Improved anaerobic co-digestion of food waste and domestic wastewater by copper supplementation - Microbial community change and enhanced effluent quality.

Anaerobic co-digesters are biorefineries for energy recovery from food waste and domestic wastewater via methane production. Nonetheless, the performance of this technology was not always satisfied due to the long chain fatty acids (LCFAs) generation from food waste. Micronutrient supplementation is an effective strategy that could be applied during the anaerobic (co-)digestion to further enhance the digestion efficiency while treating food waste. In this study, supplementing copper (as CuSO4 and CuCl2) at 10, 30, and 50 mg/L Cu2+ was selected to further enhance the methane production of anaerobic co-digester while treating food waste and domestic wastewater. Overall, with the supplementation of copper, the chemical oxygen demand (COD) removal efficiency was over 90%, while higher methane yields (0.260-0.325 L CH4/g COD removed) were obtained compared to the control without supplementation (0.175 L CH4/g COD removed). For the cumulative methane yield, the highest increment of 94.1% was obtained when 10 mg/L of Cu2+ were added. The results showed copper as a cofactor of many microbial enzymes and coenzymes involved in the methane production further improved both methane production and COD removal efficiency. Meanwhile, the microbial community analysis verified the copper supplementation significantly changed the bacterial communities but with the limited effect on the diversity of archaea. Furthermore, since the anaerobic co-digester was not that much efficient on the nutrients removal, the effluent from the upflow anaerobic sludge blanket (UASB) reactor was further treated by the anaerobic/anoxic/oxic (A2O) rector and the resulting effluent reached the satisfying quality in terms of COD, total nitrogen (TN), and NH3-N removal, meeting the regional effluent discharge limits.

Microbial transformation of chiral organohalides: Distribution, microorganisms and mechanisms.

Chiral organohalides including dichlorodiphenyltrichloroethane (DDT), Hexabromocyclododecane (HBCD) and polychlorinated biphenyls (PCBs) raise a significant concern in the environmental occurrence, fate and ecotoxicology due to their enantioselective biological effects. This review provides a state-of-the-art overview on enantioselective microbial transformation of the chiral organohalides. We firstly summarized worldwide field assessments of chiral organohalides in a variety of environmental matrices, which suggested the pivotal role of microorganisms in enantioselective transformation of chiral organohalides. Then, laboratory studies provided experimental evidences to further link enantioselective attenuation of chiral organohalides to specific functional microorganisms and enzymes, revealing mechanistic insights into the enantioselective microbial transformation processes. Particularly, a few amino acid residues in the functional enzymes could play a key role in mediating the enantioselectivity at the molecular level. Finally, major challenges and further developments toward an in-depth understanding of the enantioselective microbial transformation of chiral organohalides are identified and discussed.

Development of hybrid processes for the removal of volatile organic compounds, plasticizer, and pharmaceutically active compound using sewage sludge, waste scrap tires, and wood chips as sorbents and microbial immobilization matrices.

This study evaluated the reutilization of waste materials (scrap tires, sewage sludge, and wood chips) to remove volatile organic compounds (VOCs) benzene/toluene/ethylbenzene/xylenes/trichloroethylene/cis-1,2-dichloroethylene (BTEX/TCE/cis-DCE), plasticizer di(2-ethylhexyl) phthalate (DEHP), and pharmaceutically active compound carbamazepine from artificially contaminated water. Different hybrid removal processes were developed: (1) 300 mg/L BTEX + 20 mg/L TCE + 10 mg/L cis-DCE + tires + Pseudomonas sp.; (2) 250 mg/L toluene + sewage sludge biochar + Pseudomonas sp.; (3) 100 mg/L DEHP + tires + Acinetobacter sp.; and (4) 20 mg/L carbamazepine + wood chips + Phanerochaete chrysosporium. For the hybrid process (1), the removal of xylenes, TCE, and cis-DCE was enhanced, resulted from the contribution of both physical adsorption and biological immobilization removal. The hybrid process (2) was also superior for the removal of DEHP and required a shorter time (2 days) for the bioremoval. For the process (3), the biochar promoted the microbial immobilization on its surface and substantially enhanced/speed up the bioremoval of toluene. The fungal immobilization on wood chips in the hybrid process (4) also improved the carbamazepine removal considerably (removal efficiencies of 61.3 ± 0.6%) compared to the suspended system without wood chips (removal efficiencies of 34.4 ± 1.8%). These hybrid processes would not only be promising for the bioremediation of environmentally concerned contaminants but also reutilize waste materials as sorbents without any further treatment.

