Total Phenol Removal Research Articles

Electrical stimulation on biodegradation of phenolics in a novel anaerobic–aerobic-coupled upflow bioelectrochemical reactor

• An anaerobic–aerobic-coupled upflow bioelectrochemical reactor was constructed. • Intermittent electrical stimulation mode promoted phenolics degradation. • Aerobic cathodic chamber showed high contribution to the phenolics removal. • Specific microbes were enriched in the cathodic and anodic chambers of the system. Phenolics were widespread in the effluents of coal gasification plants and oil refineries processes, while the impact of electrical stimulation on phenolics degradation in the combined biological processes remained unclear. Here, a novel anaerobic–aerobic–coupled upflow bioelectrochemical reactor (AO-UBER) was used to treat phenol-containing synthetic wastewater and simulated phenolic wastewater. The AO-UBER could treat phenolic compounds effectively via electrical stimulation. Phenol and total phenol removal efficiencies in the intermittently electrically stimulated system with a hydraulic retention time of 6 h were about 22.6% and 31.1%, respectively, higher than that in the biological system not exposed to voltage. The contribution of the aerobic cathodic chamber to the removal of phenolic compounds was higher than that of the anaerobic anodic chamber under the intermittent voltage application mode. High-throughput sequencing analysis indicated that electrical stimulation selectively enriched Acinetobacter , Cloacibacterium , Acidovorax, and Zoogloea in the phenol-containing synthetic wastewater treatment process, and Rhodococcus , Achromobacter , Chryseobacterium, and PSB-M-3 in the simulated phenolic wastewater treatment process. These results demonstrate that the AO-UBER under intermittent voltage application mode holds good potential for efficient phenolic wastewater treatment.

W-Ag-Ti@γ-Al2O3 particle electrodes for enhanced electrocatalytic pretreatment of coal chemical wastewater

The preparation of W-Ag-Ti@γ-Al2O3 3D particle electrode was studied, and the preparation process was optimized on the basis of its electrolytic performance and treatment efficiency on coal chemical wastewater. Infrared spectroscopy, X-ray fluorescence, scanning electron microscopy, X-ray diffraction, and energy dispersive X-ray spectroscopy were used to characterize the loaded element, element morphology, and micromorphology of W-Ag-Ti@γ-Al2O3 3D particle electrode. Results show that the optimal conditions for the preparation of W-Ag-Ti@γ-Al2O3 3D particle electrode are as follows: Ti:Ag:W = 10:10:5, the calcination temperature of the particle electrode is 450 ℃, and the number of times of loading is twice. Coal chemical wastewater degradation was significantly influenced by operating conditions. The research on particle electrode regeneration and stability shows good electrolysis performance after four electrolysis procedures. The effects of conductivity, pH, current intensity, aeration, plate spacing, and filling degree on the removal efficiency of chemical oxygen demand (COD), ammonia nitrogen, and total phenol by W-Ag-Ti@γ-Al2O3 particle electrode were studied. Under the optimal optimization conditions, the COD removal rate was 67.6%, the ammonia nitrogen removal rate was 42.8%, and the total phenol removal rate was 51.7%. Three dimensional electrocatalytic system shows good degradation ability and capacity.

Contamination reduction of real olive oil mill wastewater using innovative acid and basic chemical precipitation processes

