Degradation of plastic waste using stimulated and naturally occurring microbial strains.

The capability of different strains derived from soil, activated sludge, farm sludge, and worms' excreta were investigated for biodegradation of high-density polyethylene, polystyrene foam, polypropylene and polyethylene terephthalate in unstimulated and stimulated conditions. Biodegradation using naturally occurring microbial strains examined in mixed (270 days) and individual (100 days) systems, while H2O2 stimulated strains were tested only in the mixed system (30 days). Penicillium raperi, Aspergillus flavus, Penicillium glaucoroseum and Pseudomonas sp. were isolated as the most plastic degrading microbes. Maximum weight loss was seen by incubation of polyethylene with Aspergillus flavus (5.5%) in unstimulated mix condition. Fourier Transform Infrared Spectroscopy (FT-IR) revealed formation of new functional groups as hydroxyl, carbonyl, alkene and alkoxy in the treated plastics. Visualisation of plastics by optical, atomic force (AFM) and electron microscopy (SEM) were also illustrated biodegradation. The derived by-products from microbial degradation was tested, and found no inhibition on microbial growth and performance.

Analysis of time varying response on uptake patterns of Cu and Zn ions under application of ethylene diamine disuccinic acid and gibberellic acid in Lolium perenne.

The present study explores the effect of ethylene diamine disuccinic acid (EDDS) and gibberellic acid (GA) application on the phytoextraction of copper and zinc ions by Lolium perenne. When Cu was individually applied, accumulation diminished over time with little translocation from roots to shoots. In contrast, Zn accumulation and damage to roots rapidly increased over 3 days with increase in Zn translocation to shoots. Co-application of Zn to Cu amended treatments enhanced Cu concentration in shoots. For the CuEDDS application, EDDS significantly increased Cu accumulation and the damage to root increased over time, while gibberellic acid applied with Cu and Zn generally lowered metal uptake and decreased cell membrane damage. The application of EDDS and GA-EDDS, by themselves or with Cu and Zn, lowered transpiration and increased translocation, while GA increased transpiration but decreased translocation. EDDS application typically increased metal ion uptake by causing more cell damage, while GA typically lowered the damage and decreased metal uptake even though the transpiration increased over time and plant growth occurred. Furthermore, the behaviour of metal uptake changed over time and, for some treatments, the short-term and long-term response differed greatly. These results show that EDDS can be successfully used in phytoextraction of both Cu and Zn ions by Lolium perenne while GA can resist damage and protect against plant stress.

Effect of O2, Ni0 coatings, and iron oxide phases on pentachlorophenol dechlorination by zero-valent iron.

This study explores the zero-valent iron (ZVI) dechlorination of pentachlorophenol (PCP) and its dependence on the dissolved oxygen (O2), presence/formation of iron oxides, and presence of nickel metal on the ZVI surface. Compared to the anoxic system, PCP dechlorination was slower in the presence of O2, which is a potential competitive electron acceptor. Despite O2 presence, Ni0 deposited on the ZVI surfaces catalyzed the hydrogenation reactions and enhanced the PCP dechlorination by Ni-coated ZVI bimetal (Nic/Fe). The presence of O2 led to the formation of passivating oxides (maghemite, hematite, lepidocrocite, ferrihydrite) on the ZVI and Nic/Fe bimetallic surfaces. These passive oxides resulted in greater PCP incorporation (sorption, co-precipitation, and/or physical entrapment with the oxides) and decreased PCP dechlorination in the oxic systems compared to the anoxic systems. As received ZVI comprised of a wustite film, and in the presence of O2, only ≈ 17% PCP dechlorination observed after 25 days of exposure with tetrachlorophenol being detected as the end product. Wustite remained as the predominant oxide on as received ZVI during the 25 days of reaction with PCP under oxic and anoxic conditions. ZVI acid-pretreatment resulted in the replacement of wustite with magnetite and enhanced PCP degradation (e.g. ≈ 52% of the initial PCP dechlorinated after 25 days under oxic condition) with accumulation of mixtures of tetra-, tri-, and dichlorophenols. When the acid-washed ZVI was rinsed in NiSO4/H2SO4 solution, Ni0 deposited on the ZVI surface and all the wustite were replaced with magnetite. After 25 days of exposure to the Nic/Fe, ≈ 78% and 97% PCP dechlorination occurred under oxic and anoxic conditions, respectively, producing predominantly phenol. Wustite and magnetite are respectively electrically insulating and conducting oxides and influenced the dechlorination and H2 production. In conclusion, this study clearly demonstrates that the dissolved oxygen present in the aqueous solution decreases the PCP dechlorination and increases the PCP incorporation when using ZVI and Nic/Fe bimetallic systems. The findings provide novel insights towards deciphering and optimizing the performance of complex ZVI and bimetallic systems for PCP dechlorination in the presence of O2.

