Oxygen biological processes

Many different factors influence the performance of biological treatment systems. Although each specific biological process has special requirements, factors common to biological processes, besides biodegradabihty, include organic concentration, temperature, pH, nutrients, and oxygen (aerobic or anaerobic). 

A number of biological processes result in the marine production of gases that have a greenhouse role, similar to water vapour and COj. In low oxygen environments, of the sort discussed in the next section, methane is produced by anaerobic bacterial decay ... 

Biochemical oxygen demand (BOD)- Amount of dissolved oxygen consumed in five days by biological processes breaking down organic matter. 

Nitrogen oxide (NO) has been found to be a key component in many biological processes. It also can react with oxygen to give die brown gas N02. When one mole of NO reacts with oxygen, 57.0 kj ofheat is evolved. 

To facilitate biodegradation, the leachate may require modification through pH adjustment, removal or addition of oxygen, amendment with nutrients, or dilution or removal of toxic species. Microbial nutrition is complex and is better understood for aerobes than for anaerobes.34 Biological processes typically favor a pH near 7. Pretreatment processes to remove inhibitory components include coagulation and precipitation, carbon adsorption, and possibly ozonation. 

Biochemical Oxygen Demand A numerical estimate of contamination in water expressed in milligrams per liter of dissolved oxygen. A measure of the amount of oxygen consumed in biological processes that break down organic matter in water. 

In many crucial biological processes, such as oxygen transport, electron transport, intermediary metabolism, metals play an important part. Therefore, disorders of metal homeostasis, metal bioavailability or toxicity caused by metal excess, are responsible for a large number of human diseases. We have already mentioned disorders of iron metabolism (see Chapter 7) and of copper metabolism (see Chapter 14). The important role, particularly of redox metals such as copper and iron, and also of zinc, in neurodegenerative diseases, such as Parkinson s disease, Alzheimer s disease, etc. has also been discussed (see Chapter 18). We will not further discuss them here. 

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