Iron　bacteria　(IB)　and　slime-forming　bacteria　(SFB)　are　the　most　common　in　circulating　cooling　water.　In　order　to　study　on　the　characteristics　of　microbial　fouling　in　plate　heat　exchangers,　an　experimental　study　was　carried　out　for　the　fouling　characteristics　of　IB　and　SFB.　The　fouling　characteristics　in　the　plate　heat　exchanger　under　the　different　flow　velocity,　temperature　and　concentration　were　investigated　for　these　two　bacteria　and　the　mixture　of　them.　The　results　show　that　the　asymptotic　value　of　fouling　resistance　and　the　time　of　reaching　the　asymptotic　value　decreases　with　the　increase　of　fluid　velocity.　The　asymptotic　value　of　fouling　resistance　increases　with　the　increase　of　concentration.　And　the　influence　of　temperature　is　different　for　the　two　kinds　of　bacteria.　When　these　two　bacteria　are　mixed,　the　IB　and　the　SFB　grow　synergistically　because　the　IB　have　strong　ability　in　microbial　fouling　and　the　SFB　have　the　high　secretion　rate　of　extracellular　polymeric　substances.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.