Gallionella is a type of iron-oxidizing bacteria found in various aquatic environments. These microorganisms have a unique way of obtaining energy, which leads to noticeable changes in water. Understanding Gallionella can help clarify why water sometimes exhibits unusual characteristics, providing insight into the microscopic world that influences water quality.
Understanding Gallionella
Gallionella is a chemolithoautotrophic, iron-oxidizing bacterium. It generates its own food using chemical reactions involving inorganic compounds, deriving energy by oxidizing ferrous iron (Fe2+) into ferric iron (Fe3+).
The bacterium exhibits a distinctive morphology, with kidney-shaped or ovoid cells that produce twisted, ribbon-like stalks. These extracellular stalks are composed of intertwined microfibrils, which become encrusted with ferric iron minerals as a byproduct of its metabolism. The deposition of these iron oxide minerals on the stalks helps prevent iron accumulation on the cell itself, which could hinder nutrient uptake and waste release, causing cell death.
Habitats of Gallionella
Gallionella thrives where dissolved ferrous iron is abundant and oxygen levels are low, often called microaerobic conditions. They are common in natural settings like freshwater springs, bogs, wetlands, and groundwater, where iron-rich anaerobic groundwater meets oxygenated environments. Their growth has been observed across a temperature range of 4°C to 47°C, with an optimal pH range of 6.0-7.6, though they can also be found in more acidic conditions.
Beyond natural occurrences, Gallionella is also prevalent in man-made water infrastructure systems. This includes wells, water pipes, cooling towers, and industrial water systems. These engineered environments often provide specific conditions—such as a continuous supply of iron and limited oxygen—ideal for Gallionella to flourish.
How Gallionella Affects Water
The metabolic activity of Gallionella can impact water quality and infrastructure. One common effect is biofouling, which forms slimy, reddish-brown deposits, often called ochre, within pipes and on submerged surfaces. This accumulation results from the ferric iron precipitates produced by the bacteria.
The presence of Gallionella also contributes to pipe corrosion. The byproducts of its metabolism, particularly the iron oxides, create an environment that accelerates the degradation of metal pipes. Water discoloration is another symptom, with affected water often appearing rust-colored due to high concentrations of iron precipitates.
Taste and odor issues are associated with Gallionella contamination, leading to unpleasant metallic or earthy tastes and smells. The build-up of iron precipitates can lead to clogging and reduced water flow in pipes and well screens, rendering well systems less effective or useless. The presence of these bacteria can also interfere with water treatment processes like filtration and disinfection, making it more challenging to achieve desired water quality.
Identifying and Addressing Gallionella Issues
Identifying Gallionella problems begins with recognizing common visual and sensory signs. These include water discoloration, slimy reddish-brown deposits, or changes in the water’s taste and odor. For a definitive diagnosis, laboratory testing methods are employed, such as microscopic examination to identify the characteristic twisted stalk structures, or specific iron bacteria tests.
Addressing Gallionella issues involves a combination of strategies. Physical cleaning methods, such as flushing pipes and mechanical removal of deposits, clear existing build-ups. Chemical treatments, which may involve disinfectants like chlorine or specialized iron-sequestering agents, control bacterial growth and manage iron precipitation. Such chemical treatments should be handled by water treatment professionals.
Managing the water source is also a consideration, especially if high iron levels contribute to the problem. Preventive measures, including proper well maintenance and the selection of appropriate pipe materials, reduce the likelihood of Gallionella proliferation in water systems.