Most commonly, for the quantification of the dry weight of the precipitate in terms of weight analysis, the indicators of total dry solids and undissolved substances at 105 ° C are used.
In order to determine the energy potential of the sludge, a link can be made between the expression of the organic matter concentration (COD) and the chemical energy contained in the substances, based on the well-founded thermodynamic concept that the energy released during a chemical reaction is determined as the amount of useful energy.
It is extremely important to note the fact that 1 g of COD is equivalent to 14 Kj. This in turn allows us to define the organic matter in the sludge as a first step. We can then express the energy in the sludge and plot the COD as an energy balance, considering mathematical models based on the COD balance.
In the water sector, the transformation of sludge energy is associated with anaerobic decay. This fermentation is characterized by the fact that the end products are methane and carbon dioxide. In particular, methane cannot be further reduced and carbon dioxide oxidized, so anaerobic decay is the most complete fermentation process.