Carbon reduction: New challenges for the water industry

Meeting UK carbon reduction targets looks a tough challenge for the water and wastewater industry. To help slow the pace of climate change, the government has pledged that emissions of greenhouse gases will be cut by 80% CO2 equivalent – measured against 1990 levels – within the next 40 years.

Yet over the same time Britain’s population is expected to grow by anywhere from 15% to 30%, per capita water use is rising, and it is likely the industry will be required to meet higher quality and environmental standards – all driving up energy consumption. How are companies going to square the circle?

Seizing opportunties

Opportunities to cut carbon already exist in the form of demand reduction, improved design, adoption of new technologies, operational improvements, better management of catchments and drainage systems, and wider use of renewable energy.

But, warns Ofwat head of climate change policy Mike Keil, “looking at the next five to 10 years you can say with some certainty there won’t be a technical revolution. Certainly there’ll be innovation contributing to carbon reductions, but not a huge step change.”

“The industry and society more widely need to ask what contribution the water sector should be expected to make to the national target.”

Mike Keil, Ofwat head of climate change policy

Beyond 2020 it is quite possible there will be major breakthroughs as research and development bears fruit and new technologies come to maturity.

Based on current technologies, though, an 80% reduction looks difficult, verging on impossible, to attain.

“The industry and society more widely need to ask what contribution the water sector should be expected to make to the national target,” Keil urges, pointing out that the 80% cut is not intended to be applied uniformly.

“It’s important that nationally we pursue the most cost effective route rather than demanding the same cut across the board. We want water companies to play their part in reducing emissions but, while it may be laudable for them to aspire to the national target, we need to be pragmatic.

“The challenge for our sector is to understand what that means. It’s not sensible to commit without more exploration and analysis of whether it is possible.”

Eight ways of cutting carbon:

1) Demand reduction

“Reducing consumer demand offers the greatest opportunity for carbon saving,” says Mott MacDonald 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.”

Can a 50% demand reduction be achieved? Water saving devices such as low water shower heads and taps are up to 80% more efficient than their standard counterparts.

“Seasonally variable tariffs might make people think more about the way they use water and its wider environmental and social impact.”

Maria Manidaki, Mott McDonald sustainabiliy leader

Education will also 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% and sustain it.”

Alongside developing awareness of the environmental cost of water, the price of water should be adjusted to reflect it, argues 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.”

2) Catchment management

Ofwat has agreed on over 100 projects in the upcoming AMP 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,” summarises Mott MacDonald sustainability leader Maria Manidaki.

Effective catchment management often involves looking at land use on a field by field basis to determine the sources of different pollution types. Challenges include resourcing, gaining support of stakeholders, and enforcement.

3) SUDs

Sustainable drainage solutions – SUDs – offer a means of reducing the volume of wastewater needing treatment.

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 over who is responsible for their ownership and maintenance – water authorities or local authorities.

The government’s forthcoming Floods and Water Management Bill looks set to make SUDs mandatory on all new developments, assigning responsibility for their upkeep and performance to local authorities.

4) Operational efficiencies

A review of wastewater treatment plants carried out by Mott MacDonald has revealed opportunities for cuts in energy and carbon emissions of up to 15%.

These include installing real time monitoring, enabling treatment intensity to be adjusted according to pollution loads.

Pumping efficiency can be gained by improving maintenance, replacing worn or poorly fitting impellers, selectively upgrading equipment, taking full advantage of gravity where opportunity exists, reducing pressure in pumping systems when practicable and scheduling pumping to match demand.

5) Variable standards

Some companies have been allowed to vary the quality of the treated wastewater they discharge. During summer and dry weather periods, when flow rates in receiving rivers are low and people are swimming in the sea, maximum treatment standards have to be met.

However, standards are relaxed when rivers are in full flow, providing greater dilution, or when coastal bathing has ceased.

New Environment Agency guidance for the water industry on reducing carbon emissions is due for publication in late October. It is expected to indicate the Agency will consider more applications for variable discharge on condition that companies are able to demonstrate that agreed seasonal quality standards can be met.

6) 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. Much investment to date has been driven by the desire to realise scale economies measured in terms of asset numbers and manpower, resulting in large-scale, centralised treatment operations.

7) 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 and reduce the final volume of biosolids waste for disposal.

“By using biogas to drive combined heat and power engines, enhanced biodigestion offers potential to make sewage treatment works energy self-sufficient.”

Andrew Heather, Mott McDonald head of water regulation

“By using biogas to drive combined heat and power engines, enhanced biodigestion offers potential to make sewage treatment works energy self-sufficient,” Heather says. Some are also planning to clean-up biogas so that it can be used as a vehicle fuel or sold into the national gas grid.

Companies are looking to increase energy from biodigestion by supplementing sewage sludge with food and industrial waste.

Water companies are looking for opportunities to diversify into other renewable power technologies. Ofwat wants to see companies exploiting hydropower and, with caveats, maximising gas yield from biodigestion.

8) Curbing construction

“Research we’ve carried out shows that embodied carbon accounts for a third of water industry carbon emissions and sometimes more,” Heather says.

“It’s extremely important that water companies consider this when planning investment aimed at reducing their carbon emissions.

“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.”

Carbon reduction hurdles

The European Union’s 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”, comments Wessex Water sustainability planning manager Dan Green.

Meanwhile, rising water consumption will be accompanied by growing volumes of wastewater requiring treatment and return to the environment.

“An increase in treated water volumes, especially in water stressed areas, is likely to lead to a proportionately greater increase in greenhouse gas emissions.”

Andrew Heather, Mott McDonald

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.

The increase in power and chemical consumption with increasing effluent quality is non-linear, Heather comments. “Emissions have increased significantly in the last 10 years as result of quality drivers. An increase in treated water volumes, especially in water stressed areas, is likely to lead to a proportionately greater increase in greenhouse gas emissions.”

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

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