Reutilization of waste scrap tyre as the immobilization matrix for the enhanced bioremoval of a monoaromatic hydrocarbons, methyl tert-butyl ether, and chlorinated ethenes mixture from water.

BTEX (benzene, toluene, ethylbenzene, ortho-, meta-, and para-xylenes), methyl tert-butyl ether (MTBE), cis-1,2-dichloroethylene (cis-DCE), and trichloroethylene (TCE) are among the major soil and groundwater contaminants frequently co-existing, as a result of their widespread uses. Pseudomonas plecoglossicida was immobilized on waste scrap tyre to remove these contaminants mixture from synthetic contaminated water. The microbial activity was enhanced in the immobilized system, shown by the higher colony forming units (CFUs) (40%), while BTEX were used as growth substrates. The adsorption capacity of tyres toward contaminants reached a maximum within one day, with BTEX (76.3%) and TCE (64.3%) showing the highest sorption removal capacities, followed by cis-DCE (30.0%) and MTBE (11.0%). The adsorption data fitted the Freundlich isotherm with a good linear correlation (0.989-0.999) for the initial contaminants concentration range applied (25-125mg/L). The monoaromatic hydrocarbons were almost completely removed in the immobilized system and the favourable removal efficiencies of 78% and 90% were obtained for cis-DCE and TCE, respectively. The hybrid (biological, immobilization/physical, sorption) system was further evaluated with the contaminants spiked intermittently for the stable performance. The addition of mineral salt medium further enhanced the bioremoval of contaminants by stimulating the microbial growth to some extent.

Multivariate optimization for the simultaneous bioremoval of BTEX and chlorinated aliphatic hydrocarbons by Pseudomonas plecoglossicida.

This study aimed to evaluate the effects of some major parameters on the cometabolic removal of cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE), mixed with benzene, toluene, ethylbenzene, and xylenes, by an indigenous bacterial isolate Pseudomonas plecoglossicida. Such statistical methodologies as hierarchical cluster analysis heat map and principal component analysis were applied to better evaluate the effects of major parameters (soil pH, temperature, moisture, and cis-DCE/TCE concentrations) on the biological process. The bioremoval experiments were carried out in microcosms containing soil slurry, and the headspace concentrations of contaminants were analyzed by gas chromatography. The optimal bioremoval conditions for the mixture were soil water content >110%, pH 8-9, and temperature 15-20°C, while the cis-DCE/TCE concentration did not significantly affect the mixture bioremoval within the tested range (∼10mg per kg soil). Under the optimal conditions, benzene (97.7%), toluene (96.3%), and ethylbenzene (89.8%) were almost completely removed, while cis-DCE (24.5%), TCE (29.0%), m,p-xylene (36.3%), and o-xylene (29.6%) showed lower removal efficiencies. The obtained results would help to better design a remediation technology to be applied to the sites contaminated with mixed wastes, and the statistical methodologies used in this study appear to be very efficient and could serve as a template for optimization.

Effect of COD/TP ratio on biological nutrient removal in A²O and SBR processes coupled with microfiltration and effluent reuse potential.

Two bench-scale hybrid processes, anaerobic/anoxic/oxic (A(2)O) reactor and sequencing batch reactor (SBR), each followed by the microfiltration (MF) system, were simultaneously operated to compare their performances on the removal of organics and phosphorus from both synthetic and real wastewater to further explore the potential for effluent reuse. The effects of different influent chemical oxygen demand (COD) to total phosphorus (TP) ratios (27, 50, 80, and 200) were investigated. For both processes, when the influent COD/TP ratio was 200, the effluent quality was satisfactory for some reuse potential. The MF membrane system showed an evident further removal of COD (20-89%) and color (18-60%), especially the removal of suspended solids (SS) and turbidity with the final effluent SS <1 mg/L and turbidity <0.1 NTU. When real wastewater was tested, the effluent quality was adequate and met the standard goals for regional reuse purposes.

Enhanced removal of naproxen and carbamazepine from wastewater using a novel countercurrent seepage bioreactor immobilized with Phanerochaete chrysosporium under non-sterile conditions.

