Anoxic compartments

Figure 1 presents the most widely used ASWWTP configurations for combined N and P removal. The A2/0 process presents a sequence of anaerobic reactors (to promote the growth of PAOs) followed by a sequence of anoxic to promote denitrification, and finally aerobic reactors. It has one internal and one external recycle stream. The internal recycle stream conducts a fraction of the nitrified liquor from the last aerobic to the P anoxic compartment, and the external recycle conducts a fraction of the sludge from the underflow of the sedimentation tank to the P compartment. In the UCT process, both recycle streams are feed to the anoxic zone and a second internal recycle stream is present from the anoxic to the anaerobic compartment. The modified UCT process has 2 internal recycles and 1 external one as in the original UCT process but the anoxic zone is divided into 2 zones. The external recycle is directed from the underflow of the decanter to the P anoxic zone. The P internal recycle stream conducts a fraction of the nitrified liquor from the aerobic to the 2 anoxic zone. Finally, the second internal recycle stream pumps a fraction of the mixed liquor from the P anoxic back to the anaerobic compartment. The Bardenpho process configuration has also an external... 

It is not only the properties of the compound in question that influence its behaviour but also the environmental and operational conditions it is subjected to (temperature, pressure, pH, redox conditions), as well as the particular configurations of the (biological) reactors (in particular, their partitioning into compartments featuring different conditions mainly aerobic, anoxic and anaerobic), SRT and, to variable extents, HRT. Moreover, in chemical processes, reagent... 

FIGURE 9.10 A sanitary landfill. The refuse is placed in compartments that may be separated with poorly permeable fill dirt, typically after each day s disposal, then covered with dirt. In larger, more advanced landfills, the methane produced by anoxic fermentation of biodegradable biomass is collected and used as fuel. 

Schematic of key chemical transformations that may occur on the addition of iron-based coagulant to a MBR (Wang and Waite, 2010). Addition of inorganic Fe(lll) salts will result in either precipitation as amorphous ferric oxide (AFO) (reaction b), complexation by soluble microbial products (SMPs) (reaction c) or reduction to Fe(ll) (reaction j). Fe(lll) in both inorganic (as AFO) and SMP-bound forms (as Fe(lll)SMP) may undergo reduction (especially in the low Eh (<-0.2 mV) anoxic region (reactions e, a and j). Any Fe(ll) present may be oxidized (especially in the aerated oxic compartment) (reactions i and f). Fe(ll) may form insoluble precipitates such as ferrous phosphate or vivianite (reaction k). 

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