Water is vital to our daily lives, both for personal and domestic use and industrial/commercial applications. Whether a facility focuses on the production of clean, potable water or treating effluent, Crowcon is proud to serve a wide variety of water industry clients, providing gas detection equipment that keeps workers safe around the world.
Gas detectors must be chosen to suit the specific environment in which they operate. The water industry frequently involves wet and dirty environments, with multiple toxic and flammable gas hazards and the risk of oxygen depletion.
European Commission Directive 2017/164 (EU Directive 2017/164) issued in January 2017, established a new list of indicative occupational exposure limit values (IOELVs, as the directive calls them). The list includes carbon monoxide, sulphur dioxide, hydrogen cyanide, manganese, diacetyl and many other chemicals. Member states were required to enact the relevant laws, regulations and administrative provisions to comply by late August 2018.
Typical processes and associated gas detection issues
The pipelines used to transport the water require regular cleaning and safety checks; during these operations, portable multigas monitors are used to protect the workforce. Pre-entry checks must be completed prior to entering any confined space and commonly O2, CO, H2S and CH4 are monitored
Confined spaces are small, so portable monitors must be compact and unobtrusive for the user, yet able to withstand the wet and dirty environments in which they must perform. Clear and prompt indication of any increase in gas monitored (or any decrease for oxygen) is of paramount importance – loud and bright alarms are effective in raising the alarm to the user.
The preliminary treatment process removes debris. Pumping stations and lift stations are usually unmanned and designed to handle raw sewage that is fed from underground gravity distribution pipelines.
Commonly monitored gases include O2, H2S and CH4 and, depending on the site, other gases may form part of the overall requirement.
Activated sludge is transferred to anaerobic digesters, where it is mixed with a different culture of micro-organism, which thrives in an oxygen-deficient environment and further breaks down the sludge into biogas. This process takes 20 to 30 days.
Biogas is high in CH4 (54%) and CO2 (40%), but it also has over 3000 ppm of H2S. High levels of H2S can cause corrosion and mechanical failure in generators, so biogas must be treated before it can be used as a source of energy.
Two different types of gas sensor are used to monitor the biogas – infrared for methane and electrochemical for hydrogen sulphide. The methane measurement is in the range 0-100% by volume and is continuous.