Robert Almstrand at the University of Gothenburg, Sweden, has shown in his thesis that better removal of nitrogen from wastewater can be achieved by providing the bacteria that purify the water with alternating high and low levels of nutrients.
An image of a nitrifying biofilm taken in a confocal microscope showing how different bacterial populations can be distinguished with the aid of species-specific labellinglabelling (in situ fluorescence hybridisation).
Photo: Robert Almstrand
The emission of wastewater to oceans, lakes and rivers contributes nutrients in the form of nitrogen and phosphorus to these recipients. This causes large algal blooms, and to prevent this the wastewater must be purified in wastewater treatment plants before being released.
The removal of nitrogen is a biological process in which different groups of bacteria are used to convert the nitrogen compounds to nitrogen gas in a number of steps. The nitrogen gas is then emitted to the atmosphere. The first, and rate-limiting step is nitrification. Nitrification is carried out by bacteria that oxidize ammonia via nitrite to nitrate ions.
Robert Almstrand at the Department of Chemistry and Molecular Biology shows in his thesis that the ability of the bacteria to carry out nitrification is improved if the bacteria receive alternating high and low levels of substrate (in the form of dissolved ammonium), rather than a constant low level. This will enable the wastewater treatment plant to cope better with variations in the concentration of nitrogen in the wastewater.“Since the composition of the wastewater varies continuously, it was important to carry out the studies in a set-up that was as similar as possible to real wastewater treatment plants. For this reason we constructed a pilot plant at Ryaverket in Gothenburg”, says Robert Almstrand.
The bacteria grew in what are known as “biofilms”, which are dense collections of microorganisms on surfaces. Robert Almstrand used microscopy and digital image analysis to study how the bacterial colonies in the biofilms changed when exposed to different levels of nutrients.
“Different species of bacteria are promoted or inhibited to different extents by changes in their habitat”, he says. “These properties are reflected in their positions in the biofilm, and so we developed new methods to analyse these in detail. The new methods are very flexible and can be used to analyse pretty much any type of biofilms.”
Furthermore, Robert discovered that groups of bacteria that are normally considered to be the same species (Nitrosomonas oligotropha) were affected differently by the changes. It is, thus, important to understand the diversity within species of nitrifying bacteria, in order to improve the removal of nitrogen.
The thesis was successfully defended on 3 February 2012.Author: email@example.com
From the Arctic to the tropics: researchers present a unique database on Earth’s vegetation
20.11.2018 | Martin-Luther-Universität Halle-Wittenberg
Fading stripes in Southeast Asia: First insight into the ecology of an elusive and threatened rabbit
20.11.2018 | Forschungsverbund Berlin e.V.
Max Planck researchers revel the nano-structure of molecular trains and the reason for smooth transport in cellular antennas.
Moving around, sensing the extracellular environment, and signaling to other cells are important for a cell to function properly. Responsible for those tasks...
Researchers at the University of New Hampshire have captured a difficult-to-view singular event involving "magnetic reconnection"--the process by which sparse particles and energy around Earth collide producing a quick but mighty explosion--in the Earth's magnetotail, the magnetic environment that trails behind the planet.
Magnetic reconnection has remained a bit of a mystery to scientists. They know it exists and have documented the effects that the energy explosions can...
Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.
Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...
Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.
In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
19.11.2018 | Event News
09.11.2018 | Event News
06.11.2018 | Event News
20.11.2018 | Life Sciences
20.11.2018 | Life Sciences
20.11.2018 | Physics and Astronomy