Removal of malachite green (MG) from aqueous solutions by native and heat-treated anaerobic granular sludge

The performance of native and heat-treated anaerobic granular sludge in removing of malachite green (MG) from aqueous solution was investigated with different conditions, such as pH, ionic strength, initial concentration and temperature. The maximum biosorption was both observed at pH 5.0 on the native and heat-treated anaerobic granular sludge. The ionic strength had negative effect on MG removal. Kinetic studies showed that the biosorption process followed pseudo-second-order and q_e for native and heat-treated anaerobic granular sludge is 61.73 and 59.17 mg/g at initial concentration 150 mg/L, respectively. Intraparticle diffusion model could well illuminate adsorption process and faster adsorption rate of native anaerobic granular sludge than heat-treated anaerobic granular sludge. The equilibrium data were analyzed using Langmuir and Freundlich model, and well fitted Langmuir model. The negative values of ΔG° and ΔH° suggested that the interaction of MG adsorbed by native and heat-treated anaerobic granular sludge was spontaneous and exothermic. Desorption studies revealed that MG could be well removed from anaerobic granular sludge by 1% (v/v) of HCl–alcohol solution.     

Anammox反应器启动过程中颗粒污泥性状变化特性

以厌氧颗粒污泥作为接种物,通过185 d的运行,成功启动了上流式厌氧氨氧化污泥床(Upflow anaerobic sludge blanket,UASB)反应器。反应器的进水氨氮与亚硝氮浓度分别提升至224 mg/L和255 mg/L,容积氮去除速率提升至3.76 kg/(m3·d)。采用红外光谱、扫描电镜和透射电镜等对厌氧氨氧化颗粒污泥的性状进行观察,发现颗粒污泥在启动过程中经历了污泥颗粒裂解到污泥颗粒重组的过程,且厌氧氨氧化颗粒污泥表面含有丰富的官能团,说明厌氧氨氧化颗粒污泥可能具有良好的吸附性能。采用宏基因组测序的方法对启动前后颗粒污泥的生态结构进行分析,发现原接种污泥优势菌群(变形菌门、厚壁菌门、拟杆菌门)丰度大幅减少,厌氧氨氧化菌所属的浮霉状菌门丰度则由1.59%提升到23.24%。     

Toxic and essential elements in children's blood (<6 years) from Kinshasa,DRC (the Democratic Republic of Congo)

In this study we determined the concentration of 9 trace elements (As, Cd, Cu, Hg, Mn, Mo, Pb, Se and Zn) in whole blood of children (n = 100, 64 girls, 36 boys and median age: 36 months) using inductively coupled plasma mass spectrometry (ICP-MS). The proportion of children potentially deficient in essential elements or poisoned by toxic elements was evaluated. The aging effects on the concentration of these elements were also investigated. The median values were 3.17 μg/L (As), 0.15 μg/L (Cd), 1.1 mg/L (Cu), 2.1 μg/L (Hg), 10.4 μg/L (Mn), 17.7 μg/L (Mo), 8.7 μg/dL (Pb), 10.7 μg/L (Se) and 5.0 mg/L (Zn). The concentration of many elements (As, Cd, Hg, Mn, Pb and Zn) showed significant age variations but not sex influence. Regarding levels of the essential elements (Cu, Mn, Mo, Se and Zn), B-Cu, B-Mn, B-Se and B-Zn were in the normal range, whereas exceeded levels were observed for B-Mo. None of these children was deficient in essential elements. Except B-Cd, all toxic elements showed exceeded blood levels. The proportion of children potentially poisoned by toxic elements varies from 10% (n = 10) to 95% (n = 95) and depends on toxic element: 95% for As, 10% for Hg and 35% for Pb. The main health concerns emerging from this study are the high As, Hg and Pb exposures of the Kinshasan children requiring further documentation, corrective actions and the implementation of appropriate regulations.     

