Electron density-based transformation of trimethoprim during biological wastewater treatment

This research investigated the biological transformation of trimethoprim (TMP). Partial TMP removal was observed in the presence of ammonia and toluene, and increasing the solids retention time from 20 days to 60 days improved TMP removal in both the nitrifying and heterotrophic bioreactors. Two TMP-related metabolites were identified, the first (5-(3,4,5-trimethoxybenzyl) pyrimidine-2,4-diamine, 5-hydroxyl) showing that a hydroxylation reaction took place, and the second (5-(1-carboxyl, 1-methoxy, 5-methoxy 1-,4-pentene) pyrimidine-2,4-diamine, 5-hydroxyl) showing that the trimethoxybenzyl ring was cleaved. This research is the first that we are aware of to report these two TMP-related byproducts. TMP metabolites show that initiating reactions take place where the electron density is highest, and that these initiating reactions shift the electron density of TMP, likely affecting the course of transformation.     

Heterogeneous photo-catalysis system for the degradation of azo dye Reactive Black 5 (RB5)

This study investigated a heterogeneous photo-catalysis system by introducing a novel brick supported iron oxide (denoted as B1) for the heterogeneous photoassisted degradation of Reactive Black 5 (RB5) at pH value from 3 to 7 in a three-phase (gas-liquid-solid) fluidized bed reactor (3P-FBR). Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD) and N(2) adsorption/desorption were used to characterize the B1 catalyst. The in situ formation of hydrogen peroxide and the depletion of oxalic acid by photochemical cycle of Fe(III)-oxalate complex under UVA light (λ = 365 nm) were studied. The effects of the solution pH and the concentration of oxalic acid on the degradation of RB5 are elucidated. About 90% decolourization was measured and 80% of the total organic carbon (TOC) was eliminated at pH 5.0 after 120 min for 20 mg/L RB5 in presence of 10 g/L B1 catalyst, 30 mg/L oxalic acid under 15 W UVA light. A mechanism for the photocatalytic degradation of RB5 over B1 catalyst is proposed.     

大颗粒柱状淡水冰无侧限剪切强度及其影响因素

针对大颗粒柱状冰无侧限剪切强度同加载方向、加载应变速率和冰样温度有关,在加载应变速率5.00×10-5/s~5.00×10-2/s区间内、试验温度分别为-0.5℃、-2℃、-5℃和-10℃、进行两个加载方向分别为垂直加载(加载力平行于晶体生长方向)和水平加载(加载力垂直于晶体生长方向)的无侧限剪切试验。结果发现,在既定试验条件下,剪切强度随着温度和应变速率的减小有增大趋势;比较两个加载方向剪切强度可知,在-5℃和-10℃条件下力学性质的各向异性更为明显,而在-0.5℃和-2℃时两个加载方向剪切强度相差不大;另外在气泡含量小于8.65%情况下,冰内气泡含量对大颗粒柱状冰剪切强度影响不大。     

Operation of a full-scale pumped flow biofilm reactor (PFBR) under two aeration regimes

A novel technology suitable for centralised and decentralised wastewater treatment has been developed, extensively tested at laboratory-scale, and trialled at a number of sites for populations ranging from 15 to 400 population equivalents (PE). The two-reactor-tank pumped flow biofilm reactor (PFBR) is characterised by: (i) its simple construction; (ii) its ease of operation and maintenance; (iii) low operating costs; (iv) low sludge production; and (v) comprising no moving parts or compressors, other than hydraulic pumps. By operating the system in a sequencing batch biofilm reactor (SBBR) mode, the following treatment can be achieved: 5-day biochemical oxygen demand (BOD5), chemical oxygen demand (COD) and total suspended solids (TSS) reduction; nitrification and denitrification. During a 100-day full-scale plant study treating municipal wastewater and operating at 165 PE and 200 PE (Experiments 1 and 2, respectively), maximum average removals of 94% BOD5, 86% TSS and 80% ammonium-nitrogen (NH4-N) were achieved. During the latter part of Experiment 2, effluent concentrations averaged: 14 mg BOD5/l; 32 mg COD(filtered)/l; 14 mg TSS/l; 4.4 mg NH4-N/l; and 4.0 mg NO3-N/l (nitrate-nitrogen). The average energy consumption was 0.46-0.63 kWh/m3(treated) or 1.25-1.76 kWh/kg BOD5 removed. No maintenance was required during these experiments. The PFBR technology offers a low energy, minimal maintenance technology for the treatment of municipal wastewater.     

