Influence of temperature on performance of an anaerobic sequencing biofilm batch reactor with circulation applied to treatment of low-strength wastewater

The effect of temperature on the performance of an anaerobic sequencing biofilm batch reactor (ASBBR) with liquid-phase recirculation was assessed. Assays were performed using a recirculation velocity of 0.20 cm/s, 8-h cycles, and an average treated synthetic wastewater volume of 2 L/cycle with a concentration of 500 mg of Chemical Oxygen Demand (COD)/L. Operation temperatures were 15, 20, 25, 30, and 35°C. At 25, 30, and 35°C, organic matter removal efficiencies for filtered samples ranged from 81 to 83%. At lower temperatures, namely 15 and 20°C, removal efficiency decreased significantly to 61 and 65%, respectively. A first-order model could be fitted to the experimental concentration profile values. The first-order kinetic parameter value of this model varied from 0.46 to 0.81 h¹ considering the lowest and highest temperature studied. Moreover, analysis of the removal profile values allowed fitting of an Arrhenius-type equation with an activation energy of 5715 cal/mol.     

Statistical Optimization for Succinic Acid Production from E. Coli in a Cost-Effective Medium

Response surface methodology (RSM) was employed for optimization of medium components and cultural parameters in cost effective cane molasses based medium for attaining high yield of succinic acid. The important factors obtained by “one-variable-at-a-time-approach” (cane molasses, corn steep liquor, sodium carbonate, and inoculum density) were further optimized by RSM. The optimum values of the parameters obtained through RSM (cane molasses 12.5%, corn steep liquor 7.5%, and sodium carbonate 25 mM) led to almost double yield of succinic acid (15.2 g/l in 36 h) as against “one-variable-at-a-time-approach” (7.1 g/l in 36 h) in 500-ml anaerobic bottles containing 300-ml cane molasses based medium. Subsequently, in 10-l bioreactor succinic acid production from Escherichia coli was further improved to 26.2 g/l in 30 h under conditions optimized through RSM. This fermentation-derived succinic acid will definitely help in replacing existing environmentally hazardous and cost-intensive chemical methods for the production of succinic acid.     

Removal of pharmaceutical residues in a pilot wastewater treatment plant

Concern is growing over the contamination of the environment with pharmaceutical residues, among which non-steroidal anti-inflammatory drugs (NSAIDs) are one of the most abundant groups. Their widespread appearance in the aquatic environment is because of their high consumption and their incomplete removal during wastewater treatment. Because effective operation of wastewater-treatment plants is important for minimising the release of xenobiotic compounds, for example pharmaceutical products, into the aquatic environment, our study focuses on removal of commonly used NSAIDs (ibuprofen, naproxen, ketoprofen, diclofenac) and clofibric acid in a specially designed small-scale pilot wastewater treatment plant (PWWTP). This study shows that, except for diclofenac, steady-rate removal of NSAIDs over a two-year monitoring period has been achieved. Elimination of the compounds in the PWWTP was ≥87% for ibuprofen, naproxen and ketoprofen but only 49–59% for diclofenac. We also studied clofibric acid. Results after one month of operation revealed 30% elimination with no sign of adaptation by the biomass. Also described are degradation products of diclofenac, which we were able to identify because of the similarity of their mass spectra with those in the NIST library and by comparing the retention times of different compounds. Although the structures of these compounds were confirmed with a high probability (99%), we still need to compare the fragmentation of authentic compounds with degradation products formed under our experimental conditions. Degradation products of ibuprofen, naproxen, ketoprofen, and clofibric acid were found but these must be identified by use of high-resolution mass spectrometry and analysis of authentic compounds.     

