Over 1000 people from 84 countries registered for the recent webinar on thermal and chemical energy recovery from wastewater. More than 50% of attendees were young water professionals. Over 100 questions were raised and discussed in a lively exchange of experiences and expectations between scientists, practitioners and students. Case studies from Denmark and Finland were presented to uncover new and emerging technologies for wastewater treatment, from heat-pumps to anaerobic digestion and incineration. These promising case studies show that there is an enormous potential in the treatment of wastewater, which can be a precious source of energy and revenue.

The webinar’s main goal was to provide food for thought on how resource recovery could contribute to facilitate the adoption of wastewater treatment in regions where wastewater is still discharged untreated into surface waters. This way, what can be considered as a precious resource, becomes a dangerous pollutant.  Untreated wastewater is not only a missed opportunity, but also a real threat to human health, biodiversity and aquatic life in rivers, lakes and oceans.

In March 2021, the UN Environment Programme, the African Development Bank and Grid Arendal presented the result of a multi-annual joint effort: The Sanitation and Wastewater Atlas of Africa.

The report emphasises that 750 million people, 69% of the total population in Africa, do not even have access to basic sanitation services. Achievement of SDG 6, halving the number of people without access to basic sanitation, is not on target for Africa, except for the countries of North Africa that increased the population gaining access by 41% since 1990. Almost no progress was made in sub-Saharan Africa.

The overwhelming interest in energy recovery and the robust evidence for energy positive sewage treatment plants provided by practitioners in charge of mid-size (300,000 PE) and larger (1.200,000 PE) wastewater treatment plants in Europe may contribute to a re-assessment of the options for economically viable wastewater treatment plants in low-income countries.

Such plants could provide energy for heat and/or air-conditioning services from the treatment of wastewater of all citizens, thus generating revenue and removing the need to collect fees for purification from citizens that cannot afford them. Next steps should focus on carrying out a high number of feasibility studies in countries with a low rate of wastewater purification, regardless of the size of plants, in many fast-growing megacities such as Nairobi, Lagos, or Kigali, each with many millions of citizens in need of wastewater treatment.

However, access to sanitation and wastewater treatment are not the only, and possibly not even the most severe problems related to water in Africa. Approximately 60% of African countries suffer from scarcity and severe water stress, indicating a strong need for water safety planning and climate resilience, and also water re-use, which will be subject of the next Resource Recovery webinar scheduled for early July 2021.

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One third of the global population has no access to toilets or latrines, while six in 10 do not have access to safely managed sanitation facilities. Furthermore, 80% of wastewater from human activities is discharged into rivers and seas without any pollution removal, according to the latest data[1].

Yet by 2030, for compliance with SDG6, access to safely managed sanitation should be made available for all (target 6.2) and the volume of untreated, discharged wastewater should be halved (target 6.3).

These alarming facts make it hard to believe that SDG6 targets can be achieved in less than 10 years, especially given the negligible progress achieved in the past  years (fig. 1). Significant progress is still required, especially in the field of wastewater management.

Current sewage treatment systems consume large amounts of energy, estimated at between 1% and 3% of global energy output. While over 20% of municipality electrical energy consumption on public utilities is used for sewage plant operations.[2]

High capital expenses and high operational costs are major barriers to the implementation of sewage systems, particularly in low-income countries. In addition, full implementation of currently prevailing technologies would significantly increase the negative climate impacts of wastewater treatment, with a notable rise in energy consumption.

Circular economy

Alternative, more affordable and sustainable pathways are possible. In the next IWA webinar “Circular Economy: Tapping the Power of Wastewater” on 23^rd February at 15:00 CET, we will demonstrate alternative solutions to reduce the energy consumption of wastewater treatment.

Two case studies of energy-positive wastewater treatment plants will be presented, namely the Copenhagen (Denmark) and Turku (Finland) plants, which use systems for harvesting the intrinsic thermal and chemical power of wastewater.

Real-life cases show that just by converting the chemical energy, twice as much energy can be supplied than consumed. While by utilising both the thermal and chemical energy, energy supply can be nine times higher than consumption. Both pathways have their benefits and limitations that need to be considered when planning facilities. However, the best practice scenarios exist for application in smaller and larger sewage plants under different, albeit moderate, climatic conditions[3].

In addition to the case studies outlined by practitioners in the webinar, students will also present their visions for energy recovery from wastewater. At the end of the presentations, a Q&A session will be held, giving the audience the opportunity to engage with the experts.

Don’t miss this opportunity to learn from real life experiences around tapping the power of wastewater. This free webinar is a practical opportunity that will help you shape a water and energy-wise world for the future!

We invite interested participants to reflect on two crucial questions which will be discussed:

• How can we implement the presented technologies under all climatic conditions?
• How can we use the supply of energy, cooling and heating to finance wastewater treatment in low-income countries?

We look forward to seeing you at the webinar on 23rd February, 15:00 CET – sign-up here to reserve your place.

[1] https://www.un.org/sustainabledevelopment/water-and-sanitation/

[2] Capodaglio and Olsson, 2019, Energy Issues in Sustainable Urban Wastewater Management: Use, Demand Reduction and Recovery in the Urban Water Cycle, Sustainability 2020, 12, 266; doi:10.3390/su12010266

[3] Hao et al., 2019, Energy recovery from wastewater: Heat over organics, Water Research, Volume 161, 2019, Pages 74-77, ISSN 0043-1354 https://doi.org/10.1016/j.watres.2019.05.106