Anaerobic biodegradability and methanogenic toxicity of key constituents in copper chemical mechanical planarization effluents of the semiconductor industry

Preparation, Property Characterization of Gd2YSbO7/ZnBiNbO5 Heterojunction Photocatalyst for Photocatalytic Degradation of Benzotriazole under Visible Light Irradiation

The Gd2YSbO7/ZnBiNbO5 heterojunction photocatalyst was synthesized for the first time by the facile in situ precipitation method. The structural properties of a Gd2YSbO7/ZnBiNbO5 heterojunction photocatalyst were characterized by X-ray diffractometer, scanning electron microscope-X ray energy dispersive spectra, X-ray photoelectron spectrograph and UV-Vis diffuse reflectance spectrophotometer. The band gap energy (BGE) of Gd2YSbO7 or ZnBiNbO5 was found to be 2.396 eV or 2.696 eV, respectively. The photocatalytic property of Gd2YSbO7 or ZnBiNbO5 or Gd2YSbO7/ZnBiNbO5 heterojunction photocatalyst (GZHP) was reported. After a visible-light irradiation of 145 minutes (VLI-145 min), the removal rate (RER) of benzotriazole reached 99.05%, 82.45%, 78.23% or 47.30% with Gd2YSbO7/ZnBiNbO5 heterojunction (GZH), Gd2YSbO7, ZnBiNbO5 or N-doped TiO2 (NTO) as photocatalyst. In addition, the kinetic constant k, derived from the dynamic curve toward benzotriazole concentration and visible light irradiation time with GZH as a photocatalyst, reached 0.0213 min−1. Compared with Gd2YSbO7 or ZnBiNbO5 or NTO, GZHP showed maximal photocatalytic activity (PHA) for the photocatalytic degradation of benzotriazole under visible-light irradiation. The RER of total organic carbon during the photocatalytic degradation of benzotriazole reached 90.18%, 74.35%, 70.73% or 42.15% with GZH as a photocatalyst or with Gd2YSbO7, ZnBiNbO5 or NTO as a photocatalyst after VLI-145 min. Moreover, the kinetic constant k, which came from the dynamic curve toward total organic carbon concentration and visible light irradiation time with GZH as a photocatalyst, reached 0.0110 min−1. Based on above results, GZHP showed the maximal mineralization percentage ratio when GZHP degraded benzotriazole. The results showed that hydroxyl radicals was the main oxidation radical during the degradation of benzotriazole. The photocatalytic degradation of benzotriazole with GZH as a photocatalyst conformed to the first-order reaction kinetics. Our research aimed to improve the photocatalytic properties of the single photocatalyst.

Fabrication of cylindrical 3D cellulose nanofibril(CNF) aerogel for continuous removal of copper(Cu2+) from wastewater

Heavy metal contamination in wastewater is a serious problem due to its high toxicity. In this study, three-dimensional porous and flexible polyethylene imine grafted cellulose nanofibril aerogel (PEI@CNF aerogel) is synthesized as a highly efficient biosorbent for continuous treatment of wastewater containing copper (Cu²⁺). The synthesized PEI@CNF aerogel efficiently separates Cu²⁺ from wastewater and exhibits outstanding selectivity for Cu²⁺ in the presence of other metal ions. The amine groups in polyethylene imine (PEI) grafted onto the porous cellulose nanofibrils (CNFs) scaffold form chelates with Cu²⁺ thereby effectively adsorbing Cu²⁺. The combination of a flexible CNF scaffold and rigid PEI results in a durable elastic matrix of the aerogel providing excellent wet stability, shape recovery property and recycle ability of PEI@CNF aerogel. Finally, in the column test, the PEI@CNF aerogel treats 88 bed volumes of wastewater containing Cu²⁺(∼20 mg/L). This result demonstrates that PEI@CNF aerogels are practically viable and highly efficient bio-sorbents for the treatment of wastewater containing Cu²⁺.

