Evaluation of ozone for the removal of phenolic compounds in wastewater from the Merisol Plant (Sasolburg)
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Date
2009-03-12T11:38:00Z
Authors
Mooketsi, Olebogeng Ishmael
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Abstract
Ozone was evaluated for the removal of phenolic compounds in wastewater from
the Merisol Plant. Oxidation was conducted under both acidic (pH = 4.70) and
basic (pH = 10.45) conditions. Phenol and acetic acid (as well as traces of formic,
butyric and propionic acids) were identified as major components in the Merisol
effluent. The results from the study have indicated that the phenol concentrations
in the Merisol effluent were reduced from an average of 355 mg/L to below
detectable levels within 60 min of oxidation period under both acidic and basic
conditions. Furthermore, the effluent COD concentration was reduced from
approximately 1200 mg/L to: 678 mg/L at 40 ppm O3; 590 mg/L at 80 ppm O3;
and to 579 mg/L at 120 ppm O3 under acidic conditions. Under basic conditions,
the effluent COD concentration was reduced to: 656 mg/L at 40 ppm O3; 510
mg/L at 80 ppm O3; and 397 mg/L at 120 ppm. These results were well below the
required 1000 mg/L COD specification level. Moreover, the results also indicated
that oxidation of the Merisol effluent sample under basic conditions yielded better
results when compared to oxidation under the normal pH of the effluent
(acidic).The degradation products of phenol ozone oxidation were identified as
formic, butyric and propionic acids. These acids occurred in various proportions
during the oxidation and were also removed during the process.
In conclusion, ozone oxidation technology has proven to capably treat the Merisol
effluent to the required specifications. This technology may be applied to increase
the degree of compliance of the Merisol Plant and that of Sasol One with regard to
the Department of Water Affairs and Forestry (DWAF) phenol specification under
the discharge water licence conditions.