Ecotoxicity evaluation of a WWTP effluent treated by solar photo-Fenton at neutral pH in a raceway pond reactor

Abstract

Some pollutants can be resistant to wastewater treatment, hence becoming a risk to aquatic and terrestrial biota even at the very low concentrations (ng L-μg L) they are commonly found at. Tertiary treatments are used for micropollutant removal but little is known about the ecotoxicity of the treated effluent. In this study, a municipal secondary effluent was treated by a solar photo-Fenton reactor at initial neutral pH in a raceway pond reactor, and ecotoxicity was evaluated before and after micropollutant removal. Thirty-nine micropollutants were identified in the secondary effluent, mainly pharmaceuticals, with a total concentration of ≈80 μg L. After treatment, 99 % microcontaminant degradation was reached. As for ecotoxicity reduction, the assayed organisms showed the following sensitivity levels: Tetrahymena thermophila > Daphnia magna > Lactuca sativa > Spirodela polyrhiza ≈ Vibrio fischeri. The initial effluent showed an inhibitory effect of 40 % for T. thermophila and 20 % for D. magna. After 20 min of photo-Fenton treatment, no toxic effect was observed for T. thermophila and toxicity dropped to 5 % for D. magna. Graphical abstract Ecotoxicity removal by solar photo-Fenton at neutral pH. ᅟ.

Does micropollutant removal by solar photo‐Fenton reduce ecotoxicity in municipal wastewater? A comprehensive study at pilot scale open reactors

“…These results are in accordance with recent studies demonstrating the high efficiency of solar photo‐Fenton treatment at initial neutral pH using Fe–EDDS in real municipal wastewater to remove micropollutants. In particular, Miralles‐Cuevas et al . reported 96.8% and Klamerth et al .…”

“…The first filter had a pore diameter of 100 µm and it was connected to a second filter with a pore diameter of 20 µm. According to the common experimental procedure, after the filtration process, the collected secondary effluents were stored in the dark in a 500 L recirculation tank and the pH was adjusted to 6.5 ± 0.05 using diluted H 2 SO 4 (≈0.8 L, 1 mol L −1 ) to partially remove bicarbonates until a final concentration of 5 mg L −1 (expressed as total inorganic carbon, TIC) . The presence of carbonate (CO 3 2− )/bicarbonate (HCO 3 − ) slows AOPs down because these anions may react with HO • , resulting in HO • scavenging, which inhibits the oxidative attack of the hydroxyl radical …”

“…These results are in accordance with recent studies demonstrating the high efficiency of solar photo-Fenton treatment at initial neutral pH using Fe-EDDS in real municipal wastewater to remove micropollutants. In particular, Miralles-Cuevas et al 19 reported 96.8% and Klamerth et al 5 95.5% efficiency using Fe-EDDS but the treatment was performed in a compound parabolic collector (CPC). Although the sequential iron dosage strategy has been proven successful for micropollutant removal in a simulated secondary effluent, 11 this is the first time it has been applied to real municipal wastewater in a raceway pond reactor.…”

Metallurgical Wastes Employed as Catalysts and Photocatalysts for Water Treatment: A Review

“…Nanoparticles are a preferable option, but it must be considered that a high density of suspended particles may block out the light source and reduce the efficiency of the process [63][64][65]. Raceway reactors, where the catalyst is not suspended but rests at the bottom of the raceway with the contaminated water flowing over it, eliminate such considerations but require high amounts of catalysts [66][67][68]. Here, the development of low-cost alternatives to highly specific nanoparticle materials is particularly interesting.…”

Degradation of persistent pesticides via advanced oxidation and reductive processes.

“…Five ecotoxicity tests were selected: V. fischeri (acute toxicity), T. thermophila (chronic toxicity), C. vulgaris (chronic toxicity), and antimicrobial activity against Grampositive (B. subtilis) and Gram-negative (E. coli) bacteria. These species were chosen because some tests are standardized and others are commonly used to evaluate the toxicity reduction during the treatment of contaminated waters by AOPs (CAIANELO et al, 2016;FREITAS et al, 2016;SAGGIORO et al, 2015;URBANO et al, 2016). For all the assays, serial dilutions of a 414-µmol L -1 (100 mg L -1 ) AMZ solution were used to find the dose at which 50% of the population exhibited a loss in their response (luminescence loss or growth inhibition), in order to calculate the EC 50 values.…”