Diazole and triazole inhibition of nitrification process in return activated sludge

Azoles are emerging contaminants that are resistant to biodegradation during wastewater treatment. Their presence has been widely reported in wastewater effluents and receiving waters. In this work, the potential inhibition of nitrification process by six different azole compounds in wastewater treatment plants was investigated in batch bioassays. The azoles studied included three diazoles: pyrazole (Pz); 1-methylpyrazole (MePz); 3,5-dimethylpyrazole (DMePz); and three triazoles: 1,2,4-triazole (Tz); benzotriazole (BTz); and 5-methyl benzotriazole (MeBTz). The concentration of azoles causing 50% inhibition (IC₅₀) increased (azoles became less inhibitory) in the following order (mg L^-1): BTz (1.99) < MeBTz (2.18) < Pz (2.69) < Tz (3.53) < DMePz (17.3) < MePz (49.6). No clear structure-inhibitory relationships were found using Log P and pKa as structural properties. The toxicity of any given azole may be related to the role of substituent groups on disabling/enabling binding to the active sites of metallo-enzymes in nitrifying microorganisms. This is exemplified by the low toxicity of MePz, which has a cyclic N blocked by a methyl group. The observed inhibition caused to nitrifying bacteria is more severe than their cytotoxicity to other target organisms (e.g., methanogens and heterotrophic bacteria), suggesting a specific inhibition to the copper-containing enzyme, ammonium monooxygenase, in ammonia oxidizing nitrifying microorganisms.

Photophysical and Photocatalytic Properties of BiSnSbO₆ under Visible Light Irradiation

BiSnSbO₆ with strong photocatalytic activity was first fabricated by a high-temperature, solid-state sintering method. The resulting BiSnSbO₆ was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). The results showed that BiSnSbO₆, with a pyrochlore structure and a cubic crystal system by a space group Fd3m, was well crystallized. The lattice parameter or the band gap of BiSnSbO₆ was 10.234594 Å or 2.83 eV. Compared with N-doped TiO₂, BiSnSbO₆ showed higher photocatalytic activity in the degradation of benzotriazole and rhodamine B. The apparent first-order rate constant for BiSnSbO₆ in the degradation of benzotriazole and rhodamine B was 0.0182 min^-1 and 0.0147 min^-1, respectively. On the basis of the scavenger experiment, during the photocatalytic process, the main active species were arranged in order of increasing photodegradation rate: •OH < •O₂^- < h⁺. The removal rate of benzotriazole or rhodamine B was approximately estimated to be 100% with BiSnSbO₆ as a photocatalyst after 200 min visible-light irradiation. Plentiful CO₂ produced by the experiment indicated that benzotriazole or rhodamine B was continuously mineralized during the photocatalytic process. Finally, the possible photodegradation pathways of benzotriazole and rhodamine B were deduced.

Anaerobic biotransformation of N-methyl perfluorobutanesulfonamido ethanol and N-ethyl perfluorooctanesulfonamido ethanol

Some fluorochemical products are manufactured using N-methyl perfluorobutanesulfonamido ethanol (MeFBSE), a short-chain replacement for perfluorooctyl-based chemistries N-methyl and N-ethyl perfluorooctanesulfonamido ethanols (EtFOSE). The present study shows for the first time the anaerobic biodegradation of MeFBSE and EtFOSE in municipal digester sludge under methanogenic conditions. Both MeFBSE and EtFOSE were incubated for 108 d with anaerobic digester sludge. Although sterile controls did not remove MeFBSE, it was degraded in live sludge. The loss of MeFBSE coincided with production of N-methyl perfluorobutanesulfonamido acetate (MeFBSAA) and perfluorobutane sulfinate (PFBSI). The biodegradation appeared biphasic, with pseudo first-order loss between days 0 and 70, resulting in approximately 75% removal but no further depletion of MeFBSE between days 70 and 108. By day 108 MeFBSAA and PFBSI accounted for 57 and 40 mol% of initial dose, respectively. Mass balance values in live cultures on days 0, 10, 21, 29, 70, and 108 were 103, 92, 94, 100, 93, and 122%, respectively. The apparent first-order biodegradation rate constant for MeFBSE over the first 70 d was 0.0194 d^-1 , and the apparent half-life was 35.8 d. Incubation of EtFOSE with live digester sludge resulted in low-level formation of N-ethyl perfluorooctane-sulfonamido acetate and perfluorooctane sulfinate, which did not form in sterile controls. Although it was not measurably lost, 2 to 3% loss of EtFOSE was calculated based on product concentrations. The total product formation rate constant was determined by first-order kinetic evaluation over the first 72 d to estimate a first-order biodegradation rate constant for EtFOSE at 0.000374 d^-1 , and the apparent half-life time was 1860 d. Environ Toxicol Chem 2018;37:768-779. © 2017 SETAC.

