Webinar chat - energy neutrality in the wastewater sector on the road to climate

1. Is there any water authority using O2 from elektrolysers for green H2 for airation of active sludge tanks? this would reduce the energy use of SWTP by 50%. We are doing research at the Netherlands. any other EU-water authority?
2. What is your strategy for N2O reduction ?
3. What is the temperature difference that you create with the heat recovery from the treated wastewater?
- I don't have the exact figure here, but my understanding is about 10 C
4. Thank you for the very interesting Finland case. When you mention the % energy neutrality, do you calcultate this as a yearly average? Or is 90% of the electricity consumption directly covered with own renewables?
5. What’s the market for the biocoal? Can it be sold?
6. Have you measured the fate of PFAS in the Dehydris process? Is it decomposed, remaining in the biocoal or perhaps most probable?
7. We are starting up a comparable process in Flanders. In the view of energy neutralitity, it's better not to install Dehydris Ultra (without waste to energy plant)? Because in this case, net production of energy of the plant is higher (although, of course, a much larger amount of sludge has to be disposed of)...caught in a condensate stream.
- To be more clear: not all plants allow incineration. By using the biogas for sludge drying (HTC+dewatering), the energy can not be used for wwtp operation anymore...
8. How to mitigate N2O that comes form biological treatment?
- There are several ways. According to our experience, adding alkalinity, increasing sludge age and boosting denitrification by turning aeration off in switch zones and/or increasing the dose of external carbon work well.

9. You mentioned carbon neutrality by 2030. What solutions are you considering for neutralizing emissions from treatment, sludge and purchased equipment? Do you consider scope 3 emissions (vehicles and consumables)?
- We consider the essential consumables (such as chemicals) and external services (eg. transport of sludge). The single most important goal is to reduce N2O emissions from WWTPs. Other examples: pivoting from open windrow composting to closed-vessel composting, requiring use of biofuels in sludge and chemical transport, implementing carbon footprint calculation in procurement etc.
10. Will you use physical PPA to achieve 100% energy neutrality ? Can we include them in the numerator (renewable energy produced)?
11. What is the percentage of Electric Energy recovered via ORC?
- A bit less than 10 % of what the WWTP consumes. The maximum output is about 150 kW per engine.
12. So, the water that you discharge is 10°C lower than normal? Does that not create problems in the receiving surface water?
- No. We are discharging to the Baltic Sea, so the dilution effect is big. Also, the Sea is rather suffering from too high water temperatures due to climate change, so we are actually helping the situation.
13. Is heat recovered from wastewater going to be counted as renewable energy? Diifcult to understand from the definition in article 2 in the (renewable energy directive) directive 2018/2001.

Dear all, 

The ppts from the webinar on 05.11.24 on Meeting the challenge of energy neutrality in the wastewater sector on the road to climate neutrality are here:
www.eureau-innovation.org/library/climat...o-climate-neutrality  

Caroline