Integrated modelling of advanced oxidation processes: modelling of a full-scale UV/H2O2 reactor for horticultural water reuse

Introduction: The last few decades, Advanced Oxidation Processes (AOP's) are being considered to be promising technologies to implement where other techniques fail. Modelling of these processes can offer an elegant and cost-effective tool to answer some research questions. The latter often refer to the oxidation dynamics of organic matter which are very complex and not yet completely unravelled. The aim of this study is to get more insight in organic matter dynamics by extending an existing AOP model Methods: The dynamics between different organic matter fractions during AOP treatment of water for horticultural reuse were studied. A kinetic model from literature that uses UV absorbance at 310nm (UVA310) as a surrogate for natural organic matter (NOM), was used to study the scavenging effect of NOM on hydroxyl radicals and the overall process kinetics. A full-scale UV/H2O2 reactor of a horticultural industry treating effluent of a reed bed was used for validation. To further extend this model in terms of organic matter, the chemical oxygen demand (COD) was split up into four fractions based on the particulate/soluble and inert/biodegradable character. Results: To some extent, the UVA310 concentration could be modelled with the existing model. However, once UVA310 reached its minimum level, the model assumed the end of the reaction although measured COD levels kept changing. The dynamic screening of the COD revealed that solubilisation of particulate organic matter takes place and conversion of large inert organic chains into smaller assimilable ones can provide new substrate for bacterial growth. Conclusions: This study demonstrated that UVA310 can be used to describe an initial reaction phase but does not cover the whole organic matter content. Due to the complexity of these matrices present in (waste)water, more extended models are needed to build a tool that is more reliable and widely applicable. As such, a first screening of the organic loading in a closed water cycle of a horticultural industry indicated the dynamic character of four COD fractions. Consequently, the combination of AOPU+2019s and biological treatment processes can lower the overall organic matter content drastically and hence, increases the biostability of the water cycle.

Publication year:2010