Influence of the apparent molecular size of aquatic humic substances on colour removal by coagulation and filtration

• Published in: Environmental technology 2011-11, Vol.32 (15), p.1767-1777
• