Anoxicity

In the two-stage process, nitrification occurs under aerobic conditions in the second stage. The nitrified mixed Hquor from the second stage is internally recycled to the anoxic first stage, where denitrification occurs. 

Aerobic systems including trickling filters and rotating biological contactors (RBC) are operated in a nonflooded mode to ensure adequate oxygen supply. Other aerobic, anoxic, and anaerobic systems employ flooded reactors. The most common systems are packed beds (anaerobic trickling filter) and fluidized or expanded bed systems. 

CBOD, Denitrification—municipal, Nevada Anoxic 1450 NH3-N Aerohic <25 0.05-0.3 0.1-0.5 7-14... 

Owing to the stability of the uranyl carbonate complex, uranium is universally present in seawater at an average concentration of ca. 3.2/rgL with a daughter/parent activity ratio U) of 1.14. " In particulate matter and bottom sediments that are roughly 1 x 10 " years old, the ratio should approach unity (secular equilibrium). The principal source of dissolved uranium to the ocean is from physicochemical weathering on the continents and subsequent transport by rivers. Potentially significant oceanic U sinks include anoxic basins, organic rich sediments, phosphorites and oceanic basalts, metalliferous sediments, carbonate sediments, and saltwater marshes. " ... 

Anoxic Literally "without oxygen." An adjective describing a microbial habitat devoid of oxygen. 

The nervous system is vulnerable to attack from several directions. Neurons do not divide, and, therefore, death of a neuron always causes a permanent loss of a cell. The brain has a high demand for oxy gen. Lack of oxygen (hypoxia) rapidly causes brain damage. This manifests itself both on neurons and oligodendroglial cells. Anoxic brain damage may result from acute carbon monoxide, cyanide, and hydrogen sulfide poisonings. Carbon monoxide may also be formed in situ in the metabolism of dichloromethylene. 

Several oxohalides are also known, mostly of the types An OaXa, An OaX, An OXa and An "OX, but they have been less thoroughly studied than the halides. They are commonly prepared by oxygenation of the halide with O2 or Sb203, or in case of AnOX by hydrolysis (sometimes accidental) of AnX3. As is to be expected, the higher oxidation states are formed more readily by the lighter actinides thus An02X2, apart from the fluoro compounds, are confined to An = U. Conversely the lower oxidation states are favoured by the heavier actinides (from Am onwards). 

Normally, these reactive species are destroyed by protective enzymes, such as superoxide dismutase in mitochondria and cytosol and catalase in peroxisomes, but if a tissue has been anoxic the respiratory chain is very reduced and reoxygenation allows dangerous amounts to be formed. Muscle also contains significant quantities of the dipeptide, camosine ((J-alanylhistidine) (10—25 mM). The functions of camosine are obscure although it has been suggested to be an effective antioxidant (Pavlov et al., 1993). 

Although it is possible to identify a group of particularly toxic components in venom, it should be noted that the venoms are complex mixtures of components, many of which are synergistic. Muscle damage is particularly severe if myotoxic activity is combined with hemorrhagic activity. In this case, muscle regeneration is impaired, because the regenerating tissue is rendered anoxic at a time of intense metabolic activity. 

---