The significance of the biofouling problems and its control is now well recognized. Along with investigations of molecular mechanisms which are involved in bacteria-membrane interactions, a simplified approach is offered to evaluate biofouling potential for certain RO system conditions. Guidelines are needed to evaluate pretreatrnent efficiency, to identify feedwater constituents that promote biofilm formation, to predict biological foulant behavior and loss of membrane, and to determine cleaning and disinfection schedules.
The test program used experimental tools previously applied for fouling predictions and included three steps:
Step 1: Microorganism accumulation experiments to predict amount of adhered foulant and to evaluate the time period of the first (attachment) phase of biofouling. The test procedure enabled us to calculate rates of cell adhesion for various feedwater conditions and brine concentration in each module of the RO unit. The decrease of adhesion rate corresponded to the end of the first phase of biofouling.
Step 2: Biofilm growth experiments, predictions of flux and rejection decline as well as delta pressure increase with time. The determination of the amount of consumed feedwater constituents enables us to obtain an indirect description of the biological growth process. The most unlikely feedwater constituents could be easily identified and pretreatment requirements could be developed. Every value of product flux and rejection decrease during test runs corresponds to the amount of the microbial feed material consumed, and membrane performance can be predicted through the treatment of these experimental data.
Step 3: Cleaning experiments to identify types of various biofilm constituents and their cleaning amenabilities. Experimental data treatment provides efficient cleaning schedules. For different RO applications feedwater chemical/bacterial analysis data can provide biofouling prognosis and outline measures for its control.