The present study aims to assess the removal of 3-amino-5-methylisoxazole (AMI), a recalcitrant by-product resulting from the biological breakdown of some pharmaceuticals, applying a solar ...photo-Fenton process assisted by ferrioxalate complexes (SPFF) (Fe
3+
/H
2
O
2
/oxalic acid/UVA-Vis) and classical solar photo-Fenton process (SPF) (Fe
2+
/H
2
O
2
/UVA-Vis). The oxidation ability of SPFF was evaluated at different iron/oxalate molar ratios (1:3, 1:6, and 1:9, with total iron = 3.58 × 10
−2
mM and oxalic acid = 1.07 × 10
−1
, 2.14 × 10
−1
and 3.22 × 10
−1
mM, respectively) and pH values (3.5–6.5), using low iron contents (2.0 mg Fe
3+
L
−1
). Additionally, the use of other organic ligands such as citrate and ethylenediamine-N,N′-disuccinic acid (EDDS) was tested. The oxidation power of the classical SPF was assessed at different pH values (2.8–4.0) using 2.0 mg Fe
2+
per liter. Furthermore, the effect of AMI concentration (2–20 mg L
−1
), presence of inorganic ions (Cl
−
, SO
4
2−
, NO
3
−
, HCO
3
−
, NH
4
+
), and radical scavengers (sodium azide and D-mannitol) on the SPF method at pH 3.5 was also assessed. Experiments were done using a lab-scale photoreactor with a compound parabolic collector (CPC) under simulated solar radiation. A pilot-scale assay was conducted using the best operation conditions. While at near neutral pH, an iron/oxalate molar ratio of 1:9 led to the removal of 72 % of AMI after 90 min of SPFF, at pH 3.5, an iron/oxalate molar ratio of 1:3 was enough to achieve complete AMI degradation (below the detection limit) after 30 min of reaction. The SPF process at pH 3.5 underwent a slower AMI degradation, reaching total AMI degradation after 40 min of reaction. The scale up of SPF process showed a good reproducibility. Oxalic and oxamic acids were identified as the main low-molecular-weight carboxylic acids detected during the pilot-scale SPF reaction.
Graphical abstract
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•Leachate very rich in biodegradable and recalcitrant organics, ammonium and chromium.•Treatment line: initial bio treatment – coagulation – AOP/EAOP - final bio treatment.•Bio ...treatment including nitrification-denitrification chosen as the best first stage.•Photoelectro-Fenton process selected as the best AOP/EAOP.•Final leachate fulfilling the discharge limits into waterbodies.
This study aimed at developing an efficient multistage treatment strategy for a complex industrial landfill leachate: a leather tannery landfill leachate. Based on the leachate physicochemical characteristics, the following treatment train was delineated and tested: (i) initial biological process for removal of biodegradable organics, ammonium and alkalinity, (ii) coagulation/flocculation process for total removal of chromium and partial removal of recalcitrant organics and suspended solids, (iii) advanced oxidation process (AOP) or electrochemical AOP (EAOP) for degradation of recalcitrant organics and biodegradability enhancement, and (iv) final biological polishing step. Two initial biological treatment configurations were applied: one comprising nitrification and the other nitrification-denitrification. Coagulation/flocculation was optimized in terms of pH, coagulant dosage (iron(III) chloride) and flocculant nature and dosage. The following AOPs/EAOPs were tested: Fenton, photo-Fenton with UVA or UVC radiation (PF-UVA or PF-UVC), anodic oxidation (AO), electro-Fenton (EF) and photoelectro-Fenton with UVA radiation (PEF-UVA). The biological nitrification-denitrification was beneficial not only because it avoided the need for alkalinity addition during nitrification and decreased the amount of substrate added during denitrification, as expected. Over and above that, it reduced the acid consumption in the coagulation/flocculation, avoided the application of an additional stage comprising nitrites oxidation to nitrates prior to the AOP/EAOP, and improved the efficiency of Fenton’s reaction based processes. Following nitrification-denitrification, the coagulation/flocculation was maximized at pH 3.0 and 400 mg Fe L−1 with no flocculant addition. The PEF-UVA process was the best AOP/EAOP. The final leachate fulfilled the discharge limits into waterbodies.
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► Biological oxidation and solar AOPs were applied to winery wastewater treatment. ► Pilot plant equipped with an IBR and a photocatalytic system with CPCs. ► The photo-Fenton ...reaction presents the highest degradation rate.