Concentrations of cadmium,lead, selenium,and zinc in human blood and seminal plasma

The concentrations of cadmium, lead, selenium, and zinc in blood and seminal plasma were determined in 76 Singapore males. Except for zinc, the concentrations were generally higher in blood than in seminal plasma (cadmium, 1.31 μg/L vs 0.61 μg/L; lead, 82.6 μg/L vs 12.4 μg/L, and selenium, 163.6 μg/L vs 71.5 μg/L). The mean concentration of zinc in seminal plasma was more than 30 times higher than in blood (202 mg/L vs 6.2 mg/L). Significant positive correlations were found between the concentrations in blood and seminal plasma for the two essential trace elements: selenium (r=0.45,p<0.001) and zinc (r=0.25,p<0.05). However, no relationships were found between the concentrations in blood and seminal plasma for two toxic metals (cadmium and lead). Significant inverse correlations were observed between Cd and Zn (r=−0.40,p<0.01), and Pb and Se (r=−0.32,p<0.05) in blood, whereas significant positive correlations were noted between Cd and Se (r=0.45,p<0.01), Cd and Zn (r=0.35,p<0.05), and Se and Zn (r=0.57,p<0.001) in seminal plasma. The physiological significance of these relationships are also discussed in this paper.     

Long-term effects of multi-walled carbon nanotubes on the performance and microbial community structures of an anaerobic granular sludge system

Multi-walled carbon nanotubes (MWCNTs) released into the sewage may cause negative and/or positive effects on the treatment system. The objective of this study was to explore over 110 days’ effect of MWCNTs on the performance of anaerobic granular sludge and microbial community structures in an upflow anaerobic sludge blanket (UASB) reactor. The results showed that MWCNTs had no significant effect on the removal of chemical oxidation demand (COD) and ammonia in UASB reactor, but the total phosphorus (TP) removal efficiency increased by 29.34%. The biogas production of the reactor did not change. The anaerobic granular sludge tended to excrete more EPS to resist the effects of MWCNTs during the long-term impact. Illumina MiSeq sequencing of 16S rRNA gene revealed that MWCNTs did not affect the microbial diversity, but altered the composition and structure of microbial community in the reactor. In this process, Saccharibacteria replaced Proteobacteria as the highest abundant bacterial phylum. MWCNTs promoted the differentiation of methanogen structure, resulting in increase of Methanomassiliicoccus, Methanoculleus, and the uncultured WCHA1–57. These results indicated that MWCNTs impacted the performance of UASB reactor and the structures of the microbial community in anaerobic granular sludge.

     

Methanotroph and methanogen coupling in granular biofilm under O2-limited conditions

Summary The co-culture between Methylosinus sporium, a strictly aerobic methanotroph, and strictly anaerobic methanogens was studied in 5 L aerobic/anaerobic coupled granular sludge reactors under O₂-limited conditions. The methanogenic bacteria maintained very good metabolic activities and were able to produce sufficient methane which serviced as substrate for methanotrophic growth. Although other strictly aerobic population proliferated by two orders of magnitude after the granular sludge had been operated under O₂-limited conditions for one month, only a limited amount of the added methanotroph remained in the sludge. This result may indicate that M. sporium lacks sufficient O₂ affinity to compete with facultative bacteria for the dissolved O₂ for their growth.     

Anaerobic granule development for removal of pentachlorophenol in an upflow anaerobic sludge blanket (UASB) reactor

