Removal of micropollutants by UASB reactor and post-treatment by Fenton and photo-Fenton: Matrix effect and toxicity responses.

Literature is scarce on the performance of Fenton-based processes as post-treatment of municipal wastewater treated by upflow anaerobic sludge blanket (UASB) reactor. This study aims to perform Fenton and photo-Fenton from UASB influent and effluent matrices to remove micropollutants (MPs) models: atrazine (ATZ), rifampicin (RIF), and 17α-ethynylestradiol (EE2). A UASB reactor at bench-scale (14 L) was operated with these MPs, and the AOPs experiments at bench-scale were performed on a conventional photochemical reactor (1 L). A high-pressure vapor mercury lamp was used for photo-Fenton process (UVA-Vis) as a radiation source. Microcrustacean Daphnia magna (acute toxicity) and seeds of Lactuca sativa (phytotoxicity) were indicator organisms for toxicity monitoring. The UASB reactor showed stability removing 90% of the mean chemical oxygen demand, and removal efficiencies for ATZ, RIF, and EE2 were 16.5%, 45.9%, and 15.7%, respectively. A matrix effect was noted regarding the application of both Fenton and photo-Fenton in UASB influent and effluent to remove MPs and toxicity responses. The pesticide ATZ was the most recalcitrant compound, yet the processes carried out from UASB effluent achieved removal >99.99%. The post-treatment of the UASB reactor by photo-Fenton removed acute toxicity in D. magna for all treatment times. However, only the photo-Fenton conducted for 90 min did not result in a phytotoxic effect in L. sativa.

Aerobic removal of stigmasterol contained in kraft mill effluents

Kraft mill effluent, due to its organic matter content and acute toxicity, must be treated. A primary treatment followed by a secondary treatment is the most common system. Aerated lagoon is also considered an effective biological treatment, although this technology has some drawbacks related with operation parameters and land extension space. Moreover, the recovery efficiency for micropollutants contained in kraft mill effluent is questioned due to the anoxic zone in the system. The goal of this work is to evaluate the performance of the aerated lagoon to remove stigmasterol contained in kraft mill effluents. Kraft mill effluent was treated by an aerated lagoon (AL), which was operated with three different stigmasterol load rates (SLR = 0.2, 0.6 and 1.1 mg/L x d) and a hydraulic retention time of 1 day. The AL’s maximum Chemical Oxygen Demand (COD) removal was 65 percent, whereas the Biological Oxygen Demand (BOD5) was around 95 percent. The removal efficiency of stigmasterol removal was 96 percent when SLR 1.1 mg/L x d, although an accumulation of stigmasterol was detected for lower SLR.