Biological oxidation and solar driven advanced oxidation processes (AOPs) applied as a single stages were tested at a pilot plant equipped with an immobilized biological reactor (IBR) and a photocatalytic system with compound parabolic collectors (CPCs) for the remediation of a winery wastewater (DOCaverage=882mgL−1; pH 4.1). Due to the variable nature of winery wastewater composition and quantity, the application of AOPs as a single or as preliminary stage can be an effective alternative to only conventional biological treatment. Regarding the AOPs systems tested (TiO2/H2O2/UV and Fe2+/H2O2/UV), the solar photo-Fenton reaction (optimized at pH 2.8 and 55mg Fe2+L−1) showed the highest efficiency, being necessary an UV dose of 100kJUVL−1 and 338mM H2O2 (15mg H2O2mg C−1) to achieve a COD value lower than 150mg O2L−1, which is agreement with the discharge limits into receiving waters imposed by the Portuguese Legislation (Decree-law n° 236/98). To achieve the same COD target value using only the IBR system or the combination of solar-photo-Fenton (22kJUVL−1; 80mM H2O2 consumed) and biological systems, approximately 10 and 6 days (time necessary for the biological oxidation) are required. The efficiency of the AOPs in the treatment of simulated and real winery wastewaters was also compared.
The main goal of this study was to evaluate the removal of bromate from drinking water using a heterogeneous photocatalytic mili-photoreactor, based on NETmix technology. The NETmix mili-reactor ...consists of a network of channels and chambers imprinted in a back slab made of acrylic (AS) or stainless steel (SSS) sealed, through mechanical compression and o-rings, with an UVA-transparent front borosilicate glass slab (BGS). A plate of UVA-LEDs was placed above the BGS window. TiO
2
-P25 thin films were immobilized on the BGS (back-side illumination, BSI) or SSS (front-side illumination, FSI) by using a spray deposition method. The photoreduction rate of a 200 μg L
−1
(1.56 μM) BrO
3
−
solution was assessed taking into account the following: (i) catalyst film thickness, (ii) catalyst coated surface and illumination mechanism (BSI or FSI), (iii) solution pH, (iv) type and dose of sacrificial agent (SA), (v) reactor material, and (vi) water matrix. In acidic conditions (pH 3.0) and in the absence of light/catalyst/SA, 28% and 36% of BrO
3
−
was reduced into Br
−
only by contacting with AS and SSS during 2-h, respectively. This effect prevailed during BSI experiments, but not for FSI ones since back SSS was coated with the photocatalyst. The results obtained have demonstrated that (i) the molar rate of disappearance of bromates was similar to the molar rate of formation of bromides; (ii) higher BrO
3
−
reduction efficiencies were reached in the presence of an SA using the FSI at pH 3.0; (iii) formic acid (BrO
3
−
:CH
2
O
2
molar ratio of 1:3) presented higher performance than humic acids (HA = 1 mg C L
−1
) as SA; (iv) high amounts of HA impaired the BrO
3
−
photoreduction reaction; (v) SSS coated catalyst surface revealed to be stable for at least 4 consecutive cycles, keeping its photonic efficiency. Under the best operating conditions (FSI, 18 mL of 2% wt. TiO
2
-P25 suspension, pH 3.0), the use of freshwater matrices led to (i) equal or higher reaction rates, when compared with a synthetic water in the absence of SA, and (ii) lower reaction rates, when compared with a synthetic water containing formic acid with a BrO
3
−
:CH
2
O
2
molar ratio of 1:3. Notwithstanding, heterogeneous TiO
2
photocatalysis, using the NETmix mili-reactor can be used to promote the reduction of BrO
3
−
into Br
−
, attaining concentrations below 10 μg L
−1
(guideline value) after 2-h reaction.
Graphical Abstract
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•Long term operation with real industrial wastewater, beyond 700 days.•Both pretreated and raw pesticide wastewater were used to feed the reactor.•Great variety of conditions tested ...such as HRTs, effluent lots and concentrations.•MBBR can efficiently remove organic matter and ammonia even in stressed conditions.•Assessment of biofilm quantity, quality, and kinetics of TAN and COD removal.
