|MadSci Network: Environment & Ecology|
Hi, Stephanie - biodegradation is a process in which organic or carbon- based molecules are broken down into smaller, more simple molecules which are ordinarily found in the environment. This breaking down, or degradation, is called biodegradation when it is reliant on simple organisms – bacteria most commonly, to make it happen. All chemical reactions involve oxidation and reduction – one reagent gets oxidised, the other reduced – and biodegradation reactions are no different. Oxidative biodegradation is one kind, and reductive is the other, and you will often see these referred to as “aerobic” and “anaerobic” degradations. Aerobic simply means that it occurs in the air, or on the presence of oxygen – it requires oxygen as a key reagent, whereas anaerobic reactions will continue happily in the complete absence of oxygen. An common example is in our landfill sites where while the air (and water) are available, most organic wastes decompose rapidly, but if the landfill is sealed, and fresh air cannot get to the wastes, the air gets used up, and is replaced by methane, and everything slows down, with only anerobic processes of degradation occurring. You may have heard of a couple of terms used: BOD and COD – as characteristics of wastes. These stand for biological oxygen demand and chemical oxygen demand. The first is actually a measure of biodegradability – and is measured by observing the consumption of oxygen when a sample is allowed to react under controlled conditions for a specific length of time (e.g. 28 days) with a carefully prepared sample of acclimatised “bugs”. Chemical oxygen demand simply measures the amount of oxygen required to convert the organic wastes such that all the carbon in it ends up as carbon dioxide and the rest is water and a few other residuals. This works with chemicals that are not very biodegradable or as they say, persistent, and might accumulate in the environment. Of course, biodegradation is not the only degradation route for chemicals to break down in the environment – photolysis is a common route by which some chemicals are degraded – the sun’s energy can break up wastes as well as give you sunburn. So, the question of oxidation in the sea is really about the ability of the air and oxygen to get to the chemicals that need to be degraded in the sea. Because the sea is so vast, there is no practical way we could compete with the mechanisms that already exist between air and sunlight by adding oxidising chemicals to the sea. Fortunately, though, nature has provided the oceans with a very effective self-cleaning mechanism which means we don’t have to treat sea water to keep it clean – there is an awful lot of it! We just have to be careful we don’t overload the system and give it more work than it can cope with. So the fundamental answers to your two questions are: 1. Can a chemical oxidizer speed up the process of biodegadation? - Yes 2. Are there any oxidizers that would be effective in the ocean? – No ( just because of the volume of water) I hope this all helps, and here is a web-site you may find of interest. E- mail me for more help if you need it. Biodegradation web-site: http://www.labmed.umn.edu/umbbd/index.html My e-mail: firstname.lastname@example.org
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