Everything I Know About Bio P, the Bugs Taught Me

The most important thing for a phosphorus accumulating organism (PAO/Bio P bug) is an adequate source of volatile fatty acids (VFAs) and readily biodegradable COD (rbCOD). The Eagles Point Plant in Minnesota, USA, was designed for biological phosphorus removal, with no provisions for chemical feed. The VFAs at startup were much less than anticipated and then a subsequent collection system odor and corrosion control project reduced the VFAs even further. Plant staff took a number of steps over the past 11 years to maintain compliance, including the installation of a bulk chemical feed system. Along the way, staff experimented with process control methods to increase the VFA and rbCOD production on site, and hopefully reduce or eliminate the need for chemicals. An important finding was that the primary clarifiers can act as a fermenter to produce many more VFAs on site. The sludge thickener/fermenter can also be optimized, with the addition of a good elutriation pump. An extended anaerobic detention time, well beyond traditional design parameters can also benefit the Bio P process by increasing VFA production right in this zone. These, plus other findings enabled the plant to eliminate the use of chemicals and save about $80,000 per year, by putting the Bio P bugs back to work.