Abstract
The migration of bioavailable organic compounds (‘bioavailable migration’) from polymeric materials used for drinking water distribution was investigated by an abiotic test: Extracting materials under sterile conditions, and a biotic test: Extracting materials in presence of bacteria. Both tests showed elevated bioavailable migration during the first two weeks of incubation followed by a lower constant level, which was maintained during the test period of 16 weeks.
Problems with aftergrowth due to bioavailable migration from polymeric materials are therefore not solved by initial flushing. The bioavailable migration from the polymer surface was influence by diffusion over the solid-liquid boundary layer under sterile conditions, which resulted in an inversely proportionally relationship between bioavailable migration expressed
per unit surface area of material and the surface to volume ratio (S/V-ratio), corresponding to lower bioavailable migration at smaller pipe diameters. Under sterile conditions gentle shaking of the water phase reduced the thickness of the boundary layer resulting in an increased bioavailable migration from the surfaces. The presence of bacteria together with the material overruled the effect of the boundary layer, since bioavailable migration was continuously
consumed by the bacteria. Thus the driving force for the diffusion process was maintained at a maximum, thereby enhancing the bioavailable migration from the material surfaces. Thus neither non-static conditions nor varying S/V-ratios had any effect on the bioavailable migration in the biotic tests. Not to underestimate growth potential of polymers, investigations should thus
be performed in the presence of a diverse microbial population with paired measurements of biomass in the water phase and on the material surfaces.
Problems with aftergrowth due to bioavailable migration from polymeric materials are therefore not solved by initial flushing. The bioavailable migration from the polymer surface was influence by diffusion over the solid-liquid boundary layer under sterile conditions, which resulted in an inversely proportionally relationship between bioavailable migration expressed
per unit surface area of material and the surface to volume ratio (S/V-ratio), corresponding to lower bioavailable migration at smaller pipe diameters. Under sterile conditions gentle shaking of the water phase reduced the thickness of the boundary layer resulting in an increased bioavailable migration from the surfaces. The presence of bacteria together with the material overruled the effect of the boundary layer, since bioavailable migration was continuously
consumed by the bacteria. Thus the driving force for the diffusion process was maintained at a maximum, thereby enhancing the bioavailable migration from the material surfaces. Thus neither non-static conditions nor varying S/V-ratios had any effect on the bioavailable migration in the biotic tests. Not to underestimate growth potential of polymers, investigations should thus
be performed in the presence of a diverse microbial population with paired measurements of biomass in the water phase and on the material surfaces.
| Original language | English |
|---|---|
| Publisher | DTU Environment |
| Number of pages | 16 |
| Publication status | Published - 2004 |
Keywords
- Polymers
- Drinking water
- Bacterial growth
- ATP
- AOC
- Diffusion