德惠市浅层地下水污染源识别及空间分布

为实现德惠市浅层地下水的污染源识别及其空间分布特征研究,收集德惠市2014年43组水质资料,进行水化学特征统计分析,在此基础上采用因子分析法进行多元统计分析,提取5个公因子(F1—F5)分别为矿化度、有机物和硝酸盐氮、氨氮、铁锰、氯化物作为浅层地下水水质的主控因子,进一步分析其污染物来源,并根据因子得分利用ArcGIS差值工具绘图分析各污染源的污染程度及空间分布特征。结果表明:5个公因子(F1—F5)的方差贡献率分别为19. 947%、14. 082%、13. 661%、12. 630%和12. 144%。其中,有机物和硝酸盐氮、氨氮(F2、F3)是研究区内的主要污染物,受控于人为作用;矿化度污染则受控于迁移-富集作用;铁锰、氯化物污染分别受控于自然作用和地表水地下水交互作用。研究区范围内,城区、郭家镇、菜园子镇、大房身镇、五台乡污染较严重,其他乡镇水质状况良好;依据综合得分可以将浅层地下水划分为3个区域:禁止开采区、农业用水区和生活饮用水区,评价结果可以为政府决策提供参考。     

Slag columns for upgrading phosphorus removal from constructed wetland effluents.

The current best option to upgrade constructed wetlands (CWs) for phosphorus (P) retention, in terms of efficiency, cost and simplicity, consists in using media having a strong P affinity. The media can be used either in the planted beds or in a filtration system downstream of the beds. The use of slag filters was shown to be efficient for removing P from wastewater as it represented a slow release source of calcium and hydroxide, favouring the formation of hydroxyapatite. Our study aimed at maximising the P retention capacity of slag filters located at the outlet of CWs since electric arc furnace slag has been shown to inhibit the growth of macrophytes when used in the filtration matrix. Bench-scale columns (Vtot = 6.2 L) filled with various combinations of filter media (slag, granite, limestone) of different sizes (2-5, 5-10, 10-20 mm) were fed on-site during four months with a CW effluent (in mg/L: 30 COD, 30 TSS, 10 Pt). Results showed that the best media combination enabling the maximum o-PO4 retention (more than 80% removal without clogging) consisted in a series of a ternary mix column (slag 5-10 mm, granite 2-5 mm, limestone 5-10 mm) followed by a slag column (slag 5-10 mm). Pilot scale columns (Vtot = 300 L), filled with the best media combination, were installed at the outlet of a 28 m2 CW. These columns showed more than 75% removal efficiency during one year and were designed to be easily replaced each year.     

Utilization of the Bayesian Method to Improve Hydrological Drought Prediction Accuracy

This study established a hydrological drought forecasting system based on the Bayesian method and evaluated its utilization for South Korea. The regression result between Historical Runoff (HR) and Ensemble Streamflow Prediction Runoff (ESP_R) was used as prior information in the Bayesian method. Additionally Global seasonal forecast System 5 Runoff (GS5_R) produced using a dynamic prediction method was used in a likelihood function. Bayesian Runoff (BAY_R), as posterior information, was generated and compared with the ESP_R and GS5_R results for predictive ability evaluation. The Standardized Runoff Index (SRI) was selected for the drought prediction, and the BAY_SRI, GS5_SRI and ESP_SRI were computed using BAY_R, GS5_R and ESP_R, respectively. The Correlation Coefficient (CC), Nash-Sutcliffe Efficiency (NSE) and Receiver Operating Characteristic (ROC) score of BAY_SRI were the highest, and the Root Mean Square Error (RMSE) of BAY_SRI was the lowest among the methods. The Bayesian method improved the behavioral and quantitative error of drought prediction and the predictive ability of the occurrence of drought. In particular, the simulation accuracy was significantly improved during the flood season. Additionally, BAY_SRI represented past drought scenarios better than did the other two methods. Overall, we found that the Bayesian method could be applied for hydrological drought predictions for based on 1- and 2-month lead times.     

