What must the VA/ALK ratio be less than to ensure proper digestion operation?

In the context of anaerobic digestion and wastewater treatment, the VA/ALK ratio is a critical parameter that helps to assess the stability of the digestion process. The ratio compares the concentrations of volatile acids (VA) to alkalinity (ALK) in the digester.

A VA/ALK ratio of less than 0.35 indicates that the alkalinity is sufficient to buffer the system against acidification. When the ratio is higher, it suggests an increase in volatile acids, which can lead to an unstable environment for the microorganisms responsible for digestion. High levels of volatile acids can inhibit microbial activity, potentially resulting in digester performance issues, such as decreased biogas production and even digester failure.

Thus, maintaining the VA/ALK ratio below 0.35 is essential for ensuring that the anaerobic digestion process operates efficiently and is resilient to fluctuations in waste feed composition. This helps prevent operational problems and supports the overall health of the microbial community within the digester.