Inhibition of Biodegradation of Hydraulic Fracturing Compounds by Glutaraldehyde: Groundwater Column and Microcosm Experiments

The rapid expansion of unconventional oil and gas development has raised concerns about the potential contamination of aquifers; however, the groundwater fate and transport of hydraulic fracturing fluid compounds and mixtures remains a significant data gap. Degradation kinetics of five hydraulic fracturing compounds (2-propanol, ethylene glycol, propargyl alcohol, 2-butoxyethanol, and 2-ethylhexanol) in the absence and presence of the biocide glutaraldehyde were investigated under a range of redox conditions using sediment-groundwater microcosms and flow-through columns. Microcosms were used to elucidate biodegradation inhibition at varying glutaraldehyde concentrations. In the absence of glutaraldehyde, half-lives ranged from 13 d to >93 d. Accurate mass spectrometry indicated that a trimer was the dominant aqueous-phase glutaraldehyde species. Microbial inhibition was observed at glutaraldehyde trimer concentrations as low as 5 mg L^-1, which demonstrated that the trimer retained some biocidal activity. For most of the compounds, biodegradation rates slowed with increasing glutaraldehyde concentrations. For many of the compounds, degradation was faster in the columns than the microcosms. Four compounds (2-propanol, ethylene glycol, propargyl alcohol, and 2-butoxyethanol) were found to be both mobile and persistent in groundwater under a range of redox conditions. The glutaraldehyde trimer and 2-ethylhexanol were more rapidly degraded, particularly under oxic conditions.

Bioremoval of Cu2+ from CMP wastewater by a novel copper-resistant bacterium Cupriavidus gilardii CR3: characteristics and mechanisms

Bacteria of the genus Cupriavidus are known for the ability of resistance to various heavy metals and metal-binding capability.

Irradiation of ultrasound to 5-methylbenzotriazole in aqueous phase: Degradation kinetics and mechanisms

Ultrasonic irradiation (640 kHz) leads to the effective degradation of 5-methyl-benzotriazole (5-MBT) in O2 saturated aqueous solution. Up to 97% of 5-MBT is eliminated within 2h of treatment. Upon extended treatment of 6h, UV absorbance of the n→π(∗) and π→π(∗) transitions associated with aromatic and conjugated systems are completely removed, indicating complete destruction of the aromatic system in 5-MBT. The decomposition of 5-MBT follows pseudo-first order kinetics and the observed decomposition rate dropped significantly in the presence of tertiary butyl alcohol. Detailed product studies were performed employing a negative mode ESI LC-MS. Twenty eight intermediate products were detected during ultrasonic mediated degradation of 5-MBT. Reaction pathways are proposed based on the structures of products assigned to observed 28 masses from LC-MS and commonly accepted degradation pathways observed by thermal and hydroxyl radical mediated pathways often associated with ultrasonic treatment.