This study examined the treatability of a wastewater composed by industrial pesticide formulation and sanitary wastewaters using a bench scale moving bed biofilm reactor (MBBR). Throughout 742 days and 7 operational phases, tests were performed for several experimental conditions, including: 3 and 6 h hydraulic retention time (HRT); variation of the industrial effluent proportion from 2 to 8% v/v; utilization of various lots of the pretreated pesticide effluent or its raw form. Distinct responses were obtained regarding removal of chemical oxygen demand (COD) (varying from 48 to 84 %) and ammoniacal nitrogen (varying from 36 to 95 %), whereas sludge production remained always low (average 0.18 kg/(m3.d)). Maximum specific removal rates obtained in batch trials showed that the pretreatment of the pesticide wastewater is truly beneficial for keeping higher biofilm activities and preventing nitrification inhibition. Nevertheless, even in the absence of pretreatment, the pesticide wastewater showed high biodegradability, corresponding to 65 % of soluble COD for the operational conditions. Overall, it was shown that the MBBR, at HRT of 6 h and media filling ratio of 50 %, is a viable alternative for the secondary treatment of highly polluted pesticide wastewater even in the absence of pretreatment while preserving a biofilm with good depuration capacity, diverse microfauna and volatile fraction consistently over 85 %.
Advanced oxidation processes (AOPs) constitute a promising technology for the treatment of wastewaters containing pharmaceuticals and personal care products (PPCPs) and especially endocrine ...disrupting chemicals (EDCs). Data concerning the degradation of PPCPs and EDCs by means of AOPs reported during the period January 2000–May 2007 are evaluated in this work. Ozonation was the oxidation process most studied, gives the best expectatives to be applied with successful results.
Contaminants of emerging concern (CECs) are released daily into surface water, and their recalcitrant properties often require tertiary treatment. Electrochemical oxidation (EO) is often used as an ...alternative way to eliminate these compounds from water, although the literature barely addresses the neurotoxic effects of residual by-products. Therefore, this study investigated the performance of EO in the removal of five CECs (alprazolam, clonazepam, diazepam, lorazepam, and carbamazepine) and performed neurotoxicity evaluations of residual EO by-products in Wistar rat brain hippocampal slices. Platinum-coated titanium (Ti/Pt) and boron-doped diamond (BDD) electrodes were studied as anodes. Different current densities (13–75 A m
-2
), pH values (3–10), electrolyte dosages (NaCl), and matrix effects were assessed using municipal wastewater (MWW). The drugs were successfully degraded after 5 min of reaction for both the Ti/Pt and BDD electrodes when a current density of 75 A m
-2
was applied. For Ti/Pt and BDD, neutral and acidic pH demonstrated better CEC removal performance, respectively. Compound degradation using MWW achieved 40% removal after 120 min for Ti/Pt and ranged between 33 and 52% for the BDD anode. For Ti/Pt, neurotoxicity studies using MWW indicated a decrease in reactive oxygen species (ROS) signals. However, when an artificial cerebrospinal fluid (ACSF) medium was reapplied, the signal recovered and increased to a value above the baseline, indicating that cells recovered part of their normal activity but remained in a different condition. For the BDD anode, the treated MWW did not cause significant ROS production variations, suggesting that he EO was effective in eliminating the toxicity of the treated solution.
For treating pulp and paper (P&P) industry wastewaters, the high-loaded/nutrient-limited moving bed biofilm reactor (MBBR) is frequently followed by an activated sludge, in the Biofilm-Activated ...Sludge (BAS) configuration. Evidences show that the MBBR performance relies on a complex surface-volume relation, affecting the biosolids dynamics. That subject was addressed in parallel lab-scale MBBRs, with carrier filling degrees of 15% and 45%, fed with P&P wastewater. The removal of chemical oxygen demand (COD) and utilization of nutrients were evaluated for varying hydraulic retention times (HRT, 1.6–4.9 h), and availabilities of nitrogen and phosphorous. Nutrients excess and 4.9 h HRT led to soluble COD removal close to 50% (totality of the biodegradable portion) in both reactors, but only 32% was achieved at 1.6 h HRT and 45% filling degree. Restrained wastewater-biosolids contact time rather than overload justified that, as the maximum capacity (Kincannon–Stover model, 30.6 kg sCOD/(m3 d)) was substantially higher than the apparent removal rates (≤ 14.1 kg sCOD/(m3 d)). The performance at 4.9 h HRT was matched at 3.2 h HRT with threefold filling ratio, which compensated the lower contact time. Higher HRT was also responsible for i) improving nutrients usage (up to 1.72 times higher sCOD/P and 1.47 sCOD/N); ii) superior suspended solids content, corresponding up to 30% of total biomass at 4.9 h, against 8.6% at 1.6 h; and iii) up to 2.45 times greater planktonic maximum specific activity. Nutrients restriction boosted the sCOD/nutrient consumption ratio up to 2.65 times for the limited nutrient and 1.70 for the abundant one, with minimal sCOD:N:P (100:0.70:0.14) at limited N and 4.9 h HRT.
