THE PROBLEM Sewer odour and septicity problems are generally caused by the presence of significant concentration of Hydrogen Sulphide gas. This gas is produced by micro-organisms, which metabolise Sulphates which are present in sewage - at times and in places where there is no free Oxygen available.

Prevention/correction methodologies generally rely on either ensuring that the Oxygen supply does not become depleted (eg. Oxygen injection; Nitrate dosing), or precipitating the Sulphur out of solution (eg. Iron Salts).

Typically stated objectives (and contractual performance criteria) are to maintain a positive Dissolved Oxygen concentration, and near to zero dissolved Sulphides in the sewage, and near to zero Hydrogen Sulphide gas at a given location.

This approach is extremely conservative, very costly, although willingly undertaken, often out of a desperate need to eliminate a problem (ie. odour complaints).

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