Hydrogen sulphide

Hydrogen sulphide (H₂S) is a toxic gas which causes major health and corrosion problems for both the wastewater and oil & gas industries. As a leading provider of nitrate products, Yara has solutions for preventing the formation of and removal of H₂S from wastewater and oil & gas installations.

The presence of hydrogen sulphide (H₂S) in wastewater and sludge occurs in septic conditions. Septicity is a result of anaerobic bacterial activity due to the absence of oxygen or nitrate.  As well as being corrosive to metals and concrete and reducing efficiency of water treatment, H₂S can cause serious damage to eyes and respiratory passages and even short exposure to high concentrations can result in brain damage or death. The solution to this problem is Nutriox.

Nutriox is a natural biological method of preventing septicity through the removal of H₂S with a controlled dosage of nitrate. Nutriox works by causing a change in the microbial population in the water. It supplies nitrate to the bacteria present so that carbon dioxide and nitrogen gas will be formed and any H₂S already present is oxidized back into harmless sulphur or sulphate.

An optimal dosing of Nutriox completely removes any existing H₂S and continued use prevents any future hydrogen sulphide formation. The right level of Nutriox is found by using our process control system and dynamic dosing model so that the right amount of nitrate is applied and none is left over in the environment.

Specially tailored to the needs of the oil & gas sector, Yara has developed a range of concentrated liquid and dry PetroCare nitrate products.

Souring treatment

Reservoir souring can be caused by the activity of sulphate- reducing bacteria (SRB) that produce H₂S. PetroCare is a concentrated water-based nitrate formulation designed for delivery to the reservoir through dosing into the injection water stream. Dosing of nitrate maintains a stable environment for the nitrate-reducing bacteria (NRB) community which competes with the sulphate- reducing bacteria that cause souring.

Ballast- and oil-polluted water

In the same way that Nutriox is used in the wastewater industry, PetroCare can be used in the oil sector.  Oil terminals and oil refineries receive and handle large quantities of ballast water or other oil-polluted water, for treatment and oil recovery. Toxic H₂S is often found in this water, formed by the decomposition of organic material, causing unpleasant odour and representing a health risk. Conventional chemical treatment of hydrogen sulphide may produce large quantities of corrosive sludge, but PetroCare eliminates odour and reduces health risks - without the generation of sludge - in one simple process. The PetroCare  process uses a nitrate salt to convert up to 95 per cent of the sulphides and organic materials into non-harmful substances like sulphur, sulphate, nitrogen gas and carbon dioxide, markedly increasing the quality of the recovered oil.