The NHS has set an admirable and ambitious goal to deliver the world’s first net zero national health service. It has already reduced its carbon footprint by 11 percent between 2007 and 2015. But achieving net zero in all aspects of sustainability is challenging and while much attention usually goes to reducing carbon footprint, reducing water consumption is also an important area to address.
Clinical laboratories can be big water consumers, tending to use much more per square metre than typical commercial buildings. At some US universities for example, laboratories account for up to 50 percent of the total campus water consumption. Cooling towers are particularly thirsty but many other lab processes require a substantial water supply.
The role of lab water purification systems in reducing water footprints
Lab water purification equipment takes a small but significant share and should be seriously considered on the basis that every drop counts.
When confronted with water recovery rate figures for water purification systems based on reverse osmosis (RO), lab staff are often surprised to see how wasteful they can be. In some cases, recovery is as low as 10%.
In other words, for every 100 litres of input water, only 10 litres of purified water may be produced, leaving 90 litres to flow down the drain.
Saving water in the lab
The key features of an encapsulated RO element are a permeate tube, feed and permeate spacers, and a membrane. The rectangular TLC (thin layer composite) membrane is rolled together with the spacers onto the tube, like a wound-up scroll. Input water, under pressure, enters the scrolled membrane from one end. Some passes through it into the permeate spacer and exits through the permeate tube. The rest exits as a drain flow from the other end of the scroll.
In the standard arrangement, feedwater flow is perpendicular to the rectangle’s width. In newer designs, it flows along the full length of the rectangle. This maintains an ideal flow rate across the membrane, creating the necessary turbulence to help prevent clogging, but with a reduced volumetric flow rate in the drain stream
Saving energy in the lab
If purified water is not being dispensed for a period of several hours or more, it makes sense to put the unit on standby and save both electricity and water. It should not be entirely idle in this ‘sleep’ mode, as some circulation is needed to discourage microbiological activity.
In SUEZ machines the sleep cycle involves a 10-minute flushing programme every 2 hours. At its simplest, a standby switch is a manual feature which is operated – provided someone remembers – at the end of the working day and especially before weekend closedowns. SUEZ has now introduced an intelligent standby option, which automatically imposes the sleep cycle at any time that a set period has elapsed without water being dispensed.
This may seem like an obvious feature for all manufacturers to provide, but it is not as easy as it sounds. It requires someone to write the necessary programme and to recode whenever changes in software become necessary. This is a costly service to buy in, so only manufacturers like SUEZ with in-house code writing specialists and a commitment to keeping machine software up to date will consider it.
Conserving energy, water and costs in the lab
With innovative membrane technology water recovery rates can be as much as 50 percent, allowing for significant net gains to be made in reducing overall water footprints. Advances such as the intelligent standby mode also impact on electricity bills and energy consumption. Combined, innovations such as these can achieve savings of around £100 per month for a typical clinical laboratory. With results such as these and at a time when there’s pressure to conserve every penny, choosing a sustainable ‘eco’ option for a clinical water purification system seems like an obvious choice.
