Water & Wastewater Treatment

20 | june 2014 | WWT | www.wwtonline.co.uk Project focus: Nitrous emissions monitoring determined the yearly emissions for methane to be approximately 350 tonnes, and about 134 tonnes for nitrous oxide. Therefore, the emissions per cubic metre of wastewater equate to 3.5 g and 1.34 g of methane and nitrous oxide respectively. Precious little data has ever been published on the GHG emissions resulting from wastewater treatment. According to the plant at Viikinmäki, it is the only facility of its type in the world undertaking monitoring of this ilk. As a consequence, any results published are certain to be of huge industry interest. However, just imagine if this process could be put into reverse, using gaseous emissions data to control and refine the treatment process – the benefits to the wastewater sector would be little short of enormous. issues may indicate concerns that could help bring about better process control, but more scientific research is required that deliberates the destiny of nitrogenous compounds beyond simply those contained in the wastewater," states Heinonen. "Yes, the extraction of nitrogen from wastewater is an important goal, but if the outcome is high N 2 O emissions, the process may require managing in a different way." For now, the Viikinmäki wastewater treatment plant, which is the biggest in Finland processing circa 270,000 m³ of wastewater a day, is proving a beacon of excellence in monitoring GHG emissions to help Helsinki tackle climate change. Monitoring has been in place at the facility since 2007 following the implementation of the European Regulation on Pollutant Release and Transfer Register (E-PRTR). Initially, Viikinmäki modelled its yearly gas emissions by analysing grab samples. However, the facility took a step forward by hiring a portable multi-gas FTIR (Fourier Transform InfraRed) from Gasmet to assess emissions in more detail for research purposes. The results proved interesting enough for the plant to purchase a continuous emissions monitoring system (CEMS) from Gasmet in late 2012; technology that was selected due to its potential to monitor multiple gases simultaneously. "The system has performed admirably with the need for hardly any maintenance," says Heinonen. "Only a few minutes each day is required for zero point calibration with nitrogen. Furthermore, the process is fully automated. Water vapour calibration is performed once every year at the bare minimum, but in typical circumstances no other calibration is required." Leveraging the data collected since the CEMS was installed at the end of 2012, Heinonen has "The system has performed admirably with the need for hardly any maintenance" Mari Heinonen Process manager Viikinmaki plant • Perspectives The plant "We knew that Gasmet were not specialists in the wastewater industry per se, but they were clearly specialists in measurement. In some respects, the project is easier than many of the industrial applications with which they are familiar. For instance, in an underground plant such as Viikinmäki, the air temperature is cool and fairly consistent, which is obviously vastly different to a number of industrial applications where heat is a primary and o en fluctuating factor. "Gasmet were very professional and pro- vided excellent advice throughout the project, particularly when we first commenced the measurements. Today the work has become a normal part of opera- tions at Viikinmäki." Mari Heinonen Process manager Viikinmäki plant of HSY The supplier "In all honesty it was quite a straightforward project. The tempera- ture underground at Viikinmäki is stable and the air is clean and benign. This is in stark contrast to some of the highly corro- sive atmospheres we normally encounter for gas analysis. It proved a successful project and there is some hope that the same or a slightly modified solution could be used elsewhere in wastewater plants that don't have single point ventilation stacks." Antti Heikkilä Senior manager Gasmet Europe OY Results from a portable multi-gas FTIR proved in- teresting enough for the plant (above) to purchase a continuous emissions monitoring system (CeMS) from Gasmet in late 2012 (top); technology that was selected due to its potential to monitor multiple gases simultaneously.

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