Olive oil mill wastewater is a strong pollutant with low pH (4.63) and high salinity (2.70 dS m−1), organic matter (chemical oxygen demand (COD) = 7910 mg L−1), total phosphorus (1049.7 mg L−1), total phenols (540.4 mg L−1) and turbidity (280.1 NTU). This study provides the first application of precipitation processes using HCl, H2SO4, HNO3, NaOH and Ca(OH)2 to olive oil mill wastewater in order to reduce COD, total phosphorus, turbidity, calcium, total phenols and absorbances at 220, 254, 410 and 600 nm. Application of HCl was capable of reducing initial COD (11.4%), turbidity (87.8–98.4%), calcium (100%), total phosphorus (22.1%) and absorbances at 254 nm (12.5–23.5%), 410 nm (46.1–57.9%) and 600 nm (47.4–63.6%) due to the destabilization of suspended and colloidal matter. H2SO4 process allowed removals of turbidity (82.5–97.4%), total phosphorus (14.3–26.9%), calcium (100%) and absorbances at 254 nm (10.9–22.9%), 410 nm (43.4–56.6%) and 600 nm (94.2–96.8%). Experiments conducted using HNO3 showed a positive effect on the removal of COD (10.5–23.6%), total phosphorus (18.9%), turbidity (78.3–94.3%), total phenols (4.6–24.6%) and absorbances at 254 nm (40.5–72.0%), 410 nm (59.1–70.3%) and 600 nm (82.5–91.4%). The advantages of the application of Ca(OH)2 precipitation constituted the removals of COD (11.4–17.8%), total phosphorus (23.6–42.2), turbidity (60.9–100%), total phenols (25.9–48.0%) and absorbances at 220 nm (10.3–33.5%), 254 nm (18.5–45.9%), 410 nm (34.2–81.6%) and 600 nm (22.1–77.3%) owing to formation and precipitation of calcium and magnesium carbonates, magnesium hydroxide and phosphates. Similar results were obtained for NaOH precipitation: COD (19.9–21.5%), total phosphorus (5.9–22.7%), turbidity (80.3–99.4%), total phenols (32.9–55.4%) and absorbances at 220 nm (2.8–11.9%), 410 nm (10.4–44.5%) and 600 nm (24.4–91.9%).

New insights into enhanced anaerobic degradation of coal gasification wastewater (CGW) with the assistance of magnetite nanoparticles

Magnetite nanoparticles (Fe3O4 NPs) was firstly used to enhance pollutants removal during coal gasification wastewater (CGW) treatment in anaerobic digestion (AD) system. Bench-scale results revealed that 200 mg/L and 20–40 nm of Fe3O4 NPs addition resulted in a maximum removal capacity of total phenol (TPh) at a temperature of 36 °C and hydraulic retention time (HRT) of 36 h. Meanwhile, Fe3O4 NPs addition reduced the oxidation reduction potential (ORP) values and biological toxicity, and enhanced the stability of AD system. Pilot-scale results showed that the TPh and chemical oxygen demand (COD) removal efficiency (53% and 49%) were obtained with the optimal dosage of Fe3O4 NPs. Moreover, electron nanowires may be established with Fe3O4 NPs assisted to perform direct interspecies electron transfer (DIET) among Geobacter, Pseudomonas and Methanosaeta species, and finally enhanced the pollutants removal efficiency.

Removal of phenol from aqueous solution by coupling alternating current with biosorption.

The present research was devoted to water decontamination through the valorization of cellulosic fibers for the preparation of performing biosorbent, with high pollutant-uptake capacity and low cost. Luffa cylindrica (L.C) and zinc oxide were chosen for the synthesis of hybrid materials by precipitation with and without alternating current (AC). AC was used as a new alternative able to accelerate the reaction kinetics and to enhance the biosorption speed. The potential to remove phenol, from aqueous solution by coupling biosorption and AC, was highlighted. Pure L.C and hybrid materials (L.C + 4% Zn2+) synthesized with and without AC were chosen for the biosorption tests. The effects of pH, initial concentration, frequency, and contact time were studied. The efficiency of the coupling process was evaluated according to the quality of the treated water before and after purification. Results have shown that the percentages of chemical oxygen demand (COD), total organic carbon (TOC), germination indexes, and phenol removals have increased when adopting the coupling process. The maximal uptakes of phenol reached 15.4, 28.07, and 28.9mgg-1 for a concentration of 30mgL-1 of phenol, respectively, for raw L.C, L.C + 4% Zn2+ + AC, and L.C + 4% Zn2+ at pH = 2. Quantitative and qualitative characterizations confirmed the efficiency of the synthesized hybrid materials compared with pure L.C. The fractal model of Brouers Sotolongo was chosen for the description of the random distribution of the active sites. The kinetic and isotherm data showed a good correlation with the experimental results.