Environmentally Compatible Hybrid-Type Polyurethane Foams Containing Saccharide and Lignin Components

Semi-rigid polyurethane (PU) foams were prepared using lignin-molasses- poly(ethylene glycol) polyols. Two kinds of lignin, kraft lignin (KL) and sodium lignosulfonate (LS), were used. Both lignin and molasses polyols were mixed with various ratios and were reacted with poly(phenylene methylene) polyisocyanate (MDI) in the presence of silicone surfactant and di-n-butyltin dilaurate. A small amount of water was used as a foaming agent. The apparent density of PU foams increased with increasing lignin content. The compression strength and elastic modulus linearly increase with increasing apparent density, suggesting that mechanical properties are controllable by changing reaction conditions. The PU foams were amorphous and glass transition was detected by differential scanning calorimetry. The glass transition temperature (T_g ) maintained an almost constant value, regardless of the mixing ratio. This indicates that both the phenolic group of lignin and the glucopyranose ring of molasses act as rigid components in PU crosslinking network structures, and both groups contribute to the main chain motion to the same extent. By thermogravimetry (TG), it was confirmed that PU foams are thermally stable up to around 300 °C. By differential scanning calorimetry, T_g was observed at temperatures from 80 to 120 °C.     

Polypyrrole‐magnetite dispersive micro‐solid‐phase extraction combined with ultraviolet‐visible spectrophotometry for the determination of rhodamine 6G and crystal violet in textile wastewater

Polypyrrole‐magnetite dispersive micro‐solid‐phase extraction method combined with ultraviolet‐visible spectrophotometry was developed for the determination of selected cationic dyes in textile wastewater. Polypyrrole‐magnetite was used as adsorbent due to its thermal stability, magnetic properties, and ability to adsorb Rhodamine 6G and crystal violet. Dispersive micro‐solid‐phase extraction parameters were optimized, including sample pH, adsorbent amount, extraction time, and desorption solvent. The optimum polypyrrole‐magnetite dispersive micro‐solid phase‐extraction conditions were sample pH 8, 60 mg polypyrrole‐magnetite adsorbent, 5 min of extraction time, and acetonitrile as the desorption solvent. Under the optimized conditions, the polypyrrole‐magnetite dispersive micro‐solid‐phase extraction with ultraviolet‐visible method showed good linearity in the range of 0.05–7 mg/L (R ² > 0.9980). The method also showed a good limit of detection for the dyes (0.05 mg/L) and good analyte recoveries (97.4–111.3%) with relative standard deviations < 10%. The method was successfully applied to the analysis of dyes in textile wastewater samples where the concentration found was 1.03 mg (RSD ±7.9%) and 1.13 mg/L (RSD ± 4.6%) for Rhodamine 6G and crystal violet, respectively. It can be concluded that this method can be adopted for the rapid extraction and determination of dyes at trace concentration levels.     

零价铁耦合厌氧微生物法在废水处理中的应用

零价铁(ZVI)与厌氧微生物的耦合是一项很有前景的技术,在难降解有机废水的去除中得到了广泛关注。该耦合技术将ZVI技术的高效性与厌氧生物技术的经济性有效融合,在多元微电场和厌氧微生物协同作用下,有效降低难降解有机物的生物抑制性和毒性。本文综述了此技术处理工业废水的潜在机理、实际应用中主要操作参数及影响条件以及处理含氯化合物、重金属、染料等生物难降解污染物的研究进展。归纳了ZVI与厌氧微生物耦合对上述污染物进行高效去除的研究现状,并对该技术在实际工程应用方面的可行策略进行了展望。     

印染废水的植物修复及在线监测技术研究

采用空心莲子草对印染废水进行修复,研究净化效果,并利用在线监测技术对植物修复前后的印染废水中氨氮、COD、TOC指标进行测定。结果表明：在线监测技术成熟,植物修复印染废水可行。     

Combining Coagulation and Electrocoagulation with UVA-LED Photo-Fenton to Improve the Efficiency and Reduce the Cost of Mature Landfill Leachate Treatment

