Impact of ozonation in removing organic micro-pollutants in primary and secondary municipal wastewater: effect of process parameters

Journal article

Authors / Editors

Ochieng, Aoyi

Research Areas

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Publication Details

Author list: Mecha AC, Onyango MS, Ochieng A, Momba MNB

Publisher: IWA Publishing

Place: LONDON

Publication year: 2016

Journal: Water Science & Technology (0273-1223)

Journal acronym: WATER SCI TECHNOL

Volume number: 74

Issue number: 3

Start page: 756

End page: 765

Number of pages: 10

ISSN: 0273-1223

eISSN: 1996-9732

Languages: English-Great Britain (EN-GB)

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Abstract

The study investigates the influence of process parameters on the effectiveness of ozonation in the removal of organic micro-pollutants from wastewater. Primary and secondary municipal wastewater containing phenol was treated. The effect of operating parameters such as initial pH, ozone dosage, and initial contaminant concentration was studied. An increase in contaminant decomposition with pH (3-11) was observed. The contaminant removal efficiencies increased with an increase in ozone dose rate (5.5-36.17 mg L-1 min(-1)). Furthermore, the ultraviolet absorbance (UV 254 nm) of the wastewater decreased during ozonation indicating the breakdown of complex organic compounds into low molecular weight organics. Along the reaction, the pH of wastewater decreased from 11 to around 8.5 due to the formation of intermediate acidic species. Moreover, the biodegradability of wastewaters, measured as biological and chemical oxygen demand (BOD5/COD), increased from 0.22 to 0.53. High ozone utilization efficiencies of up to 95% were attained thereby increasing the process efficiency; and they were dependent on the ozone dosage and pH of solution. Ozonation of secondary wastewater attained the South African water standards in terms of COD required for wastewater discharge and dissolved organic carbon in drinking water and increased significantly the biodegradability of primary wastewater.

Keywords

chemical oxygen demand, dissolved organic carbon, Municipal wastewater, ozone utilization, phenol

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