The SM 2540 Solids standard includes test methods for total solids, stationary and volatile solids and precipitable solids. Among these methods, the method relates to 2540D, 550 flammable stationary and volatile solids. Standard Methods is a joint publication of the American Society for Public Health, the American Water Affairs Association and the Water Environment Federation.

SM 2540D method is used for determination of total dissolved solids by using gravimetric analysis method in wastewater.

Suspended or dissolved substances found in domestic water and wastewater are called solids. After drying between 103-105 degrees, all of the remaining substances are called solids. Wastewater containing high amounts of solids adversely affect effluent quality and receiving environments in treatment plants. One of these effects is the formation of bottom sludge by collapsing in receiving environments. Therefore, the amount of solids at the outlet of treatment plants is not allowed to exceed a certain limit. It is also not possible to use water containing high solids as drinking water or potable water.

For housing and business water supply, it is important to determine the total amount of solids. When water softening is required, the choice of softening method to be applied depends on the total solids content.

Generally, gravimetric methods are used to determine the total fixed solids content. After determining the total amount of solids, the remaining material is kept in the 550 oven and the remaining material is weighed again. In the meantime, the volatile solids are evaporated.

Within the scope of chemical food analysis, total fixed solids determination studies are performed by 550 burning and gravimetric method in authorized laboratories. In these studies, standards and test methods published by domestic and foreign organizations are followed.