Silver and titanium oxides for the removal of phenols from pharmaceutical wastewater

This study is focused on the removal of total phenols from pharmaceutical effluent using an adsorbent of silver and titanium oxides-doped activated carbon. The adsorbent was biosynthesized by reducing AgNO3 and Ti (NO3)4·4H2O into their oxides by whole extracts of Shea butter leaves and subsequently doped on activated carbon. The properties of the adsorbent were investigated for its morphology, elemental composition, crystallinity, and surface functional group modifications using HRSEM, EDS, XRD, and FTIR respectively. It was found to exhibit high crystallinity from rutile titania, with particle sizes in the sub – 200 nm range, and surface-modified with aromatics, nitrates, and nitramines that favor adsorption. Batch adsorption studies were performed at different contact time (20–230 min.), temperature (35–50 °C), and adsorbent dosage (0.1–0.5 g/50 mL). An optimum percent phenol removal of 99.86% (conc. 0.3299 mg/L) was obtained at 3 h. 42 min., temperature of 35 °C, and adsorbent dosage of 0.1 g/50 mL. Using the Ag/Ti co-doped activated carbon, removal of phenol from pharmaceutical effluent followed pseudo-second order model, and fitted the Langmuir isotherm.

CuO coated olive cake nanocomposites for rapid phenol removal and effective discoloration of high strength olive mill wastewater

The potential of solid olive wastes-based adsorbent (CuO−OC) with photocatalytic power was established for the removal of total phenolics and photocatalytic discolourization of high strength olive mill wastewater (OMW). Clear insight of the FTIR and Brunauer−Emmett−Teller analyses showed that oxygen-containing functional groups of CuO−OC likely participated in the adsorption of total phenols from the OMW via a π−π interaction, hydrogen bonding and electrostatic interaction. Also, the total pore volume of CuO−OC decreased from 0.068 to 0.052 cm3 g−1 after adsorption, which suggested that phenolics were trapped within the micro- and mesopores of CuO−OC. The adsorption kinetics revealed that ∼82.7–95% of the phenolic compounds were removed within the first 360 min which is relatively faster than adsorbents and methods reported elsewhere. The isotherm results showed that Redlich–Peterson equation fit the experimental data very well with least error (χ2 = 1.46–3.19) and high correlation coefficients (0.992–0.996), which suggested a mixture of hetero- and monolayer coverage of the phenolics on the CuO−OC surface. Results obtained herein are of practical interest and the reuse efficiency of CuO−OC remained ∼60% after 5 successive recycling.

Ozone catalytic oxidation capacity of Ti-Co@Al2 O3 for the treatment of biochemical tailwater from the coal chemical industry.

A Ti-Co@γ-Al2 O3 composite catalyst was prepared using impregnation and sol-gel methods to degrade biochemical tailwater from the coal chemical industry, and its preparation conditions (active component doping ratio, load times, and calcination temperature) were optimized through single-factor experiments. The surface properties of the Ti-Co@γ-Al2 O3 composite catalyst and the crystal structure characteristics of the catalytically active components were characterized via scanning electron microscopy-energy dispersive spectrometry, X-ray diffraction, and X-ray fluorescence. The effects of reaction time, initial pH, ozone aeration, and catalyst dosage on degradation performance were investigated through an experiment on the catalytic ozonation degradation of biochemical tail water. Results showed that the optimal conditions were as follows: reaction time of 30min, pH of 8.2, ozone aeration of 30mg/min, and catalyst dosage of 20g/L. The total phenol and total organic carbon removal rates for biochemical tailwater were 66.1% and 57.6%, respectively, in the catalytic system. The mechanism of degradation of organic pollutants by catalytic ozonation was investigated by adding tert-butanol to the catalytic ozone oxidation system. The degradation of chemical oxygen demand in biochemical tailwater was caused primarily by the synergy between the Ti-Co@γ-Al2 O3 catalyst and ozone. PRACTITIONER POINTS: Ti-Co/γ-Al2 O3 catalyst was prepared for the catalytic oxidation of biochemical tail water. The optimal removal rates of total phenol and TOC were 67.7% and 58.8%, respectively. The organic matter was degraded rapidly and efficiently after 5min of ozone catalytic oxidation reaction. It provides theoretical guidance for the practical application of ozone catalytic oxidation.

