Remediation of water contaminated with diesel oil using a coupled process: Biological degradation followed by heterogeneous Fenton-like oxidation

The phenol efficient degradation using co‐culture coupled with enhanced electricity generation capability

The co‐culture of strain Citrobacter sp. RDC and Geobacter sulfurreducens PCA was used in this study and it was found that the co‐culture using 200 mg/L phenol as carbon source exhibited higher maximum current density than using the single strain RDC and G. sulfurreducens PCA, respectively. Meanwhile, the co‐culture was used to generate electricity by degrading phenol with the current density of 699.07 μA/cm2 by using 200 mg/L phenol as the sole carbon source, which was higher than that only using G. sulfurreducens PCA (236.20 μA/cm2). Especially, the degradation efficiency of 200 mg/L phenol by co‐culture can reach 55.16 % within 36 h being 4.16‐fold higher than the single strain G. sulfurreducens PCA. Furthermore, the component ratio of two strains was optimized for increasing electricity generation using 500 mg/L phenol as carbon source. The maximum current density was 501.54 μA/cm2 under the ratio of 3 : 1 for strain RDC to G. sulfurreducens PCA. These results highlight that phenol is good carbon source for co‐culture to produce electricity. The co‐culture system provides a promising application pathway for phenol degradation treatment coupled with electricity generation in the future.

Fenton pre-oxidation of natural organic matter in drinking water treatment through the application of iron nails

This study investigated for the first time the efficiency of an advanced oxidation process (AOP) zero valent iron/hydrogen peroxide (ZVI/H₂O₂) employing iron nails for the removal of Natural Organic Matter (NOM) from natural water of Regent's Park lake, London, UK. The low cost of nails and their easy separation from the water after the treatment make this AOP attractive for water utilities in low- and middle-income countries. The process was investigated as a pre-oxidation step for drinking water treatment. Results showed that UV254 removal in the natural water was lower than that of simulated water containing commercial humic acid (HA), indicating a matrix effect. Statistical analysis confirmed the maximum removal of dissolved organic carbon (DOC) in natural water depends on the initial pH (best at 4.5) and H₂O₂ dosage (best at 100% excess of stoichiometric dosage). DOC and UV254 removals under this operational condition were 51% and 89%, respectively. Molecular weight (MW) and specific UV absorbance (SUVA254) were significantly reduced to 74% and 78%, respectively. Formation of Chloroform THM in natural water sample after the ZVI/H₂O₂ process (initial pH 4.5) was below the limit for drinking water, and 48% less than the THM formation in the same water not subjected to pre-oxidation. Characterization of oxidation products on the iron-nail-ZVI surface after the ZVI/H₂O₂ treatment by SEM, XRD, and XPS identified the formation of magnetite and lepidocrocite. Results suggest that the investigated ZVI/H₂O₂ process is a promising technology for removing NOM and reducing THM formation during drinking water treatment.

Remediation of Pb-diesel fuel co-contaminated soil using nano/bio process: subsequent use of nanoscale zero-valent iron and bioremediation approaches

The effectiveness of the nano/bio process was investigated as a remediation option for co-contaminated soils. Nano/bio process is a hybrid treatment method that may be defined as the use of nanoscale zero-valent iron (nZVI) and bioremediation approaches subsequently/concurrently. Different bioremediation approaches (bioattenuation, biostimulation, and/or bioaugmentation) were performed together with nZVI application to remediate Pb- and diesel fuel-spiked soils. Nutrient (N and P) and activated sludge amendment were made to realize biostimulation and bioaugmentation, respectively. The nZVI application decreased the total percentage of the most mobile and bioavailable soil Pb fractions (exchangeable and carbonate-bound) from 68.3 to 31.7%. The biodegradation levels of nZVI-applied co-contaminated soils were significantly higher than the soils without nZVI indicating the positive effect of the reduced mobility, bioavailability, and toxicity of Pb content. The use of nano/biostimulation or nano/bioaugmentation treatments resulted in higher than 60% total n-alkane degradation, whereas 89.5% degradation was obtained by using nano/biostimulation + bioaugmentation. Hydrocarbon-degrader strains belonging to phyla Actinobacteria, Proteobacteria, or Firmicutes were identified from samples subjected to nano/bio process and the strains from biostimulation and bioaugmentation treatments were different. These results indicate that the stress on the microbial population caused by the co-contamination might be subsided and the biodegradation of alkanes might be improved by using the nano/bio process.