The granulation process using synthetic wastewater containing pentachlorophenol (PCP) in four 1.1 l laboratory scale upflow anaerobic sludge blanket (UASB) reactors was studied, and the anaerobic biotransformation of PCP during the granulation process investigated. After 110 days granular sludge was developed and up to 160 and 180 mg/l of PCP was added into the reactors R1 and R2, respectively, when they were inoculated with acclimated anaerobic sludge from an anaerobic digester of a citric acid plant. The inoculum was predominately composed of bacilli and filamentous bacteria. Granulation did not occur in reactors R3 and R4 which were inoculated with acclimated anaerobic sludge from aerobic sludge of the municipal sewage treatment plant which consisted mainly of cocci. Despite similar bacilli in the granule, the filamentous bacteria from reactor R1 were thicker than those of reactor R2. The granular sludge had a maximum diameter of 2.5 and 2.2 mm, and SMA of 1.44 and 1.32 gCOD/gTVS per day for reactors R1 and R2, respectively. Over 98% chemical oxygen demand (COD) removal rate and 99% of PCP removal rate were achieved when reactors R1 and R2 were operated at PCP and COD loading rates of 150 and 7.5 g/l per day, respectively. H₂-producing acetogens were the dominant anaerobes in the granular sludge.     

Anammox bacteria enrichment in upflow anaerobic sludge blanket (UASB) reactor

We investigated the anaerobic ammonium oxidation (anammox) reaction in a labscale upflow anaerobic sludge blanket (UASB) reactor. Our aim was to detect and enrich the organisms responsible for the anammox reaction using a synthetic medium that contained low concentrations of substrates (ammonium and nitrite). The reactor was inoculated with granular sludge collected from a full-scale anaerobic digestor used for treating brewery wastewater. The experiment was performed during 260 days under conditions of constant ammonium concentration (50 mg NH₄/⁺-N/L) and different nitrite concentrations (50∼150 mg NO₂-N/L). After 200 days, anammox activity was observed in the system. The microorganisms involved in this anammox reaction were identified as CandidatusB. Anammoxidans andK. Stuttgartiensis using fluorescencein situ hybridization (FISH) method.     

The Heavy Metal Content of Wild Edible Mushroom Samples Collected in Canakkale Province,Turkey

In this study, concentrations of heavy metals (Cd, Cr, Cu, Pb, and Zn) were determined in three edible mushroom species (Lactarius deliciosus, Russula delica, and Rhizopogon roseolus) collected in five sampling sites in Canakkale province, Turkey. Mean values of Cd, Cr, Cu, Pb, and Zn were 0.72, 0.26, 28.34, 1.53, and 64.62 mg/kg, respectively. The highest concentrations of Cd, Cu, Pb, and Zn were determined in species R. delica, while Cr was observed in L. deliciosus. In terms of the nutritional aspect, taking into account the concentration of Provisional Tolerable Weekly Intake recommended by FAO/WHO, the maximum concentration of Cd is a restrictive factor for consumption of the collected mushroom species. The concentrations of the other elements have no health risks when consumed at optimal levels.     

Biosorption and biodegradation of pentachlorophenol (PCP) in an upflow anaerobic sludge blanket (UASB) reactor

In order to understand the fate of PCP in upflow anaerobic sludge blanket reactor (UASB) more completely, the sorption and biodegradation of pentachlorophenol (PCP) by anaerobic sludge granules were investigated. The anaerobic granular sludge degrading PCP was formed in UASB reactor, which was seeded with anaerobic sludge acclimated by chlorophenols. At the hydraulic retention time (HRT) of 20–22 h, and PCP loading rate of 200–220 mg l⁻¹ d⁻¹, UASB reactor exhibited good performance in treating wastewater which containing 170–180 mg l⁻¹ PCP and the PCP removal rate of 99.5% was achieved. Sequential appearance of tetra-, tri-, di-, and mono-chlorophenol was observed in the reactor effluent after 20 mg l⁻¹ PCP introduction. Sorption and desorption of PCP on the anaerobic sludge granules were all fitted to the Freundlich isotherm equation. Sorption of PCP was partly irreversible. The Freundlich equation could describe the behavior of PCP amount sorbed by granular sludge in anaerobic reactor reasonably well. The results demonstrated that the main mechanism leading to removal of PCP on anaerobic granular sludge was biodegradation, not sorption or volatization.     