This study focused on the reduction of the treatment cost of mature landfill leachate (LL) by enhancing the coagulation pre-treatment before a UVA-LED photo-Fenton process. A more efficient advanced coagulation pretreatment was designed by combining conventional coagulation (CC) and electro-coagulation (EC). Regardless of the order in which the two coagulations were applied, the combination achieved more than 73% color removal, 80% COD removal, and 27% SUVA removal. However, the coagulation order had a great influence on both final pH and total dissolved iron, which were key parameters for the UVA-LED photo-Fenton post-treatment. CC (pH = 5; 2 g L⁻¹ of FeCl₃6H₂O) followed by EC (pH = 5; 10 mA cm⁻²) resulted in a pH of 6.4 and 100 mg L⁻¹ of dissolved iron, whereas EC (pH = 4; 10 mA cm⁻²) followed by CC (pH = 6; 1 g L⁻¹ FeCl₃6H₂O) led to a final pH of 3.4 and 210 mg L⁻¹ dissolved iron. This last combination was therefore considered better for the posterior photo-Fenton treatment. Results at the best cost-efficient [H₂O₂]:COD ratio of 1.063 showed a high treatment efficiency, namely the removal of 99% of the color, 89% of the COD, and 60% of the SUVA. Conductivity was reduced by 17%, and biodegradability increased to BOD₅:COD = 0.40. With this proposed treatment, a final COD of only 453 mg O₂ L⁻¹ was obtained at a treatment cost of EUR 3.42 kg COD⁻¹.     

Carbon Nanotubes Hybrid Hydrogels for Environmental Remediation: Evaluation of Adsorption Efficiency under Electric Field

The performance of Carbon Nanotubes hybrid hydrogels for environmental remediation was investigated using Methylene Blue (MB), Rhodamine B (RD), and Bengal Rose (BR) as model contaminating dyes. An acrylate hydrogel network with incorporated CNT was synthesized by photo-polymerization without any preliminary derivatization of CNT surface. Thermodynamics, isothermal and kinetic studies showed favorable sorption processes with the application of an external 12 V electric field found to be able to influence the amount of adsorbed dyes: stronger interactions with cationic MB molecules (qexp and qexp12 of 19.72 and 33.45 mg g⁻¹, respectively) and reduced affinity for anionic RD (qexp and qexp12 of 28.93 and 13.06 mg g⁻¹, respectively) and neutral BR (qexp and qexp12 of 36.75 and 15.85 mg g⁻¹, respectively) molecules were recorded. The influence of pH variation on dyes adsorption was finally highlighted by reusability studies, with the negligible variation of adsorption capacity after five repeated sorption cycles claiming for the suitability of the proposed systems as effective sorbent for wastewater treatment.     

Efficient Removal of Lead from Washing Effluent of Lead-contaminated Soil with Garlic Peel

Wastewater produced from the soil washing process contains heavy metals, which limits its reuse for washing. So it is necessary to develop an efficient and economical way to recycle it, and this study presented a biosorption method to realize this goal. A typical soil sample contaminated by lead was taken from the real field near a lead smelting factory, used for the toxic metals extraction with dilute citric acid. A leach liquor was obtained with lead ions at the level of 12.35 mg/L, Cd 1.2 mg/L, Cu 1.5 mg/L, Zn 2.6 mg/L, as well as the coexisting anions, such as sulphate, silicate, chloride at the concentration of several hundred miligram per liter. The garlic peel was modified by a simple chemical saponification process and used as the biosorbent for toxic metal removal. Firstly, the adsorption behavior of lead ions on the saponified garlic peel was systematically investigated using the synthetic solutions, and then the adsorption mechanisms were explored by detailed experiments combining with the thermodynamic calculation reuslts of the aqueous system of Pb(Ⅱ)-citrate-H₂O. It was found that in artificial solution containing 0.01 mol/L citrate, the maximum adsorption capacity of 261.0 mg/g was reached at pH near 3.0, and also at this very pH value the Pb²⁺ and Pb(H₂Cit)⁺ were the dominant lead species, which are favorable for adsorption due to its easier approaching to the -COO^- ligands in the saponified garlic peel partilces via charge attraction, and the appearance of Pb(HCit)⁰ and Pb(Cit)^- at pH above 3.0 inhibits the adsorption. Secondly, the real leach liquor was used for adsorption tests, and twice adsorption under the optimal conditons would decrease the residual concentrations of Pb, Cd, Cu and Zn to zero. After elution by using 0.1 mol/L nitric acid, the adsorbed metals can be recovered and garlic peel can be reused for at least 10 cycles effectively. This study presents a prospective biosorption method for economical and efficient removal of the lead ions from soil washing wastewater with citric acid as the leaching reagent.