Activated Persulfate Oxidation of Perfluorooctanoic Acid (PFOA) in Groundwater under Acidic Conditions

Perfluorooctanoic acid (PFOA) is an emerging contaminant of concern due to its toxicity for human health and ecosystems. However, successful degradation of PFOA in aqueous solutions with a cost-effective method remains a challenge, especially for groundwater. In this study, the degradation of PFOA using activated persulfate under mild conditions was investigated. The impact of different factors on persulfate activity, including pH, temperature (25 °C–50 °C), persulfate dosage and reaction time, was evaluated under different experimental conditions. Contrary to the traditional alkaline-activated persulfate oxidation, it was found that PFOA can be effectively degraded using activated persulfate under acidic conditions, with the degradation kinetics following the pseudo-first-order decay model. Higher temperature, higher persulfate dosage and increased reaction time generally result in higher PFOA degradation efficiency. Experimental results show that a PFOA degradation efficiency of 89.9% can be achieved by activated persulfate at pH of 2.0, with the reaction temperature of 50 °C, molar ratio of PFOA to persulfate as 1:100, and a reaction time of 100 h. The corresponding defluorination ratio under these conditions was 23.9%, indicating that not all PFOA decomposed via fluorine removal. The electron paramagnetic resonance spectrometer analysis results indicate that both SO₄⁻• and •OH contribute to the decomposition of PFOA. It is proposed that PFOA degradation occurs via a decarboxylation reaction triggered by SO₄⁻•, followed by a HF elimination process aided by •OH, which produces one-CF₂-unit-shortened perfluoroalkyl carboxylic acids (PFCAs, C_n−1F_2n−1COOH). The decarboxylation and HF elimination processes would repeat and eventually lead to the complete mineralization all PFCAs.

The Effect of Perfluorooctane Sulfonate, Exposure Time, and Chemical Mixtures on Methanogenic Community Structure and Function

A plethora of organic micropollutant mixtures are found in untreated municipal wastewater. Anaerobic digesters receive large loadings of hydrophobic micropollutants that sorb to wastewater biosolids. Despite micropollutants being pervasive as mixtures, little research is available to explain the impact that mixtures of compounds, as well as exposure time, have on microbial communities in anaerobic digesters. Perfluorooctane sulfonate (PFOS) was added to anaerobic enrichment cultures in both short-term (14 days) and long-term (140 days) studies to determine the impact of exposure time. Additionally, triclosan was added during the experiments to investigate the impact of mixtures on community structure and function. PFOS did not alter methane production in short-term studies, but in long-term studies, methane production increased, consistent with our hypothesis that PFOS may act as a metabolic uncoupler. The impact of triclosan on methane production was exacerbated when PFOS was already present in the anaerobic enrichment cultures. Triclosan also had greater impacts on microbial community structures in the bottles that had been exposed to PFOS long-term. These results demonstrate that both chemical mixtures and exposure time are important parameters to address when trying to define the impacts of micropollutants on anaerobic microbial communities.

Fate of benzotriazole and 5-methylbenzotriazole in recycled water recharged into an anaerobic aquifer: column studies

The fate of benzotriazole (BTri) and 5-methylbenzotriazole (5-MeBT) was investigated under anaerobic conditions at nano gram per litre concentrations in large-scale laboratory columns to mimic a managed aquifer recharge replenishment strategy in Western Australia. Investigations of BTri and 5-MeBT sorption behaviour demonstrated mobility of the compounds with retardation coefficients of 2.0 and 2.2, respectively. Degradation processes over a period of 220 days indicated first order biodegradation of the BTri and 5-MeBT under anaerobic aquifer conditions after a biological lag-time of approximately 30-60 days. Biodegradation half-lives of 29 ± 2 and 26 ± 1 days for BTri and 5-MeBT were respectively observed, with no threshold effect to biodegradation observed at the 200 ng L(-1). The detection of degradation products provided further evidence of BTri and 5-MeBT biodegradation. These results suggested that if BTri and 5-MeBT were present in recycled water recharged to the Leederville aquifer, biodegradation during aquifer passage is likely given sufficient aquifer residence times or travel distances between recycled water injection and groundwater extraction.

