Phenol, oxygen demand

Toxic or malodorous pollutants can be removed from industrial gas streams by reaction with hydrogen peroxide (174,175). Many Hquid-phase methods have been patented for the removal of NO gases (138,142,174,176—178), sulfur dioxide, reduced sulfur compounds, amines (154,171,172), and phenols (169). Other effluent treatments include the reduction of biological oxygen demand (BOD) and COD, color, odor (142,179,180), and chlorine concentration. 

Petrochemical units generate waste waters from process operations such as vapor condensation, from cooling tower blowdown, and from stormwater runoff. Process waste waters are generated at a rate of about 15 cubic meters per hour (m /hr), based on 500,000 tpy ethylene production, and may contain biochemical oxygen demand (BOD) levels of 100 mg/1, as well as chemical oxygen demand (COD) of 1,500 to 6,000 mg/1, suspended solids of 100 to 400 mg/1, and oil and grease of 30 to 600 mg/1. Phenol levels of up to 200 mg/1 and benzene levels of up to 100 mg/1 may also be present. 

Isomerization wastewaters present no major pollutant discharge problems. Sulfides and ammonia are not likely to be present in the effluent. Isomerization wastewaters should also be low in phenolics and oxygen demand. 

Wastewaters from asphalt blowing contain high concentrations of oil and have high oxygen demand. Small quantities of phenols may also be present. 

When the oxygen concentration is equal to 300% in excess of stoichiometric oxygen demand, the global rate of phenol destruction can be expressed as ... 

Autoxidation can lead to deterioration of food, drugs, cosmetics, or polymers, and inhibition of this reaction is therefore an important technical issue. The most important classes of autoxidation inhibitors are radical scavengers (phenols, sterically demanding amines [65, 66]), oxygen scavengers (e.g. ascorbic acid), UV-light absorbers, and chelators such as EDTA (to stabilize high oxidation states of metals and thereby suppress the metal-catalyzed conversion of peroxides to alkoxyl radicals) [67]. 

The use of Fenton s reagent for waste water treatment is relatively new compared to its use in mechanistic investigations in organic chemistry.13-15 Fenton s reagent is able to destroy phenols (Figure 5.2), chlorinated phenols and herbicides in water media, as well as reducing chemical oxygen demand in municipal waste. 

In the experiments involved the amount of water from the gas scrubber related to the amount of raw input material was about 0.18 m3/t. The pH-value of the water was mildly alkaline, the chloride concentration was about 290 mg Cl /1 and the total amount of phenols about 23 mg/1. Annealing loss of the scrubber water sediment was 2800 mg/1, and the annealing residue amounted to 8000 mg/1. Sulphur was found mainly in an oxidized form. Results of initial experiments using an apparatus for the determination of the biochemical oxygen demand allowed the conclusion that an undisturbed decomposition of the organic components can take place. 

In the case of industrial wastewater, several other compounds can also be involved, such as sulphide, hexavalent chromium or organic molecules. This last group of compounds is considered hereafter with regard to their economic and/or environmental importance. For example, Fig. 5 presents several specific compounds encountered in refinery and petrochemical wastewater. Thus, phenol, EPA (ethylpropylacrolein), TBC (tertiobutylcatechol), NMP (/V-methylpyrolidone) and nitrite can be detected in effluents or process water [21], Moreover, the estimation of complementary aggregate parameters, such as total oxygen demand (TOD), is possible from the estimation of one of the previous organic compounds [3] (Fig. 6). 

On account of the high toxicity and considerable stability of phenols, these compounds lead to important problems in wastewater treatment. The biological treatment of water flows was inhibited by phenol at a concentration of 75 mg hydroquinone at a concentration of 15 mg 1 inhibited the biochemical treatment of wastewaters and the threshold concentration of the effect of 2,4-dinitrophenol on the biological treatment was found to be 20 mg 1 - m-aminophenol at a concentration of 1 mg 1 inhibited the BOD (biochemical oxygen demand) and nitrification of wastewaters. 

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