Table 3.
Toxicity evaluation during post-treatment of municipal wastewater treatment plant effluent by solar photo-Fenton at pilot-scale.
| Test-Organism | Matrix (treatment technology effluent) | Reactor | Reactor features | Iron source | pH | Experimental scale | Results | Reference |
|---|---|---|---|---|---|---|---|---|
| Daphnia magna (acute toxicity), Sinapis alba, Lepidium sativum, and Sorghum saccharatum (phytotoxicity) | MSE (CAS) |
CPC | Twelve borosilicate glass tubes with diameter of 55 mm and mounted on curved polished aluminum reflectors. The overall volume capacity of the reactor was 250 L and total irradiated volume was 85.4 L | Fe2+ (5 mg L−1) | 2.8 | Pilot scale | Treated samples (180 min) were more toxic than CAS effluent for D. magna. Toxic effect only decreased (6.7 %) after 300 min. The three plant species used on phytotoxicity assays displayed an interesting profile concerning germination, root and shoot inhibition stimulated by the presence of oxidation by-products. Solar photo-Fenton reduced phytotoxicity. | (Michael et al., 2012) |
| Daphnia magna (acute toxicity), Sinapis alba, Lepidium sativum, and Sorghum saccharatum (phytotoxicity) | MSE (CAS) |
CPC | Total volume of 100 L with irradiated volume of 21.4 L. Glass tubes mounted on a fixed platform tilted at the local latitude (35°), reflecting surface was made of resistant and highly reflecting polished aluminum. | Fe2+ at (5 mg L−1) | 2.8–2.9 | Pilot scale | Neither plant growth nor the immobilization of D. magna were affected by the presence of CECs nor their transformation products after solar photo-Fenton. Therefore, toxic effects were associated to dissolved organic matter and its oxidation products. The post-treatment reduced toxicity and phytotoxicity through time. | (Michael et al., 2019) |
| Daphnia magna and Aliivibrio fischeri (acute toxicity), Raphidocelis subcapitata (chronic toxicity). | UP and MSE (CAS) |
CTC | Irradiated volume of 10.24 L, consisted of 8 acrylic glass tubes (length of 150 cm, external diameter of 3.3 cm, and thickness of 0.25 cm). | Fe2+ (5.6 mg L−1) Fe3+-EDDS (5.6:58 mg L−1) |
Natural | Pilot scale | Photo-Fenton performance was toxic to A. fischeri < R. subcapitata < D. magna. Toxicity to R. subcapitata decreased from 100 % up to 53 % (solar photo-Fenton) and from 57 % to 38 % (solar photo-Fenton with EDDS) within 300 min of treatment. High toxicity levels (100 %) were detected for D. magna test for both treatments. None of the treatments were able to reduce toxicity to 50 % of initial effect, and toxicity increased as treatment time increased from 0 to 300 min for all endpoints. | (Maniakova et al., 2020) |
| Aliivibrio fischeri and Drosophila melanogaster flies (acute toxicity) | UP and MSE (UASB + PT) |
Solar reactor | Conventional glass recipient depth: 4.9 cm; diameter: 15.5 cm, irradiated surface: 189 cm2, total volume: 500 mL Artificial irradiation by two black light lamps (10 W each, 350–400 nm) placed in parallel (3.5 cm) 1.0 cm above the surface | Fe3+-EDDS Molar ratio of 1:1; 1:2; 1:3 |
2.7 and 6.0 | Laboratory scale |
UP: inhibition of the bioluminescence emitted by A. fischeri at 13.6 kJ m−2 increased for both artificial and solar irradiation indicating the generation of toxic byproducts. Toxic effect to A. fischeri was eliminated within 41.5 kJ m−2 of treatment. MWW: Photo-Fenton treatment reduced the toxicity to D. melanogaster flies. |
(Gonçalves et al., 2020) |
| Daphnia magna and Aliivibrio fischeri (acute toxicity), Tetrahymena thermophila (chronic toxicity), and Spirodela polyrhiza and Lactuca sativa (phytotoxicity) | MSE (CAS) |
RPR | PVC, 0.98 m length and 0.36 m width separated by a central wall. The paddlewheel set at 200 rpm, mixing time of ~1.52 min. | Fe2+ (3 × 20 mg L−1) |
Natural | Pilot Scale | Inhibition of D. magna by CAS effluent was equivalent to 20 %. After 20 min of photo-Fenton treatment, inhibition dropped to 5 %. A. fischeri bioassays presented no sensitivity before or after photo-Fenton. For chronic toxicity, inhibition of T. thermophila exposed to CAS effluent was equivalent to 40.9 %. After 20 and 90 min of photo-Fenton, no toxic effect was observed. CAS effluent showed stimulation of L. sativa, while solar photo-Fenton inhibited seeds growth after 20 min of treatment and no effect was observed within 90 min. | (Freitas et al., 2017) |
| Daphnia magna and Aliivibrio fischeri (acute toxicity), and Tetrahymena thermophila (chronic toxicity) | MSE (CAS) |
CPC and RPR |
CPC: Two twin reactor of Pyrex tubes, length of 1.5 m and diameter of 5 cm, volume of 7 L and illuminated volume of 2.1 L, mixing time of 5 min. RPR: maximum volume of 18 L, 5 cm liquid depth, of 0.98 m length and 0.37 m width. 3 min mixing time. |
Fe2+ (20 mg L−1) |
7.0 | Pilot Scale | CAS effluent was not toxicity to D. magna nor A. fischeri. Likewise, there was no increase in toxicity for D. magna after solar photo-Fenton for both reactors. Meanwhile, there was an increase in luminescence after 30 min of treatment. Bioassays with T. thermophila showed an inhibitory effect of 13.8 % for CAS effluent, and photo-Fenton in the RPR had higher reduction upon chronic toxicity compared to CPC. | (Esteban García et al., 2018) |
Note: MSE = municipal secondary effluent; UP = ultrapure water; CAS = conventional activated sludge; UASB + PT = upflow anaerobic sludge blanket reactor followed by post-treatment; CPC = compound parabolic collector; RPR = raceway pond reactor.