Electrochemical pretreatment of coal gasification wastewater with Bi-doped PbO2 electrode: Preparation of anode, efficiency and mechanism

Coal gasification wastewater (CGW) contains a large amount of toxic pollutants, which seriously affects the subsequent biochemical treatment. In order to investigate the efficiency of electrocatalytic oxidation on pretreatment of CGW, lead dioxide electrodes doped with PEG and Bi were successfully prepared. Scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction were comprehensively used to characterize the lead dioxide electrode and the electrochemical performance was also tested by linear sweep voltammetry curve, cyclic voltammetry curve and AC impedance. Biodegradability and toxicity of CGW were evaluated by dehydrogenase activity and acute toxicity, respectively. Results showed that the doping of PEG and Bi significantly improved the electrochemical performance and catalytic oxidation performance of lead dioxide electrodes. The degradation rate of phenol by Sn–Sb/PbO2 (PEG + Bi) electrode were 1.57 times of that by pure lead dioxide electrode. The removal of TOC and total phenols were 53.2% and 82.7%, respectively at 120 min under 40 mA cm−2 by Sn–Sb/PbO2 (PEG + Bi) electrode. The changes of biodegradability, biological toxicity and by-products were analyzed. Furthermore, 3,5-dimethylphenol was used as characteristic pollutant to study the degradation mechanism of phenolic pollutants in electrocatalytic system. According to the intermediate products detected by GC-MS, possible degradation pathways in electrocatalytic system were proposed.

Application of the central composite design to mineralization of olive mill wastewater by the electro/FeII/persulfate oxidation method

The olive mill wastewater is a major environmental problem, which is waiting for effective treatment. In this study, the mineralization of olive mill wastewater was investigated using the electro/FeII/persulfate process. The central composite design was utilized to examine the effect of each experimental variables (concentration of persulphate and FeII, treatment time and constant current) on the mineralization of olive mill wastewater. The optimum chemical oxygen demand removal percentage was obtained as 71.2% where the reaction conditions were 200 mA current, 250 mM persulphate, 25 mM FeII, and 6 h reaction time. In addition, the maximum percentage of total phenolic removal and the energy consumption were 88% and 4.50 kWh/kgCOD, respectively, which were obtained at the same reaction conditions mentioned above. ANOVA test was used to examine the reliability of the experimental method. The R2 and adjusted R2 coefficients were obtained as 0.9634 and 0.9305, respectively. Optimum experimental parameters were determined and theoretical equations were obtained for the degradation of olive mill wastewater. For the treatment of olive mill wastewater, an environmentally friendly oxidation process was examined and the effect of each experimental variables was clearly demonstrated. The obtained data was optimized for future applications.

Catalytic activity and evaluation of Fe-Mn@Bt for ozonizing coal chemical biochemical tail water

The purpose of this study was to improve the ozone utilization rate by preparing a high-efficiency ozone catalyst, and establish an effective model to evaluate catalytic oxidation systems. In this study, Fe-Mn@Bt ozone catalyst prepared by a doping-baking method was used to deeply treat the biochemical tail water of coal chemical wastewater. The catalyst had an extremely developed pore structure characterized by SEM. The catalytically active elements inside and on the catalyst in the form of α-Fe2O3 and MnO2 had good stability. The effects of operating conditions, such as ozone dosage, hydraulic retention time, and catalyst dosage, on total phenol and total organic carbon (TOC) removal rate were systematically investigated. Under optimal working conditions, the chemical oxygen demand (COD) after the degradation of coal chemical biochemical tail water was used as the evaluation index to explore the actual utilization rate of ozone. The addition of Fe-Mn@Bt porous catalyst upgraded the actual utilization rate of ozone from 0.14. kgCOD/kgO3 (ozone alone oxidation system) to 0.22 kg COD/kg O3. The mechanism of catalytic oxidation was investigated by adding a free radical inhibitor to a catalytic oxidation system, demonstrating that the dominant processes in a deep degradation system was that the catalysis of ozone-generated hydroxyl radicals by active elements and ozone oxidation. To further evaluate the operating conditions for Fe-Mn@Bt ozone catalyst, the “3E” evaluation system where economy, energy, and environment were the key factors was established and evaluated. At optimal levels, the removal ratios of total phenol and TOC were 58.7% and 53.5%, respectively. Fe-Mn@Bt ozone catalysts can effectively improve ozone utilization rate and has a good application prospect for the advanced treatment of coal chemical wastewater.

