Meeting water reduction targets
?Graham Fisher, Business Development Director at CME Sanitary Systems, looks at how greywater recycling is helping to meet the latest requirements for water conservation in buildings.
April 2010 saw changes to Part G of the Building Regulations, which covers sanitation, water conservation and safety and sets a minimum water efficiency standard for all new homes. It also allows, for the first time, recycled water to be approved for use in applications where it is not necessary for water to be treated to the same high standard as that required for drinking purposes.
This meant that recycled water and harvested rainwater could be used to flush WCs and urinals. The latest updates also introduced a new water efficiency standard for new homes of 125 litres of water per person per day.
This standard, however, is less rigorous than the higher levels of the Code for Sustainable Homes in the new build sector, where water reduction is one of the main areas where credits can be achieved. The weighting factor in the Code means that the five credits available for potable water reduction account for 9% of the total possible points score available. For example, up to five credits are available for reducing the amount of potable water used in a dwelling.
To help meet the regulations, greywater systems are being widely specified for new builds and refurbishments to achieve the water efficiency requirements, especially as such systems can be more reliable than, for example, rainwater harvesting. They are also more popular than restricted flow showers and taps, as residents now expect certain levels of luxury in the bathroom, which they may see as being compromised. With greywater systems, it is possible to retain luxury fittings in the bathroom, whilst still achieving water reduction targets.
Micro greywater recycling involves reusing bath and shower water to flush WCs. Studies show that the volume of fresh water used to flush the toilet is typically around 30% per household, which is slightly less than the volume of water available from showers and baths (approximately 33%), so there should always be sufficient water available.
Such systems are now widely used in domestic settings, as well as schools and healthcare environments.
Micro greywater systems, such as Ecoplay, use no complex filtration and are proving very popular for new builds and refurbishments.
How do they work?
Micro greywater recycling systems work by drawing waste water from baths and showers into a cleaning tank. As the water enters the system, a flow sensor picks up the incoming supply and registers the input time with the ECU (electronic control unit). At the same instant, this same sensor is instructing the ECU to activate the dosing units and injects a pre-prescribed amount of disinfectant into the incoming water to neutralise odours and maximise the longevity of the water.
As the greywater enters the floatation section of the cleaning tank, any light waste materials such as hair, oils and suds are skimmed from the surface, while heavier ones sink to the bottom.
This water, which is now cleared of its contaminants, is then transferred to the integral storage tank using gravity alone, where it can be re-used, again using gravity to flush the master toilet, whilst keeping the energy usage to as little as 13.1 kilowatt hours per year.
Alternatively, a two toilet system on the same or different floors utilises an in-line pump to transfer the water to the secondary toilet increasing the energy units to approximately 16.1 kilowatt hours per year.
It is advisable to choose simple micro greywater recycling systems, as they do not use complex filtration processes or chemical filtrations which tend to require professional maintenance contracts. However, some units do contain an antibacterial disinfectant that will need to be replaced once or twice a year dependent on usage. This maintains the highest hygiene standards and keeps maintenance to a minimum. The system recognises if the building is not in use and after an additional two hours, Ecoplay will flush, replacing the greywater stored in the cistern and the toilet bowl with fresh water.
Such systems typically have a storage capacity of 100 litres, which is sufficient for approximately 16 -20 toilet flushes and can comfortably be fitted in a ground floor cloakroom or toilet and hidden behind a decorative panel.
The occupants of a building welcome the fact that their water bills are reduced and many organisations are integrating greywater within their building, as part of enhancing their environmental credentials. Another benefit is that systems like Ecoplay can also be retrofitted in existing buildings, where a major bathroom refurbishment is taking place. There is a general consensus that in the next few years, the Government will seek to limit water use in existing buildings and this is resulting in increased interest in micro greywater recycling systems for refurbishments.
When we were developing our greywater management system, we talked to building service engineers and found that one of their concerns was ongoing maintenance. We were conscious of the need to minimise any running or maintenance issues, which is why the system does not use complex filtration processes.
As legislation begins to tighten on existing buildings, building owners and operators are taking more interest in greywater systems, as they enable them to meet future water usage requirements before they become mandatory.
As well as the obvious water saving benefits of this type of system, greywater recycling also offers excellent life time values. With an expected lifespan of at least 20 years, a typical greywater system can pay for itself in as little as six years, depending on the geographic location of the building and the prices charged by the utility company.
As many service engineers are looking at the ways they can integrate sustainable and renewable technology into their buildings, it is systems like micro greywater recycling that will ensure that the buildings of the future are more sustainable, have less of a carbon footprint and are more affordable to run in the long term.