Biofilms

Eawag News 60, July 2006

complete issue [pdf]

Biofilms: Both a Curse and a Blessing
Thomas Egli

Biofilms are Ubiquitous
Oskar Wanner and Martina Bauchrowitz

The slime we brush off our teeth in the morning is a bacterial biofilm. If we neglect this daily cleaning, we get mouth odour, our gums become inflamed, and our teeth would in time be damaged by caries. This is well-known, but it is perhaps less well-appreciated that in many fields, biofilms can serve a useful role as well. [...]

Biofilm Models: Tools for Research
Oskar Wanner

Scientific investigation is a process of rigorously testing hypotheses by observation and experiment. Mathematical models provide valuable aids to science, expressing data in a quantitative form, which allows experimental evidence to support or refuse the model. Through the modelling of complex systems, such as wastewater treatment plants, engineers are able to reproduce, control and optimise the behaviour of the plants. [...]

Biofilms in the Tagliamento
Michael Döring and Urs Uehlinger

Biofilms play an important role in the metabolism of streams and rivers. In the Tagliamento River, their growth and activity depend essentially on the water exchange between surface waters and the sediments in the river bed. [...]

Calcite Precipitation on Cyanobacteria
Sabine Sibler and Maria Dittrich

Calcite, or calcium carbonate CaCO3, is found as a natural product in calcium-rich lakes all over the world. It precipitates in the water column and is then deposited at the bottom of the lakes. What actually causes the formation of calcite? [...]

What Effects do Metals Have on Algal Biofilms?
Renata Behra

Much smaller quantities of metals are currently discharged into water bodies than in the past. However, even low metal concentrations can have negative impacts on water organisms and thus on the whole ecosystem. This is the challenge for ecotoxicologists. It is important to draw up concepts and methods for assessing the ecological consequences. [...]

Metal Accumulation in Algal Biofilms
Sébastien Meylan

When it rains, the metal content of rivers can increase dramatically. Algal biofilms react particularly sensitively to such changes. They have a tendency to accumulate metals. Uptake by the algae depends on whether the metals are present in free or bound form. [...]

Phytochelatins as Bioindicators of Metal Exposure?
Séverine Le Faucheur and Laura Sigg

Algae protect themselves against toxic metals with phytochelatins. They synthesize these short polypeptides when metal concentrations in the water are elevated. Is it possible to use phytochelatins as bioindicators for metal stress? We discovered some surprising answers. [...]

Biofilters on the Test Bed
Adriano Joss and Max Maurer

Biofilters are currently experiencing a revival in the area of wastewater treatment. In such systems, biofilms develop on solid surfaces such as polystyrene globules. The great advantage of the biofilters is their low space requirement due to the short retention time of waste water in the reactor. But how is the elimination efficiency? Are the pollutants effectively removed from the waste water? [...]

Activated Sludge – Biofilm Flocs
Reto Manser and Hansruedi Siegrist

Activated sludge flocs in wastewater treatment plants are biofilms of a special kind, lacking a carrier material. Depending on the type of system used, the size of flocs formed in treatment plants varies: flocs in membrane bioreactors are smaller than those in conventional systems. Does this affect purification performance? [...]

Biofilms Hamper Heat Recovery
Oskar Wanner

With our ever-increasing need for energy, its efficient use becomes more and more important. An attractive possibility is to recover heat energy from the relatively warm waste water. Biofilms, however, developing rapidly on heat exchangers in sewage pipes, can hamper heat recovery from waste water in the sewer. Is this avoidable? [...]

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