Helea®: An effective pre-treatment for advanced anaerobic digestion

Wastewater has the potential to deliver five times more energy than is required to carry out its treatment. Which means that if a wastewater treatment plant (WwTP) can fully harness its resources, it can become not just self-sufficient, but a net exporter of energy.

Many modern WwTPs already cap anaerobic digestion (AD) tanks to collect the methane-containing biogas produced when sludge is broken down. This fuel can be used on-site – to produce electricity or provide heating for wastewater treatment – or transported for off-site processing.

However, inefficient digestion can reduce biogas yield, meaning the sludge that leaves the digesters still has the potential to generate methane. When sludge is stored or spread on fields, this methane will escape into the atmosphere, where it has a greenhouse effect around 85 times more powerful than carbon dioxide.

One way for WwTPs to control emissions is by maximising the amount of biogas they capture during AD. Longer treatments or expanding capacity may help, but a growing population means that load and flow are also increasing, putting pressure on WwTPs to improve efficiency as well as capacity.

Enhancing efficiency in advanced anaerobic digestion

Helea® from Haskoning combines three processes – heating, pasteurisation, and biological hydrolysis – in one energy-efficient pre-treatment step. By breaking down the sludge more effectively, Helea® makes the methane easier to access, dramatically increasing biogas production during digestion.

Producing enough methane and heat to reuse in the treatment process is an important step in making WwTPs more sustainable. However, if surplus biomethane can be sold to the energy grid or used to generate renewable power on-site, it will further reduce a plant’s carbon footprint.

Helea® is proven to generate a ‘best-in-class’ yield of approximately 1 MWh of renewable electricity from the biogas produced from each dry tonne of processed biosolids.

Deliver additional CapEx and OpEx savings

Deployed upstream of existing anaerobic digesters, Helea® separates sludge digestion into two phases: hydrolysis and methanogenesis. This enables digesters to operate at a significantly increased organic loading rate, boosting solids destruction and biogas yield.

Even greater efficiency and operational savings can be achieved when low-carbon heat recovery systems are integrated into the process. Helea® reduces a plant’s carbon footprint through the efficient use of surplus energy as renewable power, by supplying biomethane to the grid, and through heat generation.

In addition, the process offers reduced capital costs and increased operational savings because it requires less energy for process heating and uses direct steam heating for pasteurisation.

Providing high-quality biosolids for reuse

The reuse of digestate as a nutrient-rich soil enhancer can play a vital role in increasing circularity in food production. The global market for biosolids is predicted to reach US$2.7 billion by the end of 2033.

To achieve maximum value from sludge, WwTPs can produce high-quality biosolids in addition to their biogas. By combining biological hydrolysis and pasteurisation, Helea® transforms the residual biosolids from sludge digestion into a soil conditioner that can be used safely in agriculture.

As influent quality can vary, each WwTP will need the ability to adjust parameters to maximise the potential in every revenue stream. Helea® provides complete operational flexibility to WwTPs so they can deliver enhanced biosolids for reuse, as well as increase solids destruction and biogas yields.

Helea®: Reliable, easy to operate, and safe

Compared to other pre-treatment technologies, such as thermal hydrolysis, Helea® is easier to operate and maintain. The technology also provides built-in flexibility to deal with variations in load and sludge quality, enabling WwTPs to respond more quickly to changing conditions.

Helea®’s advanced control system ensures optimum performance and enables remote monitoring. And because its continuous process has high availability, it can operate without routine plant shutdowns.

Biological hydrolysis has further advantages over thermal hydrolysis in terms of health and safety because it doesn’t require high operating temperatures and elevated pressures.

A tried and tested sludge pre-treatment

For more than a decade, Helea® has provided an affordable and sustainable route to advanced digestion. And the UK’s WwTPs were among the first to benefit.

Between 2013 and 2014, Anglian Water – who developed Helea®’s original HpH pre-treatment process for their own benefit – implemented the process at four of its sludge treatment centres. Since then, these plants have proved to be Anglian Water's most efficient and reliable treatment facilities .

Helea® is set to play an important part in water companies’ journey to net zero. Talk to one of our experts today to see how Helea® can help you generate revenue and reduce your WwTP’s carbon footprint.