Bioremediation of selenium oxyanions in San Joaquin drainage water using Thauera selenatis in a biological reactor system

This report describes the use of a new selenate-respiring bacterium, Thauera selenatis, for the bioremediation of selenium (Se, as selenate) in drainage water from the Westlands Water District, San Joaquin Valley. The organism respires selenate anaerobically using acetate as the preferred electron donor. The reduction of selenate is not inhibited by nitrate; both electron acceptors are reduced concomitantly. T. selenatis was inoculated into, and was maintained in, a biological reactor system for anaerobic treatment of selenate-nitrate containing drainage water; a population of denitrifying bacteria was also present. When the pH of inflowing water was 6.9, and 2 mm acetate plus 0.56 mm ammonium chloride were fed into the reactor, selenate/selenite levels were reduced from 350–450 g Se/l to 5.39±3.6 g Se/l. The final product of selenate reduction was elemental Se. Analysis of reactor contents revealed that T. selenatis was the only selenate-respiring organism present in the system. Nitrate in the drainage water was also reduced in the reactor system by 98%. The lab-scale biological reactor system consisted of recycled sludge-blanket (1 l; 400 g sand) and fluidized-bed (1 l; 300 g sand) reactors. At a system flow rate of 6.5 ml/min, the retention time was 140 min. Correspondence to: J. M. Macy     

Mobility and Distribution of Zinc,Cadmium and Lead in Calcareous Soils Receiving Spiked Sewage Sludge

Leaching column experiments were conducted to determine the degree of mobility and the distribution of zinc (Zn), cadmium (Cd), and lead (Pb) because of an application of spiked sewage sludge in calcareous soils. A total of 20 leaching columns were set up for four calcareous soils. Each column was leached with one of these inflows: sewage sludge (only for two soils), spiked sewage sludge, or artificial well water (control). The columns were irrigated with spiked sewage sludge containing 8.5 mg Zn l^?1, 8.5 mg Cd l^?1, and 170 mg Pb l^?1 and then allowed to equilibrate for 30 days. At the end of leaching experiments, soil samples from each column were divided into 18 layers, each being 1 cm down to 6 cm and 2 cm below that, and analyzed for total and extractable Zn, Cd and Pb. The fractionation of the heavy metals in the top three layers of the surface soil samples was investigated by the sequential extraction method. Spiked sewage sludge had little effect on metal mobility. In all soils, the surface soil layers (0-1 cm) of the columns receiving spiked sewage sludge had significantly higher concentrations of total Zn, Cd and Pb than control soils. Concentration of the heavy metals declined significantly with depth. The mobility of Zn was usually greater than Cd and Pb. The proportion of exchangeable heavy metals in soils receiving spiked sewage sludge was significantly higher than that found in the control columns. Sequential extraction results showed that in native soils the major proportion of Zn and Pb was associated with residual (RES) and organic matter (OM) fractions and major proportion of Cd was associated with carbonate (CARB) fraction, whereas after leaching with spiked sewage sludge, the major proportion of Zn and Pb was associated with Fe-oxcide (FEO), RES, and CARB fractions and major proportion of Cd was associated with CARB, RES and exchangeable (EXCH) fractions. Based on relative percent, Cd in the EXCH fraction was higher than Zn and Pb in soils leached with spiked sewage sludge.     

Start-up performance and granular sludge features of an improved external circulating anaerobic reactor for algae-laden water treatment

The microbial characteristics of granular sludge during the rapid start of an enhanced external circulating anaerobic reactor were studied to improve algae-laden water treatment efficiency. Results showed that algae laden water was effectively removed after about 35 d, and the removal rates of chemical oxygen demand (COD) and algal toxin were around 85% and 92%, respectively. Simultaneously, the gas generation rate was around 380 mL/gCOD. The microbial community structure in the granular sludge of the reactor was complicated, and dominated by coccus and filamentous bacteria. Methanosphaera, Methanolinea, Thermogymnomonas, Methanoregula, Methanomethylovorans, and Methanosaeta were the major microorganisms in the granular sludge. The activities of protease and coenzyme F₄₂₀ were high in the granular sludge. The intermittent stirring device and the reverse-flow system were further found to overcome the disadvantage of the floating and crusting of cyanobacteria inside the reactor. Meanwhile, the effect of mass transfer inside the reactor can be accelerated to help give the reactor a rapid start.     

