Anoxic conditions, plants under

Nitrate and oxygen also may play an important role in determining the rate of azo dyes reduction. Wuhrmann et al. demonstrated that obligate aerobes might actually decolorize azo dye compounds under temporary anoxic conditions. However, high nitrite concentrations in the mixed liquor of activated sludge plants could significantly inhibit dye removal. 

Figure 6.1 Pathways involved in glucose oxidation by plant cells (a) glycolysis, (b) Krebs cycle, (c) mitochondrial cytochrome chain. Under anoxic conditions. Reactions 1, 2 and 3 of glycolysis are catalysed by lactate dehydrogenase, pyruvate decarboxylase and alcohol dehydrogenase, respectively. ATP and ADP, adenosine tri- and diphosphate NAD and NADHa, oxidized and reduced forms of nicotinamide adenine dinucleotide PGA, phosphoglyceraldehyde PEP, phosphoenolpyruvate Acetyl-CoA, acetyl coenzyme A FP, flavoprotein cyt, cytochrome e, electron. (Modified from Fitter and Hay, 2002). Reprinted with permission from Elsevier...

Short-chain acids accumulate.under anoxic conditions/-which favor fermentative metabolism of bacteria. Such phytotoxins nay damage the plant directly or predispose plants to infection by pathogens. However plant residues nay also be used as substrates for beneficial micro-organisms to produce plant nutrients, soil conditioners, and plant protection chemicals. There is scope to promote the beneficial microbial effects against the harmful by soil management and by inoculation. 

The potential exists for denitrification to occur in the secondary clarifier sludge bed in the refinery wastewater treatment plant under anoxic conditions. The biological reduction rate of nitrate to nitrogen in the sludge blanket is typically slow due to limited soluble Chemical Oxygen Demand (COD), the food source for denitrifying... 

Local emissions from specific plants were investigated by Holzinger et al. who have identified methanol, acetaldehyde, ethanol, acetone, acetic acid, isoprene, monoterpenes, toluene, and Cio-benzenes emitted from the Mediterranean helm oak (Quercus ilex L.) [36]. After flooding, ethanol and acetaldehyde were found to increase, indicating ethanol production under anoxic condition of the root system and the subsequent transport and partial oxidation to acetaldehyde inside the green leaves. Additionally, bursts of acetaldehyde with lower ethanol emission were also found in the case of the fast light/dark changes. The rapid formation of acet-... 

Acetaldehyde is mostly formed by the enzymatic oxidation of ethanol, the latter is formed in roots under anoxic conditions or in anoxic stems of woody plants [13]. Large fluxes of acetaldehyde have been observed from the leaves when roots are flooded (limited access to oxygen) or exposed to anoxia. It has also recently been discovered that acetaldehyde can arise in leaves directly from metabolism that occurs during light-dark transitions [14]. 

The denitrifying mixed culture was obtained from sludge taken from a wastewater treatment plant, enriched in a synthetic medium (Barreiros, et al., 1998), and grown under anoxic conditions at 28°C and pH 7.0. The groundwater employed (Estarreja, Portugal), which was contaminated with nitrate concentrations in the range 140-190 mg NOJ/L, was supplemented with phosphate before each run. 

---