Combining Constructed Wetlands and UV Photolysis for the Advanced Removal of Organic Matter, Nitrogen, and Emerging Pollutants from Wastewater

This study reports the performance of a three-step lab-scale system including a hybrid digester (HD), a vertical flow (VF) constructed wetland, and a photodegradation (PD) lamp, with two different arrangements regarding the position of the recirculation point. In addition to total suspended solids (TSS), chemical oxygen demand (COD), and nitrogen compounds, removal of the following pollutants was investigated: paracetamol (ACE), ofloxacin (OFL), caffeine (CAF), ketoprofen (KET), ibuprofen (IBU), clofibric acid (ACB), bisphenol A (BPA), and sotalol (SOT). An excellent performance of HD was achieved on the elimination of TSS (82.2 +/- 18.5% on average) and COD (63.9 +/- 4.1%). TSS and COD removal increased to 91.2 +/- 0.4% and 83.4 +/- 2.9%, respectively, for the combined HD-VF system. Ammonia removal was 57.0 +/- 7.8% in the VF unit while significant denitrification occurred in the HD. The overall HD-VF-PD system achieved mean removals of 100% for OFL, KET, SOT, and IBU, 98 +/- 2% for ACE, 87 +/- 8% for CAF, 81 +/- 38% for ACB and 26 +/- 9% for BPA. The removal of ACE, OFL, CAF, and IBU was mostly by biodegradation in the HD and VF units while the PD unit was responsible for the removal of KET, ACB, and SOT.

Automated summary

This study evaluated the performance of a three-step lab-scale system consisting of a hybrid digester, a vertical flow constructed wetland, and a photodegradation lamp. Different arrangements of the recirculation point were tested. The system achieved excellent removal of total suspended solids (TSS) and chemical oxygen demand (COD). Additionally, the system showed significant removal of various pharmaceutical and personal care products (PPCPs), with different removal mechanisms observed in different units of the system.