Hydrogen sulphide, or H₂S, is a toxic gas that is often found in sewerage systems, sewage treatment works and industrial waste water treatment facilities. It develops in sewers because of biological activity in the waste water.
There are many systems to combat odour pollution linked to hydrogen sulphide. Some only mask the problem; others, such as YaraNutriox are preventive. YaraNutriox is a natural process developed by Yara since the late 1980s. It is used by municipals at hundreds of locations with hydrogen sulphide problems.
YaraNutriox is a system for preventing hydrogen sulphide and the odours it produces. YaraNutriox acts at the source of the problem and automatically injects precise amounts of specific nutrients, where and when needed, into sewerage systems or sewage treatment works. Using complex modeling and dosing equipment it ensures the optimum injection rate to eliminate odour complaints from the community, and also prevent the risk of employee or public exposure to this highly toxic gas.
In New Zealand, hydrogen sulphide (H₂S) is included in the Workplace Exposure Standards and Biological Exposure Indices for the implementation of the Health and Safety in Employment Act (1992). The National Occupational Health and Safety Advisory Committee (NOHSAC) sets Occupational Exposure Limit values (OEL) for hydrogen sulphide of 10ppm (TWA-OEL) and 15ppm (Short Term OEL).
The gas is deadly if concentrations become too large (> 1000 ppm) and its presence is usually detected by its characteristic “rotten eggs” smell. However, above a certain concentration, hydrogen sulphide anaesthetises the olfactory nerve, so that the smell cannot be detected. Hence the importance of preventive measures, such as YaraNutriox sold by Yara.