Page 7 - SIMPLIFIED WASTEWATER TREATMENT FUNDAMENTALS\ Advanced Activated Sludge P3
P. 7
F:M Ratio
Food to Mass ratio measures the amount of Food (wastewater organic
content – BOD mg/L) in pounds, to Mass (mixed liquor biomass mg/L
MLVSS) pounds.
It is a common oversight within the industry to measure the ratio of Food to
Mixed Liquor Suspended Solids (MLSS). This ratio can be misleading.
The total contents of mixed liquor include Organic material (microorganisms,
nutrients like ammonia, nitrites and nitrates, phosphates, energy sources like
amino acids, carbohydrates (sugars), etc…).
However, mixed liquor also contains Inorganic material (residual grit, sand,
rags, and other inert materials).
