The F:M in the wastewater treatment network at a
National Park in Wyoming was optimal from July –
October. There was consistent organic carbon loading
during this time from tourist activities. However, when
the park closed for the winter, the biomass declined
due to reduced influent flows. This caused treatment
issues in the beginning of the next tourist season in
May and June because biomass declined during the
slow recreation months November-April. Thousands of
visitors arrived in the spring and the park did not have
the necessary biomass to process the increased loads.
The Utilities Supervisor contacted BioLynceus® for a
solution to support biomass in their system year-round.
Figure 1. A small mechanical plant with a primary and secondary
clarifier similar to the National Park mechanical system.
The operator started adding ProBiotic Scrubber® II
(PBII) into their collection lines, 0.05 MGD mechanical
treatment plant (Figure 1), lagoon systems, septic tanks,
RV dump stations, and pit toilets. This increased the
biomass in the wastewater systems which enabled more
efficient wastewater processing.
In addition to PBII, the operators dosed the mechanical
treatment plant with BioLynceus® Candy Carbon®
(CC) from November to May. This treatment provided
an organic carbon food source for the biomass when
wastewater inputs were minimal. CC kept the plant
biology active through the off season so there was no
lag time in the treatment process when visitors arrived
the following spring.
The bioaugmentation and organic carbon treatment
helped promote TSS, BOD, and nutrient removal
throughout the system. Additionally, NPDES permit
violations were avoided at the treatment plant while the
park was using BioLynceus® products. The combined
PBII and CC treatment sustained biomass in the system
all year and improved the quality of wastewater treated.
The F:M was stabilized for more efficient wastewater
processing.
Wastewater treatment systems servicing seasonal
populations often encounter issues with biomass
stability. A consistent supply of organic carbon is required
to sustain the biological growth and metabolism
essential for treating wastewater. Variable influent
carbon availability can impact biomass formation and
function. The organotrophic bacteria that facilitate
biological oxygen demand (BOD) and total suspended
solids (TSS) removal are impaired by insufficient organic
substrate availability.1 The food to microbe ratio (F:M)
of a system describes the relationship between quantity
of organic carbon and biomass. Optimal F:M can vary
at different plants depending on operational and plant
design factors.2 However, when the F:M in a system
decreases from optimal, this indicates an insufficient
organic substrate supply, a diminished biomass, or
both analogously. Applying bioaugmentation and
supplementing external organic carbon in wastewater
treatment can help to maintain a balanced biomass.
1 Gerardi, M. (2006). Wastewater Bacteria. Hoboken, New Jersey: John Wiley & Sons, Inc. Pp.73, 181.
2 Mishoe, G.H. (1999). F/M ratio and the operation of an activated sludge
process. Florida Water Resources Journal 3, 20–21.
BioLynceus® ProBiotic Scrubber® II and Candy Carbon® balance F:M in wastewater systems.