The main aim of this study was to examine the influence of soil properties on the leaching of Cd, Cr, Cu, Ni, Pb, and Zn following the application of polluted sewage sludge to contrasting topsoils. Seventy agricultural soil samples from different parts of Spain were amended with a single dose of sewage sludge (equivalent to 50 t dry weight ha?1) and a column study was performed under controlled conditions. After two, four, and six months of incubation, 283 ml of distilled water (equivalent to a rainfall event of 25 l m?2) was applied. The leachates were then collected and analyzed for metals. For all of the soils considered, the pH was the most important parameter for the control of mobility metals (except for Cu, determined by the sand and soil organic carbon and only to a lesser extent by the soil pH r2 = 0.604, p < 0.001) and was negatively related to all of the studied metals. For Pb and Zn, soil pH was the single soil property explaining their mobility (r2 = 0.411, p < 0.001 for Pb; r2 = 0.713, p < 0.001 for Zn) while for Cd, Cr and Ni, EC, sand and silt also appeared in the statistical models (r2 = 0.753, p < 0.001 for Cd; r2 = 0.366, p < 0.001 for Cr; r2 = 0.784, p < 0.001 for Ni). In the basic soils, soil texture was the most important soil property controlling the mobility of metals (except for that of Pb, which it only weakly predicted). For the acidic-neutral soils, the soil pH was the most important soil property controlling metal mobility (except for that of Cr, which was mainly determined by the pseudo-total Cr content). 相似文献
Dry and wet sludge samples were collected from the sewage sludge storage site and primary treatment ponds at As-Samra Wastewater Treatment Ponds in Al Hayshmia, Jordan. The concentrations of polynuclear aromatic hydrocarbons (PAH) and macro- and microelements were determined using gas chromatography-mass spectrometry (GC-MS) and inductively coupled plasma-mass spectrometry (ICP-MS), respectively.
Environmentally relevant concentrations of PAH were detected ranging from 62 μg g?1 to 70 μg g?1 for dry sludge and from 35 μg g?1 to 47 μg g?1 for wet sludge. These results indicated a potential environmental risk if sewage sludge is reused in Jordan as organic fertilizer without first being treated. The results of the study showed that the sewage sludge samples were contaminated with low levels of heavy metals, as the dry sludge samples were characterized by higher concentrations of most analyzed elements than for wet sludge samples. Still, none of the trace metal concentrations exceeded the threshold concentration levels for agricultural-related sludge.
Unlike many other nutrients found in sludge, the Total Organic Carbon (TOC%) found in dry and wet sludge revealed similar values, at 13.18 percent and 13.29 percent, respectively. The total phosphorus ranged from 0.25% for dry sludge to 0.47% for wet sludge. Total nitrogen varied from 0.80% for wet sludge to 1.01% for the dry sludge samples. The overall nutrients levels are close to those found in the literature. The findings of this study have improved the understanding of sewage sludge characteristics in a semiarid environment. 相似文献
The giant water bug, subfamily Lethocerinae, which has the largest body size among Belostomatidae, is known to be a vertebrate specialist that preys upon fish, amphibians and snakes. However, there have been no reports concerning predation on a turtle by Lethocerinae. Here, I report that a male giant water bug Kirkaldyia (Lethocerus) deyrolli (Heteroptera: Belostomatidae) (58.09 mm in total length) was catching hold of a turtle Chinemys reevesii (34.14 mm in carapace length) in a ditch adjoining a paddy rice field. This is a first report of K. deyrolli eating a turtle. 相似文献
Biosolids, also known as sewage sludge, are reusable organic materials separated from sewage during treatment. They can be managed in a variety of ways. Different options for biosolids handling in Sydney, Australia, are compared in this study using life-cycle assessment. Two key comparisons are made: of system scenarios (scenario 1 is local dewatering and lime amendment; scenario 2 is a centralized drying system) and of technologies (thermal drying versus lime amendment). The environmental issues addressed are energy consumption, global warming potential (GWP), and human toxicity potential (HTP). Scenario 2 would consume 24% more energy than scenario 1. This is due to the additional electricity for pumping and particularly the petrochemical methane that supplements biogas in the drier. A centralized system using the same technologies as scenario 1 has approximately the same impacts. The GWP and HTP of the different scenarios do not differ significantly. The assessment of technology choices shows significant differences. The ample supply of endogenous biogas at North Head sewage treatment plant for the drying option allows reductions, relative to the lime-amendment option, of 68% in energy consumption, 45% in GWP, and 23% in HTP. Technology choices have more significant influence on the environmental profile of biosolids processing than does the choice of system configurations. Controlling variables for environmental improvement are the selection of biogas fuel, avoidance of coalsourced electrical energy, minimization of trucking distances, and raising the solids content of biosolids products. 相似文献