Pentachlorophenol dechlorination with zero valent iron: a Raman and GCMS study of the complex role of surficial iron oxides.

The dechlorination of chlorinated organic pollutants by zero valent iron (ZVI) is an important water treatment process with a complex dependence on many variables. This complexity means that there are reported inconsistencies in terms of dechlorination with ZVI and the effect of ZVI acid treatment, which are significant and are as yet unexplained. This study aims to decipher some of this complexity by combining Raman spectroscopy with gas chromatography-mass spectrometry (GC-MS) to investigate the influence of the mineralogy of the iron oxide phases on the surface of ZVI on the reductive dechlorination of pentachlorophenol (PCP). Two electrolytic iron samples (ZVI-T and ZVI-H) were found to have quite different PCP dechlorination reactivity in batch reactors under anoxic conditions. Raman analysis of the "as-received" ZVI-T indicated the iron was mainly covered with the ferrous oxide (FeO) wustite, which is non-conducting and led to a low rate of PCP dechlorination. In contrast, the dominant oxide on the "as-received" ZVI-H was magnetite which is conducting and, compared to ZVI-T, the ZVI-H rate of PCP dechlorination was four times faster. Treating the ZVI-H sample with 1 N H2SO4 made small change to the composition of the oxide layers and also minute change to the rate of PCP dechlorination. However, treating the ZVI-T sample with H2SO4 led to the loss of wustite so that magnetite became the dominant oxide and the rate of PCP dechlorination increased to that of the ZVI-H material. In conclusion, this study clearly shows that iron oxide mineralogy can be a contributing factor to apparent inconsistencies in the literature related to ZVI performance towards dechlorination and the effect of acid treatment on ZVI reactivity.

Changes in estrogenicity and micropollutant concentrations across unit processes in a biological wastewater treatment system.

The behavior of 10 micropollutants, i.e. four estrogens (estrone, 17ß-estradiol, estriol, 17α-ethynylestradiol), carbamazepine (CBZ), sulfamethoxazole (SMX), triclosan, oxybenzone, 4-nonylphenol, and bisphenol A, was investigated in a typical domestic wastewater treatment plant. LC-MS and yeast estrogen screen bioassay were used to study the changes in micropollutants and estrogenicity across unit processes in the treatment system. Primary treatment via sedimentation showed that only 4-nonylphenol was removed, but led to no significant change in estrogenicity. Secondary treatment by the biological nitrification-dentrification process showed complete removal of oxybenzone and partial removal of the estrogens, which led to a decrease in estrogenic activity from 80 to 48 ng/L as estradiol equivalent (EEq). Ultraviolet treatment completely degraded the estrogens and triclosan, but failed to lower the concentrations of bisphenol A, SMX, and CBZ; a decrease in estrogenic activity from 48 to 5 ng/L EEq across the unit, a value that was only slightly larger than the observed EEq of 1 ng/L for the deionized control. Similarly, the anaerobic digestion of sludge completely degraded estrogens, oxybenzone, and SMX, but had no impact on bisphenol A, triclosan, and CBZ. The study emphasises the need to complement chemical analyses with estrogenic bioassays to evaluate the efficacy of waste water treatment plants.

Estrogenic activity of cylindrospermopsin and anatoxin-a and their oxidative products by FeIII-B*/H2O2.

The cyanotoxins released into waters during cyanobacterial blooms can pose serious hazards to humans and animals. Apart from their toxicological mechanisms, cyanotoxins have been shown to be involved in estrogenic activity by in vivo and in vitro assays; however, there is limited information on the change in estrogenicity of cyanotoxins following chemical oxidation. In this study, the estrogenic activity of cylindrospermopsin (CYL) and anatoxin-a (ANA) at concentrations ranging from 2.4 × 10-7 M to 2.4 × 10-12 M (CYL) and 7.1 × 10-6 M to 7.1 × 10-11 M (ANA), and after treatment by the FeIII-B*/H2O2 catalyst system, was investigated by the yeast estrogen screen (YES) assay. The results indicate that CYL and ANA acted as agonists in the YES assay (CYL logEC50 = -8.901; ANA logEC50 = -6.789), their binding affinity to estrogen receptors is associated with their intrinsic properties, including ring structures and toxicant properties. CYL and ANA were shown to simulate endocrine disrupting chemicals (EDCs) to modulate the 17ß-estradiol-induced estrogenic activity, resulting in non-monotonic dose responses. The treated CYL showed a significantly altered estrogenicity compared to the untreated CYL (T(2) = 8.168, p ≤ .05), while the estrogenicity of the treated ANA was not significantly different to the untreated ANA (T(2) = 1.295, p > .05). Intermediate products generated from CYL and ANA oxidized by FeIII-B*/H2O2 were identified using Q-Exactive Tandem Mass Spectrometry (LC-MS/MS). Treatment with FeIII-B*/H2O2 yielded open-ring by-products which likely resulted in CYL's reduced binding affinity to estrogen receptors. The insignificant change in the estrogenicity of treated ANA was possibly a result of its multiple ring structure products, which were likely able to bind to estrogen receptors. The comparisons for the estrogenicity of these cyanotoxins before and after FeIII-B*/H2O2 treatment suggest that the reductions in estrogenicity achieved by oxidation were dependent on the levels of cyanotoxins removed, as well as the estrogenicity of the degradation products. This is the first study on the change in the estrogenicity of CYL and ANA upon oxidation by FeIII-B*/H2O2, a high activity catalyst system.

Degradation of 17α-ethinylestradiol by nano zero valent iron under different pH and dissolved oxygen levels.

The catalytic properties of nanoparticles (e.g., nano zero valent iron, nZVI) have been used to effectively treat a wide range of environmental contaminants. Emerging contaminants such as endocrine disrupting chemicals (EDCs) are susceptible to degradation by nanoparticles. Despite extensive investigations, questions remain on the transformation mechanism on the nZVI surface under different environmental conditions (redox and pH). Furthermore, in terms of the large-scale requirement for nanomaterials in field applications, the effect of polymer-stabilization used by commercial vendors on the above processes is unclear. To address these factors, we investigated the degradation of a model EDC, the steroidal estrogen 17α-ethinylestradiol (EE2), by commercially sourced nZVI at pH 3, 5 and 7 under different oxygen conditions. Following the use of radical scavengers, an assessment of the EE2 transformation products shows that under nitrogen purging direct reduction of EE2 by nZVI occurred at all pHs. The radicals transforming EE2 in the absence of purging and upon air purging were similar for a given pH, but the dominant radical varied with pH. Upon air purging, EE2 was transformed by the same radical species as the non-purged system at the same respective pH, but the degradation rate was lower with more oxygen - most likely due to faster nZVI oxidation upon aeration, coupled with radical scavenging. The dominant radicals were OH at pH 3 and O2- at pH 5, and while neither radical was involved at pH 7, no conclusive inferences could be made on the actual radical involved at pH 7. Similar transformation products were observed without purging and upon air purging.

Catalytic oxidative degradation of 17α-ethinylestradiol by FeIII-TAML/H2O2: estrogenicities of the products of partial, and extensive oxidation.

