Sulfite ions are mostly used to control the amount of dissolved oxygen present in boilers and boiler feed water. Therefore, sulphides are present in this type of water and in the effluent of treatment plants using chlorindioxide, one of the chlorine-based disinfectants, which are not affected by sulfur dioxide and organic substances.

Excess sulphide ion, especially in boiler water, decreases the pH of the water, which increases the hardness of the water and accelerates the corrosion in the boiler.

Controlling the access of industrial wastewater containing sulphide ions to natural receiving environments such as lakes, ponds, rivers and streams is of great importance for the protection of the environment. Sulfite-containing wastewater causes poisoning to fish and plants that feed on these waters and causes the depletion of oxygen in the water.

In the accredited laboratories, the basis of the sulfide measurements carried out within the scope of water and wastewater measurements is to determine the concentration of the acidified water sample containing sulphide with standardized potassium iodide. When the sulphide is completely oxidized, free iodine is released.

During measurements, other oxidizable substances, such as sulfur and iron ions, which may be present in wastewaters, interfere with the sulfide determination and result in greater results than actual values. If nitrite is present in the measured wastewater, this time it reacts with sulfide ions in an acidic environment and leads to low results. In this case, sulphamic acid should be added to the medium and nitrite ions should be broken down. The copper ion in the medium acts as a catalyst and accelerates the oxidation of the sulphide solution. All these are the points that should be taken into consideration by measurement laboratories. In order for the measurement values ​​to be accurate and high quality, laboratories must operate in accordance with the relevant standards.

In addition, accredited laboratories from national and international accreditation organizations comply with TS EN ISO / IEC 17025 standards.