Characterizing the roughness of freshwater biofilms using a photogrammetric methodology

Abstract

The physical roughness of a surface changes when freshwater biofilms colonize and grow on it and this has significant implications for surfaces enclosing water conveying systems such as pipelines and canals. Plates with surfaces initially artificially roughened with varying grit size were deployed in an open channel system and biofilms were allowed to grow on the exposed surface. The plates were retrieved at intervals in time and their surfaces mapped using close range photogrammetry. For a fine grit surface (0.5-4 mm particles), diatom-dominated biofilms initially grew between the roughness elements; they subsequently developed as a mat to create a physically smoother outer surface than the underlying rough surface. For a coarse grit surface (2-4 mm), biofilms colonized faster; in one instance, larger clumps of biofilm were observed as transverse ripples across the plate.

Effects of naturally occurring grit on the reactor performance and microbial community structure of membrane bioreactors

“…Although the grit does not contribute to biological reactions directly, these particles can be potentially involved in the formation of sludge flocs; e.g., small grit can be entrapped by sludge flocs. Because of the high specific area, the grit could be considered as a bacterial media that can affect the growth of the bacteria and thus change the structure of the bacterial community [7,8].…”

Biofilm development in water distribution and drainage systems: dynamics and implications for hydraulic efficiency

“…Typical assessments of flow-related impacts on pipeline biofouling found in the literature involved the mean flow speed and turbulence intensity, as inferred based on Re. [10,15,27,29,108] Biofilms have also been documented to compress themselves under pressure, which tends to confer an increased ability to resist the effects of flow shear. [5,67] Such effects have been shown to occur even when the surface is classified as hydraulically smooth.…”

“…Particularly, the current prevailing understanding of the biofilm dynamics and flow interaction is predominantly based on observation within hydropower [12,15,27,108,113,114] and marine [18,21] applications, which have inherently different conditions to those typical within DWDSs and DNs.…”

Measurement Studies on Superhydrophobic Materials

“…Measurements were taken by Kulkulka et al, [31] using PocketSurf I, a portable surface roughness gage with a traverse speed of 0.2" (5.08mm) per second and a probe radius of 0.0004" (10µm). Surface roughness due to biofouling photogrammetric techni-ques to the measurement of surface roughness [32]. An optical profiler (NT-3300,Wyko Corp., Tuscon, AZ) was used for measuring the surface roughness of different patterned surface structures by Bhushan and Jung [12].…”