Effect of Immobilizing Substances and Salinity on Heavy Metals Availability to Wheat Grown on Sewage Sludge-Contaminated Soil

The objective of the investigation was to evaluate the effect of immobilizing substances and NaCl salinity on the availability of heavy metals: Zn, Cd, Cu, Ni, and Pb to wheat (Triticum aestivum L.). In greenhouse pot experiment, a sewage sludge amended soil was treated with the following immobilizing substances: three clay minerals (Na-bentonite, Ca-bentonite and zeolite), iron oxides (goethite and hematite), and phosphate fertilizers (superphosphate and Novaphos). The pots were planted with wheat and were irrigated either with deionized or saline water containing 1600 mg L^?1 NaCl. Wheat was harvested two times for shoot metal concentrations and biomass measurements. Metal species in soil solution were estimated using the software MINEQL+.

The addition of metal immobilizing substances to the soil significantly decreased metal availability to wheat. The largest reduction in metal bioavailability was found for bentonites. The irrigation with saline water (1600 mg L^?1 NaCl) resulted in a significant increase in metal chloride species (MCl⁺ and MCl₂ ⁰). The highest metal complexation with Cl occurred for Cd, which was about 53% of its total soil solution concentration. The total concentration of Cd (Cd_T) in soil solution increased by 1.6–2.8-fold due to saline water. The NaCl salinity caused a significant increase in uptake and shoot concentration of Cd for two harvests and small but significant increase in shoot Pb concentration for the second harvest. It was concluded that the use of bentonites is the most promising for the reduction of heavy metal availability to plants. Saline water containing 1600 mg L^{? 1} NaCl increased the availability of Cd and Pb to wheat and decreased the efficiency of bentonites to immobilize soluble Cd.     

Development of nutritious rice with high zinc/selenium and low cadmium in grains through QTL pyramiding

Enriching zinc (Zn) and selenium (Se) levels, while reducing cadmium (Cd) concentration in rice grains is of great benefit for human diet and health. Large natural variations in grain Zn, Se, and Cd concentrations in different rice accessions enable Zn/Se‐biofortification and Cd‐minimization through molecular breeding. Here, we report the development of new elite varieties by pyramiding major quantitative trait loci (QTLs) that significantly contribute to high Zn/Se and low Cd accumulation in grains. A chromosome segment substitution line CSSL^GCC7 with the PA64s‐derived GCC7 allele in the 93‐11 background, exhibited steadily higher Mn and lower Cd concentrations in grains than those of 93‐11. This elite chromosome segment substitution line (CSSL) was used as the core breeding material to cross with CSSLs harboring other major QTLs for essential mineral elements, especially CSSL^GZC6 for grain Zn concentration and CSSL^GSC5 for grain Se concentration. The CSSL^GCC7+GZC6 and CSSL^GCC7+GSC5 exhibited lower Cd concentration with higher Zn and Se concentrations in grains, respectively. Our study thus provides elite materials for rice breeding targeting high Zn/Se and low Cd concentrations in grains.     

