title: Effect of calcium ions on the evolution of biofouling by Bacillus subtilis in plate heat exchangers simulating the heat pump system used with treated sewage in the 2008 Olympic Village.
abstract: Heat pump systems using treated sewage water as the heat source were used in the Beijing Olympic Village for domestic heating and cooling. However, considerable biofouling occurred in the plate heat exchangers used in the heat pump system, greatly limiting the system efficiency. This study investigates the biofouling characteristics using a plate heat exchanger in parallel with a flow cell system to focus on the effect of calcium ions on the biofilm development. The interactions between the microorganisms and Ca(2+) enhances both the extent and the rate of biofilm development with increasing Ca(2+) concentration, leading to increased heat transfer and flow resistances. Three stages of biofouling development were identified in the presence of Ca(2+) from different biofouling mass growth rates with an initial stage, a rapid growth stage and an extended growth stage. Each growth stage had different biofouling morphologies influenced by the Ca(2+) concentration. The effects of Ca(2+) on the biofouling heat transfer and flow resistances had a synergistic effect related to both the biofouling mass and the morphology. The effect of Ca(2+) on the biofouling development was most prominent during the rapid growth stage.
authors.affiliation: Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Thermal Engineering, Tsinghua University, Beijing, PR China.
authors.forename: Lei
authors.initials: L
authors.lastname: Tian
authors.forename: Xiao Dong
authors.initials: XD
authors.lastname: Chen
authors.forename: Qian Peng
authors.initials: QP
authors.lastname: Yang
authors.forename: Jin Chun
authors.initials: JC
authors.lastname: Chen
authors.forename: Lin
authors.initials: L
authors.lastname: Shi
authors.forename: Qiong
authors.initials: Q
authors.lastname: Li
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects* / Q000254:growth & development / Q000648:ultrastructure; D018441:Biofilms / Q000187:drug effects* / Q000254:growth & development; D057219:Biofouling; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D004735:Energy Transfer; D006361:Heating; D008855:Microscopy, Electron, Scanning; D012722:Sewage; D013816:Thermodynamics; D014867:Water
chemical_list: D002413:Cations, Divalent; D012722:Sewage; D014867:Water; D002118:Calcium