Identification of Drought Occurrences Using Ensemble Predictions up to 20-Days in Advance

In the present study, skill of an extended range forecast system has been evaluated for identifying droughts over central India 20-days in advance. Rainfall forecasts from 44 ensemble members of the forecast system developed Indian Institute of Tropical Meteorology (IITM), Pune have been used to prepare probabilistic rainfall forecasts. It is seen that the uncertainties in the forecasts (in terms of ensemble spread) increases from day-5 to day 20. As the focus of the study is for drought predictions, forecasts in the bins 0-5 mm/5 day and 5-25 mm/5 day (no rain or less rain) were studied in detail. It is found that the modeling system has a tendency to over-forecast rainfall probabilities. With bias correction, the forecasts become more reliable. Various drought indices were computed using the mean of the forecast distribution up to 20-days in advance. Standardized precipitation index (SPI) computed using Gamma and Pearson type-III distributions are similar in the study region. It was found that these are in reasonable agreement with those from observations. Probabilistic forecasts of standardized precipitation index (SPI) were made and the relative operating characteristics (ROC) scores indicate that the forecasted SPI values are suitable for application.     

A new strategy for determination of current efficiency during electro-oxidation of aromatic compounds in a packed-bed system

The electro-oxidation of aromatic compounds in 4,4'-diaminostilbene-2,2'-disulfonic (DSD) acid wastewater on IrO2-Ta2O5/Ti anodes was studied. The current efficiency was evaluated in terms of chemical oxygen demand (COD) by introducing a new factor, the fraction of the Faradaic current to the total cell current (beta) through the network analysis of packed bed electrode system (PBEs). Experimental results using an up-flow PBEs at current intensities ranging from 5 to 16 A m(-2), flow rates ranging from 20 to 80 L h(-1) and inter-electrode distance of 5 to 50 cm are in good agreement with the proposed equation. In addition, lower current density, increasing flow rate and larger inter-electrode distance are beneficial to enhance the current efficiency.     

不同龄期混凝土动态力学性能研究

对不同龄期(28,112,183,345,810,1 248,1 550d)的混凝土进行了不同应变速率(10^-5,5×10^-5,10^-4,5×10^-4,10^-3,5×10^-3,10^-2/s)下的单轴压缩试验,试件尺寸为Φ150 mm×300 mm,研究了龄期和加载速率对混凝土的力学性能影响。结果表明:①在同一龄期下,混凝土的峰值应力随着应变速率增长而增大;在同一应变速率下,混凝土的峰值应力随着龄期的增长而增大,800d后峰值应力趋于稳定;②在同一应变速率下,混凝土的吸能能力随着龄期的增长而增加,表现出了峰值应力与龄期之间相似的规律。     

Effect of organic load and nutrient ratio on the operation stability of the moving bed bioreactor for kraft mill wastewater treatment and the incidence of polyhydroxyalkanoate biosynthesis

This paper studies the effect of organic load rate (OLR) and nutrient ratio on operation stability of the moving bed bioreactor (MBBR) for kraft mill wastewater treatment, analyzing the incidence of polyhydroxyalkanoate (PHA) production. The MBBR operating strategy was to increase OLR from 0.25 ± 0.05 to 2.41 ± 0.19 kg COD m(-3) d(-1) between phases I and IV. The BOD(5):N:P ratio (100:5:1 and 100:1:0.2) was evaluated as an operation strategy for phases IV to V. A stable MBBR operation was found when the OLR was increased during 225 days in five phases. The maximum absolute fluorescence against the proportion of cells accumulating PHA was obtained for an OLR of 2.41 ± 0.19 kg COD m(-3)d(-1) and a BOD(5):N:P relationship of 100:1:0.2. The increase of PHA biosynthesis is due to the increased OLR and is not attributable to the increased cell concentration, which is maintained constant in stationary status during bioreactor biosynthesis.     

Photooxidation of azo dye reactive black 5 using a novel supported iron oxide: heterogeneous and homogeneous approach.

