Determining C/N ratios for typical organic wastes using biodegradable fractions

It is well established that an optimal aerobic and anaerobic microbial metabolism is achieved with a C/N ratio between 20 and 30. Most studies are currently based on chemically-measured carbon and nitrogen contents. However, some organic wastes can be composed of recalcitrant carbon fractions that are not bioavailable. To know the biodegradable C/N ratio, two different methods to determine the aerobic and anaerobic biodegradable organic carbon (BOC_AE and BOC_AN) are proposed and used to analyze a wide variety of different organic samples. In general, raw wastes and digested products have more amount of BOC_AE. On the contrast, the samples collected after an aerobic treatment have higher content of BOC_AN. In any case, all the BOC fractions are lower than the total organic carbon (TOC). Therefore, the C/N ratios based on BOC are always lower than the total C/N ratio based on the TOC measure. The knowledge of the real bioavailable C/N ratio is crucial for the biological treatments of organic materials. To reduce the test time necessary for BOC determination, the values of BOC for all the samples obtained at different times were compared and correlated with the final BOC. A method that allows for the determination of BOC_AE in 4 d is proposed. In relation to the anaerobic assay, the biogas potential calculated after 21 and 50 d was positively correlated with the final potential defined after 100 d of assay.     

Identifying different types of bulking in an activated sludge system through quantitative image analysis

The present study proposes an image analysis methodology for the identification of different types of disturbances in wastewater treatment activated sludge systems. Up to date, most reported image analysis methodologies have been used in activated sludge processes with the aim of filamentous bulking detection, however, other disturbances could be foreseen in wastewater treatment plants. Such disturbances can lead to fluctuations in the biomass contents, affecting the mixed liquor suspended solids (MLSS), and in the sludge settling ability, affecting the sludge volume index (SVI). Therefore, this work focuses on predicting the MLSS and SVI parameters for different types of disturbances affecting an activated sludge system. Four experiments were conducted simulating filamentous bulking, zoogleal or viscous bulking, pinpoint floc formation, and normal operating conditions. Alongside the MLSS and SVI determination, the aggregated and filamentous biomass contents and morphology were studied as well as the biomass Gram and viability status, by means of image analysis.     

The microbial status of natural waters in a protected wilderness area

Waters derived from remote 'wilderness' locations have been assumed to be largely free of bacterial contamination and thus such, near-pristine, protected catchments, unused for agriculture, have been first in the multiple line of protection (pristine catchment-long storage-treatment-disinfection) employed by the water industry. This assumption is challenged by a bacterial survey of the waters derived from the New Cairngorm National Park, Scotland. Over 480 spot samples were taken for 59 sites between March 2001 and October 2002 during nine field campaigns each of three to five days duration. Over 75% of samples tested positive for Escherichia coli (E. coli) and 85% for total coliforms. Concentrations displayed both temporal and spatial patterns. Largest values occurred over the summer months and particularly at weekends at sites frequented by visitors, either for 'wild' camping or day visits, or where water was drawn from the river for drinking. Overall the spatial and temporal variations in bacterial concentrations suggest a relationship with visitor numbers and in particular wild camping. The implications of the results for drinking water quality and visitors health are discussed along with possible management options for the area in terms of improving the disposal of human waste.     

Mass Load-Based Pollution Management of the Han River and Its Tributaries, Korea

Spatio-temporal variations of biochemical oxygen demand (BOD) and total coliform (TC) in the Han River, Korea, were investigated in terms of concentration-based and mass loading-based approaches. Considering the river water quality criteria regulated by the Ministry of Environment in Korea, the tributaries linked to the mainstream of the Han River were found to be highly contaminated with respect to both BOD and TC and, in fact, most of the tributaries exceeded the maximum water quality criteria. To evaluate the pollution impact of tributaries on the mainstream, the monthly water quality monitoring data for six years (from 1995 to 2000) were collected from the Han River basin, and statistically analyzed using Pearson’s correlation coefficient. The results revealed that mass loading-based approach was superior to the concentration-based approach for effective Han River watershed management. Overall results supported that the mass loading-based approach associated with total maximum daily loads (TMDL) management would be a useful and suitable protocol in watershed management for improving the water quality of the Han River and protecting public health. Therefore, this study supporting TMDL management can be applicable to a wide array of contaminants and watershed settings in Korea.     

A summary of total mercury concentrations in flora and fauna near common contaminant sources in the Gulf of Mexico

Total mercury concentrations are summarized for environmental media and biota collected from near-coastal areas, several impacted by contaminant sources common to the Gulf of Mexico. Water, sediment, fish, blue crabs, oysters, clams, mussels, periphyton and seagrasses were collected during 1993–2002 from targeted areas affected by point and non-point source contaminants. Mean concentrations in water and sediment were 0.02 (±1 standard deviation = 0.06) μg l⁻¹ and 96.3 (230.8) ng g⁻¹ dry wt, respectively. Mean total mercury concentrations in fish, blue crabs, brackish clams and mussels were significantly greater than those in sediment, seagrass, colonized periphyton and oysters. Concentrations (ng g⁻¹ dry wt) averaged 23.1 (two seagrass species), 220.1 (oysters), 287.8 (colonized periphyton), 604.0 (four species of freshwater mussels), 772.4 (brackish clam), 857.9 (blue crabs) and 933.1 (nine fish species). Spatial, intraspecific and interspecific variability in results limited most generalizations concerning the relative mercury contributions of different stressor types. However, concentrations were significantly greater for some biota collected from areas receiving wastewater discharges and golf course runoff (fish), agricultural runoff (oysters) and urban stormwater runoff (colonized periphyton and sediment). Marine water quality criteria and proposed sediment quality guidelines were exceeded in 1–12% of total samples. At least one seafood consumption guideline, criteria or screening value were exceeded in edible tissues of blue crabs (6% total samples) and nine fish species (8–33% total samples) but all residues were less than the US Federal Drug Administration action limit of 1.0 ppm and the few reported toxic effect concentrations available for the targeted biota.     

