Wastewater treatment plant monitors greenhouse gas emissions

A large underground wastewater treatment works is using a Gasmet FTIR gas analyser to continuously monitor the levels of pollutants, such as greenhouse gases (GHGs).

The plant in Helsinki, Finland, will be one of the first to measure the gaseous emissions from wastewater treatment processes as the focus usually lies on regulatory monitoring the quality of water emissions from such facilities.

It will use a Gasmet multigas FTIR (Fourier Transform InfraRed) analyser, which will allow it to measure the effects of the process on the level of emissions of GHGs such as carbon dioxide, methane and nitrous oxide. This will also give the team insight into what happens to nitrogenous compounds in the wastewater stream. 

The Viikinmäki wastewater treatment plant in Helsinki was built in 1994 to process wastewater from both domestic (85 per cent) and industrial (15 per cent) sources. However, with the temperatures in the area often well below freezing, it was built almost entirely underground to protect it from the hostile temperatures.

Constructing buildings underground is a common practice in Nordic areas as it offers a number of other advantages, such as land availability above the plant and the provision of stable conditions for process control and odour management.

The Viikinmäki plant is the largest wastewater treatment facility in Finland, handling approximately 270,000m³ of wastewater per day, which amounts to about 100 million m³ per year. 

All wastewater from the facility complies with the Finnish Wastewater Discharge Permit, which is stricter than the continent's EU Water Framework Directive for levels of nitrogen removal, phosphate content, and suspended solids.

Mari Heinonen, process manager at Viikinmäki, said: “The gas emissions data were very interesting but they were not representative of the annual emissions, and posed more questions than they answered. 

“We therefore purchased a continuous emissions monitoring system (CEMS) from Gasmet, which was installed in late 2012 and we now have our first full year’s data for 2013."

She added that very little data has been published on the GHG emissions of wastewater treatment, making Viikinmäki the only plant in the world conducting this type of monitoring.