Survey of Residual Aluminum in Filtered Water

Letterman, Raymond D.; Driscoll, Charles T.

doi:10.1002/j.1551-8833.1988.tb03020.x

Cited by 77 publications

(35 citation statements)

References 10 publications

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“…The use of coagulant at its optimum pH displays maximum pollutant removal. In addition, with such optimum pH conditions, the soluble residual aluminium and iron content in the wastewater will be lower than 0.5 mg/L and 2 mg/L, respectively (Amokrane, et al, 1997;Letterman and Driscoll, 1988). It can be seen that turbidity removal is most effective at a pH range between 7 and 8 for Al 2 (SO 4 ) 3 , 18H 2 O and between 5 and 7 for FeCl 3 (Fig.…”

Section: Resultsmentioning

confidence: 88%

Pollution reduction and biodegradability index improvement of tannery effluents

Aboulhassan¹,

Souabi²,

Yaacoubi

2007

Int. J. Environ. Sci. Technol.

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Al 2 (SO 4 ) 3 , 18H 2 O, FeCl 3 and Ca (OH) 2 were used for the treatment of tannery wastewaters. The influences of pH and coagulant dosages were studied. Conditions were optimised according to the pollutant removal efficiencies, the volume of decanted sludge and the biodegradability index improvement. The results indicate that 67-71% of total COD, 76-92% of color and 79-97% of Cr can be removed using the optimum coagulant dosages at the optimum pH range. Al 2 (SO 4 ) 3 , 18H 2 O and Ca (OH) 2 produced better results than FeCl 3 in terms of COD, color and Cr removal as well as in terms of biodegradability improvement. Moreover, Al 2 (SO 4 ) 3 , 18H 2 O and FeCl 3 produced the least amount of sludges for a given amounts of COD, color and Cr removed in comparison with Ca (OH) 2 . Al 2 (SO 4 ) 3 , 18H 2 O seems to be suitable for yielding high pollutant removals and corresponding low volumes of decanted sludges in addition to improving wastewaters biodegradability index.

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Section: Resultsmentioning

confidence: 88%

Pollution reduction and biodegradability index improvement of tannery effluents

Aboulhassan¹,

Souabi²,

Yaacoubi

2007

Int. J. Environ. Sci. Technol.

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“…The aluminum content from the raw and filtered water was subdivided into total and soluble fractions [5]. The soluble fraction was defined as that material not retained by a 0.45 µm filter (ZapCap CR 0.45 micron nylon, VWR Scientific Products, San Diego, Calif.).…”

Section: Methodsmentioning

confidence: 99%

“…Thus, maintaining high flux rates in downstream membrane processes requires effective pre-treatment for particle removal. Coagulation processes, though efficient in achieving turbidity removal, are known to have coagulant "carryover" or residuals [5]. Potential methods to minimize coagulant residuals include coagulant dose optimization, pH control, alternative coagulant selection, or additional chemical additives.…”

Section: Introductionmentioning

confidence: 99%

Control of residual aluminum from conventional treatment to improve reverse osmosis performance

Gabelich¹,

Ishida

Gerringer³

et al. 2006

Desalination

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Soluble aluminum (Al 3+ ) may react with both ambient silica and antiscalant components to form colloidal foulants during reverse osmosis (RO) treatment. Whereas conventional treatment (coagulation/filtration/sedimentation/dual-media filtration) was being used prior to RO, aluminum sulfate (alum) and polyaluminum chloride (PACl) coagulants were evaluated at ambient pH (pH 7.8 to 7.9) and suppressed pH (pH 6.7) in an effort to lower the total aluminum to below 50 µg/L-a level previously observed to prevent RO membrane fouling. Additional tests were conducted with 5 mg/L citric acid added to the RO influent to chelate the soluble aluminum fraction. All tests were conducted with 1.5 to 2.5 mg/L chloramines present. Testing of a RO process fed with optimized alum-or PACl-coagulated water showed that PACl outperformed alum regardless of pH. Alum coagulation at ambient pH resulted in 184 to 273 µg/L total aluminum passing through the filtration process. Only by lowering the mean influent water pH to 6.7 was the mean soluble aluminum residual (45 µg/L) for alum coagulation reduced to below the 50 µg/L aluminum goal. Regardless of pH, for alum-coagulated waters, the higher aluminum carryover resulted in severe RO membrane fouling within 500 hours of operation. Only when a chelating agent (citric acid) was added to the RO feed was the loss in productivity and selectivity arrested. However, PACl consistently met the 50-µg/L goal for both total and soluble aluminum for all pH levels tested, which resulted in more stable membrane performance over time. Further research on the compatibility of PACl and polyamide membranes in the presence of chloramines is needed as data from this project suggest PACl coagulation may facilitate membrane oxidation.

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“…Some domestic tap-water supplies contain Al(III) in high concentration, either naturally or because aluminum compound (alum) has been added as a flocculent in the purification process. This often results in increased water concentrations of Al(III), but if the treatment process is functioning optimally, the addition of Al(III) may actually result in lower Al values in the treated water than in the raw water [34]. For the preparation of PS the process of deionization and particularly reverse osmosis is much more effective in removing aluminum from the water used for preparation of these very important pharmaceutical formulations.…”

Section: Applicationmentioning

confidence: 99%