CEW investigates laughing gas emissions from WWTPs

4 Nov 2019.

In the Netherlands, lowering the CO2 footprint of the Wastewater Treatment Plants (WWTPs) is an important issue. Nitrous oxide and methane emissions make up a relatively large part of the CO2 footprint (>15%) in part because these gasses are much stronger greenhouse gasses compared to CO2. In the past years, methane detection and reduction has been investigated, and STOWA presented a report with direct measures to reduce methane emissions (STOWA 2016-09).

Nitrous oxide, however, is much more complex to measure. In a recent report by STOWA (STOWA 2019-05) the concentration of ammonium and nitride in the WWTP effluent can be a risk indicator for nitrous oxide formation. Based on this report, they presented a protocol for selecting WWTPS that are suspected of producing nitrous oxide, and included a measuring protocol.

The background of nitrous oxide formation and release in WWTPs, and especially the opportunities to reduce the release, are not well explored yet. It is not completely clear how it is possible to reduce the formation and release in the current treatment practice. Alternatively, different treatment methods might be used to reduce the nitrous oxide release, such as physiochemical separation methods. Whereas these processes might release less nitrous oxide, the comparison in terms of CO2 footprint might still be in favour of current practice.

Li terature research
CEW will perform a literature research into the formation and release of nitrous oxide in various types of WWTPs, and investigate possible alternatives to traditional water treatment.

Research questions:
• Where in the WWTP is the nitrous oxide formed and released?
• What is the difference in nitrous oxide formation between communal WWTP’s and industrial WWTP’s?
• What are alternative treatment options, and what are their pros and cons??
• What is the CO2e balance of those alternative treatment options?

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