Oxidative stress in duckweed (Lemna minor L.) caused by short-term cadmium exposure

The mechanisms of plant defence against cadmium toxicity have been studied by short-term exposure of Lemna minor L. (common duckweed) to concentrations of CdCl2 ranging from 0 to 500microM. High accumulation of cadmium was observed (12,320+/-2155microgg(-1) at 500microM CdCl2), which caused a gradual decrease of plant growth, increased lipid peroxidation, and weakened the entire antioxidative defence. Total glutathione concentration decreased significantly; however, the concentration of oxidized glutathione remained stable. The responses of four antioxidant enzymes showed that catalase was the most inhibited after CdCl2 exposure, ascorbate peroxidase and guaiacol peroxidase moderately, and glutathione reductase least. The total antioxidative potential revealed an induced antioxidative network at 0.1microM CdCl2 (137+/-13.2% of the control) and its reduction to only 47.4+/-4.0% of the control at higher cadmium concentrations. The possible application of the examined biomarkers in ecotoxicological research is discussed.     

Comparison of total mercury and methylmercury cycling at five sites using the small watershed approach

The small watershed approach is well-suited but underutilized in mercury research. We applied the small watershed approach to investigate total mercury (THg) and methylmercury (MeHg) dynamics in streamwater at the five diverse forested headwater catchments of the US Geological Survey Water, Energy, and Biogeochemical Budgets (WEBB) program. At all sites, baseflow THg was generally less than 1ng L(-1) and MeHg was less than 0.2ng L(-1). THg and MeHg concentrations increased with streamflow, so export was primarily episodic. At three sites, THg and MeHg concentration and export were dominated by the particulate fraction in association with POC at high flows, with maximum THg (MeHg) concentrations of 94 (2.56)ng L(-1) at Sleepers River, Vermont; 112 (0.75)ng L(-1) at Rio Icacos, Puerto Rico; and 55 (0.80)ng L(-1) at Panola Mt., Georgia. Filtered (<0.7microm) THg increased more modestly with flow in association with the hydrophobic acid fraction (HPOA) of DOC, with maximum filtered THg concentrations near 5ng L(-1) at both Sleepers and Icacos. At Andrews Creek, Colorado, THg export was also episodic but was dominated by filtered THg, as POC concentrations were low. MeHg typically tracked THg so that each site had a fairly constant MeHg/THg ratio, which ranged from near zero at Andrews to 15% at the low-relief, groundwater-dominated Allequash Creek, Wisconsin. Allequash was the only site with filtered MeHg consistently above detection, and the filtered fraction dominated both THg and MeHg. Relative to inputs in wet deposition, watershed retention of THg (minus any subsequent volatilization) was 96.6% at Allequash, 60% at Sleepers, and 83% at Andrews. Icacos had a net export of THg, possibly due to historic gold mining or frequent disturbance from landslides. Quantification and interpretation of Hg dynamics was facilitated by the small watershed approach with emphasis on event sampling.     

分段流动分析法测定水中总氰化物

水样预蒸馏后,经分段流动分析仪自动进样器进入分析模块对水中的总氰化物进行分析。通过试验,确定了最佳测定参数,方法检测限为0 002mg/L,对高低两个不同浓度的标准样品分析,测定值均在其保证值范围内,相对标准差<2 %,准确度和精密度均较好。循环周期约70s,每小时可测定50个样品,分析速度快,尤适于大批量样品的测定。     

白洋淀湿地土壤氮素空间分布特征研究

为了了解白洋淀湿地土壤氮素空间分布规律,于2011年4月在研究区内部耕地和芦苇地采集土样进行分析、研究。研究结果显示,湿地土壤氮素含量总体趋势随着土层的加深而减少;表层土壤全氮和碱解氮呈现出西北高、东南低的趋势。耕地土壤氮素含量和变异性均高于芦苇地,反映出人类活动对土壤氮素的空间分布有较大影响。相关性分析显示土壤有机质含量和含水量与氮素联系紧密,是影响其分布的重要因素。     

硝酸体系微波消解-偏钼酸铵分光光度法测定固废中总磷方法的研究

固体废物经硝酸体系微波消解,其中难溶盐和含磷有机物分解形成正磷酸盐进入溶液,在酸性条件下,正磷酸盐与偏钒酸铵和钼酸铵反应,生成黄色的三元杂多酸,于波长420nm处进行比色测定.样品量为0.5g,定容体积50ml,使用3cm比色皿,方法检出限为1.1mg/kg,测定下限为4.4mg/kg,满足固废总磷的监测要求.