What is the typical range for VAs in a primary digester?

In a primary digester, volatile acids (VAs) serve as indicators of the degree of fermentation occurring during the anaerobic digestion process. The typical range for volatile acids in a primary digester is generally recognized as being between 50 to 300 mg/L. This range reflects a healthy balance in the digestion process, indicating effective microbial activity that breaks down organic material while not overwhelming the system with excessive acid production.

Beyond this range, particularly at levels exceeding 300 mg/L, there might be concerns about process stability and potential inhibition of methane-generating microorganisms. Understanding this typical range assists operators in monitoring the digestion process and making necessary adjustments to maintain optimal conditions for anaerobic digestion.