Photooxidation of azo dye Reactive Black 5 (RB5) by H202 was performed with a novel supported iron oxide in a batch reactor in the range of pH 2.5-6.0. The iron oxide was prepared through a fluidized-bed reactor (FBR) and much cheaper than the Nafion-based catalysts. Experimental results indicate that the iron oxide can significantly accelerate the degradation of RB5 under the irradiation of UVA light (wavelength = 365 nm). An advantage of the catalyst is its long-term stability, which was confirmed through using the catalyst for multiple runs in the degradation of RB5. In addition, this study focused mainly on determining the proportions of homogeneous catalysis and heterogeneous catalysis in the batch reactor. Conclusively, although heterogeneous catalysis contributes primarily to the oxidation of RB5 during pH 4.5-6.0, the homogeneous catalysis is of increasing importance below pH 4.0 because of the Fe ions leaching from the catalyst to solution.     

The impact of reduced phosphorus levels on microbial floc properties during biological treatment of pulp and paper wastewaters.

The effect of limiting P in activated sludge was investigated in laboratory scale sequencing batch reactors (SBRs) fed effluent from a container board mill. Floc characterization included measurement of hydrophobicity, surface charge, and analysis of extracellular polymeric substances (EPS). Reactor performance was assessed by monitoring COD and inorganic P removal, MLSS, and sludge settleability (SVI and batch settling flux) over a period of eight months. Control reactors (BOD:N:P of 100:5:1) were compared to reactors run under P-limited conditions (100:5:0.3; 100:5:0.1). Reactor performance at lower temperatures (14 degrees C; control = 26 degrees C) was also studied to assess the impact of P-limitation. Changes in floc structure and the composition of EPS occurred within 1 to 3 days following a reduction in P levels. There was an insignificant increase in SVI; however, gravitational settling velocity and batch settling flux values for low P floc were consistently higher than for floc generated under control conditions. Lower temperatures (14 degrees C) resulted in a deterioration in floc settling properties at a BOD:N:P of 100:5:1. This impact on settling was significantly reduced at a BOD:P of 100:0.1. Reducing P concentrations in the wastewater treatment system has the potential to improve sludge settleability and reduce final P discharges.     

Microphyte and macrophyte-based lagooning in tropical regions.

A 720 m2 plant made of 8 ponds in series, set in Yaounde (Cameroon), was successively operated as a macrophyte-based system (type M) from November 1997 to October 98, a microphyte-based system (type m) from October 1999 to September 2000 and a combination of macrophyte and microphyte ponds (type M + m) from May to July 2001. Average applied loads varied over the years; from 420 kg. BOD5 ha(-1)d(-1) on the year 1997/98, the loads reached 510 kg BOD5 ha(-1)d(-1) in 1999/2000 and 500 in 2001. Though the system became more and more overloaded and sludge accumulated rapidly in the first ponds, it provided average removals of SS, BOD5 and COD that were always higher than 90% whatever the type of lagooning. Performances in the removal of SS, organic matter and the abatement of N-NH4+ and PO4(3-) did not significantly differ according to the type of lagooning and the applied load. Macrophyte lagooning did not show any definitive superiority as to nutrient removal when compared to microphyte lagooning. Microphyte lagooning was the most effective process in faecal indicators removal.     

基于Copula函数的海绵城市日气温设计

极端温度和温差影响混凝土微观结构特征和力学性能,气温被视作混凝土施工维养的重要设计依据。基于中国819个气象站1961—2015年日气象和地理信息资料,采用地统计方法和Copula函数对海绵城市进行气象分区,分析分区日均温和日温差边际、联合概率分布,设计日均温、日温差和相应混凝土抗压强度。结果表明:海绵城市气象分区与行政分区一致;各分区日均温和日温差多服从正态分布,冬、夏日均温期望值在0～13.6℃和23.2～26.4℃间变化、标准差在3.2～5.4℃和2.5～3.5℃间变化,冬、夏日温差期望值在7.4～12.1℃和7.4～11.8℃间变化、标准差在2.9～3.7℃和1.8～3.4℃间变化;日均温和日温差联合概率分布冬季对称,夏季不对称,相应AMH Copula函数参数值分别在-5.68×10~(-6)～4.93×10~(-6)和-6.37×10~(-6)～4.89×10~(-6)间变化;冬季,东北、华北和西北分区设计频率分别处于50%、5%、5%,低于国标设计温度,设计出的混凝土无法达到抗冻要求,其余分区设计频率在国标设计温度内满足设计要求;夏季,各分区日均温均高于混凝土国标养护温度,易使得混凝土内外温度失调而产生热胀破坏。设计的极端温度、温差及抗压强度是对现有国标混凝土养护温度的补充和完善,为海绵城市新性能混凝土构建提供科学依据。     

