Light as a key driver of freshwater biofouling surface roughness in an experimental hydrocanal pipe rig

Abstract

Biofouling in canals and pipelines used for hydroelectric power generation decreases the flow capacity of conduits. A pipeline rig was designed consisting of test sections of varying substrata (PVC, painted steel) and light levels (transparent, frosted, opaque). Stalk-forming diatoms were abundant in both the frosted and transparent PVC pipes but negligible in the painted steel and opaque PVC pipes. Fungi were slightly more abundant in the painted steel pipe but equally present in all the other pipes while bacterial diversity was similar in all pipes. Photosynthetically functional biofouling (mainly diatoms) was able to develop in near darkness. Different biological fouling compositions generated differing friction factors. The highest friction factor was observed in the transparent pipe (densest diatom fouling), the lowest peak friction for the opaque PVC pipe (lowest fouling biomass), and with the painted steel pipe (high fouling biomass, but composed of fungal and bacterial crusts) being intermediate between the opaque and frosted PVC pipes.

Key words:

• Diatoms
• freshwater fouling
• pipeline rig
• microfouling

Acknowledgements

The authors acknowledge valuable support from many people from Hydro Tasmania over many years: Angus Swindon, Daryl Polzin, Norm Cribbin, and Joshua Kline. Thanks are due to Martin Doyle, Darren Nichols, Stephen Kelly and Brett Nichols for the arrangement of the site visits. The authors are also indebted to technical staff in the school of Engineering: Andrew Bylett, James Lamont and Peter Seward for building the pipe rigs in the hydraulics laboratory and on site.