Indicator parameters, dissolved organic

Although the investigations of both Raunkjaer et al. (1995) and Almeida (1999) showed that removal of COD — measured as a dissolved fraction — took place in aerobic sewers, a total COD removal was more difficult to identify. From a process point of view, it is clear that total COD is a parameter with fundamental limitations, because it does not reflect the transformation of dissolved organic fractions of substrates into particulate biomass. The dissolved organic fractions (i.e., VFAs and part of the carbohydrates and proteins) are, from an analytical point of view and under aerobic conditions, considered to be useful indicators of microbial activity and substrate removal in a sewer. The kinetics of the removal or transformations of these components can, however, not clearly be expressed. Removal of dissolved carbohydrates can be empirically described in terms of 1 -order kinetics, but a conceptual formulation of a theory of the microbial activity in a sewer in this way is not possible. The conclusion is that theoretical limitations and methodological problems are major obstacles for characterization of microbial processes in sewers based on bulk parameters like COD, even when these parameters are determined as specific chemical or physical fractions. 

Along the same line, UV-vis based scanning for deviations from a blank reference in industrial wastewaters can indicate problems on an upstream level that remain undetected using conventional parameters. The so-called alarm parameters need not even be based on detailed interpretation of all absorption bands. In a coarse manner, absorption in certain spectral regions may correlate with lump parameters such as total organic carbon (TOC), dissolved organic carbon (DOC) and the like. ... 

As indicated earlier (Section 3.1.1) the sorption of organic compounds onto dissolved matter can significantly increase the solubility of the compound. This can in turn affect the fate of these chemicals in the environment. We can use physicochemical parameters such as distribution coefficients (log D), aqueous acid dissociation constants (pAia), and octanol-water partition coefficients (p/to )-These attributes are also linked to the acidity and alkalinity of the environment as well as lipohilicity of the compound. The mathematical relationships between these attributes are outlined below to explore how each of these impacts the fate of PPCPs in the environment. 

On time scales of oceanic circulation (1000 y and less) the internal distribution of carbonate system parameters is modified primarily by biological processes. Gross sections of the distribution of Aj and DIG in the world s oceans (Fig. 4.4) and scatter plots of the data for these quantities as a function of depth in the different ocean basins (Fig. 4.5) indicate that the concentrations increase in deep waters (1-4 Ion) from the North Atlantic to the Antarctic and into the Indian and Pacific Oceans following the conveyer belt circulation (Fig. 1.12). Degradation of organic matter (OM) and dissolution of GaGOs cause these increases in the deep waters. The chemical character of the particulate material that degrades and dissolves determines the ratio of At to DIG. 

Comparison of humic substances from different lakes indicates a high variation in concentration, composition, and molecular weight. The extent to which differences in methodology contribute to this variation has not been evaluated. Temporal and spatial distributions of dissolved humic substances and humic-associated organic substances are presented for five representative lakes. General parameters (UV absorbance, DOC measurements with or without fractionation on the basis of molecular size) do not adequately reflect the dynamic nature of various humic substances in lake ecosystems. 

Romanian regimentations about water quality protection show that between the strictly surveyed parameters that can indicate organic pollution degree are chemical oxygen demand (CODMn), dissolved oxygen (DO), and biochemical oxygen demand (BOD). 

In terms of polymer matrices for composite materials, there will be a compromise between solvent and water resistance. Thus non-polar resins are likely to be less resistant to hydrocarbon solvents, which have low polarity, but more resistant to moisture absorption. Polar resins behave in the opposite way. Strongly polar solvents, such as dimethyl sulphoxide or similar, can interact with polar structures in the resin and are difficult to resist. Crystalline thermoplastic polymers are often better for such applications. For example, polyethene will only dissolve in hydrocarbon solvents (of similar solubility parameter) at temperatures above the crystalline melting point. Polar semi-crystalline polymers such as the polyamides or nylons can be dissolved in highly polar solvents, such as cresol, because of a stronger interaction than that between molecules within the crystallites. High performance thermoplastic polymers such as polyether ether ketone (PEEK) have been promoted for their resistance to organic solvents (see Table 3.5) [12], The chemical resistance of unsaturated polyester and vinyl ester and urethane resins is indicated in Table 3.6 [15]. 

The second criterion for the selection of a proper organic solvent was its effects on the enzyme activity and stability. Seven organic solvents were tested, chloroform, cyclohexane, n-hexane, n-octane, isooctane, dodecanol, and n-decane, with logP values of 2.0, 3.2, 3.5, 4.5, 4.5, 5.0, and 5.6, respectively. The logP of a solvent, the logarithm of the partition coefficient of the solvent in a standard mixture of 1-octanol and water, is a parameter often used for predicting its biocompatibility, and is usually more indicative of the dissolved solvent. 

The chemical characteristics of water are most commonly described by the concentrations of a limited number of dissolved inoiganic ions, lumped parameters such as alka-Unity, acidity, hardness, conductivity, the aqueous caibon dioxide concentration, the radioactivity, and lumped mea-suies of the organic content such as biochemical oxygen demand, as indicated in Table VI. Concentrations of other inorganic ions and spedlic or nic compounds are important in relation to particular rrses. The most common issues with respect to concentrations of particular ions and compounds are related to toxicity. For example, the maximum concentration limit (MCL) for arsenic in drinking water of 50 /tg/L is based on the average ability to excrete approximately 900 of arsenic per day, the probable intake of arsenic from other soirrces (principally food), and the assumption that we will follow recommendations to... 

The complexity with respect to water quality is reflected in the many types of physical, chemical and biological indicators. Therefore, depending on specific project requirements, information about a wide variation of additional parameters may be required in order to describe the state of and the effect on the water quality. Simple measurements such as temperature, pH, dissolved oxygen, conductivity, conductivity, alkalinity (pH) and ammonia can be made on-site in direct contact with the water source. More complex measurements such as toxic contaminants and the presence of micro organisms may require water sampling followed by an analysis in the laboratory. 

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