Effect of Silver or Copper Nanoparticles-Dispersed Silane Coatings on Biofilm Formation in Cooling Water Systems.

Akiko Ogawa,Hideyuki Kanematsu,Osamu Suzuki,Toshihiro Tanaka,Katsuhiko Sano,Yoshiyuki Sakai,Iwona Beech,Kunimitsu Ishida

doi:10.3390/ma9080632

Abstract

Biofouling often occurs in cooling water systems, resulting in the reduction of heat exchange efficiency and corrosion of the cooling pipes, which raises the running costs. Therefore, controlling biofouling is very important. To regulate biofouling, we focus on the formation of biofilm, which is the early step of biofouling. In this study, we investigated whether silver or copper nanoparticles-dispersed silane coatings inhibited biofilm formation in cooling systems. We developed a closed laboratory biofilm reactor as a model of a cooling pipe and used seawater as a model for cooling water. Silver or copper nanoparticles-dispersed silane coating (Ag coating and Cu coating) coupons were soaked in seawater, and the seawater was circulated in the laboratory biofilm reactor for several days to create biofilms. Three-dimensional images of the surface showed that sea-island-like structures were formed on silane coatings and low concentration Cu coating, whereas nothing was formed on high concentration Cu coatings and low concentration Ag coating. The sea-island-like structures were analyzed by Raman spectroscopy to estimate the components of the biofilm. We found that both the Cu coating and Ag coating were effective methods to inhibit biofilm formation in cooling pipes.

Highlights

Cooling systems significantly influence the energy conversion efficiency of chemical plants and thermal power plants
We examined whether or not Ise Bay (IB) seawater would have the capacity to create a biofilm on the surface of the coupons using the laboratory biofilm reactor (LBR) system
IB seawater, filtered with a 0.1 μm pore size filter, was separately used as cooling water to verify that the microbes in the seawater would take part in biofilm formation

Summary

Introduction

Cooling systems significantly influence the energy conversion efficiency of chemical plants and thermal power plants. Cooling systems are classified as either wet or dry. Wet type cooling systems use water or other liquid solutions as the heat transfer medium, whereas dry ones use air. Many plants adopt water cooling systems because water has a higher heat efficiency than air. Natural water such as seawater and river water is used as the heat transfer medium because this system needs a lot of water. 11 million liters of water per day are used in a nuclear power plant [1]. Such natural water is abundant in microbes and minerals, which causes biofouling

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