Determination of volatile matter reduction in sludge is complicated because of the changes occurring during sludge digestion.

The calculation used to determine percent volatile matter (VM) reduction is

[%VM_in – %VM_out] X100

% of Volatile Matter Reduction (VM)    = ——————————-

[%VM_in – (%VM_in X % VM_out)]

Using the digester data provided below, Determine the percent volatile matter reduction for the digester.

Raw Sludge Volatile Matter = 72%; Digested Sludge Volatile Matter = 51%

According to the afore said formula, % VM (reduction) =59%