Filamentous Bacteria Controlled: A Quick And Easy Solution

By Rebecca J. Bodnar, chemist and industrial pretreatment coordinator, Kalispell Advanced Wastewater Treatment Plant

The City of Kalispell used ingenuity, and just a few inexpensive parts, to solve a problem common to biological nutrient removal facilities.

Filamentous foaming bacteria: the nuisance of many biological nutrient removal (BNR) wastewater treatment plants. Although filamentous microorganisms are a natural part of the biomass in plants and are the backbone of floc formation and settling, the overproliferation of filamentous microorganisms causes the sludge to float (foaming) and causes problems with nitrification and phosphorus removal, aesthetics, poor settling, and the formation of high-sludge blankets. Left unresolved, filamentous bacteria can reduce clarifier capacity, cause digester foaming, and carry over to effluent. The City of Kalispell (MT) Advanced Wastewater Treatment Plant (WWTP) upgraded in 2007 to a Modified Johannesburg configuration for phosphorus and nitrogen removal. Seasonally in spring, filamentous bacteria growth consistently rises sharply and becomes a problem in the aeration basins. A huge amount of floating sludge accumulates in the tanks, and removal of the floating layer is a serious problem.