This case comes from a wastewater treatment plant that had a recurring foaming problem linked to Microthrix parvicella.
Microthrix parvicella is one of the most common organisms associated with stable foam in activated sludge systems. It is typically linked with operating conditions such as:
Low F:M conditions
Low temperatures
High FOG loading
Once Microthrix becomes established, foam can become difficult to control. It can accumulate on aeration basins, increase cleaning work, create safety and access issues, and become a recurring operational problem.
Maji has been working with this plant for almost 1 year. During this period, the platform built a regular biomass baseline for the facility. This baseline made it possible to understand what the plant’s normal biomass condition looked like and detect when the biology started to shift away from that baseline.
At a certain point, Maji detected a clear red flag: an increase in Microthrix parvicella compared with the plant’s regular biomass baseline.
Microthrix filament.
This was the key part of the case. The finding was not simply that Microthrix was present. The important point was that Microthrix was increasing compared with the plant’s normal condition. Because the biomass was being monitored over time, the change was detected early enough for the plant team to respond before the foaming developed into a larger recurring event.
The team focused on the operational conditions that were supporting Microthrix growth. The main actions were:
Reducing sludge age to increase F:M and reduce the conditions that favor Microthrix dominance
Stopping scavenger waste temporarily to lower FOG input and reduce the load contributing to foaming conditions
Physically removing existing foam using a sewer vacuum to control the visible foam while the biological conditions were being corrected
This combination was important. The plant did not only remove the foam from the surface. It also addressed the process conditions that were allowing the foam-forming organism to increase.
After the operational changes, Maji continued to track the biomass trend. This allowed the team to follow whether Microthrix was decreasing, stabilizing, or continuing to increase. Instead of relying only on visual foam observations, the team had a biological indicator showing whether the process was moving back toward its normal baseline.
Following the early detection, operational response, and continued biomass monitoring, the plant has had 8 months without foaming.
For the plant, this had both operational and cost value. Less foaming means less cleaning, fewer emergency responses, lower operational disruption, and a more stable activated sludge process. It also helped the team avoid treating foam only as a surface problem and instead manage it through the underlying biomass condition.
This case shows the practical value of a plant-specific biomass baseline. A single sample can show that Microthrix is present. A baseline shows when Microthrix is increasing in a way that matters for that specific plant.
In this case, Maji helped the team detect the biological shift early, connect it to operating conditions, take targeted actions, and follow the recovery over time. After almost 1 year of monitoring and 8 months without foaming, the plant moved from reacting to foam events toward preventing them earlier.