Removal of Non-Biodegradable Organic Matters from Membrane Bioreactor Permeate By Oxidation Processes

Bui Xuan Thanh, Vo Thi Kim Quyen, Nguyen Phuoc Dan

 

ABSTRACT

This study aimed to optimize the operational parameters of oxidation processes in removing the non-biodegradable matters from the permeate of membrane bioreactor (MBR) which is used to treat dyeing and textile wastewater. The MBR was operated at the OLR of 1.3–1.7 kg COD/m3.day, HRT of 11 hours, and SRT of 60 days. The quality of MBR permeate were stable during operation period with COD and colour of 107±7 mg/L (96-114 mg/L) and 85±10 Pt-Co (70-90 Pt-Co), respectively. The insight of the advanced oxidation processes (AOPs) is to generate hydroxyl free radical (OH·) as strong oxidant to decompose the recalcitrants which cannot be oxidized by the conventional biological processes. The results show that the single ozone oxidation process removed 50% of COD and 41% of colour with the ozone generation rate of 104 mg O3/h for 25 minutes at pH 9. For the Peroxone oxidation, about 59% of COD and 53% of colour removal were achieved at the same operating conditions at pH 8.5, and molar ratio H2O2/O3 of 1:2. While for the O3/UV oxidation, COD and colour reduced to 55% and 54% after 25 minutes at pH 9. The Fenton oxidation achieved removal efficiency of 90% of colour and 84% of COD at pH 3 and the mass ratio Fe2+/H2O2/COD of 1:1:1. It indicates that the three oxidation processes could removed refractory residue from MBR permeate to meet the Vietnam National Technical Regulation for dyeing and textile wastewater (level B, QCVN 13:2008/BTNMT). In general, the single ozonation shows advantages in term of simple operation, reasonable treatment cost and rational removal color and part of non-biodegradable COD among the other AOPs. During ozonation process, non-biodegradable COD in MBR permeate converted to biodegradable COD fraction which can be further mineralized by biological process.

 

Keywords: Advanced oxidation processes (AOPs); hydroxyl free radical; Ozone; Peroxone; O3/UV; Fenton; Dyeing and textile wastewater

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doi:10.11912/jws.1.3.289-299