Sewage gas / biogas quantity measurement in wastewater treatment

Process data

Measuring task: Flow velocity for determining flow rate

Measuring point: Directly at the digestion tower’s exit and on the other side before the combined heat and power plant and before the flare

Measuring range: Up to 40 m/s

Process pressure Atmospheric

Process environment ATEX Zone 1

Process: ATEX Zone 0

Application

Anaerobic degradation processes happen in the digestion tower during wastewater treatment in a sewage plant, causing biogas (also sewage or fermentation gas) to arise, which mainly consists of methane and carbon dioxide.

Exact measuring of biogas quantity is one oft he most challenging applications in flow measuring technology. Biogas is very moist, tends to condensate and is particle-laden. Its composition varies and is quite aggressive. Combined with air it can turn into explosive mixtures which is why it’s important to take according safety measures. Applied instruments have to be certified for the defined ex zone

Fermentation gas is measured directly at the digestion tower’s exit and on the other side before the combined heat and power plant. Flow rate towards the flare is also partly measured.

Measuring flow rate at the digestion tower and before the combined heat and power plant

Sewage plants are a pivotal part of our wastewater treatment. Processing requires a lot of energy mainly for the biological treatment processes (ventilation). Municipal sewage plants are the greatest consumer of energy with about 20 % of the entire municipal use. There’s great potential for possible savings. Part of the required energy can be self generated in the sewage plant with the sewage gas from wastewater treatment.

How is fermentation gas created from sewage sludge?

Sewage sludge is collected in the digestion tower. Bacteria decompose it in a anaerobic degradation process (without oxygen) causing different gases in different amounts to occur.

Biogas, sewage gas, fermentation gas

are different names for the created gas in a digestion tower. Depending on the sewage sludge’s composition and the envorinmental circumstances each gas has its own consistency and therefore also another density. Main components are methane, carbon dioxide and hydrocarbon.

Methane is flammable and there for ideal for energy production. It is fed to a combustion engine which in return creates electricity and as well as heat. The heat can then also be further used energetically.

Making the measuring of sewage gas quick

For short term measurements to check the current status of a plant at a certain point our mobile sensor with a handheld device is the perfect option. The system is also available for ATEX zone 1.