According to the provisions of the Regulation on the Use of Domestic and Urban Treatment Sludges in Soil, which was put into force by the Ministry of Environment and Forestry in 2010, the treatment sludge is dried in a drying oven to a constant weight of seventy degrees in order to prevent organic material losses. The amount of solids remaining as a result of this process is called dry matter.

According to the regulations, sewage sludges formed in treatment plants with a capacity of more than one million population must be dried to at least 90 dry matter value. However, if the enterprises producing sewage sludge prove that their use is economically and technically feasible before reaching the 90 dry matter value, it is not necessary to reach the 90 dry matter value sought by the Ministry of Environment and Forestry.

Authorized laboratories also carry out dry matter determination in soil within the framework of soil measurements and analyzes. The standards published by the Turkish Standards Institute are as follows:

• TS 9546 EN 12880 Characterization of sludges - Determination of dry residue and water content
• TS ISO 11465 Soil Quality - Determination of Dry Matter and Water by Mass - Gravimetric Method

Organic materials in the soil consist of decomposition and degradation of plant and animal residues in various geological periods and under the influence of various factors. Soils formed by humusification of organic substances are called organic soils. Organic soils generally arise by drying large swamps. These soils are fertile soils. This land is found in many parts of our country.

The reliability of the measurements and analyzes carried out by the laboratories is related to the quality of the measurements. The quality of the measurements is directly proportional to the accuracy of the measurement results. Therefore, accredited laboratories operate in accordance with TS EN ISO / IEC 17025 standard.