The Spatiotemporal Characteristics of Extreme Precipitation Events in the Western United States

Changes in the frequency or intensity of extreme precipitation events would have profound impacts on both human society and the natural environment. In this paper, we present the results of a comprehensive analysis of the spatiotemporal changes of extreme precipitation in the western United States. The analyses explore the spatial characterization of the El Nino-Southern Oscillation (ENSO)-extreme precipitation response pattern and identify the multi-scale temporal variability in precipitation extremes in the western United States. Results indicate: (1) Extreme precipitation expressed in indices such as seasonal count of days when precipitation is large than 10 mm (R10), seasonal maximum 5-day precipitation (R5D), maximum length of dry spell (CDD), and seasonal total precipitation exceeding 95 percentile (R95) have a dipolar pattern and a transition zone which separates the west into two main dipolar centers regarded as Pacific Northwest and Desert Southwest. The simple precipitation intensity index (SDII) has little correlation with large scale natural oscillations over most of the west. (2) The spatial distributions of annual trend of R10, R5D, SDII, and R95 have seasonal variability in southern California and Lower Colorado River Basin. (3) There are consistent multi-year bands ranging from 2 to 20 years in the R10, R5D, CDD, and R95 winter time series which may be caused by the inter-decadal or multi-decadal modulation of ENSO effects on precipitation extremes. The results can provide beneficial reference to the prediction of precipitation extremes in the west.

     

Comparison of different statistical downscaling methods for climate change rainfall projections over the Lake Victoria basin considering CMIP3 and CMIP5

In this study, outputs of three statistical downscaling (SD) methods including the change factor (Delta), simplified (simQP) and advanced (wetQP) quantile-perturbation-based approaches were compared based on daily rainfall series at 9 meteorological stations in the Lake Victoria basin (LVB) in Eastern Africa. The comparison was made considering phase 5 and phase 3 of the Coupled Model Inter-comparison Project, i.e. CMIP5 and CMIP3 respectively. For the CMIP5 (CMIP3) at each station, there were a total of 7 (14) GCMs, 18 (20) daily historical (control) simulations over the period 1961–2000, and 35 (49) daily future projection series of the periods 2050s and 2090s. The ensemble mean of the GCMs' Bias in reproducing rainfall extremes for return periods in the range of 1 to 40 years for the CMIP5 (CMIP3) varied from −19.05% to 3.11% (−65.85% to −4.86%). For the high greenhouse gas scenario rcp8.5 (A2) of the CMIP5 (CMIP3), the ensemble mean of the projected changes over the LVB in the 10-year rainfall intensity quantile obtained from the Delta, simQP, wetQP SD goes up to 5.8, 10 and 22.4% (11.7, 15.9 and 43.6%) in the 2050s and 8, 11.4, and 25.4% (14.2, 23.3 and 40.6%) in the 2090s. Rainfall totals of the main wet (dry) season are generally projected to increase (decrease) in both the 2050s and 2090s. Because the outputs from the three SD methods captured well the pattern of monthly rainfall totals, the difference between the projected changes of seasonal or annual rainfall totals from the Delta, simQP and wetQP was shown to be insignificant. However, the differences in the results from the Delta, simQP and wetQP methods with respect to the projections of rainfall quantiles indicate that the choice of the SD method can be made on a case by case basis in line with the objectives of the climate change impact study, e.g. the Delta does not capture well the changes in rainfall extremes, whereas the wetQP is suitable for both rainfall extremes and rainfall totals at both seasonal and annual time scales. The findings of this study also show the need to consider evaluations of the inter-GCM differences in the LVB as a data scarce region in assessing the discernible impact of climate change on rainfall extremes and/totals for decision making related to water resources management and engineering.     

Using ozone to reduce recalcitrant compounds and to enhance biodegradability of pulp and paper effluents.