Electrocoagulation and electrooxidation pre-treatment effect on fungal treatment of pistachio processing wastewater.

The effect of electrochemical pre-treatment on fungal treatment of pistachio processing wastewater (PPW) was investigated. Electrocoagulation (EC) and electrooxidation (EO) were used as electrochemical pre-treatment step before fungal treatment of PPW. Aluminum (Al/Al), iron (Fe/Fe), and stainless steel (SS/SS) electrode pairs were selected as anode/cathode for EC whereas boron doped diamond (BDD/SS) was preferred as anode/cathode electrode pairs for EO experiments in this study. The impact of current density (50-300 A/m2) and operating time (0-240min) were tested for chemical oxygen demand (COD) and total phenol removal. After pre-treatment of PPW, four different fungus species (Coriolus versicolor, Funalia trogii, Aspergillus carbonarius, and Penicillium glabrum) were tested for further treatment. Penicillium glabrum supplied maximum COD and total phenol removal efficiency compared to other fungus strains. The combined electrochemical-assisted fungal treatment process supplied 90.1% COD and 88.7% total phenol removal efficiency when supported with EO pre-treatment. Pre-treatment of PPW with EO method provided better results than EC method for fungal treatment. Operating cost of the combined process was calculated as 6.12 US$/m3. The results indicated that the proposed combined process supplied higher pollutant removal compared to the individual electrocoagulation, electrooxidation, and fungal treatment process.

Treatment of slaughterhouse wastewater by acid precipitation (H2SO4, HCl and HNO3) and oxidation (Ca(ClO)₂, H2O2 and CaO₂)

The treatment of slaughterhouse wastewater was investigated by both acid precipitations and by oxidation processes. Precipitation tests were developed using three acids (H2SO4, HCl and HNO3) at different operating pH (1–6). A decrease of the precipitation pH led to an increase of the conductivity values of the supernatant. Precipitation processes allowed the removal of chemical oxygen demand (COD) (41–97%), turbidity (56–99%) and total phosphorus (27–56%). Total phenols were removed (15–96%) from pH ≥ 2, depending on the precipitation process. Generally, precipitation processes decreased the hydroxide and bicarbonates species. Additionally, three different oxidation processes were tested at different concentrations (1–15 g L−1): Ca(ClO)₂, H2O2 and CaO₂. When Ca(ClO)₂ and CaO₂ were applied, an increase of the supernatant conductivity was achieved. COD removal ≥71% and turbidity elimination in the range of 85–100% were achieved by using oxidation processes. CaO₂ was very effective to remove total phosphorus (81–96%). The increase of the oxidant concentration in H2O2 and Ca(ClO)₂ oxidation processes led to a decrease in the removal of total phenols and bicarbonates species. Optical density of the microorganism cultures was efficiently eliminated (up to 100%) by oxidation processes. In addition, acid precipitation and oxidation allowed to remove total solids (TS), total volatile solids (TVS), total suspended solids (TSS), ammonia nitrogen, nitrates and biochemical oxygen demand (BOD5). Acid precipitation and oxidation produced sludge rich in organic matter and nutrients (Ca, Mg, P, Cl, Na and K). Despite the high removal efficiencies, a post-treatment following the precipitation and oxidation processes can be required.

Evaluation of aerated lagoon modified with spongy support medium treating Kraft pulp mill effluent

The pulp industry generates high effluent flows, which contain high chemical oxygen demand (COD), biochemical oxygen demand (BOD5), colour and ecotoxicity. This study aimed to evaluate the treatment of Kraft pulp effluent by aerated lagoon modified with sponge support media (APG). It was assessed the arrangement of the support media in the aerated lagoons in the organic load rate (OLR) of 0.2 kgCOD m-3 d-1, and after that, with OLR variation from 0.2 to 1.2 kgCOD m-3 d-1. The parameters evaluated were BOD5, COD, colour, lignin derivatives, total phenolic compounds and acute ecotoxicity in D. magna. COD and BOD5 removals were 32% and 88%, respectively, for free and confined support media in 0.2 kgCOD m-3 d-1. There was no colour or total phenolic compounds removal under these conditions. Considering the treatment in which there was a variation of the organic load rate, 1.2 kgCOD m-3 d-1 had the best performance. In this case, 50% and 75% of COD and BOD5 were removed, respectively. Removal of colour, total phenolic compounds and lignin derivatives were around 20%, 18% and 10%, respectively. The acute ecotoxicity was reduced to toxicity factor equal to 1 in all treatments. Comparing the aerated lagoon modified systems with those without the APG, it was suggested to apply spongy support in higher organic load rate than these typically used in aerated lagoons.

