TITLE:
Reclaiming Biologically Pretreated Greywater for Reuse by Photocatalytic Oxidation: Qualitative Study on the Removal of Trace Organics
AUTHORS:
Holger Gulyas, Carlos F. Liriano Jorge, Margrit Reich, Ralf Otterpohl
KEYWORDS:
Flame Retardants; Greywater; Photocatalytic Oxidation; Reuse; Trace Organics
JOURNAL NAME:
Journal of Water Resource and Protection,
Vol.5 No.6,
June
14,
2013
ABSTRACT:
This study was carried out for gathering qualitative information about the potential of photocatalytic oxidation for the removal of trace organics (analysed by gas chromatography coupled to mass spectrometry, GC/MS) from biologically pretreated greywater to make it suitable for high quality reuse applications like groundwater recharge. Additionally, fractions of bulk organics (humic substances, building blocks, and low molecular weight organic acids) were quantified by liquid chromatography with organic carbon detection. Biologically pretreated greywater was subjected to photocatalytic oxidation in open stirred vessel reactors with UV lamps positioned over the reactors. UV doses of 0, 5, and 15 Wh·L-1 and TiO2 P25 photocatalyst concentrations of 1, 5, 10, and 20 g·L-1 were investigated. Photocatalysis experiments with a 15 Wh·L-1 UV dose were also conducted in the presence of 1 g·L-1 powdered activated carbon. Subsequent to mere contact of the photocatalyst to biologically pretreated greywater without UV, GC/MS did not indicate a substantial removal of trace organics, while humic substances were increasingly adsorbed by increasing photocatalyst concentration. A UV dose of 15 Wh·L-1 and TiO2 concentrations > 5 g·L-1 were favorable conditions for photocatalytic oxidation resulting in the removal of most of the trace organics, especially chlorinated phosphate flame retardants. Also humic substances were efficiently removed under these conditions. Photocatalytic oxidation is thus a promising process for advanced greywater treatment prior to groundwater recharge. Addition of powdered activated carbon did not improve trace and bulk organics removal by photocatalysis with a UV dose of 15 Wh·L-1 and with photocatalyst concentrations > 5 g·L-1.