Water Science and Technology
0273-1223
Cơ quản chủ quản: IWA Publishing
Lĩnh vực:
Water Science and TechnologyEnvironmental Engineering
Các bài báo tiêu biểu
The IWA Anaerobic Digestion Model No 1 (ADM1) The IWA Anaerobic Digestion Modelling Task Group was established in 1997 at the 8th World Congress on Anaerobic Digestion (Sendai, Japan) with the goal of developing a generalised anaerobic digestion model. The structured model includes multiple steps describing biochemical as well as physico-chemical processes. The biochemical steps include disintegration from homogeneous particulates to carbohydrates, proteins and lipids; extracellular hydrolysis of these particulate substrates to sugars, amino acids, and long chain fatty acids (LCFA), respectively; acidogenesis from sugars and amino acids to volatile fatty acids (VFAs) and hydrogen; acetogenesis of LCFA and VFAs to acetate; and separate methanogenesis steps from acetate and hydrogen/CO2. The physico-chemical equations describe ion association and dissociation, and gas-liquid transfer. Implemented as a differential and algebraic equation (DAE) set, there are 26 dynamic state concentration variables, and 8 implicit algebraic variables per reactor vessel or element. Implemented as differential equations (DE) only, there are 32 dynamic concentration state variables.
Tập 45 Số 10 - Trang 65-73 - 2002
Defining the biomethane potential (BMP) of solid organic wastes and energy crops: a proposed protocol for batch assays The application of anaerobic digestion technology is growing worldwide because of its economic and environmental benefits. As a consequence, a number of studies and research activities dealing with the determination of the biogas potential of solid organic substrates have been carrying out in the recent years. Therefore, it is of particular importance to define a protocol for the determination of the ultimate methane potential for a given solid substrates. In fact, this parameter determines, to a certain extent, both design and economic details of a biogas plant. Furthermore, the definition of common units to be used in anaerobic assays is increasingly requested from the scientific and engineering community. This paper presents some guidelines for biomethane potential assays prepared by the Task Group for the Anaerobic Biodegradation, Activity and Inhibition Assays of the Anaerobic Digestion Specialist Group of the International Water Association. This is the first step for the definition of a standard protocol.
Tập 59 Số 5 - Trang 927-934 - 2009
Relevance of microbial extracellular polymeric substances (EPSs) - Part I: Structural and ecological aspects Extracellular polymeric substances are the construction materials for microbial aggregates such as biofilms, flocs (“planktonic biofilms”) and sludge. Their major components are not only polysaccharides but also proteins and in some cases lipids, with minor contents of nucleic acids and other biopolymers. In the EPS, biofilm organisms can establish stable arrangements and function multicellularly as synergistic microconsortia. The matrix facilitates the retention of exoenzymes, cellular debris and genetic material; it can be considered as a microbial recycling yard. Gradients can develop due to the physiological activity and the fact that diffusive mass transport prevails over convective transport in the matrix. Biofilm cells tolerate higher concentrations of many biocides. The EPS matrix sequesters nutrients from the water phase. In photosynthetic communities, EPS molecules can function as light transmitters and provide photons to organisms located deeper in a microbial mat. The EPS matrix is a dynamic system, constructed by the organisms and responding to environmental changes. It enables the cells to function in a manner similar to multicellular organisms.
Tập 43 Số 6 - Trang 1-8 - 2001
Towards a standardization of biomethane potential tests Production of biogas from different organic materials is a most interesting source of renewable energy. The biomethane potential (BMP) of these materials has to be determined to get insight in design parameters for anaerobic digesters. Although several norms and guidelines for BMP tests exist, inter-laboratory tests regularly show high variability of BMPs for the same substrate. A workshop was held in June 2015, in Leysin, Switzerland, with over 40 attendees from 30 laboratories around the world, to agree on common solutions to the conundrum of inconsistent BMP test results. This paper presents the consensus of the intense roundtable discussions and cross-comparison of methodologies used in respective laboratories. Compulsory elements for the validation of BMP results were defined. They include the minimal number of replicates, the request to carry out blank and positive control assays, a criterion for the test duration, details on BMP calculation, and last but not least criteria for rejection of the BMP tests. Finally, recommendations on items that strongly influence the outcome of BMP tests such as inoculum characteristics, substrate preparation, test setup, and data analysis are presented to increase the probability of obtaining validated and reproducible results.
Tập 74 Số 11 - Trang 2515-2522 - 2016
AQUASIM – A TOOL FOR SIMULATION AND DATA ANALYSIS OF AQUATIC SYSTEMS A survey over the capabilities of a new simulation and data analysis program for laboratory, technical and natural aquatic systems is given. In this program, the spatial configuration of a model system is represented by compartments, which are connected by links. The program allows the user to define an arbitrary number of substances to be modelled and it is extremely flexible in the formulation of transformation processes. It not only offers the possibility of performing simulations of the time evolution of the user-specified system, but it provides also methods for system identification (sensitivity analysis and automatic parameter estimation) and it allows us to estimate the uncertainty of calculated results. These features, together with the user-friendly interface, very much support scientist in analyzing their data. Three examples illustrate the capabilities of the program.