A countercurrent seepage bioreactor immobilized with Phanerochaete chrysosporium was continuously operated under non-sterile conditions to treat a synthetic wastewater spiked with naproxen and carbamazepine (1000µg/L each) for 165days. There were no serious bacterial contaminations occurred during the operational period. Naproxen was always removed to the undetectable level regardless of the experimental conditions, while the average removal efficiency for carbamazepine, a well-known recalcitrant pharmaceutically active compound, reached around 80%. The excellent removal performance was mainly attributed to the application of countercurrent seepage mode and the cardhouse fabric of the carriers, which provided the high efficiency in the transfer of oxygen and nutrients inside the bioreactor. From the fungal immobilization combined with the temperature adjustment, the fungal activity including the enzyme production was protected as well as the bacterial contamination inside the reactor was suppressed effectively.

Combined removal of a BTEX, TCE, and cis-DCE mixture using Pseudomonas sp. immobilized on scrap tyres.

The simultaneous aerobic removal of a mixture of benzene, toluene, ethylbenzene, and o,m,p-xylene (BTEX); cis-dichloroethylene (cis-DCE); and trichloroethylene (TCE) from the artificially contaminated water using an indigenous bacterial isolate identified as Pseudomonas plecoglossicida immobilized on waste scrap tyres was investigated. Suspended and immobilized conditions were compared for the removal of these volatile organic compounds. For the immobilized system, toluene, benzene, and ethylbenzene were completely removed, while the highest removal efficiencies of 99.0 ± 0.1, 96.8 ± 0.3, 73.6 ± 2.5, and 61.6 ± 0.9% were obtained for o-xylene, m,p-xylene, TCE, and cis-DCE, respectively. The sorption kinetics of contaminants towards tyre surface was also evaluated, and the sorption capacity generally followed the order of toluene > benzene > m,p-xylene > o-xylene > ethylbenzene > TCE > cis-DCE. Scrap tyres showed a good capability for the simultaneous sorption and bioremoval of BTEX/cis-DCE/TCE mixture, implying a promising waste material for the removal of contaminant mixture from industrial wastewater or contaminated groundwater.

Effect of toluene concentration and hydrogen peroxide on Pseudomonas plecoglossicida cometabolizing mixture of cis-DCE and TCE in soil slurry.

An indigenous Pseudomonas sp., isolated from the regional contaminated soil and identified as P. plecoglossicida, was evaluated for its aerobic cometabolic removal of cis-1,2-dichloroethylene (cis-DCE) and trichloroethylene (TCE) using toluene as growth substrate in a laboratory-scale soil slurry. The aerobic simultaneous bioremoval of the cis-DCE/TCE/toluene mixture was studied under different conditions. Results showed that an increase in toluene concentration level from 300 to 900 mg/kg prolonged the lag phase for the bacterial growth, while the bioremoval extent for cis-DCE, TCE, and toluene declined as the initial toluene concentration increased. In addition, the cometabolic bioremoval of cis-DCE and TCE was inhibited by the presence of hydrogen peroxide as the additional oxygen source, while the bioremoval of toluene (900 mg/kg) was enhanced after 9 days of incubation. The subsequent addition of toluene did not improve the cometabolic bioremoval of cis-DCE and TCE. The obtained results would help to enhance the applicability of bioremediation technology to the mixed waste contaminated sites.

Characterization of refractory matters in dyeing wastewater during a full-scale Fenton process following pure-oxygen activated sludge treatment.

Refractory pollutants in raw and treated dyeing wastewaters were characterized using fractional molecular weight cut-off, Ultraviolet-vis spectrophotometry, and high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI/MS). Significant organics and color compounds remained after biological (pure-oxygen activated sludge) and chemical (Fenton) treatments at a dyeing wastewater treatment plant (flow rate ∼100,000m(3)/d). HPLC-ESI/MS analysis revealed that some organic compounds disappeared after the biological treatment but reappeared after the chemical oxidation process, and some of that were originally absent in the raw dyeing wastewater was formed after the biological or chemical treatment. It appeared that the Fenton process merely impaired the color-imparting bonds in the dye materials instead of completely degrading them. Nevertheless, this process did significantly reduce the soluble chemical oxygen demand (SCOD, 66%) and color (73%) remaining after initial biological treatment which reduced SCOD by 53% and color by 13% in raw wastewater. Biological treatment decreased the degradable compounds substantially, in such a way that the following Fenton process could effectively remove recalcitrant compounds, making the overall hybrid system more economical. In addition, ferric ion inherent to the Fenton reaction effectively coagulated particulate matters not removed via biological and chemical oxidation.

Removal of carbamazepine and naproxen by immobilized Phanerochaete chrysosporium under non-sterile condition.

