World Water Day 2017: A Perspective on Wastewater and Domestic Use

World Water Day 2017: A Perspective on Wastewater and Domestic Use

Household water consumption requires the abstraction of water and treatment of that water to a high quality standard for human consumption. For certain domestic purposes (e.g. toilet flushing) this standard of water treatment is not required resulting in unnecessary wastage of water resources and energy.

In the UK, the average water use per person per day is already less than many of our closest European neighbours. The wastewater derived from this consumption is disposed of as either blackwater (derived from sewerage) or greywater (derived from plugholes, washing machines and drainpipes) first to treatment units and then to the environment.

In the UK 96% of our tap water is supplied by groundwater and surface water abstractions. The Environment Agency recognises that some of these abstractions are unsustainable, or potentially damaging to the environment, and are looking at several options, including altering abstraction licenses to work towards restoring sustainability.

At Wardell Armstrong, we deal with abstraction licences and environmental permits and the environmental impact assessments required to support these applications. In recent years we have seen growing pressure on developments to increase the level of environmental assessment undertaken to support these applications. In 2016, we were involved in a public inquiry on behalf of a client for a housing development and in respect for a groundwater abstraction. We successfully demonstrated the increase in groundwater abstraction would not impact nearby internationally recognised wetland habitat.

Water supplied to houses in the UK is treated to high standards to make it suitable for human consumption (known as potable water) and used for this purpose as well as for flushing toilets, filling baths and washing clothes – uses which do not require such stringent quality. Is this an acceptable use of this precious resource?

Currently standard practice in the UK is to supply domestic properties with potable water only. The UK government stipulate in Part G of the 2010 Building Regulations that newly built domestic properties internal water usage is limited to 120 litres per person per day (L/p/d) and is roughly used in the following ways.

This means that of the high quality potable water that enters our home only about 20L/p/d is actually required to be potable quality. Yet we are discharging nearly 40L/p/d as blackwater (sewerage) and 80L/p/d as greywater (relatively clean water from baths, sinks, washing machines etc.). Clearly potable water (drinking water) makes up a small percentage of total domestic use, why then is all water potable used in the home of potable quality? How can we reduce the amount of wastewater we generate?

Some housing developers are already taking steps in the design of developments to reduce both water consumption and production of wastewater. To meet the voluntary 2007 Code for Sustainable Homes, house builders must now restrict water consumption to 80L/p/d. To do this the build might include a water re-use system for collected rainwater to be used in toilet flushing and washing clothes or a greywater recycling system. Poundbury, located near Dorchester on the land of the Duchy of Cornwall, included 11 ecohomes with rainwater collection systems to be used in toilets and washing machines. More new ecohomes are now planned given the success of the original 11. Taylor Wimpey fitted ecoplay greywater management systems to their homes to allow bath and shower water to be used for toilet flushing. These, and many other schemes are following voluntary codes but should these codes be voluntary?

In their 2008 white paper on water strategy the UK government stopped short of enforcing rainwater or greywater recycling systems on new builds citing the risk of cross contamination with potable water. Yet in Australia and America, where water scarcity is an issue in certain states, legislation and incentives actively encourage the use of greywater recycling systems in domestic properties. Should our government go further with the aim of reducing abstractions and wastewater by insisting that alternate water supply and re-use options be considered in all new builds?

Some incentives do already exist for house builders, and other companies, which pay income or corporation tax in the form of the Water Technology List (WTL). For companies looking to purchase new equipment such as toilets if a sustainable choice is made the full cost of the purchase can be deducted from the company’s profits before tax is taken into account. These water saving devices can include combined sink and toilet combos (where the sink drains its grey water into the toilet cistern to be used on the next flush) which are common in Japan but are not readily available here (yet!) and can save 50% of the water used by a standard toilet (reducing the water consumed and wasted from this activity to 16L/p/d). Or what about replacing water washing machines with bead washing machines (already on trial in hotels and laundries in the UK and shortly to come into production for domestic use) which use 60% less water and further reduce the wastewater produced in a house by 15L/p/d). However, where housing is considered the housebuilder receives little benefit from a scheme offering tax breaks for installing water saving devices with the ultimate saving being accrued by any future owner with reduced water bills.

With the government committing to building at least 1 million new homes over the next 3 years, there is a fantastic opportunity for the long awaited, housing expansion to herald an age of water conservation.

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