Filamentous Bacteria in Wastewater Treatment

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Filamentous bacteria are common in wastewater

Filamentous bacteria are common in wastewater

Wastewater treatment is essential for human health and environment, as well as to protect and maintain the environment from the distribution of pollution and water-borne diseases.

Human sewage and waste from industries are the main sources of wastewater. Biological wastewater treatment is the largest and most commonly biotechnology method in the world. It is an important part of wastewater treatment plants, in which different types of microorganisms are used in the processing and cleaning of wastewater.

Microorganisms are able to breakdown the organic waste content and use them as a food and energy source to grow and multiply in aerobic conditions.

The individual organisms clump and flocculate together in flocs flake-like structures (which contain alive and dead cells of microorganisms and there metabolic products), around the suspended organic material they feed on, to form larger masses that settle out of the water and forms an active mass of microbes called “activated sludge”. The wide majority of the wastewater treatment plants are based on the activated sludge principle.

The biological floc is composed of bacteria, fungi and protozoa. Bacteria involve around 95% of the total microbial population of the activated sludge and they are essential for the degradation of organic substances in wastewater treatment systems.

Filamentous bacteria are normal components of activated sludge biomass. The existence of some filamentous bacteria is important and helpful for good floc formation to a biomass. Filamentous  bacteria grow in long thread-like strands, whose cells do not  separate from each other after cell division and therefore grow in the form of filaments. Then, they connect with each other to form a mesh that is the most important part in floc formation and causes the separation of a fluid or removal of sediment from a fluid.

Filamentous bacteria can provide a support structure for other bacteria to attach to as they form floc and it serves as the backbone of floc formation and settling. However, these bacteria can be dominated and compete with the floc-forming bacteria under a specific condition. The excessive growth of these bacteria can cause potential problems with the sludge settling that reduce the efficiency of the wastewater treatment plants.

Bulking and foaming are considered the major problems usually happening worldwide in the operation of activated sludge systems, which can affect continuously or seasonally in the process of biological wastewater treatment plants. Bulking sludge is a condition defined by solids with poor or bad settling and thickening characteristic. Usually this is caused by an excessive and uncontrolled growth of different types of filamentous bacteria, which interfere with the concentration settling of activated sludge in wastewater treatment plants.

Filamentous bulking is often associated with changes in physical and chemical characteristics of the wastewater process. Foaming is a serious issue caused by increase of certain types of filamentous bacteria. Foaming can lead to major operational problems; hazardous working conditions, and affects on solid separation in wastewater plants. Foaming is characterized by the formation of a sticky, thick, firm and brown scum.

It floats and accumulates on surfaces of the tanks; where the foam can also overflow onto walkways and surrounding areas, creating severe difficulties and risk to operation and environment.

Microbiological investigations found 25 common types of filamentous bacteria in activated sludge. Different types of filamentous bacteria in the activated sludge have been described. A survey of bulking activated sludge plants in the U.S. has found approximately 15 major types of filamentous microorganisms are responsible for bulking and foaming.

The dominant types of filamentous bacteria depend on the nutrient condition in the wastewater system. Nocardia spp. is one of the main filamentous bacteria, which is responsible for foaming. Microthrix Parvicella, Nocardia amarae, Nostocoida limicola, Alcaligenes paemba, Alcanivorax, borkumensis, Thiothrix spp, Sphaerotilus natans, Beggiatoa spp. and Haliscomenobacter hydrossis, are also some of the most common filamentous bacteria that cause these same problems.

Identification of filamentous bacteria is an important method because each type of these filaments can lead to a specific problem. Identifying the dominant species helps to find the solution and to control the problem. The identification of filamentous bacteria is based upon taxonomic keys.

Wet mount preparation is used to observe certain morphological characteristics such as; motility, branching, filament shape, attached growth, filament diameter, septa or transverse walls, cell shape, presence of a sheath and granules, under phase contrast and bright field microscope. Further staining reactions can help detect the presence of these microorganisms, such as; Gram stain, Neisser stain and Sulphur stain. However, the majority of filamentous bacteria in activated sludge are still unidentified beyond these simple characteristics.

Filamentous bacteria are of major concern today because of its involvement in bulking and foaming problems at wastewater treatment plants in all of the world, which influence the treatment activity and efficiency. Early detection of these problematic bacteria is needed in the wastewater treatment market.

At MBL Laboratories, we offer numerous analytical services in the detection, identification and enumeration of mould and bacteria in air, bulk, (solid and fluid) and cultures collected from homes, and work environments, using high level of scientific knowledge and methods.

For further information please contact us at:
Mold & Bacteria Consulting Laboratories
1020 Brevik Place, Unit 1A
Mississauga, ON L4W 4N7
Office: 905-290-9101 Toll-free: 1-866-813-0648
Fax: 905-290-0499

Georget Shamoon, PhD.
(Senior Microbiologist)

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