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•1-year study of various MBBR organic, N and P loads for treating P&P wastewater.•Limitation of either N or P boosts the usage efficiency of both in COD removal.•Minimal nutrients dosing was achieved at higher HRT and limited N availability.•Threefold carrier filling ratio allows 33% volume saving while keeping performance.•Suspended biomass was shown to better use restricted nutrients than the biofilm.
An aerobic granular sludge (AGS) sequencing batch reactor (SBR) adapted to salinity (12 g L−1 NaCl) was operated under alternating anaerobic-aerobic conditions for the treatment of synthetic saline ...wastewater containing endocrine-disrupting chemicals (EDCs), namely 17β–estradiol (E2), 17α–ethinylestradiol (EE2) and bisphenol-A (BPA). The SBR was intermittently fed with the EDCs at 2 mg L−1 of each compound. E2 was completely biodegraded, with 60–80% removal attained anaerobically and the remaining quickly consumed under aeration. EE2 was sorbed onto the granular sludge biomass in the anaerobic period, but it was desorbed in subsequent cycles even when the compound was not supplied to the reactor. BPA removal was poor but improved after bioaugmentation with an EDCs degrading bacteria. EDCs shock loads did not significantly affect the COD removal nor the activity of ammonium- and nitrite-oxidizing bacteria (AOB and NOB, respectively). In contrast, the activity of phosphate-accumulating organisms (PAOs) was affected, implying a decrease in P removal within the aerobic phase. AGS core microbiome grouped most bacteria belonging to the phylum Proteobacteria, followed by Bacteroidetes. The microbial profile showed that the introduction of the EDCs mixture increased the relative abundance of Chryseobacterium and Flavobacterium. AOB and NOB species were detected in the AGS biomass, with the latter showing lower relative abundance. Different PAOs, such as Rhodocyclus, Tetrasphaera and Gemmatimonas, were also part of the microbial community, but the addition of EDCs decreased significantly the relative abundance of Rhodocyclus. High microbial diversity was sustained over reactor operation, with the main bacterial groups responsible for nutrients and EDCs removal preserved in the AGS system. The results pointed to the maintenance of a core microbiome over reactor operation that may be related to the stability of the AGS process during EDCs loading.
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•Degradation of endocrine-disrupting chemicals (E2, EE2 and BPA) by AGS was assessed.•High degradation was observed for E2, which mainly occurred anaerobically.•EE2 was not biodegraded, being adsorbed and desorbed during the successive cycles.•BPA biodegradation was enhanced upon bioaugmentation with a specialized strain.•Stable COD and NH4+ removal despite EDCs shock loads, while P removal was impaired.
In this study, an aqueous solution containing the azo dye Reactive Orange 16 (RO16) was subjected to two sequential treatment processes, namely: ozonation and biological treatment in a moving-bed ...biofilm reactor (MBBR). The most appropriate ozonation pretreatment conditions for the biological process and the toxicity of the by-products resulting from RO16 ozone oxidation were evaluated. The results showed that more than 97 % of color removal from the dye solutions with RO16 concentrations ranging from 25 to 100 mg/L was observed in 5 min of ozone exposure. However, the maximum total organic carbon removal achieved by ozonation was only 48 %, indicating partial mineralization of the dye. Eleven intermediate organic compounds resulting from ozone treatment of RO16 solution were identified by LC/MS analyses at different contact times. The toxicity of the dye-containing solution decreased after 2 min of ozonation, but increased at longer contact times. The results further demonstrated that the ozonolysis products did not affect the performance of the subsequent MBBR, which achieved an average chemical oxygen demand (COD) and ammonium removal of 93 ± 1 and 97 ± 2 %, respectively. A second MBBR system fed with non-ozonated dye-containing wastewater was run in parallel for comparison purposes. This reactor also showed an appreciable COD (90 ± 1 %) and ammonium removal (97 ± 2 %), but was not effective in removing color, which remained practically invariable over the system. The use of short ozonation times (5 min) and a compact MBBR has shown to be effective for the treatment of the simulated textile wastewater containing the RO16 azo dye.
