Interaction effects of silica dioxide particles and calcium ions on the evolution of biofouling in plate heat exchangers relevant to a heat pump heat recovery system from treated sewage

Heat pump using treated sewage water as heat source and sink is an effective way to reuse urban waste heat for building heating and cooling. However, fouling occurred in plate heat exchangers of the heat pump. An experimental system has been developed to investigate the interactions of inorganic particles (silica dioxide particles) and Ca2+ on biofouling properties. Process monitoring in biofilm have been conducted and presented with the view of attempting to reduce fouling in future. The results show that the interactions of the microorganisms, Ca2+ and inorganic particles clearly influenced the biofilm development thus impacting on the thermal resistance created. It was found that the fouling thermal resistance showed a different prospect than the fouled mass time trend under different inorganic particles in the presence of Ca2+. With inorganic particles added, Ca2+ facilities the increase of biofouling mass and thermal resistance.