Study on interactions between suspended matter and biofouling formed by treated sewage

Heat exchangers used for treated sewage energy recovery usually suffer from the composite fouling problem, which seriously impairs the heat transfer efficiency. Treated sewage heat exchanger composite fouling is mostly composed of biofouling and is notably affected by interactions between the biofouling and suspended matter. Experiments were performed using simulated treated sewage and two kinds of simulated suspended matter, silicon dioxide particles and polyamide filaments, to model the interactions. Different flow velocities, particle sizes and concentrations were tested with their influences presented by the fouling wet weight changes. Empirical equation and threshold were developed based on the results to predict whether the suspended matter promotes or impedes fouling growth. The results indicate that proper control of the flow velocities, particle sizes and concentrations of suspended matter using empirical equation and threshold can inhibit fouling by reducing unwanted positive interactions and promoting beneficial negative interactions. The filament interactions were analysed and the unique attachment mechanisms of filaments were discussed for the first time.