The effect of ozone based oxidation on removing recalcitrant organic matter (ROM) and enhancing the biodegradability of alkaline bleach plant effluent was investigated. A bubble column ozonation tower was used in the study. The experiments were carried out at different temperatures (20 degrees C and 60 degrees C) and pH (9 and 11), with a number of biological and chemical parameters being monitored including BOD5, COD, TC, pH, color, and molecular weight distribution of organics (nominal cut off of 1,000 Da). Biodegradability of the effluent was determined based on BOD5/COD of the wastewater throughout the process. For all the experiments, ozonation enhanced the biodegradability of the effluent by 30-40%, which was associated with noticeable removal of ROM including high molecular weight (HMW) and color-causing organics by about 30% and 60%, respectively. While the biodegradability of HMW fraction increased by about 50%, there was no biodegradability improvement for low molecular weight (LMW) portion, which was originally readily biodegradable (with BOD5/COD of about 0.5). Statistical analysis of variance (ANOVA) revealed neither pH nor temperature played significant role on the ozonation process at 95% confidence level.     

Capability of TMPA products to simulate streamflow in upper Yellow and Yangtze River basins on Tibetan Plateau

Due to the high elevation, complex terrain, severe weather, and inaccessibility, direct meteorological observations do not exist over large portions of the Tibetan Plateau, especially the western part of it. Satellite rainfall estimates have been very important sources for precipitation information, particularly in rain gauge-sparse regions. In this study, Tropical Rainfall Measuring Mission （TRMM） Multi-satellite Precipitation Analysis （TMPA） products 3B42, RTV5V6, and RTV7 were evaluated for their applicability to the upper Yellow and Yangtze River basins on the Tibetan Plateau. Moreover, the capability of the TMPA products to simulate streamflow was also investigated using the Variable Infiltration Capacity （VIC） semi-distributed hydrological model. Results show that 3B42 performs better than RTVSV6 and RTV7, based on verification of the China Meteorological Administration （CMA） observational precipitation data. RTVSV6 can roughly capture the spatial precipitation pattern but overestimation exists throughout the entire study region. The anticipated improvements of RTV7 relative to RTVSV6 have not been realized in this study. Our results suggest that RTV7 significantly overestimates the precipitation over the two river basins, though it can capture the seasonal cycle features of precipitation. 3B42 shows the best performance in streamflow simulation of the abovementioned satellite products. Although involved in gauge adjustment at a monthly scale, 3B42 is capable of daily streamflow simulation. RTV5V6 and RTV7 have no capability to simulate streamflow in the upper Yellow and Yangtze River basins.     

The storage and provenance of fine sediment on the channel bed of two contrasting lowland permeable catchments,UK

Fine sediment (<63 µm) storage in river channels frequently represents a significant term in catchment sediment budgets and plays an important role in diffuse pollution problems. A combination of a sediment remobilization technique and the fingerprinting approach was used to examine the storage and provenance of fine sediment on the channel bed of two contrasting lowland permeable catchments in the UK. In the upper Tern (∼231 km²) study catchment, estimates of mean fine sediment storage on the channel bed ranged between 860–5500 g m⁻², with an overall average of 2391 g m⁻², compared to 470–2290 g m⁻² and 1065 g m⁻² in the Pang (∼166 km²) and 770–1760 g m⁻² and 1255 g m⁻² in the Lambourn (∼234 km²) sub‐catchments. Mean total fine sediment storage on the bed of the main channel was equivalent to 37% (upper Tern), 38% (Pang) and 21% (Lambourn) of the mean annual suspended sediment loads measured at the catchment outlets. Over the study period, the total gain (1427 t) and loss (1877 t) to fine sediment storage on the channel bed in the upper Tern catchment were equivalent to 82% and 108% of the mean annual suspended sediment load, respectively, compared to 149% (740 t) and 136% (678 t) in the Pang sub‐catchment, and 39% (422 t) and 49% (528 t) in the Lambourn sub‐catchment. The source of the fine sediment stored on the channel bed within each study area varied. In the upper Tern catchment, the weighted mean relative contributions from individual source types were estimated to be 35 ± 5% (pasture), 51 ± 5% (cultivated) and 14 ± 3% (channel banks and subsurface sources). The corresponding estimates were 49 ± 8%, 33 ± 5% and 18 ± 5% for the Pang sub‐catchment, compared to 19 ± 6%, 64 ± 5% and 17 ± 5% for the Lambourn sub‐catchment. These sediment source estimates have important implications for the design and implementation of targeted sediment control policies within the study areas. Copyright © 2007 John Wiley & Sons, Ltd.