Hydrogen peroxide cures filamentous growth in activated sludge

mentous growth is generally believed to be caused by conditions under which the filamentous organism propagates as fast or faster than the more desirable spherical aerobic (floe-forming) bacteria. Because the free-growing filamentous organisms have a higher area .'volume ratio than spherical aerobic growth, Pipes * suggests that the filamentous organisms have the metabolic advantage in activated sludge reactors with high soluble organic. sub strate, low dissolved oxygen (do) concen tration, or low nutrient condition. Smith and Purdy4 suggest that several types of filamentous organisms cause the bulking, but generally the sphaerotilus spe cies are the most common cause. Recently, Farquhar and Boyle3'4 verified the pres ence of filamentous organisms at various activated sludge plants. They developed techniques for identifying the various fila mentous species and found that the sphae rotilis and thiothrix were most commonly associated with bulking. The control of filamentous organisms and the prevention of bulking in the activated sludge process is an important factor in achieving existing and future water quality and effluent discharge requirements. Fila mentous growth not only reduces product quality of the secondary effluent but also decreases the effluent quality of subsequent tertiary treatment.5"8 Imhoff and Fair9 report that treatment used to reduce the sludge volume index (svi) of the bulking sludge includes re duction of the amount of return sludge and wasting more sludge in an attempt to build up a new microbiological population, in creasing air supply, by-passing or diluting influent wastewater to change the loading rate, addition of flocculating chemicals to help settling of the sludge, and chlorina tion of the return sludge to destroy the filamentous organisms. Chlorine, the most common treatment for elimination of fila mentous organisms, has the disadvantage that it also can destroy desirable spherical bacteria. These treatment techniques used to con trol bulking produce slow or poor re sponse. A new method is clearly needed to eliminate filamentous growth without extensive damage to the normal spherical aerobic population. In addition, opera tional procedures are needed to minimize recurrence of a filamentous condition in