*Water companies face the seemingly impossible task of drastically reducing carbon emissions while consumption and quality standards are rising. Andrew Mylius makes some suggestions.*

The water industry will have a hard time meeting carbon dioxide reduction targets. The government has pledged that greenhouse gas emissions will be cut by 80 per cent on 1990 levels in the next 40 years. Yet over the same time, Britain's population is expected to grow by between 15 and 30 per cent, per capita water use is rising, and it is likely the industry will be required to meet higher quality and environmental standards. How are companies going to square the circle?

*Technical Innovations*

Major technical innovations look unlikely before 2020, and based on current technologies, an 80 per cent reduction in emissions looks almost impossible. But Ofwat's head of climate change policy, Mike Keil, points out the 80 per cent cut is not intended to be applied uniformly. "The industry and society more widely need to ask what contribution the water sector should be expected to make to the national target," he says. Whatever the figure, water companies will still have to make carbon savings.

There are a number of areas they can target.

Demand reduction. "Reducing consumer demand offers the greatest opportunity for carbon saving," says Mott MacDonald's head of water regulation, Andrew Heather. "Though the relationship between water volume and energy consumption isn't linear, if you can cut the volume by half you've got a lot less clean water to treat and distribute, and you also get a large-scale reduction in dirty water."

Education will have to play a key role in changing water use attitudes and habits. "At the moment, everybody's ignoring the costs of water to the environment," Heather says. "Droughts prove that through education you can reduce demand. The challenge is to extend that from, say, 15 per cent and sustain it."

*The Price of Water*

Alongside developing awareness of the environmental cost of water, the price of water should be adjusted to reflect it, says Mott MacDonald sustainability leader Maria Manidaki. "Seasonally variable tariffs, rising when water's scarce and demand is greatest, then falling during wetter months, might make people think more about the way they use water and its wider environmental and social impact."

This would require universal metering.

Catchment management. Ofwat has agreed funding for more than 100 projects in the upcoming asset management plan cycle, which should pave the way for far wider use of catchment management in years to come. Simple in concept but difficult to implement comprehensively, catchment management involves acting to control and reduce water pollution at source.

"If you can reduce the chemical, organic and sedimentary pollution load in water abstracted for drinking water distribution, you need less resources to treat it," says Manidaki. The challenges here include resourcing, gaining support of stakeholders, and enforcement.

*Sustainable Drainage Solutions*

Sustainable drainage solutions (Suds). By holding back rainwater run-off and allowing it to soak into the ground, storing it for use, or releasing it slowly, Suds reduce the volume of water that ends up in sewers. Wider use of Suds has been limited until now by lack of clarity about who is responsible for their ownership and maintenance - water authorities or local authorities. These issues are being dealt with in the Flood and Water Management Bill.

Operational efficiencies. Carbon cuts of up to 15 per cent are possible at wastewater treatment plants. Making pumping systems more efficient offers big opportunities, and real-time monitoring would enable treatment intensity to be adjusted according to pollution loads.

Variable standards. Some companies have been allowed to vary the quality of the treated wastewater they discharge, according to flow rates in receiving rivers and coastal bathing seasons. The Environment Agency is expected to consider more applications for variable discharge on condition that companies demonstrate that agreed seasonal quality standards can be met.

*Low Energy Solutions*

Low energy solutions. Manidaki suggests that where land is available and planning authorities permit, water companies should consider reverting to low energy traditional treatment technologies such as trickling filter beds or facultative ponds (lagoons with large surface area that enable oxygenation through surface exchange rather than forced aeration). Adoption of small-scale, low energy treatment would be aided by disaggregating water company activities. The government has said it will consider competition for wastewater treatment, which could help to move this forward.

New technologies. In the next investment period, water companies are seizing on the opportunities offered by enhanced sewage sludge digestion technologies to generate calorific biogas. This would reduce the volume of biosolid waste for disposal and fuel treatment works. Firms are looking to increase energy from biodigestion by supplementing sewage sludge with food and industrial waste.

The industry is looking for opportunities to diversify into other renewable power technologies too. Ofwat wants to see companies exploiting hydropower and, with caveats, maximising gas yield from biodigestion. Keil also welcomes companies' interest in wind energy, but insists that water customers should not be funding capital investment and protecting the companies against commercial risk.

"If they really believe wind is a good bet, it's not difficult to create a spin-off company and borrow, like anybody else," he says.

Curbing construction. "Research we've carried out shows that embodied carbon accounts for one-third of water industry carbon emissions and sometimes more," Heather says. "New assets may well reduce carbon emissions long term by reducing power consumption, but companies need to put embodied carbon into the equation and seek to minimise the impact of the construction they do."

Set alongside these carbon reduction opportunities there are also hurdles. The Water Framework Directive is driving investment in quality improvement. While no additional quality legislation is in prospect, "it's unrealistic to expect that there won't be any", says Wessex Water sustainability planning manager Dan Green.

Meanwhile, rising water consumption will be accompanied by growing volumes of wastewater requiring treatment. Higher volumes of sewage effluent relative to the receiving water flow will mean that more nutrients must be removed to maintain river quality. In areas where climate change will reduce dry weather flows the most, the problem will be acute.

Emissions will be further increased as companies build more interconnected and robust water distribution grids to deal with security of supply and low flow rivers.

Andrew Mylius is publications editor at Mott MacDonald.

Email: Andrew.Mylius@mottmac.com