At the leading edge of sewage biogas - now and a century ago

In the city which built the UK's first anaerobic digester in 1895 and had sewage-gas street lighting around the 1900s, today's state-of-the-art sewage biogas analysis equipment is monitoring today's biogas at South West Water's Countess Wear Sewage Treatment Works in Exeter.

On watch
Countess Wear's sludge reception centre serves more than 200,000 people with an additional sludge imports from surrounding satellite works. From two anaerobic digesters biogas fuels four 165kW MAN CHP engines generating electricity-to-grid and heat, of which much is used on site. Monitoring the valuable biogas before it reaches the CHP engines is a Geotech AEMS static biogas analyser. Fully automatic, it is set to check the biogas concentrations every 10 minutes (24/7/365) and analyse methane (CH4), carbon dioxide (CO2), oxygen (O2) and hydrogen sulphide (H2S). Automatically it securely stores and transmits the data to the plant's SCADA (see screen on PDF contact sheet) and from there the data is reported to ACOM.

Data on tap
With its Geotech AEMS unit, South West Water retains its own set of data as the AEMS unit stores audit-trailed readings/data sets for well in excess of six months. The data can be viewed on-line with the password-protected Geotech AEMS Data Centre software globally from any PC downloaded to spreadsheets. Using the AEMS Data Centre, operators can remotely remove data from the on-site AEMS flashdisk memory once received by the AEMS Data Centre so the in-field unit need never reach a data capacity limit.

Operating since spring 2010 the Geotech AEMS equipment is providing South West Water with essential data on the relationship between methane and carbon dioxide. Periodic servicing of the analysers sensors will be easily handled with a 'hot swap' loan sensor unit which on-site staff will change in moments between readings. With no interruption to biogas analysis, the AEMS unit will continue to measure, monitor and analyse sewage sludge biogas in its high tech way in the city that was the UK's launch pad of anaerobic digestion more than one-hundred years ago. More:

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