Estrone (E1), 17β-estradiol (E2) and 17α-ethynylestradiol (EE2) discharged from sewage treatment plants (STPs) into surface
waters, are seen as a threat effecting aquatic life by its estrogenic character. Therefore, much research is conducted on
the fate and removal of these compounds. Since these compounds are present in influents and effluents in the ng/l range, methods
for detection deserve special attention. Most important processes that play a role in the removal of estrogens are: adsorption,
aerobic degradation, anaerobic degradation, anoxic biodegradation and photolytic degradation. Halflifes tend to vary and are
remarkably shorter when low initial concentrations are applied. In general anaerobic conditions result in longer halflifes
then aerobic conditions. EE2 shows far most persistence of the compounds, thereby also the estrogenic effect in vitro is about 2–3-fold higher compared to E2. The three compounds show a higher affinity to sorb to sludge compared to other tested
adsorption materials like sediment. Aerobic degradation is far the most efficient in removing these compounds, but adsorption
seems to play a significant role in retaining the estrogens inside full-scale STPs. Removal rates in full scale plants depend
on the HRT, SRT and loading rates, but lack of information on the exact dependency so far prevents an optimal design able
to fully eliminate estrogens from wastewater. 相似文献
Anaerobic municipal wastewater treatment in developing countries has important potential applications considering their huge
lack of sanitation infrastructure and their advantageous climatic conditions. At present, among the obstacles that this technology
encounters, odor control and biogas utilization or disposal should be properly addressed. In fact, in most of small and medium
size anaerobic municipal treatment plants, biogas is just vented, transferring pollution from water to the atmosphere, contributing
to the greenhouse gas inventory. Anaerobic municipal sewage treatment should not be considered as an energy producer, unless
a significant wastewater flow is treated. In these cases, more than half of the methane produced is dissolved and lost in
the effluent so yield values will be between 0.08 and 0.18 N m3 CH4/kg COD removed. Diverse technologies for odor control and biogas cleaning are currently available. High pollutant concentrations
may be treated with physical-chemical methods, while biological processes are used mainly for odor control to prevent negative
impacts on the treatment facilities or nearby areas. In general terms, biogas treatment is accomplished by physico-chemical
methods, scrubbing being extensively used for H2S and CO2 removal. However, dilution (venting) has been an extensive disposal method in some small- and medium-size anaerobic plants
treating municipal wastewaters. Simple technologies, such as biofilters, should be developed in order to avoid this practice,
matching with the simplicity of anaerobic wastewater treatment processes. In any case, design and specification of biogas
handling system should consider safety standards. Resource recovery can be added to anaerobic sewage treatment if methane
is used as electron donor for denitrification and nitrogen control purposes. This would result in a reduction of operational
cost and in an additional advantage for the application of anaerobic sewage treatment. In developing countries, biogas conversion
to energy may apply for the clean development mechanism (CDM) of the Kyoto Protocol. This would increase the economic feasibility
of the project through the marketing of certified emission reductions (CERs). 相似文献
Anaerobic digesters have been responsible for the removal of large fraction of organic matter (mineralization of waste sludge)
in conventional aerobic sewage treatment plants since the early years of domestic sewage treatment (DST). Attention on the
anaerobic technology for improving the sustainability of sewage treatment has been paid mainly after the energy crisis in
the 1970s. The successful use of anaerobic reactors (especially up-flow anaerobic sludge blanket (UASB) reactors) for the
treatment of raw domestic sewage in tropical and sub-tropical regions (where ambient temperatures are not restrictive for
anaerobic digestion) opened the opportunity to substitute the aerobic processes for the anaerobic technology in removal of
the influent organic matter. Despite the success, effluents from anaerobic reactors treating domestic sewage require post-treatment
in order to achieve the emission standards prevailing in most countries. Initially, the composition of this effluent rich
in reduced compounds has required the adoption of post-treatment (mainly aerobic) systems able to remove the undesirable constituents.
