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.

In many resort towns, the influent loads to the wastewater treatment system are highly variable throughout the year. During the tourist seasons there is an abundance of wastewater to sustain the biomass at treatment facilities, but when the transient population leaves, there is a drastic reduction in organic substrate. The organic carbon supplied to the system, the carbonaceous biological oxygen demand (CBOD), serves as a food source for organotrophic organisms in activated sludge systems.

Wastewater treatment plants receiving inconsistent influent loads are often challenged with maintaining an effective biological treatment. Many of the key microorganisms in wastewater processes are dependent on organic substrate to grow and divide. When influent flows are limited, the biodegradable carbon source for the treatment system may be too low to sustain biomass.

Wastewater systems located in regions with high annual precipitation, such as the Pacific Northwest, are prone to experiencing biological washouts due to high infiltration and inflow (I&I) from collection systems. I&I can critically disrupt the biological treatment at a plant.