Pilot-scale study of UVC-based AOPs towards implementation at the outlet of domestic WWTPs

The degradation of a mixture of ibuprofen, naproxen, and diclofenac in various effluents by UVC/H₂O₂ or UVC/S₂O₈^2- was studied to assess the impact of the matrix composition and of the oxidant precursor on process efficiency. Experiments were carried out in a 20-L laboratory pilot (a scaled-down version of a full-scale pilot). In effluents collected during dry weather, the rural constructed wetland effluent allowed faster degradation than the urban conventional WWTP effluent, regardless of the nature of the targets or of the oxidant precursor. This was mainly attributed to a three-times higher chemical oxygen demand in the urban effluent, likely to quench the oxidative species. UV fluences to reach 90% degradation of the three compounds were 3,800 and 5,500 mJ cm^-2 in the rural effluent, whereas they were 6,600 and 6,100 mJ cm^-2 in the urban effluent with H₂O₂ and S₂O₈^2-, respectively. After a rainfall event, the rural effluent composition was not significantly affected compared to that of the urban effluent that underwent the dilution effect. Therefore, the stability of the rural effluent composition allowed comparable degradation efficiency, whereas the dilution effect led to a significant increase in the degradation rate constants in the urban effluent (up to four times higher).