The oxidative degradation of the oral contraceptive 17α-ethinylestradiol (EE(2)) in water by a new advanced catalytic oxidation process was investigated. The oxidant employed was hydrogen peroxide in aqueous solution and the catalyst was the iron tetra-amido macrocyclic ligand (Fe(III)-TAML) complex that has been designated Na[Fe(H(2)O)(B*)] (Fe(III)-B*). EE(2) (10 µM) was oxidised rapidly by the Fe(III)-B*/H(2)O(2) (5 nM/4 mM) catalytic oxidation system at 25 °C, and for reactions at pH 8.40-11.00, no unchanged EE2 was detected in the reaction mixtures after 60 min. No oxidation of EE(2) was detected in blank reactions using either H(2)O(2) or Fe(III)-B* alone. The maximum rate of EE(2) loss occurred at pH 10.21. At this pH the half-life of EE(2) was 2.1 min and the oxidised products showed around 30% estrogenicity removal, as determined by the yeast estrogen screen (YES) bioassay. At pH 11.00, partial oxidation of EE(2) by Fe(III)-B*/H(2)O(2) (5 nM/4 mM) was studied (half-life of EE(2) was 14.5 min) and in this case the initial intermediates formed were a mixture of the epimers 17α-ethynyl-1,4-estradiene-10α,17ß-diol-3-one (1a) and 17α-ethynyl-1,4-estradiene-10ß,17ß-diol-3-one (1b) (identified by LC-ToF-MS and (1)H NMR spectroscopy). Significantly, this product mixture displayed a slightly higher estrogenicity than EE(2) itself, as determined by the YES bioassay. Upon the addition of further aliquots of Fe(III)-B* (to give a Fe(III)-B* concentration of 500 nM) and H(2)O(2) (to bring the concentration up to 4 mM assuming the final concentration had dropped to zero) to this reaction mixture the amounts of 1a and 1b slowly decreased to zero over a 60 min period as they were oxidised to unidentified products that showed no estrogenicity. Thus, partial oxidation of EE(2) gave products that have slightly increased estrogenicity, whereas more extensive oxidation by the advanced catalytic oxidation system completely removed all estrogenicity. These results underscore the importance of controlling the level of oxidation during the removal of EE(2) from water by oxidative processes.

Transformation impacts of dissolved and solid phase Fe(II) on trichloroethylene (TCE) reduction in an iron-reducing bacteria (IRB) mixed column system: a mathematical model.

In this research, we conducted trichloroethylene (TCE) reduction in a column filled with iron and iron-reducing bacteria (IRB) and developed a mathematical model to investigate the critical reactions between active species in iron/IRB/contaminant systems. The formation of ferrous iron (Fe(II)) in this system with IRB and zero-valent iron (ZVI, Fe(0)) coated with a ferric iron (Fe(III)) crust significantly affected TCE reduction and IRB respiration in various ways. This study presents a new framework for transformation property and reducing ability of both dissolved (Fe(II)(dissolved)) and solid form ferrous iron (Fe(II)(solid)). Results showed that TCE reduction was strongly depressed by Fe(II)(solid) rather than by other inhibitors (e.g., Fe(III) and lactate), suggesting that Fe(II)(solid) might reduce IRB activation due to attachment to IRB cells. Newly exposed Fe(0) from the released Fe(II)(dissolved) was a strong contributor to TCE reduction compared to Fe(II)(solid). In addition, our research confirmed that less Fe(II)(solid) production strongly supported long-term TCE reduction because it may create an easier TCE approach to Fe(0) or increase IRB growth. Our findings will aid the understanding of the contributions of iron media (e.g., Fe(II)(solid), Fe(II)(dissolved), Fe(III), and Fe(0)) to IRB for decontamination in natural groundwater systems.

Cadmium(II) speciation in complex aquatic systems: a study with ferrihydrite, bacteria, and an organic ligand.

Understanding the chemical interactions that occur in complex natural systems is fundamental to their management In this work the distribution of cadmium in the presence of phthalic acid (H2Lp), ferrihydrite, and bacteria cells (Comamonas spp., heat killed) was measured and modeled for systems with incrementally increasing complexity. In binary systems, cadmium adsorption onto bacteria or ferrihydrite was accurately predicted using the nonelectrostatic four site model (NFSM) and the diffuse layer model (DLM), respectively. Phthalic acid (0.6 mM) enhanced Cd2+ adsorption onto ferrihydrite (due to surface ternary complex formation) butinhibited Cd2 adsorption onto bacteria to the same extent as predicted by Cd-phthalate solution complex formation constants, implying no significant surface ternary interaction occurred in this system. In Cd-ferrihydrite-bacteria systems, Cd2+ adsorption was up to 10% lower than that predicted by additive adsorption onto the pure phases which suggests that an interaction between ferrihydrite and the bacteria is occupying or masking adsorption sites. By adding a generic reaction to the model for the interaction between ferrihydrite and the bacteria, the adsorption of Cd2+ onto Comamonas spp.-ferrihydrite was accurately predicted and Cd2+ distribution and speciation in systems containing ferrihydrite, Comamonas spp., and H2Lp could be predicted.

