Chlorinating the system, killing a large proportion of the bacteria present, is a common attempt to solve the problem, followed by reseeding the system with fresh commercial bacteria or sludge hauled from a properly functioning plant. Krishna R. Pagilla, David Jenkins and Wendell Kido dispute this solution in their paper Nocardia Effects in Waste Activated Sludge [2], saying that they found in their experiments that chlorination doubled the foaming potential and foam stability. In one experiment, they found that foam increased almost ten fold, following chlorination. |
US Patent 5,614,098 (1997) Nocardia Foaming Controlling Method of Wastewater Treatment by Y.J. Shao and K. Kaporis proposes the use of a cationic polymer, injected into the water coming out of the secondary aeration basin, as one means to control foaming.[3] |
US Patent 5,536,410 (1996) Method for Preventing Activated Sludge from Losing Its Settling Ability by K. Kitatsuji, T. Fukase, and K. Chu mention the use of nonionic and anionic surfactants to control Nocardia bulking and foaming.[4] |
| If chlorination is a poor solution, what other methods can provide a longer term solution than constant addition of chemical antifoam, cationic polymers or surfactants? Since Nocardia is slower growing than floc forming strains, changing the environmental conditions can help to exclude it. If additional bacteria are to be added to the system, the risk of reintroducing Nocardia spp. from sludge hauled from another plant can be avoided by using a high quality commercial bacterial blend from a reputable firm. Choose a bacterial blend that comes with a certificate of analysis, attesting to the count and absence from common pathogens and nuisance strains. Ideally, apply a bacterial blend that is selectively adapted for the express purpose of crowding out filamentous organisms, such as Alken Clear-Flo 7015 [11]. |
