Microbiologically-based procedures were used to describe biofouling phenomena on fine pore aeration devices and to determine whether biofilm characteristics could be related to diffuser process performance parameters. Fine pore diffusers were obtained from five municipal wastewater treatment plants in Wisconsin, one in Michigan, and one in California. Biofilm thickness and carbohydrate content were measured as were the film's ability to retain air bubbles. Scanning electron microscopy (SEM) procedures were used to examine biofilm structure. Diffusers were also tested for standard oxygen transfer efficiency (SOTE), bubble release vacuum (BRV), and dynamic wet pressure (DWP). Subsequently, one of the plants in Wisconsin was revisited where the three most useful of the biofilm characterization techniques were deployed to determine any relationship between biofilm thickness and content and operational parameters such as SOTE. The effect of four different cleaning procedures on diffuser characteristics was also measured. A parallel laboratory-scale investigation simulated microbially induced fouling of small-scale diffusers and the effect of bleach and acid cleaning.

Project officer: Richard C. Brenner. Cooperative agreement CR812167. Photocopy.