This study explored the utilization of a white-rot fungus (WRF), Phanerochaete chrysosporium, immobilized in wood chips, to remove carbamazepine and naproxen under non-sterile condition. The removal efficiencies for both pharmaceutically active compounds (PhACs) in artificially contaminated water were improved by 4% for naproxen and 30% for carbamazepine in seven days, compared to without wood chips. Although adsorption was crucial at the early stage, bioremoval was found to be the main removal mechanism for both PhACs. The extracellular enzymes played important roles in the naproxen removal, while the intracellular enzyme system was responsible for the carbamazepine removal. The increased of intracellular enzyme activity through the immobilization of WRF cells may contribute to the significantly enhanced removal efficiency for carbamazepine. In addition, the removal of naproxen or carbamazepine slightly increased when both compounds coexisted, compared to the system where the two pharmaceuticals existed separately. Based on the batch experimental results, a fixed-bed bioreactor packed with a mixture of WRF mycelia pellets and wood chips was developed and operated with the intermittent feeding and continuous aerating mode for 28 days under non-sterile condition, with naproxen and carbamazepine spiked into the influent at 1.0 mg L(-1). Almost complete removal of naproxen and 60-80% removal of carbamazepine were obtained in the first two weeks. However, the removal efficiencies for both compounds suddenly dropped to as low as less than 20% by the 14th day, possibly due to the contamination by other microorganisms in the reactor. After the addition of 8.25% sodium hypochlorite at the ratio of 1:100 (v/v) into the influent tank on both Day 20 and Day 25, a rapid recovery (higher than 95%) was achieved in the naproxen removal, by effectively inhibiting contamination in the reactor. In comparison, the same rebounding phenomenon was not observed for carbamazepine and this difference may be associated to the various enzyme-working systems. A longer hydraulic retention time (HRT) was conducive to improve the removal of both compounds.

Lipid production by a mixed culture of oleaginous yeast and microalga from distillery and domestic mixed wastewater.

Lipid productivity by mixed culture of Rhodosporidium toruloides and Chlorella pyrenoidosa was studied using 1:1 mixed real wastewater from distillery and local municipal wastewater treatment plant with initial soluble chemical oxygen demand (SCOD) around 25,000 mg/L, initial cell density of 2×10(7) cells/mL (yeast) and 5×10(6) cells/mL (microalga), at 30 °C and 2.93 W/m2 (2000 lux, 12:12 h light and dark cycles). Lipid content and lipid yield achieved were 63.45±2.58% and 4.60±0.36 g/L with the associated removal efficiencies for SCOD, total nitrogen (TN), and total phosphorus (TP) at 95.34±0.07%, 51.18±2.17%, and 89.29±4.91%, respectively, after 5 days of cultivation without the pH adjustment. Inoculation of microalgae at 40 h of the initial yeast cultivation and harvesting part of inactive biomass at 72 h by sedimentation could improve both lipid production and wastewater treatment efficiency under non-sterile conditions.

Determination of dipyridamole in pharmaceutical preparations using square wave voltammetry.

An analytical methodology using square wave voltammetry (SWV) at a hanging mercury drop electrode (HMDE) was developed for the quantitative determination of dipyridamole (DIP), a drug used for the treatment of several cardiovascular diseases, in pharmaceutical tablets and injections of Persantin in phosphate buffer (pH 3.0; 0.1M). After optimization of the parameters for SWV, analytical curves were obtained for application in the range of 1.28 x 10(-6)M to 7.02 x 10(-6)M. It was found a detection limit (DL) of 1.88 x 10(-8)M (9.50 ng/ml). The repeatability and the reproducibility of the method were determinated by successive measurements of DIP solutions on the range of the analytical curve with a coefficient variation of 0.97% (n=5) and 1.15%, respectively. The apparent recoveries were obtained by the IUPAC recommended procedure using the second reduction peak. Recoveries obtained by SWV were compared with the UV-vis spectrophotometric method. It was found that the determination of DIP in Persantin tablets gave a mean value of 75.6+/-0.4 mg (100.8%) and 68.9+/-0.3 mg (91.8%) for SWV and UV-vis spectrophotometry, respectively. In the case of injections, it was found 10.4+/-0.1 mg (103.4%) and 9.9+/-0.2 mg (99.9%) for SWV and UV-vis spectrophotometry. Both apparent recoveries for the two types of formulations are in good accordance with the declared value of 75 mg (tablets) and 10 mg (injections).