Anaerobic Digestion Real-Time VFA and Toxicity Event Monitoring
Woodard & Curran, a leading water and environmental consulting firm, provides wastewater treatment operations to over 300 industrial clients across the U.S. including facilities that utilize anaerobic digestion (AD) to process industrial effluents.
Similar to other AD facilities, they face the common challenges of feedstock variability and unknown wastewater composition plus potential quaternary ammonium cations (QACs or Quats) contamination disrupting biological processes and impacting digester performance and output.
Their operations teams have been seeking reliable sensors to monitor the ongoing health of anaerobic digestion processes, as the lack of effective sensors makes it difficult to detect issues early to avoid operational downtime and effluent breakthroughs.
Deployment
One of Woodard & Curran’s managed AD facilities in the food and beverage industry consists of two digesters operating in parallel, each with a total liquid volume capacity of 1.45 million gallons and a biogas production capacity of 400-708 cubic feet per minute. Two Sentry systems were installed on the recirculation line of each digester to monitor consumable Volatile Fatty Acids (VFAs) in real time, something that wasn’t possible before.
Results and Values
Benchmarking tests demonstrated strong correlations between the Sentry sensor-gathered signals, laboratory measured VFA concentrations, and biogas production. These correlations validated the accuracy of the Sentry sensors in monitoring consumable VFAs and the overall biological health of anaerobic digestion processes.
The reliability of the systems was further proven when Sentry signals detected high loading events. Investigations revealed that 1,000 gallons of chocolate syrup had been dumped into the systems, causing significant spikes in organic load.
By quickly identifying these events as they happen, operators were able to respond proactively avoiding potential system disruptions.
These incidents built operator confidence in the Sentry sensor system validating their use as a unique, reliable tool for continuous, real-time monitoring and informed process control in anaerobic digestion.
Beyond the Sentry sensors providing high VFA alerts utilized to effectively and instantly detect toxicity events, they also guided operations teams on Chemical Quat Binder dosing. These interventions stabilized the digesters and brought VFA levels back to the desired range.
Figure 1 – High VFA in the recirculation line due to shock load triggered a high alarm within the supporting SENTRY web dashboard
Figure 2 – Dosing of neutraquat to stabilize the AD based on high VFA SENTRY alert
Final Outcome
Industrial AD systems face ongoing challenges, from feedstock variability and sensitivity to process conditions like temperature, pH, and inhibitors to high costs for scaling and operations.
Sentry sensors provide low-maintenance, real-time consumable VFA signals that help monitor and prevent process imbalance events.
With Woodard & Curran specifically, Sentry systems are now being used across sites as an affordable, reliable tool for real-time digester health monitoring.
They empower operators to make smarter decisions while reducing manual sampling by 80%. As a result, clients are collectively saving £15,000 annually in operational costs per site and preventing upsets valued at £44,500 per site.
25/7/2025