Two-stage air stripping combined with hydrolysis acidification process for coal gasification wastewater pretreatment.

Coal gasification wastewater is mainly from gas washing, condensation and purification processes in the gas furnace with high NH3-N (nitrogen in water in the form of free ammonia (NH3) and ammonium ion (NH4 +)), TN (total nitrogen) and refractory organics content, which will inhibit the subsequent biological treatment. The 'air stripping - hydrolysis acidification - air stripping' process was proposed as the pretreatment for coal gasification wastewater to improve the biodegradability and nitrogen removal, which could reduce the subsequent biological treatment load. The first-stage air stripping process before hydrolysis acidification could achieve a significant removal of NH3-N (97.0%) and volatile phenol (70.0%), reducing the corresponding toxicity on hydrolysis acidification. The group with air stripping had more abundant microbial communities and a more effective organic degradation performance in hydrolysis acidification than that without air stripping. The second-stage air stripping removed NH3-N released from hydrolysis acidification, and significantly reduced the TN concentration in effluent. The whole process achieved a TN removal from 2,000 ± 100 mg/L to 160 ± 80 mg/L, and a total phenols removal from 700 ± 50 mg/L to 80 ±20 mg/L.

Pomegranate peel and orange juice by-product as new biosorbents of phenolic compounds from olive mill wastewaters

Several wastes and residues have been studied for the adsorption of phenolic compounds with varying success. However, new economical, easily available, and highly effective adsorbents are still needed. The purpose of this work is to consider the potential of two food wastes derived from agricultural activities, the non-modified pomegranate peel and orange juice by-product, after the removal of their own phenolic content, for phenolics sorption from olive mill wastewater. This procedure is the second step of an integrated approach for complete utilization of these wastes in recovering valuable ingredients, while succeeding total depollution. Initially, the equilibrium time was investigated and afterwards, the effects of sorbent mass concentration (0.01–0.02 g/mL), temperature (20–60 °C), solution’s pH (4–7), initial sorbate concentration (50–500 mg/L), and sorbent particle size on total phenols uptake were studied. The highest adsorption efficiencies obtained were 93.13 and 89.59% using pomegranate peel and orange juice by-product, respectively. Total phenols removal efficiency was maximum at pH 4.75 and was improved by decreasing adsorbents dosage, initial sorbate concentration, temperature, and sorbents particle size. The sorption followed the intra-particle diffusion model and was described better by the Freundlich sorption isotherm. The results indicated that the studied materials could be employed as alternative low-cost biosorbents.

Enhanced performance and hindered membrane fouling for the treatment of coal chemical industry wastewater using a novel membrane electro-bioreactor with intermittent direct current

A membrane electro-bioreactor (MEBR) embracing biological treatment, electrokinetic phenomena and membrane filtration was established by applying intermittent direct current (DC) to MBR. MEBR exhibited significant improvement of treatment performance and reduction of membrane fouling. COD and total phenols removal efficiencies increased to 83.53% and 93.28% at an exposure mode of 24′-OFF/6′-ON, compared to 71.24% and 82.43% in MBR. Trans-membrane pressure increment rate declined dramatically in MEBR, which was mainly attributed to the increase of sludge floc size and decrease of zeta potential, soluble microbial products and specific resistance to filtration, resulted from electrokinetic effects such as electrocoagulation, electrophoresis, electroosmosis and electromigration of ions. It was notable that DC exposure exerted distinct evolution on microbial community, with the improvement of microbial community richness and diversity. The relative abundances of functional genera were promoted noticeably in MEBR. An interactive relevance existed among microbial community structure, mixed liquor properties and operational parameters.