Copper(II) and cadmium(II) sorption onto ferrihydrite in the presence of phthalic acid: some properties of the ternary complex.

Copper, cadmium, and phthalic acid (H2Lp) adsorption by ferrihydrite was examined for binary and ternary systems. In binary systems adsorption was well reproduced using the diffuse layer model (DLM), and H2Lp adsorption was analogous to that of inorganic diprotic acids in terms of the relationship between the adsorption constants and acidity constants. In ternary systems H2Lp caused both the enhancement (due to ternary complexformation) and inhibition (due to solution complex formation) of Cu2+ and Cd2+ sorption depending on the conditions. The DLM could only describe the effect of H2Lp on metal ion sorption by including ternary complexes of the form [triple bond]FeOHMLp (0), where [triple bond]FeOH is a surface site and M is Cu or Cd. The relationship between binary metal adsorption constants and the ternary complex adsorption constants from this and previous studies suggest several properties of ternary complexes. First, ternary complex structures on both ferrihydrite and goethite are either the same or similar. Second, those cations having large adsorption constants also have large equilibrium constants for ternary complex formation. Third, ligands forming stronger solution complexes with cations will also form stronger surface ternary complexes though, because of the strong solution complex, they will not necessarily enhance cation adsorption.

The opposing effects of bacterial activity and gas production on anaerobic TCE degradation in soil columns.

This laboratory study explores the effect of growth substrate concentration on the anaerobic degradation of trichloroethylene (TCE) in sand packed columns. In all columns the growth substrate rapidly degraded to gas, that formed a separate phase. Biomass accumulated in the 0-4.8 cm section of the columns in proportion to the influent growth substrate concentration and biomass concentrations in the remaining sections of all columns were similar to the column receiving the lowest substrate concentration. Increases in growth substrate concentration up to 3030 mg-CODl(-1) promoted TCE degradation, but a further increase to 14300 mg-CODl(-1) reduced the amount of TCE completely dechlorinated but did not affect the production of chlorinated TCE intermediates. The mathematical model developed here satisfactorily described the enhancement in TCE dehalogenation for substrate concentration up to 3030 mg-CODl(-1); reproducing TCE dehalogenation for 14300 mg-CODl(-1) required that the moisture content used in simulation be lowered to 0.1. The study shows that volatilization of TCE can be significant and volatilization losses should be taken into account when anaerobic activity in in-situ bioremediation applications is stimulated via addition of growth substrates. An implication of the modeling simulations is that maintaining a lower, but uniform, substrate concentration over the contaminated region may lead to faster contaminant degradation.

Regeneration of iron for trichloroethylene reduction by Shewanella alga BrY.

Zero valent iron (ZVI), the primary reactive material in several permeable reactive barriers, is often oxidized to ferrous or ferric iron, resulting in decreased reactivity with time. Iron reducing bacteria can reconvert the ferric iron to its ferrous form, prolonging the reduction of chlorinated organic contaminants. In this study, the reduction of Fe(II,III) oxide and Fe(III) oxide by a strain of iron reducing bacteria of the group Shewanella alga BrY(S. alga BrY) was observed in both aqueous and solid phases. S. alga BrY preferentially reduced dissolved ferric iron over the solid ferric iron. In the presence of iron oxide the Fe(II) ions reduced by S. alga BrY efficiently reduced trichloroethylene (TCE). On the other hand, Fe(II) produced by S. alga BrY covered the reactive surfaces of ZVI iron filings and inhibited the reduction of TCE by ZVI. The formation of precipitates on the iron oxide or Fe0 surface was confirmed by scanning electron microscopy. The results suggest that iron-reducing bacteria in the oxidized Fe0 barriers can enhance the removal rate of chlorinated organic compounds and influence on the long-term performance of Fe0 reactive barriers.