Methanogenic granular sludge formation in an upflow anaerobic sludge blanket reactir treating synthetic methanolic waste

A laboratory upflow anaerobic sludge blanket reactor, seeded with fine, suspended, bacterial floc with 1.76 g volatile suspended solids/l, was used to treat synthetic methanolic waste. After 180 days of continuous peration, granular sludge with discrete granules of 1 to 2 mm diam. was formed, with 52 g volatile suspended solids/l. Granules were brown, relatively soft and had a settling velocity of 1.61 cm/s. Extracellular polymeric matter extracted from the granular sludge had high carbohydrate content but low nucleic acid content. The ash of the granular sludge contained Na⁺, K⁺ and Mg²⁺ up to 15.0, 11.7 and 3.75 mg/g, respectively. Scanning and transmission electron microscopy revealed that the granular sludge was dominated by methanogens resembling Methanosarcina.The authors are with the Department of Environmental Engineering, Faculty of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565, Japan     

乌鲁木齐市道路林带土壤抗重金属细菌的筛选及重金属去除能力

【背景】道路重金属污染问题日益严峻,寻找高效的微生物资源用于环境修复已迫在眉睫。【目的】从乌鲁木齐市道路林带土壤中筛选抗重金属菌株,并对其重金属去除能力进行探究。【方法】使用含5种重金属离子(铅、镉、锌、铜、镍)的4种培养基进行抗性菌株筛选,通过形态学特征和16S rRNA基因序列进行鉴定,采用电感耦合等离子体发射光谱仪(inductively coupled plasma optical emission spectrometer,ICP-OES)检测分离株对重金属离子的去除情况。【结果】4种分离培养基中,TSA是抗重金属菌株筛选的最适培养基,共筛选出16株抗重金属菌,其中4株抗Pb菌、4株抗Cd菌、4株抗Zn菌、3株抗Cu菌和1株抗Ni菌,其抗性分别高达3 000、800、600、300和400mg/L,16株菌中以芽孢杆菌属(Bacillus)数量最多。在初始浓度为700mg/L Pb²⁺下,菌株Pb6的去除率高达92.48%,菌株Pb11、Pb3和Pb9的去除率分别为27.70%、40.37%和58.88%;在200mg/L Cd²⁺...     

Anaerobic degradation of azo dye Drimaren blue HFRL in UASB reactor in the presence of yeast extract a source of carbon and redox mediator

This paper presents results on anaerobic degradation of the azo dye blue HFRL in a bench scale Upflow anaerobic sludge blanket (UASB) reactor operated at ambient temperature. The results show that the addition of yeast extract (500 mg/L) increased color removal (P < 0.05) from 62 to 93% despite the low chemical oxygen demand (COD) removal (~35%) which happened due to volatile fatty acids (VFA) accumulation. There were no differences in color removal (~91%) when yeast extract (500 mg/L) was used in the presence or absence of glucose, suggesting that yeast extract acted as source of redox mediator (riboflavin) and carbon. The specific rate of dye removal increased along the operational phases and depended on the presence of yeast extract, suggesting progressive biomass acclimatization. Analysis of bacterial diversity by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR–DGGE) method showed there was biomass selection along the bioreactor operation and no evidence of azo dye degrading bacteria predominance. This strengthens the hypothesis that color removal happens extracellularly by the reduction of azo bond by reduced redox mediators, such as riboflavin, which is present in high amount in the yeast extract.     

Potential of kenaf (Hibiscus cannabinus L.) and corn (Zea mays L.) for phytoremediation of dredging sludge contaminated by trace metals

The potential of kenaf (Hibiscus cannabinus L.) and corn (Zea mays L.) for accumulation of cadmium and zinc was investigated. Plants have been grown in lysimetres containing dredging sludge, a substratum naturally rich in trace metals. Biomass production was determined. Sludge and water percolating from lysimeters were analyzed by atomic absorption spectrometry. No visible symptoms of toxicity were observed during the three- month culture. Kenaf and corn tolerate trace metals content in sludge. Results showed that Zn and Cd were found in corn and kenaf shoots at different levels, 2.49 mg/kg of Cd and 82.5 mg/kg of Zn in kenaf shoots and 2.1 mg/kg of Cd and 10.19 mg/kg in corn shoots. Quantities of extracted trace metals showed that decontamination of Zn and Cd polluted substrates is possible by corn and kenaf crops. Tolerance and bioaccumulation factors indicated that both species could be used in phytoremediation.