Search results for "Water science"
showing 10 items of 1545 documents
Environmentally relevant precursors of carbonyl sulfide in aquatic systems
1997
Seawater solutions of environmentally relevant organosulfur compounds, commercial humic acid (HA), and natural dissolved organic matter (DOM) were incubated with and without UV light in order to determine the carbonyl sulfide (COS) producing capabilities of these compounds. COS dark- and photo-production rate constants were determined for dilute solutions of the organosulfur compounds (μmol l−1) and HA/DOM (mg l−1). Dissolved COS was determined using a purge and cryogenic trap method followed by GC/FPD detection. COS was produced in considerable amounts both non-photochemically and photochemically from the reduced form of free acid of glutathione (GSH) and photochemically from cysteine (CYS…
Calcium effect on enhanced biological phosphorus removal.
2006
The role of calcium (Ca) in enhanced biological phosphorus removal and its possible implications on the metabolic pathway have been studied. The experience has been carried out in an SBR under anaerobic–aerobic conditions for biological phosphorus removal during 8 months. The variations of influent Ca concentration showed a clear influence on the EBPR process, detecting significant changes in YPO4. These YPO4 variations were not due to influent P/COD ratio, pH, denitrification and calcium phosphate formation. The YPO4 has been found to be highly dependent on the Ca concentration, increasing as Ca concentration decreases. The results suggest that high Ca concentrations produce “inert” granul…
Sediment delivery processes and the spatial distribution of caesium-137 in a small Sicilian basin
1998
The sediment delivery processes occurring in a small Sicilian basin are modelled using the spatially distributed SEDD model recently proposed by Ferro and Minacapilli. The model is applied by using soil data (grain-size distribution, organic matter content, etc.) of 129 samples uniformly distributed over the study area and compiling the available information (topographic map, soil data, etc.) into a Geographical Information System. Finally, the predictive capability of the distributed sediment delivery approach is tested experimentally using the caesium-137 measurement technique. The comparison between calculated sediment yield and the corresponding measured caesium-137 loss is used to vali…
How Humic Substances Dominate Mercury Geochemistry in Contaminated Floodplain Soils and Sediments
1998
The interaction of mercury (Hg) and humic substances (hs) was studied in floodplain topsoils and surface sediments of the contaminated German river Elbe. An intimate coupling exists between the geochemical cycles of Hg and organic carbon (OC) in this ecosystem. Humic substances exert a dominant influence on several important parallel geochemical pathways of Hg, including binding, transformation, and transport processes. Significant differences exist between the Hg-hs associations in floodplains and sediments. Both humic acids (ha) and fulvic acids (fa) contribute to Hg binding in the sediments. In contrast, ultrafiltration experiments proved that Hg in the floodplain soils is almost exclusi…
Natural organic matter coagulation in Valencia water supply. Pilot plant studies
1998
: To reduce disinfection by-product (DBP) formation in drinking water treatment, the presence of natural organic matter in surface waters must be minimised. This paper describes pilot plant studies carried out on two surface waters to assess the effectiveness of coagulation in organic matter removal, the Turia and Jucar rivers, which supply the city of Valencia (1m inhabitants). The experiments were conducted with different coagulants (iron sulphate, polyaluminium chloride (PACl)) and treatment schemes. Process effectiveness was evaluated in terms of effluent turbidity, presence of residual metal in final water, and organic matter removal. Four parameters were used to quantify organic matte…
Natural organic matter export from boreal catchments (the Salaca River basin, Latvia) and its influencing factors
2012
A noteworthy increase in the organic matter concentration and export, as well as water colour, in the catchments of the Salaca River has been observed during the last decades. This study investigates factors behind this increase: the impact of climate, land use and human loading changes on the concentrations and export of the organic matter in the Salaca River/Lake Burtnieks catchments. Proportion of wetlands in the river basin, type of land use, and runoff regime can be considered as the main factors influencing the organic carbon loadings. Despite a steady overall tendency of increase, considerable oscillations of organic matter loadings influenced by the changes in the river discharge re…
EnzymesIn Vitro as indicators for pesticides: An examination
1992
Pesticides—a serious problem especially for drinking water quality—frequently are potent inhibitors of enzymes in their target organisms. As the established chemical analyses of pesticides are time-consuming, complicated, and expensive, so-called screening methods are urgently needed. For this purpose the sensitivity of 13 different enzymes was tested in vitro by inhibiting their kinetic rates and/or substrate conversions by 16 pesticides (herbicides and fungicides). Because of the stabilization and resulting low sensitivity of enzymes commercially available—especially in test kits—it was necessary to vary the test conditions and to develop special methods for detecting enzymatic inhibition…
Use of biological and sedimentation models for designing Peñíscola WWTP.
2004
This paper presents Peñíscola wastewater treatment plant design. Peñíscola is a tourist city in Castellón (Spain), whose population changes significantly between summer and the rest of the year. The design of the biological and settling treatment units has been confirmed by computer model simulations and provided for biological organic matter, nitrogen and phosphorus removal. Two different treatment schemes have been proposed in order to optimize the plant performance during both seasonal operations. During low-load season, the plant will be operated under extended aeration conditions, so further sludge stabilization will not be needed. During high-load season, the plant will be operated un…
Speciation of trialkyltin(IV) cations in natural fluids
2004
The hydrolysis of (CH(3))(3)Sn(+), (C(2)H(5))(3)Sn(+) and (C(3)H(7))(3)Sn(+) has been studied in a Synthetic Seawater (SSW) ionic medium simulating the major composition of natural seawater, at different salinities (5 less than or equal to S less than or equal to 45), and at t = 25 degreesC. Interactions with anionic components of SSW, considered as single sea salt, are determined by means of a complex formation model. By potentiometric measurements (ISE-H(+) and ISE-F(-) electrodes), the model has been extended to also consider interactions of organotins with carbonate and fluoride ions, which are other important components of seawater. Literature and new values of hydrolysis constants in …
Mercury Speciation in Floodplain Soils and Sediments along a Contaminated River Transect
1998
A novel mercury-specific sequential extraction procedure (SEP) for the assessment of mercury (Hg) speciation in soils and sediments, with emphasis on studying the interaction between Hg and organic matter (OM), was developed and tested. It was applied to determine Hg speciation in floodplain topsoils and surface sediments along the Hg-contaminated part of the river Elbe, and to simultaneously derive some information on the (re)mobilization potentials for Hg from these matrices. The majority of the total Hg in the ecosystem today is bound in the floodplains, which also still geographically reflect the historic emission record. Most of the Hg in both matrices is bound strongly to OM, suggesti…