Removal of tetrabromobisphenol A by conventional activated sludge, submerged membrane and membrane aerated biofilm reactors

The goal of this study was to compare removal efficiencies of tetrabromobisphenol A (TBBPA) using typical wastewater treatment technologies, and to identify the most significant mechanisms of removal. Two types of municipal wastewater reactors were studied: a full-scale conventional activated sludge (CAS) reactor with tertiary treatment; and three pilot-scale membrane bioreactors (MBRs) having different sludge retention times (SRTs). All four reactors were fed the same influent. A third reactor type, a membrane aerated biofilm reactor (MABR) was fed tap water, ammonia, and TBBPA. TBBPA in municipal influent ranged from 1 to 41 ng L⁻¹ (n = 10). The CAS effluent had an average TBBPA concentration of 0.7 ± 1.3 ng L⁻¹ (n = 3). Effluent concentrations from the MBRs were an average of 6 ± 6 ng L⁻¹ TBBPA (n = 26). Significant TBBPA removal was observed in the MABR throughout the 5 week of study (p ? 0.05). Removal of TBBPA from wastewater treatment was found to be due to a combination of adsorption and biological degradation. Based on experimental results, nitrification is likely a key process therein. No significant relationship between removal of TBBPA and SRT was identified (p ? 0.05).     

Biological degradation and microbial function effect of norfloxacin in a soil under different conditions

This paper investigated the degradation kinetics of norfloxacin in a soil, and its effects on soil respiration and nitrogen transformation under different conditions. Compared to the sterile control, the degradation rates of norfloxacin in the non-sterile soil were greatly enhanced, suggesting that microorganisms played a major role in the degradation. Accelerated degradation for norfloxacin in the soil was observed with decreasing concentrations (30 mg/kg to 5 mg/kg) with its half-life decreasing from 62 days to 31 days. Amending swine manure into the soil and increasing the soil moisture level enhanced the biological degradation of norfloxacin. No obvious inhibition of norfloxacin on soil respiration was observed in the soil, while only slight effect on nitrogen transformation was found. The results suggested that norfloxacin at the reported environmental concentrations (<100 mg/kg) would have little effect on microbial activity and functions in the soils.     

Persistence of repeated triadimefon application and its impact on soil microbial functional diversity

The effects of repeated applications of the fungicide triadimefon in agricultural soil on the microbial functional diversity of the soil and on the persistence of the fungicide in the soil were investigated under laboratory conditions. The degradation half-lives of triadimefon at the recommended dosage, simulated by a first-order kinetic model, were 23.90, 22.95, and 21.52 days for the first, second, and third applications, respectively. Throughout this study, no significant inhibition of the Shannon-Wiener index (H') was observed. However, the Simpson index (1/D) and the McIntosh index (U) were obviously reduced (p ≤ 0.05) during the initial 3 days after the first triadimefon application and thereafter, gradually recovered to or exceeded the level of the control soil. A similar trend in variation but with a faster recovery in the 1/D and U was observed after the second and third triadimefon applications, respectively. Taken together, the above results indicate that the repeated application of triadimefon enhanced the degradation rate of the fungicide and the recovery rate of the soil microbial functional diversity. It is concluded that repeated triadimefon applications in soil have a transient or temporary inhibitory effect on soil microbial communities.     

Identification of cadmium-excluding welsh onion (Allium fistulosum L.) cultivars and their mechanisms of low cadmium accumulation

Purpose

Screening out cadmium (Cd) excluding cultivars of a crop in agricultural production is an effective way to prohibit Cd entering into food chain.

Methods

A judging criterion for Cd-excluding cultivars based on food safety was suggested and used in the identification of Cd-excluding welsh onion (Allium fistulosum L.) cultivars. A pot culture experiment was carried out to screen out Cd-excluding cultivars, of which the results were confirmed by plot experiments. The relevant factors of Cd accumulation in the pseudostem were analyzed and used in the correlation analysis aiming to study the low Cd accumulation mechanisms.

Results

The concentration of Cd in the pseudostem of welsh onions was 0.08?C0.20, 0.18?C0.41, and 0.26?C0.61?mg/kg fresh weight (FW) under three treatments (1.0, 2.5, and 5.0?mg/kg), respectively. The significant (p? ₃ ^? ?CN, and eight other elements in the tested welsh onion cultivars. Two cultivars were identified as Cd-excluding cultivars, mainly because the accumulation of Cd in their pseudostem was only 0.041?±?0.003 and 0.046?±?0.002?mg/kg FW, and 0.054?±?0.001 and 0.066?±?0.011?mg/kg FW, when growing in plots with Cd concentration of 0.49 and 0.99?mg/kg, respectively.

Conclusions

Ribentiegancongwang and Wuyeqi could be identified as Cd-excluding cultivars. Low bioaccumulation factor of the roots was the main mechanism of Cd-excluding welsh onion cultivars.     