Insights into naphthalene degradation in aqueous solution and soil slurry medium: Performance and mechanisms

The performance of naphthalene (NAP) degradation in peroxodisulfate (PDS) and peroxymonosulfate (PMS) oxidation systems by nano zero valent iron (nZVI) combined with citric acid (CA) activation was reported in aqueous solution and soil slurry medium. The results in aqueous solution tests indicated that 98.1% and 98.9% of NAP were individually degraded in PDS/nZVI/CA and PMS/nZVI/CA systems within 2 h when the dosages of PDS, PMS, nZVI and CA were 1.0 mM, 0.1 mM, 0.2 mM and 0.1 mM, respectively. The consequences of scavenging tests and electron paramagnetic resonance detection demonstrated that HO• and SO₄^-• were the key factors on NAP removal. The presence of surfactants could consume ROSs and inhibit NAP removal. In addition, GC-MS was applied for the determination of NAP degradation intermediates, and three possible NAP degradation pathways were proposed in PDS oxidation process and two pathways in PMS oxidation process, respectively. The results in soil slurry medium showed that the presence of CA could promote the dissolution of soil minerals and the desorption of NAP from soil medium. 93.5% and 96.8% degradation of NAP were obtained in PDS/nZVI/CA and PMS/nZVI/CA systems within 24 h. Besides, the existence of DOM in soil could promote Fe(II)/Fe(III) cycle and NAP degradation through electron transfer. Based on the NAP degradation performance in the actual groundwater and soil medium, the above findings could provide basis and strong support for the potential application of PDS/nZVI/CA and PMS/nZVI/CA systems in the remediation of NAP contaminated sites.

Combination of biodegradation and fenton process for efficient removal of PDM/ZnO

In the present study, an investigation was conducted on the removal of polydiallyldimethylammonium chloride-acrylic-acrylamide-hydroxyethyl acrylate/ZnO nanocomposites (PDM/ZnO) through biodegradation and Fenton process coupled treatments. As revealed from the results of the chemical oxygen demand, the total organic carbon, the biochemical oxygen demand and the CO₂ production analysis, PDM/ZnO could be partially biodegraded. The optimal initial pH, the mixed liquid suspended solids concentration and additional carbon source (glucose) dosage in the biodegradation were 7.0, 4.0 g/L and 1.0 g/L, respectively. On the whole, NaCl, the coexisted metal cations (Cu²⁺, Zn²⁺ and Cr³⁺) and additional NH₄Cl inhibited the biodegradation of PDM/ZnO. PDM/ZnO was suggested to adversely affect on microbial community structure and activity. Optimum conditions for Fenton treatment were 50 mg/L Fe²⁺, 20 mL/L H₂O₂ and pH 2.0. Biodegradation showed that 64% of PDM/ZnO was removed. Besides, the combination of Fenton post-treatment could achieve an over 97% removal of PDM/ZnO. Thus, Fenton process combined biodegradation pre-treatment can act as an effective method to remove PDM/ZnO.

