Turbidity, effect, flocculation

An analogous effect has been found in the turbidity of flocculating sols. See chapter VII 8, p. 299. 

M = Al, Ga, In, Tl). The solution chemistry of Al in particular has been extensively investigated because of its industrial importance in water treatment plants, its use in many toiletry formulations, its possible implication in both Altzheimer s disease and the deleterious effects of acid rain, and the ubiquity of Al cooking utensils.For example, hydrated aluminium sulphate (10-30 gm ) can be added to turbid water supplies at pH 6.5-7.5 to flocculate the colloids, some 3 million tonnes per annum being used worldwide for this application alone. Likewise kilotonne amounts of A1(OH)2.5C1o.5 in concentrated (6m) aqueous solution are used in the manufacture of deodorants and antiperspirants. 

It was previously mentioned that PDADMAC (Cat-Floe) was the first commercial flocculant approved for potable water [26]. Since then, PDADMAC has been continuously used for coagulation/flocculation both in potable water and waste water treatment. A good example of the performance of PDADMAC in the coagulation of colloidal solids is the reduction of turbidity in fresh water of 150 mg L 1 of Ca(OH)2. A reduction of 82% in turbidity is observed with the addition of only 2 mg L 1 of branched PDADMAC [217]. In addition, PDADMAC and copolymers of DADMAC are reported to be effective in the removal of hard-to-elimi-nate impurities in the water treatment industry. Emulsified impurities from streams of a petroleum refinery waste water and an automotive oily effluent water have been removed by the use of water soluble copolymers consisting essentially of DADMAC and small amounts of anionic acrylic monomers [89]. 

Hepatic Effects. Chromium(VI) has been reported to cause severe liver effects in four of five workers exposed to chromium trioxide in the chrome plating industry. Derangement of the cells in the liver, necrosis, lymphocytic and histiocytic infiltration, and increases in Kupffer cells were reported. Abnormalities in tests for hepatic dysfunction included increases in sulfobromophthalein retention, gamma globulin, icterus, cephalin cholesterol flocculation, and thymol turbidity (Pascale et al. 1952). In a cohort of 4,227 workers involved in production of stainless steel from 1968 to 1984, excess deaths were observed from cirrhosis of the liver compared to expected deaths (0/E=55/31.6) based on national rates and matched for age, sex, and calender time having an SMR of 174 with confidence limits of 131-226 (Moulin et al. 1993). No measurements of exposure were provided. Based on limited information, however, the production of chromium compounds does not appear to be associated with liver effects. As part of a mortality and morbidity study of workers engaged in the manufacture of chromium(VI) compounds (84%) and chromium(III) compounds (16%) derived from chromium(VI) in Japan, 94 workers who had been exposed for 1-28 years were given a complete series of liver function... 

Particle counts are useful in pilot plant testing as one evaluation parameter in coiqunction with other water quality (e.g. turbidity) and operational (e.g. filter head loss) parameters. Information gained from particle counts can be used to follow flocculation kinetics and solid-removal effectiveness of unit processes. 

Bentonite particles are negatively charged and flocculation occurs when electrolytes or positively charged suspensions are added. Bentonite is thus said to be incompatible with strong electrolytes, although this effect is sometimes used beneficially to clarify turbid liquids. 

Traditionally, M. oleifera seeds have been used to clarify turbid waters in rural areas of Asia and Africa (29). Of the identified 14 species of the moringaceae family, M. oleifera has gained considerable importance as flocculants in nearly all tropical and subtropical regions (8). Further, the coagulating property of the seed powder of this plant has been used for various aspects of water treatment such as turbidity, alkahnity, total dissolved sohds, and hardness (30, 51,54, 63). The seeds of six more frequent and cultivated species of Moringa have been found to contain flocculant components. Numerous studies so far confirms that M. oleifera seeds possess effective coagulation properties (49,54,63,65). Branches of the M. oleifera when lopped and thrown into turbid and contaminated wells, over an episode of time, the previously dirty water becomes clear. The desiccated M. oleifera seeds are... 

Attempts have been made to allow for the effect of biliary obstruction by the use of a correction factor based on the 1-minute serum bilirubin concentration as a measure of the degree of obstruction (Z3). However BSP retention values corrected in this way were foimd to be less valuable in the differential diagnosis of jaundice than the results of the cephalin flocculation test or the thymol turbidity test (M21). 

Figures 9 and 10 illustrate the effectiveness of the optimum dose of two high molecular weight PEI species in producing flocculation of the singlet particles and in reducing the suspension turbidity. In these cases...

Citric acid treatment to prevent ferric casse may be reinforced by adding gum arabic, which acts as a protective colloid (Section 9.4.3). This is especially effective in preventing the flocculation of colloidal ferric phosphate. The doses of gum arabic generally nsed are on the order of 5-20 g/hl. This additive is available in aqueous solutions, at concentrations ranging from 15-30%. Gum arabic must be used in perfectly clear wines that are ready for bottling. It not only stabilizes clarity, but also turbidity, and has a very high capacity for fouling filter surfaces. 

Most turbidity occurring in wine is due to the flocculation of colloidal particles caused by chemical reactions that leave the solution clear. It is certain that the presence of natural polysaccharides, with their protective colloid properties, prevent the formation of turbidity and deposits. It is also clear that, in some cases, it may be useful to enhance this protective effect by adding a colloid such as gum arabic. 

In general, the effect of bentonite on red wines is comparable to that of protein fining. After flocculation and sedimentation, wines treated with doses of 25-40 g/hl of bentonite remain stable at low temperatures, staying brilliant and free of turbidity, even after several months. This treatment may be even more effective than gelatin (12 g/hl) or blood albumin (18 g/hl). It should, however, be taken into account that bentonite fixes anthocyanins, not only in discolored white wines but also in roses and young red wines. 

As bentonite flocculates in wine, with a behavior analogous to that of protein fining agents, experiments have been made in using it to clarify wine. In fact, its effectiveness in clarification depends on the type of bentonite and the composition of the wine. The only wines that may be properly clarified are reds or whites with low concentrations of polysaccharides and other protective colloids (Section 9.4.1), as these inhibit the flocculation and settling of the bentonite particles. In some winegrowing areas, bentonite is well suited to clarifying dry white wines, but elsewhere white wines may be more turbid after bentonite treatment than before. 

The turbidity methods are unsatisfactory for lar particles and/or high particle number concentrations when multiple scattering effects intrude. As shown by Hunter et al. (1975), rheological measurements can then be used to detect flcK ulation. Stable dispersions exhibit an Ostwald-type flow curve whereas flocculated systems behave in a pseudoplastic fashion. Bocculation is thus accompanied by a large increase in the Bingham yield value, t, of the dispersion (see Fig. 5.4). 

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