Disruptive Technology for Water: Energy

July 6, 2021 Categories: Environmental - Opinion Piece
HRS Digestate Pasteurisation System (DPS) - Agri-Gen

In his final blog on how disruptive technologies can overcome serious challenges faced by the water industry, Matt Hale, HRS Heat Exchangers’ International Sales & Marketing Director discusses the important of energy efficiency and generation.

While anaerobic digestion is widely recognised as a water treatment technology around the world, its capacity for energy generation (either through the use of combined heat and power production or to produce sustainable biomethane gas) is less well developed.

Ambitious goals for sustainable development will mean that wastewater treatment plants (WWTPs) will need to achieve net zero carbon balances by 2030. Achieving this will require recovery of the energy contained in the incoming wastewater streams and using this to provide the heat and power necessary for wastewater treatment and solids handling. It has been estimated that at present, most WWTPs are capable of producing 20 to 25% or their own energy requirements in this way².

Therefore, increasing energy production at WWTPs will be critical to making the sector self-sufficient in terms of energy. But on its own it is unlikely to be sufficient to meet the net-zero goals. Reduced energy consumption through the use of new and more efficient processes will also be required. Sludge processing and energy efficiency are intrinsically linked. For example, digestate and sludge concentration using equipment such as the HRS DCS is a more efficient and sustainable alternative to traditional drying methods.

The HRS DCS uses evaporation to reduce the overall quantity of digestate or sludge by 60-80%, greatly reducing associated storage requirements and transport costs. The system includes measures to retain the valuable nutrients while the evaporated water can be condensed and reused. In many cases the captured water is added back to the feedstock making the entire process almost self-sufficient in terms of water use and eliminating liquid discharges from the plant. After concentration, the treated digestate can contain up to 20% dry solids, making it much easier to transport and handle, and as much heat as possible is recaptured and re-used in the process, making it more energy efficient than alternative treatments.

Where sludge or digestate requires pasteurisation, for example so that it can be used as an agricultural biofertiliser and soil conditioner, the 3 Tank Batch Sludge Pasteuriser System from HRS uses up to 70% less energy than traditional technologies. The system works on a three-tank principle: while one tank is being filled, the second tank holds the digestate above 70°C, at the same time as the third tank is being emptied. Again, heat and energy recovery are maximised to increase the overall process efficiency.

 

¹ https://www.theukwaterpartnership.org/wp-content/uploads/2019/12/UK-Water-Partnership-Digital-Water.pdf

² Ver: Voutchkov, N.: Disruptive Innovation in the Water Sector. https://thesolutionsjournal.com/2020/05/14/disruptive-innovation-water-sector/

³ McKinsey Global Institute: Smart Cities: Digital Solutions for a More Liveable Future. https://tinyurl.com/y4nexe4t

 

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