Efficient degradation of tetracycline in wide pH range using MgNCN/MgO nanocomposites as novel H2O2 activator

Currently existing Fenton-like catalysts were limited in wastewater treatment owing to their potential transition-metal poisoning, narrow applicable pH range and high dependence on external energy excitation. In this work, the MgNCN/MgO nanocomposites were firstly synthesized by a facile one-pot calcination of melamine and basic magnesium carbonate, and used as novel H₂O₂ activator for antibiotic removal. It was found that the MgNCN/MgO composite calcined at 550°C with the mass ratio of melamine to basic magnesium carbonate at 2:1, exhibited an excellent catalytic ability to tetracycline (TC) degradation in a wide pH range of 4-10 without any external energy input. More than 90% of TC (100 mL, 50 mg/L) could be degraded within 30 min by 10 mg of the nanocomposite in the presence of 0.2 mL of 30 wt% H₂O₂. Based on the experimental results, it was concluded that the Mg-N coordination between MgNCN and MgO in MgNCN/MgO nanocomposites activated H₂O₂ to produce primary singlet oxygen (¹O₂) and minor hydroxyl radicals (·OH), responding for TC degradation. In addition, the degradation pathways of TC were deduced by determining the generated intermediates during the degradation process. This work provided a novel idea for designing transition-metal-free catalysts for nonradical activation of H₂O₂ in the absence of external energy excitation.

Low-cost nanoparticulate oxidation catalysts for the removal of azo and anthraquinic dyes

PURPOSE

This study aimed to test the activity of Mn ferrite, hematin-Mn ferrite and colloidal maghemite in decomposition of Orange II (O-II) and Alizarin Red S (ARS) in model aqueous solutions.

METHODS

Color removal was explored at room temperature using magnetic stirring with and without a magnetic bar, taking advantage of the solids' magnetism. Decomposition of H₂O₂ was also studied separately and as radicals provider in dye decomposition. Catalyst/dye solution was fixed at 10 mg/4 mL. pH and dye concentration were variable. Absorbance was measured during 120 min by UV-Vis. Reuse of catalysts was also performed.

RESULTS

Azo dyes such as O-II are more resistant to oxidative removal using hydrogen peroxide than anthraquinone-like ARS. CITMD5 reduced ARS absorbance up to 71.9% when dye was less than 250 mg/L. HEM-Mn-MAG completely decolorized a 62.5 mg/L O-II solution at pH 11 while CITMD5 reached half of that conversion under the same conditions. The highest color removal in O-II/ARS mixtures was obtained with HEM-Mn-MAG, 40% absorbance reduction in 2 h. Mn-MAG is not active to remove O-II in presence of hydrogen peroxide in the 3-9 pH range at rt.

CONCLUSIONS

The high activity of Mn-MAG in hydrogen peroxide decomposition may be assigned to the combination of Mn⁺²/Mn⁺³ and Fe⁺²/Fe⁺³, because the MnO_x is active in the decomposition of hydrogen peroxide. Mn-MAG can be reused, preserving high activity in this reaction. Mn-based magnetic nanoparticles should be considered as inexpensive materials to treat textile wastewaters.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40201-021-00640-x.

Optimization of Operating Conditions for Electrochemical Decolorization of Methylene Blue with Ti/α-PbO2/β-PbO2 Composite Electrode

α-PbO2 was introduced into the intermediate layer of an electrode to prevent the separation of the electrodeposited layer and maintain oxidizing power. The resulting Ti/α-PbO2/β-PbO2 composite electrode was applied to the electrochemical decolorization of methylene blue (MB) and the operating conditions for MB decolorization with the Ti/α-PbO2/β-PbO2 electrode were optimized. The morphology, structure, composition, and electrochemical performance of Ti/α-PbO2 and Ti/α-PbO2/β-PbO2 anode were evaluated using scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The optimum operating parameters for the electrochemical decolorization of MB at Ti/α-PbO2/β-PbO2 composites were as follows: Na2SO4 electrolyte 0.05 g L−1, initial concentration of MB 9 mg L−1, cell voltage 20 V, current density 0.05–0.10 A cm−2, and pH 6.0. MB dye could be completely decolorized with Ti/α-PbO2/β-PbO2 for the treatment time of less than one hour, and the dye decolorization efficiency with Ti/α-PbO2/β-PbO2 was about 5 times better, compared with those obtained with Ti/α-PbO2.

