Search results for " mixture"
showing 10 items of 1018 documents
Modelling and dynamic simulation of hybrid moving bed biofilm reactors: model concepts and application to a pilot plant.
2011
In the recent years, there has been an increasing interest in the development of hybrid reactors, especially in the up-grading of existing activated sludge plants that are no longer able to comply with concentration limits established by regulatory agencies. In such systems the biomass grows both as suspended flocs and as biofilm. In this way, it is possible to obtain a higher biomass concentration in the reactor, but without any significant increase of the load to the final clarifier. The paper presents the setting-up of a dynamic mathematical model aimed at quantitatively describing the biokinetic processes occurring in a hybrid moving bed biofilm reactor (HMBBR), and, more in general, in…
Occupational hygiene in biowaste composting
1998
Source-separated biowastes from the Helsinki Metropolitan Area have been composted in open air windrows at Ammas suo, the Helsinki regional landfill in Espoo (Finland). The most significant problem encountered in the early stages of the process has been the formation of rancid odor causing human discomfort. The offensive odor was mainly due to car boxylic acids. A total of 110 organic compounds were detected in volatile emissions from windrow composts with an integrated sensory and instrumental method. Occasionally the temperatures in the windrows exceeded 80°C. Bacterial measurements also revealed substantial populations of bacte ria at 75°C. The concentrations of airborne microbes and en…
Sorption Equilibria of Ethanol on Cork
2013
International audience; We report here for the first time a thermodynamic study of gaseous ethanol sorption on raw cork powder and plate. Our study aims at a better understanding of the reactivity of this material when used as a stopper under enological conditions, thus in close contact with a hydroethanolic solution, wine. Sorption−desorption isotherms were accurately measured by thermogravimetry at 298 K in a large range of relative pressures. Sorption enthalpies were determined by calorimetry as a function of loading. Sorption−desorption isotherms exhibit a hysteresis loop probably due to the swelling of the material and the absorption of ethanol. Surprisingly, the sorption enthalpy of e…
Short-term changes in infiltration between straw mulched and non-mulched soils after wildfire in Mediterranean forest ecosystems
2018
Abstract Water infiltration is a basic parameter to understand the hydrological response of semi-arid or arid soils – where runoff generation is dominated by infiltration-excess – subjected to wildfire. To evaluate the hydrological effects of straw application on a sandy loam soil after wildfire, the unsaturated hydraulic conductivity, water content and temperature of mulched and nonmulched (considered as control) soils were monitored throughout eight months. Compared to untreated soils, straw maintained higher temperatures and water contents in mulched plots, but reduced their unsaturated hydraulic conductivity, particularly in the drier season. These results suggest that straw release may…
A preliminary study on the ecotoxic potency of wastewater treatment plant sludge combining passive sampling and bioassays.
2021
Highlights • The passive samplers collected bioavail able and bioaccessible chemicals from the WWTP sludge samples. • The sampler extracts were acutely and chronically toxic to water flea. • The sampler extracts were cytotoxic and genotoxic. • The sludge treatment such as composting and digesting diminished the toxicity. • Effect-based methods should be part of the risk assessment of sludge recycling. Sewage sludge is an inevitable byproduct produced in wastewater treatment. Reusing nutrient-rich sludge will diminish the amount of waste ending in soil dumping areas and will promote circular economy. However, during sewage treatment process, several potentially harmful organic chemicals are …
Stabilisation of MSWI bottom ash with sulphide-rich anaerobic effluent.
2007
Effluent of an anaerobic sulphate-reducing wastewater treatment process was used to stabilise bottom ash. The effect of stabilisation on the concentration and binding of Ca, P, S, Cu, Pb, Zn, As, Cr, and Mo were studied by comparing results of sequential extraction from fresh and stabilised bottom ash. The stabilisation treatment improved the retention of Ca, Cu, Pb, S, and Zn in bottom ash compared to a treatment with ion-exchanged water. In addition to retention, Cu, S, and Zn were accumulated from the anaerobic effluent in the bottom ash. Concentrations of As, Cr, and Mo remained on the same level, whereas leaching of P increased compared to control treatment with ion-exchanged water. Im…
A method for measuring low-weight carboxylic acids from biosolid compost
2006
Concentration of low-weight carboxylic acids (LWCA) is one of the important parameters that should be taken into consideration when compost is applied as soil improver for plant cultivation, because high amounts of LWCA can be toxic to plants. The present work describes a method for analysis of LWCA in compost as a useful tool for monitoring compost quality and safety. The method was tested on compost samples of two different ages: 3 (immature) and 6 (mature) months old. Acids from compost samples were extracted at high pH, filtered, and freeze-dried. The dried sodium salts were derivatized with a sulfuric acid–methanol mixture and concentrations of 11 low-weight fatty acids (C1–C10) were a…
High-Performance Liquid Chromatographic Study on Oxidation Products of Lignin and Humic Substances
1991
We describe a convenient method of preparing samples and characterizing the mixture of degradation products obtained from alkaline cupric oxide oxidation of water samples containing lignin and humic substances. The method was applied to one unpolluted humic water sample and a total mill effluent of a kraft pulp mill. The fractions (Mr > 1000) obtained by ultrafi1tration were oxidized and the products (mixtures of degradation products) were analyzed by reversed-phase high-performance liquid chromatography (Spherisorb 5 ODS column). Acetonitrile-0.01 M phosphate buffer (pH 2) was used as the eluent in a gradient system and UV (set at 280 nm) as the detection system. Differences in the …
Sorption of humic substances on aquifer material at artificial recharge of groundwater
2003
Experiments in batch equilibrium system were carried out to evaluate the importance of physical and chemical factors determining the sorption efficiency of humic substances (HS) on aquifer material, which has been used for artificial recharge of groundwater (ARG) in drinking water production. Results showed that an increase of the amount of clay in the aquifer material and a decrease of pH in water increased the sorption efficiency. The sorption of higher molecular weight, more hydrophobic and aromatic HS (Aldrich and forest soil humic acids) were greater than the sorption of acidic HS (river fulvic acids), either on the aquifer material or to its representative sorbing phases, clay and org…
Polar organic marker compounds in PM2.5 aerosol from a mixed forest site in western Germany
2008
The molecular composition of PM2.5 (particulate matter with an aerodynamic diameter2.5 microm) aerosol samples collected during a very warm and dry 2003 summer period at a mixed forest site in Jülich, Germany, was determined by gas chromatography/mass spectrometry in an effort to evaluate photooxidation products of biogenic volatile organic compounds (BVOCs) and other markers for aerosol source characterization. Six major classes of compounds represented by twenty-four individual organic species were identified and measured, comprising tracers for biomass combustion, short-chain acids, fatty acids, sugars/sugar alcohols, and tracers for the photooxidation of isoprene and alpha-/beta-pinene.…