Defluorination of aqueous perfluorooctanesulfonate by activated persulfate oxidation

Activated persulfate oxidation technologies based on sulfate radicals were first evaluated for defluorination of aqueous perfluorooctanesulfonate (PFOS). The influences of catalytic method, time, pH and K₂S₂O₈ amounts on PFOS defluorination were investigated. The intermediate products during PFOS defluorination were detected by using LC/MS/MS. The results showed that the S₂O₈²⁻ had weak effect on the defluorination of PFOS, while the PFOS was oxidatively defluorinated by sulfate radicals in water. The defluorination efficiency of PFOS under various treatment was followed the order: HT (hydrothermal)/K₂S₂O₈ > UV (ultraviolet)/K₂S₂O₈ > Fe²⁺/K₂S₂O₈ > US (ultrasound)/K₂S₂O₈. Low pH was favorable for the PFOS defluorination with sulfate radicals. Increase in the amount of S₂O₈²⁻ had positive effect on PFOS defluorination. However, further increase in amounts of S₂O₈²⁻ caused insignificant improvement in PFOS defluorination due to elimination of sulfate radicals under high concentration of S₂O₈²⁻. CF₃(CF₂)_nCOOH (n = 0–6) were detected as intermediates during PFOS defluorination. Sulfate radicals oxidation and hydrolysis were the main mechanisms involved in defluorination process of PFOS.

Biodegradation of three selected benzotriazoles in aquifer materials under aerobic and anaerobic conditions

We investigated the biodegradation of three selected benzotriazoles (BTs), namely benzotriazole (BT), 5-methyl-benzotriazole (5-TTri) and 5-chloro-benzotriazole (CBT), in aquifer materials. Biodegradation experiments were conducted in microcosms with fresh groundwater and aquifer sediment materials under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three BTs were degraded by microorganisms in aquifer materials under aerobic and anaerobic conditions. Under aerobic conditions, BT and 5-TTri were found to be degraded fastest with their half-lives of 43 days and 31 days, respectively, among the redox conditions used. Under anaerobic conditions, CBT was found to be degraded better with its half-life of 21 days under nitrate reducing conditions than under aerobic conditions with its half-life of 47 days. The two BT derivatives 5-TTri and CBT could be biotransformed into BT via demethylation and dechlorination reactions, respectively.

Occurrence and removal of benzotriazoles and ultraviolet filters in a municipal wastewater treatment plant

We investigated the occurrence and removal of four benzotriazoles (BTs) (benzotriazole: BT; 5-methyl-benzotriazole: 5-TTri; 5-chloro-benzotriazole: CBT; 5,6-dimethyl-benzotriazole: XTri) and six UV filters (benzophenone-3: BP-3; 3-(4-methylbenzylidene)camphor: 4-MBC; octyl 4-methoxycinnamate: OMC; 2-(3-t-butyl-2-hydroxy-5-methylphenyl)-5-chloro benzotriazole: UV-326; 2-(2'-Hydroxy-5'-octylphenyl)-benzotriazole: UV-329; octocrylene: OC) in a full scale municipal wastewater treatment in South Australia. BT, 5-TTri and BP-3 were found as the dominant compounds detected in the wastewater samples with average concentrations up to 5706 ± 928 ng/L, 6758 ± 1438 ng/L and 2086 ± 1027 ng/L in influent, and up to 2439 ± 233 ng/L, 610 ± 237 ng/L and 153 ± 121 ng/L in effluent, respectively. In the biosolid, 4-MBC and OC were found with the highest concentrations of 962 ± 135 ng/g and 465 ± 65 ng/g, respectively. Sorption onto sludge played a dominant role in the removal for UV filters, especially for 4-MBC, UV-326 and OC, which accounted for 54%-92% of influent loads, while biological degradation played a significant role for the other compounds.