Improved Delivery of Remedial Agents Using Surface Foam Spraying with Vertical Holes into Unsaturated Diesel-Contaminated Soil for Total Petroleum Hydrocarbon Removal

Surface foam spraying technologies, employing natural infiltration processes, have recently been suggested to not disturb or mix contaminated soils. However, effective delivery of reactive remedial agents to the bottom area of a contaminated region using only natural infiltration processes can be a challenge. This study aimed to improve the delivery of remedial agents such as oxidants, microorganisms, and nutrients to all depths of 30 cm thick unsaturated diesel-contaminated soil using small vertical soil holes. Three vertical holes, occupying 0.8% of the total soil volume and 3% of the soil surface area, were made inside the 17.3 kg soil column. Persulfate oxidation foam and subsequent bioaugmentation foam spraying were applied for remediation of contaminated soil. Foam spraying with vertical soil holes improved the uniformity of distribution of remedial agents throughout the soil, as evidenced by the uniform pH, higher volumetric soil water content, and a microbial population of >107 CFU/g. Therefore, the total petroleum hydrocarbon (TPH) removal efficiency (88–90%) from bottom soils was enhanced compared to soil columns without holes (72–73%) and the control test (5–9%). The kinetic study revealed that relatively similar TPH biodegradation rates (0.054–0.057 d−1) can be obtained for all soil depths by using this new and simple approach.

Biodegradation and post-oxidation of fuel-weathered field soil

Owing to the less volatile and less biodegradable nature of weathered fuel-contaminated soil, it cannot be easily remediated using conventional bioremediation approaches. Therefore, this study was aimed to enhance the landfarming bioremediation process by introducing post-oxidation for the degradation of the residual total petroleum hydrocarbons (TPH) in fuel-contaminated field soil. A laboratory-scale landfarming bioaugmentation process was performed by using oil-degrading microbes, nutrients, and surfactants, followed by chemical oxidation as a post treatment. The results demonstrated that the addition of microbes and nutrients gradually decreased the TPH concentration of the soil (initial TPH = 5932 ± 267 mg/kg) with a removal efficiency of 70-72% (TPH > 800 mg/kg; Korean limit for non-residential sites). However, the use of post-oxidation treatments with 5% KMnO₄ decreased the TPH to approximately 401-453 mg/kg (TPH below 500 mg/kg; residential site limit) with an overall efficiency of 92-93% compared to the corresponding value of 13% for the control (water treatment). Performing landfarming through biodegradation followed by chemical oxidation as a post treatment could successfully remove the weathered TPH in soil below the regulatory limits. Furthermore, the post-oxidation treatment may oxidize the less biodegradable portions only after biodegradation, thereby minimizing the oxidant demand and enhancing the soil properties such as the pH, amount of natural substrates and microbial population.

Nano-Fe mediated treatment of real hydraulic fracturing flowback and its practical implication on membrane fouling in tandem anaerobic-oxic membrane bioreactor

The rising water-use intensity, and lack of cost-effective treatment strategy and reuse of hydraulic fracturing flowback (HFF) has become an increasing cause of concern. The present work evaluates the integration of parallel sets of tandem anaerobic-oxic membrane bioreactor (AMBR) with and without nano-Fe for treatment and reuse of real HFF obtained from Ordos Basin, China. Treatment efficiencies in terms of organic conversions, micro-pollutants degradation, resource recovery, and effects of nano-Fe release on membrane fouling were evaluated. Nano-Fe mediated AMBR (FAMBR) system effectively reduce target micro-pollutants (such as Acenaphthylene) at 94.4 % compared to the parallel AMBR system (17.1 % without nano-Fe). Moreover, recovery of potential economic chemicals like Al and P (1.0 and 0.6 mg/g spent nano-Fe) availed using FAMBR system. However, colonization of FAMBR membrane surface by Fe-protein/peptide hydroxocomplexes initiated by Fe-catalyzed microbial extrusions present a huge fouling challenge relative to the AMBR system. Additional evidences from microscopic/spectroscopic analysis of the FAMBR membrane system revealed that despite having a promising outlook, mediation of nano-Fe with AMBR system might result in a major fouling event during HFF treatment. Engineered design of nano-Fe to reduced leached nano-Fe ions in pre-treatment step prior to AMBR treatment system may be of potential research consideration.