Use of inorganic and organic wastes for in situ immobilisation of Pb and Zn in a contaminated alkaline soil

Purpose  

This study aims to examine whether addition of immobilising agents to a sandy, alkaline (pH = 8.1) soil, which had been contaminated with Pb and Zn by airborne particles from a Pb/Zn smelter, would substantially reduce metal bioavailability.     

Biosorption of Basic Violet 5BN and Basic Green by waste brewery’s yeast from single and multicomponent systems

Background and aim  

The biosorption of Basic Violet 5BN (BV) and Basic Green (BG) by waste brewery’s yeast (WBY) from single and binary systems was investigated.     

Origin and distribution of trace elements in high-elevation precipitation in southern China

Introduction

During a 2009 investigation of the transport and deposition of trace elements in southern China, 37 event-based precipitation samples were collected at an observatory on Mount Heng, China (1,269?m asl).

Methods

Concentrations of trace elements were analyzed using inductively coupled plasma?Cmass spectrometry and the wet deposition fluxes were established. A combination of techniques including enrichment factor analysis, principal component analysis, and back trajectory models were used to identify pollutant sources.

Results

Trace element concentrations at Mount Heng were among the highest with respect to measured values reported elsewhere. All elements were of non-marine origin. The elements Pb, As, Cu, Se, and Cd were anthropogenic, while Fe, Cr, V, Ba, Mn, and Ni were of mixed crustal/anthropogenic origin. The crustal and anthropogenic contributions of trace elements were 12.8 % (0.9?~?17.4 %) and 87.2 % (82.6?~?99.1 %), with the maximum crustal fraction being 17.4 % for Fe. Coal combustion, soil and road dust, metallurgical processes, and industrial activities contributed to the element composition.

Conclusions

Summit precipitation events were primarily distant in origin. Medium- to long-range transport of trace elements from the Yangtze River Delta and northern China played an important role in wet deposition at Mount Heng, while air masses from south or southeast of the station were generally low in trace element concentrations.     

Heterogeneous photocatalytic degradation of methyl orange in schwertmannite/oxalate suspension under UV irradiation

Introduction

Schwertmannite was synthesized through an oxidation of FeSO₄ by Acidithiobacillus ferrooxidans LX5 cell suspension at an initial pH?2.5 and 28°C for 3?days and characterized using X-ray diffraction spectroscopy and scanning electron microscope. The schwertmannite photocatalytic degradation of methyl orange (MO) by oxalate was investigated at different initial pH values, concentrations of schwertmannite, oxalate, and MO.

Results

The results demonstrated that photodegradation of MO in the presence of schwertmannite or oxalate alone was very weak. However, the removal of MO was significantly enhanced when schwertmannite and oxalate coexisted in the reaction system. Low pH (4 or less) was beneficial to the degradation of MO. The optimal doses of schwertmannite and oxalate were 0.2?g?L^?1 and 2?mM, respectively. Hydroxyl radicals (·OH) and Fe(II), the intermediate products, were also examined during the reaction to explore their correlation with the degradation of MO.

Conclusion

A possible mechanism for the photocatalytic decomposition of MO in the study was proposed. The formation of Fe(III)-oxalate complexes on the surface of schwertmannite was a precursor of H₂O₂ and Fe(II) production, further leading to the yield of ·OH responsible for the decomposition of MO.     

超声辐射浸渍法制备Fe-Ni-Mn/Al_2O_3催化剂及性能研究

以Al2O3为载体,分别采用超声辐射浸渍法和普通浸渍方法制备Fe-Ni-Mn/Al2O3催化剂。采用BET、XRD和SEM对催化剂的理化性质和孔结构进行了分析,以模拟酸性绿B废水为研究对象考察催化剂的催化性能。实验结果表明,浸渍溶液pH值和焙烧温度显著影响催化剂的性能。与普通浸渍法相比,超声浸渍法制备的Fe-Ni-Mn/Al2O3催化剂对酸性绿B脱色反应表现出较高的催化活性。     

k-C*模型的人工湿地模拟研究

采用自由表面流人工湿地,对广东省中山市某小区对应段的河涌进行生态修复改造。基于k-C*模型的计算结果表明,在对现有河涌的面积的利用下,TP和NH4+-N的去除效果受到限制。采用多因素正交实验对模型的计算结果进行实验验证和分析,研究了4种植物、4种基质,分别在2、4、6和8 d水力停留时间(HRT)下对TP和NH4+-N的去除效果,得到影响TP和NH4+-N去除效果的因素主次顺序分别为基质→植物→HRT和基质→HRT→植物;各因素的最佳水平条件分别为:风车草、颗粒活性炭、4 d(HRT)。在最佳水平条件下进行实验,结果表明,TP和NH4+-N的浓度均可达到出水排放标准浓度指标。k-C*模型的计算值总是比实验值偏高,但两者之间的误差在一个数量级范围内。