Aerobic Liquid Environments

The test system used allowed comparison of the biodegradation of different polymers in freshwater. The PHBV-copolymer degradation rate increased with the copolyester composition up to a HV content of 14 mol%, and then decreased to nearly zero for P(3HB-co-3HV) (80% HV). 

From this viewpoint, the natural environments should be better identified, in terms of ecological habitats, and test approaches should in turn be based on the typical conditions experienced by the plastic products when entering each habitat, since the microbial population (and thus biodegradation activity) could be quite different. Tosin and co-workers [13] have identified 6 habitats where plastic waste can reside when littered in the marine environment 1) pelagic domain (the plastic products float freely in estuaries and the open ocean water), 2) eulittoral zone (tides and storm waves bring great quantities of plastic waste to the shoreline, where plastic products get partly buried and kept wet by tidal inundation and waves), 3) supralittoral zone (the plastic products are washed onto the beach, exposed to a sandy soil with a low moisture level), 4) sublittoral zone (plastic products settle on marine sandy sediment where they are exposed to the seawater/sediment interface), 5) plastic products can otherwise sink to the bottom of the deep sea and 6) plastic products can be slowly buried within sediments on the sea-floor. 

A further specialised test system was used by Allen and co-workers [22], and Gonda and co-workers [23]. In these tests completely synthetic media, inoculated with individual microbial strains or defined microbial consortia, were used to investigate the biodegradation of polymers. 

Honda and Osawa [24] used a simulation test with synthetic wastewater inoculated with mud from a lake to investigate the behaviour of PCL for the denitrification of wastewater (at 25 °C) they found a remarkable degradation of the PCL plates used (erosion rates approximately 10-15 pm/week). 

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Discussing the biodegradation of plastics in a liquid environment usually means natural degradation in freshwater (lakes, rivers), in a marine environment, or in aerobic and anaerobic sludges (wastewater treatment). However, many degradation... 

The Bio-FGD process converts sulfur dioxide to sulfur via wet reduction (10). The sulfur dioxide gas and an aqueous solution of sodium hydroxide are contacted in an absorber. The sodium hydroxide reacts with the sulfur dioxide to form sodium sulfite. A sulfate-reducing bacteria converts the sodium sulfite to hydrogen sulfide in an anaerobic biological reactor. In a second bioreactor, the hydrogen sulfide is converted to elemental sulfur by Thiobacilh. The sulfur from the aerobic second reactor is separated from the solution and processed as a sulfur cake or liquid. The process, developed by Paques BV and Hoogovens Technical Services Energy and Environment BV, can achieve 98% sulfur recovery. This process is similar to the Thiopaq Bioscrubber process for hydrogen sulfide removal offered by Paques. 

Fermentations may be aerobic when the cells must be in the presence of an O2 environment or anaerobic when they cannot. Water is the standard fermentation medium and is also one of the products, as is carbon dioxide, which is removed from the liquid and leaves in a vapor product stream since it may have a negative effect on the cells. Other nutrients or media (sources of nitrogen, phosphorus, minerals, vitamins, etc.) typically must be supplied to keep the organisms happy and healthy. 

Release of liquid ethylene glycol into the environment would be expected to result in volatilization of the substance. In the atmosphere, ethylene glycol is broken down photochemically to produce hydroxyl radicals with 2day half-life. Release into soil results in near complete aerobic biodegradation within 4 days. Under anaerobic conditions, complete degradation is expected within 7 days. 

BIOLOGICAL PROPERTIES Koc 20,146 not expected to leach persistent in the aquatic environment and concentrates in sediments will probably degrade very slowly soil and aerobic half-lives 1.64-2.0 yrs surface water half-life 125-250 days ground water half-life 3.29-4.0 yrs anaerobic half-life 6.58-8.0 yrs can be detected in water by EPA Method 610 methylene chloride extraction followed by high performance liquid chromatography (HPLC) with fluorescence or UV detection or gas chromatography, or EPA Method 625 gas chromatography plus mass spectrometry... 

Jonkers, N. Knepper, T.P. de Voogt, P. Aerobic biodegradation studies of nonylphenol ethoxylates in river water using liquid chromatography-electrospray tandem mass spectrometry. Environ. Sci. Technol. 2001,35 (2), 335-340. 

Another, more drastic approach to improve the precision of CO2 measurement and ascertain that CO2 derived from a test material is effectively determined, involves the use of radiolabelled test material. An aerobic, aquatic composting test procedure in which the production of C02 is measured by absorption and liquid scintillation counting has been published as ASTM D6340-98(2007) - Standard test methods for determining aerobic biodegradation of radiolabelled plastic materials in an aqueous or compost environment. 

This combination of anaerobic and aerobic environment adds some complexity to the process but enables larger loads to be purified such as shown in Figure 2-23. One of the primary effluent gasses is trimethylamine. This tertiary amine has the very characteristic odor of rotten fish. Combustion methods can be used to treat this waste but these will produce NOj, effluents unless very special measures are employed in waste treatment. An alternative wet chemical processes was developed (Bohrer, 1999). The liquid solution waste can also be oxidized to produce a non-odoriferous solid using hydrogen peroxide. This alternative waste treatment process keeps the nitrogen fixed, reducing the atmospheric... 

Pipelines—oil, gas, water, wastewater Internal corrosion primarily at the bottom (6 00) position Dead ends and stagnant areas Low points in long-distance pipes Waste pipes—internal corrosion at the liquid/air interface Buried pipelines—on the exterior of the pipe, especially in wet clay environments under disbonded coating Aerobic and anaerobic acid producers, SRB, manganese and iron-oxidizing bacteria, sulfur-oxidizing bacteria... 

The bacteria of the two genera Acetobacter and Gluconobacter are obligatory aerobic microorganisms with an exclusively respiratory metabolism. Their growth, at the expense of substrates that they oxidize, is therefore determined by the presence of dissolved oxygen in the environment. All of these species develop on the surface of liquid media and form a halo or haze, less often a cloudiness and a deposit. 

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