Co-metabolism for enhanced phenol degradation and bioelectricity generation in microbial fuel cell

Co-metabolism is one of the effective approaches to increase the removal of refractory pollutants in microbial fuel cells (MFCs), but studies on the links between the co-substrates and biodegradation remain limited. In this study, four external carbon resources were used as co-substrates for phenol removal and power generation in MFC. The result demonstrated that acetate was the most efficient co-substrate with an initial phenol degradation of 78.8% and the voltage output of 389.0 mV. Polarization curves and cyclic voltammogram analysis indicated that acetate significantly increased the activity of extracellular electron transfer (EET) enzyme of the anodic microorganism, such as cytochrome c OmcA. GC-MS and LC-MS results suggested that phenol was biodegraded via catechol, 2-hydroxymuconic semialdehyde, and pyruvic acid, and these intermediates were reduced apparently in acetate feeding MFC. The microbial community analysis by high-throughput sequencing showed that Acidovorax, Geobacter, and Thauera were predominant species when using acetate as co-substrate. It can be concluded that the efficient removal of phenol was contributed to the positive interactions between electrochemically active bacteria and phenolic degradation bacteria. This study might provide new insight into the positive role of the co-substrate during the treatment of phenolic wastewater by MFC.

Catalytic micro-ozonation by Fe3O4 nanoparticles @ cow-dung ash for advanced treatment of biologically pre-treated leachate

In this work, the biologically pre-treated leachate was subjected to catalytic micro-ozonation using cow-dung ash composites loaded with Fe₃O₄ nanoparticles (nano-Fe₃O₄@CDA) as the catalyst. The optimal conditions used were nano-Fe₃O₄@CDA dosage of 0.8 g/L, input ozone of 3.0 g/L, and reaction time of 120 min. This environment yielded the following results: The COD and color number (CN) removal reached 53% and 89%, respectively, and the BOD₅/COD increased from 0.05 to 0.32. The catalytic micro-ozonation partially degraded the refractory substances into intermediates with lower molecular weight. The percentage of phenolic compounds decreased sharply from 28.08% to 8.56%, largely due to the opening of the ring as well as to the formation of organic intermediates with a low molecular weight. Based on the results culled from the electron paramagnetic resonance (EPR), it is evident that the nano-Fe₃O₄@CDA catalyst can accelerate in order to generate OH. This was the main mechanism involved in its excellent ability to degrade refractory pollutants. These results demonstrated the potential use of nano-Fe₃O₄@CDA as a catalyst in the catalytic micro-ozonation process.

Utilizations of agricultural waste as adsorbent for the removal of contaminants: A review

In recent years, various industrial activities have caused serious pollution to the environment. Due to the low operating costs and high flexibility, adsorption is considered as one of the most effective technologies for pollutant management. Agricultural waste has loose and porous structures, and contains functional groups such as the carboxyl group and hydroxyl group, so it can be invoked as biological adsorption material. Agricultural waste gets the advantages of a wide range of sources, low cost, and renewable. It has a good prospect for the comprehensive utilization of resources when used for environmental pollution control. This article summarized the current research status of agricultural waste in adsorbing pollutants, which pointed out the influencing factors of adsorption, expounded the adsorption mechanism of biological adsorption and introduced the related parameters of adsorption, proposed the application of adsorbents in engineering including adsorption in liquid and gas phases, at the same time it gave the future development prospect of agricultural waste as adsorbent.