Microorganisms sediments

Problems related to microorganisms, sediment and water in fuels and fuel systems can develop for a variety of reasons. TABLE 4-10 describes a typical microbiological analysis in a service water system. Sources include ... 

An accompanyiag effect of eutrophication that is more readily observable ia Table 1 is a decrease ia siUca coaceatratioa ia Lake Oatario. Some decliae ia dissolved siUca appareatiy has occurred ia all of the lakes except Lake Superior. This decliae is brought about by the growth of diatoms, a species of aquatic microorganisms ia the upper layers of lake water that is widespread ia all types of water impouadmeats where the water is clear and exposed to the sun. The siUca is used by these microorganisms to form their skeletons and is later precipitated and becomes part of the bed sediment. 

Winogradsky column Glass column with an anaerobic lower zone and an aerobic upper zone, which allows growth of microorganisms under conditions simitar to those found in nutrient-rich water and sediment. 

Carbon dioxide is produced as a result of metabolism of all heterotrophic organisms. The concentrations of CO2 in pore water of reduced sediments are therefore high. Autotrophic microorganisms consume CO2 in the oxidized part of the sediment, which can vary in depth from a meter in deep sea sediments to a few mm... 

Only a small fraction of faecal contaminants contributed to the enviromnent through human and animal faeces reach new hosts to infect them. Many of the defecated microorganisms never reach the soil and/or water bodies, since faecal wastes are submitted to purification (water) and hygienization (solids) processes, which remove a fraction of the pathogens and indicators. An important fraction of those that reach either the soil or water are removed (adsorption to soil particles and suspended solids, followed by sedimentation) and/or inactivated by natural stressors (physical, chemical and biological) in soil and water bodies. 

Endosulfan is released to the environment mainly as the result of its use as an insecticide. Significant contamination is limited to areas where endosulfan is manufactured, formulated, applied, or disposed of. The compound partitions to the atmosphere and to soils and sediments. Endosulfan can be transported over long distances in the atmosphere, but the compound is relatively immobile in soils. It is transformed by hydrolysis to the diol and by microorganisms to a number of different metabolites. It is bioconcentrated only to low levels and does not biomagnify in terrestrial or aquatic food chains. 

The refractory nature of some pollutants, notably, persistent polyhalogenated compounds, has raised problems of bioremediation of contaminated sites (e.g., sediments and dumping sites). There has been interest in the identification, or the production by genetic manipulation, of strains of microorganisms that can metabolically degrade recalcitrant molecules. For example, there are bacterial strains that can reductively dechlorinate PCBs under anaerobic conditions. 

Michaelsen M, R Hulsch, T Hdpner, L Berthe-Corti (1992) Hexadecane mineralization in oxygen-controlled sediment-seawater cultivations with autochthonous microorganisms. Appl Environ Microbiol 58 3072-3077. 

Morris PJ, JF Quensen III, JM Tiedje, SA Boyd (1992) Reductive debromination of the commercial polybro-minated biphenyl mixture Firemaster BP6 by anaerobic microorganisms from sediments. Appl Environ Microbiol 58 3249-3256. 

Bryant FO, DD Hale, JE Rogers (1991) Regiospecific dechlorination of pentachlorphenol by dichlorophenol-adapted microorganisms in freshwater anaerobic sediment slurries. Appl Environ Microbiol 57 2293-2301. 

Bedard DL, HM van Dort (1998) Complete reductive dehalogenation of brominated biphenyls by anaerobic microorganisms in sediment. Appl Environ Microbiol 64 940-947. 

Wu Q, DL Bedard, J Wiegel (1999) 2,6-dibromobiphenyl primes extensive dechlorination of Arochlor 1260 in contaminated sediment at 8-30°C by stimulating growth of PCB-dehalogenating microorganisms. 

Particularly polar contaminants may associate with polymeric humic components of soil, water, and sediment. Their biodegradation then depends on the degree to which these processes are reversible and the contaminants become accessible to microorganisms (bioavailable). This is especially significant after weathering (aging), even for nonpolar compounds. 

Ecologically, copper is a trace element essential to many plants and animals. However, high levels of copper in soil can be directly toxic to certain soil microorganisms and can disrupt important microbial processes in soil, such as nitrogen and phosphorus cycling. Copper is typically found in the environment as a solid metal in soils and soil sediment in surface water. There is no evidence that biotransformation processes have a significant bearing on the fate and transport of copper in water. 

---