Tập 30 Số 2 - Trang 21-30 - 1994
Coagulation in Drinking Water Treatment: Particles, Organics and Coagulants A review of coagulation in drinking water treatment is presented. The paper emphasizes the importance of raw water chemistry, natural organic matter (NOM) concentration and type, and the chemistry of coagulants. Mineral and organic particles may be stable in water due to electrostatic charge interactions, hydrophilic effects, or to steric interactions from adsorbed macromolecules. NOM rather than particles initially in water supplies can control coagulant dosages and selection. MOM consists of a mixture of various organic compounds including hydrophobic (humic and fulvic acids) and hydrophilic fractions. The negative charge and chemical structure of the hydrophobic acids affect chemical reactions with coagulants, particularly metal based coagulants. The removal of NOM with Al coagulants can involve hydrolysis, complexation, precipitation, and adsorption reactions. Specific ultraviolet absorbance (SUVA) can be used to estimate whether the NOM of a water is high or low in hydrophobic acids and to estimate removals of DOC by coagulation. Preozonation of water supplies containing algae may lead to microflocculation or impair coagulation depending on algae type, concentration and molecular weight of extracellular organic matter (EOM), and ozone dose.
Tập 27 Số 11 - Trang 21-35 - 1993
The water sensitive city: principles for practice With the widespread realisation of the significance of climate change, urban communities are increasingly seeking to ensure resilience to future uncertainties in urban water supplies, yet change seems slow with many cities facing ongoing investment in the conventional approach. This is because transforming cities to more sustainable urban water cities, or to Water Sensitive Cities, requires a major overhaul of the hydro-social contract that underpins conventional approaches. This paper provides an overview of the emerging research and practice focused on system resilience and principles of sustainable urban water management Three key pillars that need to underpin the development and practice of a Water Sensitive City are proposed: (i) access to a diversity of water sources underpinned by a diversity of centralised and decentralised infrastructure; (ii) provision of ecosystem services for the built and natural environment; and (iii) socio-political capital for sustainability and water sensitive behaviours. While there is not one example in the world of a Water Sensitive City, there are cities that lead on distinct and varying attributes of the water sensitive approach and examples from Australia and Singapore are presented.
Tập 60 Số 3 - Trang 673-682 - 2009
Binding and Mobilization of Heavy Metals in Contaminated Sediments Affected by pH and Redox Potential In a contaminated sediment from Hamburg harbour, acid production, mobilization of Cu, Zn, Pb, and Cd at different redox- and pH-conditions, and the transfer and change of those particle bound metals are studied. During oxidation the pH value in the sediment suspension decreases from about 7 to 3.4 because of the low acid neutralization capacity (ANC). This leads to a mobilization of heavy metals whereby Cd and Zn as distinguished from Cu and Pb are strongly released. Also a change in particulate phase specific heavy metal binding forms is found. Generally the easily and moderately reducible fractions increase during oxidation while the sulfidic fraction decreases. Also great changes were found for the dissolved Zn-and Cd-concentrations which increased continuously. The results show that at identical pH values obviously more metals are mobilized in the oxidized sediment than in the reduced state. But although the pH value is the key factor - in particular if it sinks below 4.5 - the redox conditions may also control the mobilization of certain metals. Consequently, also in well buffered sediments a mobilization of metals during oxidation cannot be excluded.
Tập 28 Số 8-9 - Trang 223-235 - 1993
Mechanisms of heavy metal removal using microorganisms as biosorbent Release and distribution of heavy metals through industrial wastewaters has adverse affects on the environment via contamination of surface- and ground-water resources. Biosorption of heavy metals from aqueous solutions has been proved to be very promising, offering significant advantages such as low cost, availability, profitability, ease of operation, and high efficiency, especially when dealing with low concentrations. Residual biomasses of industrial microorganisms including bacteria, algae, fungi, and yeast have been found to be capable of efficiently accumulating heavy metals as biosorbent. This paper presents and investigates major mechanisms of biosorption and most of the functional groups involved. The biosorption process includes the following mechanisms: transport across cell membrane, complexation, ion exchange, precipitation, and physical adsorption. In order to understand how metals bind to the biomass, it is essential to identify the functional groups responsible for metal binding. Most of these groups have been characterized on the cell walls. The biosorbent contains a variety of functional sites including carboxyl, imidazole, sulfydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl, amide, and hydroxyl moieties that are responsible for metal adsorption. These could be helpful to improve biosorbents through modification of surface reactive sites via surface grafting and/or exchange of functional groups.
Tập 69 Số 9 - Trang 1775-1787 - 2014