Currently, however, a wealth of information obtained on biological and physical-chemical processes related to the recovery
or removal of nitrogen, phosphorus and sulfur compounds creates the opportunity for new treatment systems. The design of DST
plant with the anaerobic reactor as core unit coupled to the pre- and post-treatment systems in order to promote the recovery
of resources and the polishing of effluent quality can improve the sustainability of treatment systems. This paper presents
a broader view on the possible applications of anaerobic treatment systems not only for organic matter removal but also for
resources recovery aiming at the improvement of the sustainability of DST. 相似文献
AIMS: To evaluate the occurrence and abundance of phages that carry the stx(1) and stx(2) gene in water samples of different quality. METHODS AND RESULTS: Phages growing on the Shiga toxin-negative Escherichia coli O157:H7 (ATCC 43,888) strain were enumerated by a plaque assay in concentrated raw and treated waste water samples and river water samples. Plaques were investigated for the presence of stx(1) and stx(2) genes by a multiplex/nested PCR procedure. An overall number of 805 plaques were tested for the presence of stx-carrying phages. Stx genes could be demonstrated in 2% (stx(1)) and 16% (stx(2)) of the plaques. Stx-phages were eliminated with approximately the same efficiency in comparison with somatic coliphages during the waste water treatment process. CONCLUSIONS: Due to the low numbers of phages carrying the stx genes 1 and 2 in treated waste water and river water, the dilution and inactivation of host bacteria and the unsuitable conditions for the transduction of host organisms in aquatic environments, it is difficult to derive from the data the direct evidence for a public health problem. SIGNIFICANCE AND IMPACT OF THE STUDY: The results show the quantitative occurrence of stx-carrying phages in waste and river water and confirm the frequent circulation of these viruses in the aquatic environment. 相似文献
The aim of this work was to demonstrate at pilot scale a high level of energy recovery from sewage utilising a primary Anaerobic Migrating Bed Reactor (AMBR) operating at ambient temperature to convert COD to methane. The focus is the reduction in non-renewable CO(2) emissions resulting from reduced energy requirements for sewage treatment. A pilot AMBR was operated on screened sewage over the period June 2003 to September 2004. The study was divided into two experimental phases. In Phase 1 the process operated at a feed rate of 10 L/h (HRT 50 h), SRT 63 days, average temperature 28 degrees C and mixing time fraction 0.05. In Phase 2 the operating parameters were 20 L/h, 26 days, 16 degrees C and 0.025. Methane production was 66% of total sewage COD in Phase 1 and 23% in Phase 2. Gas mixing of the reactor provided micro-aeration which suppressed sulphide production. Intermittent gas mixing at a useful power input of 6 W/m(3) provided satisfactory process performance in both phases. Energy consumption for mixing was about 1.5% of the energy conversion to methane in both operating phases. Comparative analysis with previously published data confirmed that methane supersaturation resulted in significant losses of methane in the effluent of anaerobic treatment systems. No cases have been reported where methane was considered to be supersaturated in the effluent. We have shown that methane supersaturation is likely to be significant and that methane losses in the effluent are likely to have been greater than previously predicted. Dissolved methane concentrations were measured at up to 2.2 times the saturation concentration relative to the mixing gas composition. However, this study has also demonstrated that despite methane supersaturation occurring, micro-aeration can result in significantly lower losses of methane in the effluent (<11% in this study), and has demonstrated that anaerobic sewage treatment can genuinely provide energy recovery. The goal of demonstrating a high level of energy recovery in an ambient anaerobic bioreactor was achieved. An AMBR operating at ambient temperature can achieve up to 70% conversion of sewage COD to methane, depending on SRT and temperature. 相似文献
In this study we describe the growth of several different larval cohorts (i.e. half-siblings of the same mother born on the same day) of a rare, xeric-adapted salamander Salamandra s. infraimmaculata Martens, 1885, under constant density and food conditions from birth to metamorphosis. The larvae spend the critical first phase of their lives in water, mostly in temporary ponds. Age and weight at metamorphosis were highly affected by varying food conditions. We have identified six different growth modes that these larvae use, both fast growing and slow growing. Each larval cohort was found to use 2-4 different such growth modes regardless of their initial weight. Fast growing modes (I-III) will enable larvae to survive dry years, and metamorphose bigger. Slow growing modes (IV-VI), used by 8% of the larval population, will enable survival only in rainy years. These last growth modes effect differential temporal dispersal in wet years by delaying the emergence of postmetamorphs onto land. Distribution of growth modes in the larval population is affected by food but not by density conditions. Late-born, fast-growing larvae will have an advantage in dry years being able to metamorphose and disperse, whereas the slow-growing larvae will survive only in wet years. 相似文献