H₂S: Where does it come from?
Hydrogen sulphide is produced by a biological reaction in the sewerage or in sewage treatment plants themselves. H₂S comes from the anaerobic (without oxygen) fermentation of organic matters found in wastewater. Inside a pipe, if there is a lack of oxygen, microorganisms feed and produce hydrogen sulphide, which smells like rotten eggs. This is called septicity, and is the cause of the H₂S and the bad odours that come with it.
Yara has developed YaraNutriox, an effective preventive solution based on nitrate salts. We work with many sewage treatment plants and industrial sites, in Europe and across the globe, which have eliminated the source of odour complaints. Learn more about the YaraNutriox process.
H₂S gas is insidious
Hydrogen sulphide is a colourless and insidious gas that forms itself under certain conditions – called anaerobic conditions or septicity – in sewage pipes and sewerage networks where there is no oxygen.
H₂S has adverse effects on health. It is very irritating to the eyes and the mucous membrane lining the respiratory tract. Above a certain concentration, hydrogen sulphide anaesthetises the olfactory nerve which means that the smell “disappears “ and the H₂S can’t be detected at all. Thus, H₂S can hit where we least expect it. For a healthy adult, the effects are lethal above 300 ppm (parts per million). Under certain conditions, in a confined space, hydrogen sulphide can kill instantly.
A Gas with Multiple Hazards:
| A toxic gas | An explosive gas | Unpredictable |
| Hydrogen sulphide is a poison that has a broad spectrum. It attacks and paralyzes the nervous system and blocks cellular respiration. At high concentrations, a single breath is deadly. | H₂S is extremely flammable. It forms explosive mixtures with air. Contact with oxidizing products can be a source of fire and explosion. | Hydrogen sulphide gas is insidious. Heavier than air, it can accumulate at low points in buildings at pumping stations and treatment plants. It forms pockets in stagnant wastewater and releases lethal amounts of gas when the wastewater is moved due to the flow in the pipes. It paralyses the olfactory nerve and thus thwarts the body’s natural protection against it. |
Corroded concrete: is H₂S the cause?
One of the characteristics of hydrogen sulphide is that it causes corrosion of sewerage and WWTP structures. In the hot and humid atmosphere of a sewage network, H₂S is oxidised into sulphuric acid. This sulphuric acid is corrosive and attacks wastewater and sewage treatment facilities. It attacks the concrete, copper, iron and silver that can be found in treatment tanks, buildings and electrical equipment. If no preventative action is taken, pipes exposed to this corrosion may eventually collapse. Corrosion particularly affects the headspace of structures in sewers or WWTPs where turbulence and effluent H₂S are at their greatest.
The speed of corrosion will depend on the extent of the H₂S formed and the level of preventative treatment. However, preventing H₂S odour problems with YaraNutriox also combats corrosion and avoids the collapse of pipes.
Fight effectively against H₂S
It is possible to prevent the occurrence of bad rotten egg smells in a wastewater treatment plant (WWTP) or sewer system. Yara has developed YaraNutriox, a process that prevents septicity caused by the lack of oxygen in the pipes of a sewer and in a WWTP. YaraNutriox is a mixture of nitrates specially developed by Yara, with proven effectiveness on hundreds of sites around the world in the fight against hydrogen sulphide. Communities throughout the world, such as York, Paris, Cologne and Montreal are benefitting from YaraNutriox treatment against H₂S.