Treatment of olive mill wastewater using ozonation followed by an encapsulated acclimated biomass

The environmental impacts caused by Olive Mill Wastewater (OMWW) are a concern for both developing and developed countries. In this study, an ozone pretreatment combined with a fixed biomass bio-treatment using the Small Bioreactor Platform (SBP) capsules technology encasing a pure culture of a phenol-degrading OMWW isolate named Delftia EROSY was implemented to reduce phenolic compounds and organic matter in OMWW.Up to 90% of tannic acid (TA), a synthetic phenol model, was removed after the ozonation and biological stages. Ozone pretreatment of TA expedites the biological process by decreasing the time needed for the biodegradation of phenols.Ozonation (ozone dose = 765 mg L−1 O3) of OMWW demonstrated 20% COD and 61% total phenol removal, with an additional 36% increase in COD removal after the biological step (48 h). Interestingly, our results also showed that spectral absorbance can be used as a tool for monitoring ozonation followed by bio-treatment of OMWW. Absorbance results clearly demonstrate that bio-treatment is necessary for degrading not only phenolic compounds, but also phenol transformation products and the high organic load of the OMWW, following the ozonation step.

Fenton oxidation and chromium recovery from tannery wastewater by means of iron-based coated biomass as heterogeneous catalyst in fixed-bed columns

This work deals with the treatment of a tannery wastewater by a mixed-iron coated olive stone bio-sorbent particles. Olive stones were used as the support to zero-valent iron and magnetite nanoparticles to develop a new material for the removal of chromium, organic matter and total phenols from the wastewater. The optimal operating conditions were determined in batch reactors, after which the process was scaled-up using fixed-bed columns in series. The maximum adsorption capacity for both Cr(III) and Cr(VI), up to 8.37 and 4.29 mg g−1, was attained for a sorbent mass concentration of 4 g L−1, meaning a total chromium adsorption capacity of 12.66 mg g−1, whereas equilibrium contact time was found to be 120 min. The combination of coated olive stones and hydrogen peroxide allowed to develop an heterogeneous Fenton process, that led to reach a COD removal efficiency of 58.4% and a total phenols removal of 59.2%, at H2O2/COD (w/w) = 0.875. In addition, re-use of the coated olive stones by regeneration with NaOH and C2H2O4 solutions after 5 cycles was reported. The column process was successfully described by BDST and Thomas models.

Optimization of electrocoagulation process and combination of anaerobic digestion for the treatment of pistachio processing wastewater

Abstract It is very challenging to treat raw pistachio processing wastewater (PPW) by one step process due to its high chemical oxygen demand (COD) and total phenols (TP). In this study, electrochemical (EC) process and anaerobic digestion are combined to improve treatment efficiency. Central composite design (CCD) was used in EC experimental design with three factors at three levels of the independent variables. Impact of current density (50─100 A/m2), electrode distance (2─6 cm), and reaction time (60─300 min) on the removal of COD and TP were systematically investigated. A maximum removal efficiency of 43.7 and 56.4% of COD and TP, respectively, was obtained with the current density of 100 A/m2, electrode distance of 6 cm, and reaction time of 293 min. Specific energy consumption (SEC) was measured as 7.80 kWh/kgCOD for the same experimental conditions. In order to achieve further treatment, a batch anaerobic reactor was combined with EC process to produce biogas. COD and TP removal efficiency were measured in the anaerobic reactors at appropriate time intervals (0, 10, 25, 30, 40, and 50th d) and biochemical methane potential (BMP) tests lasted up to 50 d. BMP enhancement of raw PPW was found as 35.7 and 16.5% for electrocoagulated PPW under maximum COD and TP removal efficiency condition (100 A/m2 current density, 6 cm electrode distance, and 293 min reaction time) and under cost driven approach condition (53 A/m2 current density, 2 cm electrode distance, and 182 min reaction time) compared to raw PPW. The results showed that pre-treated PPW with EC process had the highest COD and TP removal efficiencies and enhanced the biochemical methane production, by decreasing the concentration of total phenols in the PPW. Energy balance revealed that EC under cost driven approach condition combined with anaerobic digestion can be used as an energy positive process for the treatment of PPW.