Limiting organic concentration values

For these compounds the breakthrough time was defined as that time at which the aqueous phase organic concentration exceeded the lower limit of detection (LLD) values listed in Table I or was extrapolated to zero concentrations as mentioned above for those... 

Hence, organic solvents should be handled with care. In the USA, the threshold limit values [TL values) are used as a measure of the inhalation toxicity for chronic interaction with solvent vapours [90]. In the Federal Republic of Germany, the maximum concentration values at the workplace [MAK values) are used [91, 92]. Threshold limit values refer to airborne concentrations of substances and represent conditions under which it is believed that workers may be repeatedly exposed daily without adverse effect. They refer to time-weighted average concentrations for a normal 8-hour workday... 

The value for Kk, the saturation coefiicient or growth-limiting substrate concentration at which organism growth rate is one-half its maximum value, varies considerably with the reaction, the species mediating the reaction, and environmental conditions. In anaerobic methane fermentations, Kk tends to be much larger, at least with acetate and propionate, than for aerobic oxidations. Values of 10" moles/liter seem appropriate for the former and 10" for the latter. Kk also tends to increase with decrease in temperature. 

This chapter examines the fundamental structural properties of organic molecules that directly or indirectly affect pKa values of organic acids, making it possible to estimate theoretical upper limits for concentrations of common acidic functional groups, to assess methods of quantitative analysis of acidic functional groups in humic substances, and to examine several models that have been proposed for the description of proton binding by humic substances. Some of the concepts that appear obvious in the context of this chapter have been included for the simple reason that the literature on acidity of humic substances reveals that these points have frequently been either misunderstood or neglected. 

The World Health Organization recommends limiting the concentrations of nitrite and nitrate nitrogen to 10 mg 1 , emphasizing that this value exceeds the content of nitrates in water which can be used for the preparation of nourishment for sucklings. 

Both DOC and UV analysers were tested extensively to understand the limitations of these analyses. Care has to be taken when UV analysis is used to determine the organic concentration of solutions, especially in water treatment. Treatment often removes a fraction of the UV absorbing compounds selectively and the measured values are in this case not related to the organic concentration. 

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