Simultaneous evaluation of composite biodeterioration and changes in the physicochemical and biological water characteristics

Abstract

Biological factors in aquatic environments may accelerate the deterioration of composite material, while the leached material can adversely impact the surrounding ecosystem. The main objective of this study was to examine the interaction between physicochemical and biological characteristics of water and polymer composites, using four water-composite systems (distilled water with composite, river water, river water and composite, and river water plus composite and biocide). In distilled water, leaching of the composite coupon produced an increase in pH (11%); conductivity (30ppm); and total organic carbon (TOC) (31mg/l). Conversely, the presence of bacteria buffered river water pH. Bacteria in non-sterile reactors degraded the TOC leached from the composite, preventing its accumulation. However, this led to higher oxygen demands which were also indicated by increasing bacterial numbers in the three non-sterile water systems. Exposure to river water over 12 months produced an 11% reduction in the tensile modulus of composites; almost twice that for the distilled water and the system containing biocide. Biocide did prevent the tensile modulus reduction, but led to 28mg/l TOC accumulation. Visual observations corroborated the observed differences. Craters and precipitates, exposed fibres, and material debonding were observed on the coupon surface. For the river water system, biofilm growth was also observed. The presented study provides a useful and preliminary database for physicochemical and biological characterization of water interacting with deteriorating polymer composites.