Biodegradation of three selected benzotriazoles under aerobic and anaerobic conditions

We examined the biodegradability of three benzotriazoles (benzotriazole: BT, 5-methylbenzotriazole: 5-TTri and 5-chlorobenzotriazole: CBT) under aerobic and anaerobic (nitrate, sulfate, and Fe (III) reducing) conditions. All three benzotriazoles were degraded by microorganisms under aerobic and anaerobic conditions. Both the biodegradation efficiency and biodegradation products were dependent on the predominant terminal electron-accepting condition. Among the redox conditions studied, the shortest biodegradation half lives for BT and 5-TTri were 114 days and 14 days, respectively, under aerobic condition. The shortest half-life for CBT was 26 days under Fe (III) reducing condition. The longest biodegradation half lives for BT and CBT were 315 days and 96 days, respectively, under sulfate reducing condition, while that of 5-TTri was 128 days under nitrate reducing condition. These results suggest that aerobic biodegradation is the dominant natural attenuation mechanism for BT and 5-TTri, while the most favorable process for CBT was anaerobic biodegradation. This study demonstrated that different predominant terminal electron-acceptors present in natural environment play a key role on the biodegradation of BT, 5-TTri and CBT, leading to specific biodegradability. This could have significant implications on in-situ biodegradation of the selected benzotriazoles in aerobic and anaerobic waters, soils and sediments.

Photoelectrochemical activity of liquid phase deposited TiO2 film for degradation of benzotriazole

TiO(2) film deposited on glassy carbon electrode surface was prepared via the liquid phase deposition (LPD). The deposited TiO(2) film before and after calcination was characterized with scanning electron microscopy (SEM) and X-ray diffraction (XRD). Based on the high photoelectrochemical activity of calcined LPD TiO(2) film, the photoelectrocatalytic degradation of benzotriazole (BTA) was investigated. Compared with the electrochemical oxidation process, direct photolysis or photocatalysis for treatment of BTA, a synergetic photoelectrocatalytic degradation effect was observed using the LPD TiO(2) film-coated electrode. Various factors influencing the photoelectrocatalytic degradation of BTA such as film calcination, applied bias potential, pH value, supporting electrolyte concentration and initial concentration of BTA were investigated. The COD removal for BTA solution was analyzed to evaluate the mineralization of the PEC process. Based on the degradation experimental results, a possible photoelectrocatalytic degradation mechanism for BTA was proposed.

Recovery of Copper from Acid Mine Drainage by an Integrated Sulphate Reducing Process

An integrated sulfate reducing process was used to treat Acid Mine Drainage with high concentrations of Cu2+, Fe and SO42-. The water treatment system integrated a sulfidogenic UASB bioreactor with a precipitation reactor which was used to recover copper. Sodium lactate was used as energy source. The effective volume of the UASB reactor was 2 L and the hydraulic retention time was 12.57h. In the sulphate removal reactor, sulphate was removed from 21160 to 195 mg/L with a rate of 4427.8 mg/L/d. Cu2+ and Fe was removed by biologically generated S2- and OH- from 360 and 6520 to 0.049 mg/L and less than 10 mg/L respectively. The average COD, copper and iron removal rate was 2523.2, 15.21 and 274.98 mg/L/d separately. The effluent pH reached 6.0-7.0. The results showed potential usage of this bioreactor in treating Acid Mine Drainage.

Column studies on transport of deicing additive benzotriazole in a sandy aquifer and a zerovalent iron barrier

