1994
© IWA Publishing 2013 Water Science & Technology
|
68.9
|
2013
Assessing the potential of a UV-based AOP for treating high-salinity municipal wastewater reverse osmosis concentrate Muhammad Umar, Felicity Roddick and Linhua Fan
ABSTRACT The UVC/H2O2 process was studied at laboratory scale for the treatment of one moderate (conductivity ∼8 mS/cm) and two high salinity (∼23 mS/cm) municipal wastewater reverse osmosis concentrate (ROC) samples with varying organic and inorganic characteristics. The process efficiency was characterized in terms of reduction of dissolved organic carbon (DOC), chemical oxygen demand (COD), colour and absorbance at 254 nm (A254), and the improvement of biodegradability. The reduction of colour and A254 was significantly greater than for DOC and COD for all samples due to
Muhammad Umar Felicity Roddick (corresponding author) Linhua Fan School of Civil, Environmental and Chemical Engineering, Water: Effective Technologies and Tools Centre, RMIT University, Melbourne, Australia E-mail: [email protected]
the greater breakdown of humic compounds, as confirmed by fluorescence excitation-emission matrix spectra. Fairly small differences in the reduction of DOC (26–38%) and COD (25–37%) were observed for all samples, suggesting that the salinity of the ROC did not have a significant impact on the UVC/H2O2 treatment under the test conditions. The biodegradability of the treated ROC samples improved markedly (approximately 2-fold) after 60 min UVC/H2O2 treatment. This study indicates the potential of UVC/H2O2 treatment followed by biological processes for treating high-salinity concentrate, and the robustness of the process where the characteristics of the secondary effluent (influent to RO) and thus resultant ROC vary significantly. Key words
| biodegradability, COD, DOC, reverse osmosis concentrate, salinity, UVC/H2O2
INTRODUCTION Reverse osmosis (RO) based processes are being used increasingly in municipal wastewater reclamation applications. Advances in RO technology in recent years have made it a practical and affordable means for producing high quality recycled water. Due to its good and reliable performance, RO is now widely used as a polishing treatment for secondary effluent in water reclamation schemes such as aquifer recharge and indirect potable use. Furthermore, the advantages of modular construction and small footprint allow membrane technology to be combined with other treatment technologies (Chelme-Ayala et al. ). RO technology uses semi-permeable membranes capable of separating a solution into purified water (permeate) and retentate, also termed RO concentrate (ROC). The ROC comprises approximately 15–25% of the input stream (Radjenovic et al. ), and contains almost all the constituents present in the RO feed at elevated concentrations. The high concentrations of contaminants in the ROC may lead to negative environmental impact on its disposal, which doi: 10.2166/wst.2013.417
remains a critical factor limiting the applications of this technology in advanced/tertiary wastewater treatment. Over the past decade, there has been growing interest in developing cost-effective treatment strategies to remove the organic content from the ROC, and hence reduce environmental and health risks associated with its disposal or reuse. Advanced oxidation processes (AOPs), which are based on the generation of strong oxidative species (usually hydroxyl radicals (•OH)) are one of the promising techniques for the treatment of ROC. UVC/H2O2 is one of the most commonly used AOPs for the treatment of water and wastewater. Due to the successful use of UV-based AOPs for treating recalcitrant compounds in domestic and industrial wastewater, their use in the treatment of ROC has recently been investigated by several researchers (Westerhoff et al. ; Bagastyo et al. ; Liu et al. ; Zhou et al. ). They reported dissolved organic carbon (DOC) reduction of 40–80% under varying conditions of UV irradiation and H2O2 dosage,
1995
M. Umar et al.
|
UV-based AOP for treating high-salinity ROC
except Zhou et al. (), who achieved
© IWA Publishing 2013 Water Science & Technology
|
68.9
|
2013
Assessing the potential of a UV-based AOP for treating high-salinity municipal wastewater reverse osmosis concentrate Muhammad Umar, Felicity Roddick and Linhua Fan
ABSTRACT The UVC/H2O2 process was studied at laboratory scale for the treatment of one moderate (conductivity ∼8 mS/cm) and two high salinity (∼23 mS/cm) municipal wastewater reverse osmosis concentrate (ROC) samples with varying organic and inorganic characteristics. The process efficiency was characterized in terms of reduction of dissolved organic carbon (DOC), chemical oxygen demand (COD), colour and absorbance at 254 nm (A254), and the improvement of biodegradability. The reduction of colour and A254 was significantly greater than for DOC and COD for all samples due to
Muhammad Umar Felicity Roddick (corresponding author) Linhua Fan School of Civil, Environmental and Chemical Engineering, Water: Effective Technologies and Tools Centre, RMIT University, Melbourne, Australia E-mail: [email protected]
the greater breakdown of humic compounds, as confirmed by fluorescence excitation-emission matrix spectra. Fairly small differences in the reduction of DOC (26–38%) and COD (25–37%) were observed for all samples, suggesting that the salinity of the ROC did not have a significant impact on the UVC/H2O2 treatment under the test conditions. The biodegradability of the treated ROC samples improved markedly (approximately 2-fold) after 60 min UVC/H2O2 treatment. This study indicates the potential of UVC/H2O2 treatment followed by biological processes for treating high-salinity concentrate, and the robustness of the process where the characteristics of the secondary effluent (influent to RO) and thus resultant ROC vary significantly. Key words
| biodegradability, COD, DOC, reverse osmosis concentrate, salinity, UVC/H2O2
INTRODUCTION Reverse osmosis (RO) based processes are being used increasingly in municipal wastewater reclamation applications. Advances in RO technology in recent years have made it a practical and affordable means for producing high quality recycled water. Due to its good and reliable performance, RO is now widely used as a polishing treatment for secondary effluent in water reclamation schemes such as aquifer recharge and indirect potable use. Furthermore, the advantages of modular construction and small footprint allow membrane technology to be combined with other treatment technologies (Chelme-Ayala et al. ). RO technology uses semi-permeable membranes capable of separating a solution into purified water (permeate) and retentate, also termed RO concentrate (ROC). The ROC comprises approximately 15–25% of the input stream (Radjenovic et al. ), and contains almost all the constituents present in the RO feed at elevated concentrations. The high concentrations of contaminants in the ROC may lead to negative environmental impact on its disposal, which doi: 10.2166/wst.2013.417
remains a critical factor limiting the applications of this technology in advanced/tertiary wastewater treatment. Over the past decade, there has been growing interest in developing cost-effective treatment strategies to remove the organic content from the ROC, and hence reduce environmental and health risks associated with its disposal or reuse. Advanced oxidation processes (AOPs), which are based on the generation of strong oxidative species (usually hydroxyl radicals (•OH)) are one of the promising techniques for the treatment of ROC. UVC/H2O2 is one of the most commonly used AOPs for the treatment of water and wastewater. Due to the successful use of UV-based AOPs for treating recalcitrant compounds in domestic and industrial wastewater, their use in the treatment of ROC has recently been investigated by several researchers (Westerhoff et al. ; Bagastyo et al. ; Liu et al. ; Zhou et al. ). They reported dissolved organic carbon (DOC) reduction of 40–80% under varying conditions of UV irradiation and H2O2 dosage,
1995
M. Umar et al.
|
UV-based AOP for treating high-salinity ROC
except Zhou et al. (), who achieved