Benzotriazole (BTA), a chemical with wide industrial applications, is a typical additive in deicer/anti-icer used at airport. To achieve a better understanding of the transport behaviour and environmental fate of BTA, laboratory column studies have been performed on subsoil samples from Oslo Airport, Gardermoen. To explore possibilities for aquifer remediation, BTA behaviour was also studied in a column of granular zerovalent iron (Fe(0)). The subsoil column study demonstrates a very limited retardation of BTA. Consecutive loadings of BTA of the subsoil column showed no change of the break-through curve (BTC) and complete desorption was observed. The sorption behaviour of BTA to metallic iron (Fe(0)) was rather complex. Considerable retardation was observed in the Fe(0) column and repeated BTA loading resulted in an earlier break-through. Between 20% and 50% of the input concentration was retained permanently in the iron (Fe(0)) column. The BTA sorption to metallic iron was found to be enhanced by chloride which lowered the break-through concentration (i.e the C/C(0) plateau). The fraction of BTA remaining in the iron column was found to vary with the flow rate, indicating a time dependant multilayer sorption mechanism. The steady increase in the amount of adsorbed BTA to the iron column during loading corresponds to a rather strong bonding of 4-15 BTA layers to the iron surface. A very slow desorption of BTA was observed; even after flushing with 753 pore volumes of BTA free water, 7.5% of the BTA remained in the column. A geochemical model was developed based on PHREEQC-2 to simulate the sorption and transport of BTA in the tested materials. The BTA sorption was modelled with Freundlich sorption isotherms, as earlier determined in batch experiments. A slight adjustment of the Freundlich parameters was required to fit the observed column break-through. However, our model was not able to simulate the long-term retainment of BTA in the granular iron columns. The simulations confirm the high mobility of BTA in groundwater aquifers and suggest that zerovalent iron could be used to retain a BTA plume, although oxidation of the sorbent might reduce the long-term performance of such a remediation scheme and slow desorption has been observed.

Molecular characterization of mesophilic and thermophilic sulfate reducing microbial communities in expanded granular sludge bed (EGSB) reactors

The microbial communities established in mesophilic and thermophilic expanded granular sludge bed reactors operated with sulfate as the electron acceptor were analyzed using 16S rRNA targeted molecular methods, including denaturing gradient gel electrophoresis, cloning, and phylogenetic analysis. Bacterial and archaeal communities were examined over 450 days of operation treating ethanol (thermophilic reactor) or ethanol and later a simulated semiconductor manufacturing wastewater containing citrate, isopropanol, and polyethylene glycol 300 (mesophilic reactor), with and without the addition of copper(II). Analysis, of PCR-amplified 16S rRNA gene fragments using denaturing gradient gel electrophoresis revealed a defined shift in microbial diversity in both reactors following a change in substrate composition (mesophilic reactor) and in temperature of operation from 30 degrees C to 55 degrees C (thermophilic reactor). The addition of copper(II) to the influent of both reactors did not noticeably affect the composition of the bacterial or archaeal communities, which is in agreement with the very low soluble copper concentrations (3-310 microg l(-1)) present in the reactor contents as a consequence of extensive precipitation of copper with biogenic sulfides. Furthermore, clone library analysis confirmed the phylogenetic diversity of sulfate-reducing consortia in mesophilic and thermophilic sulfidogenic reactors operated with simple substrates.

Removal of copper in an integrated sulfate reducing bioreactor-crystallization reactor system

Removal of copper was investigated using an innovative water treatment system integrating a sulfidogenic bioreactor with a fluidized-bed crystallization reactor containing fine sand to facilitate the recovery of copper as a purified copper-sulfide mineral. The performance of the system was tested using a simulated semiconductor manufacturing wastewater containing high levels of Cu2+ (4-66 mg/L), sulfate, and a mixture of citrate, isopropanol, and polyethylene glycol (Mn 300). Soluble copper removal efficiencies exceeding 99% and effluent copper concentrations averaging 89 micog/L were demonstrated in the two-stage system, with near complete metal removal occurring in the crystallizer. Copper crystals deposited on sand grains were identified as covellite (CuS). The removal of organic constituents did not exceed 70% of the initial chemical oxygen demand due to incomplete degradation of isopropanol and its breakdown product (acetone). Taken as a whole, these results indicate the potential of this novel reactor configuration for the simultaneous removal of heavy metals and organic constituents. The ability of this process to recover heavy metals in a purified form makes it particularly attractive for the treatment of contaminated aqueous streams, including industrial wastewaters and acid mine drainage.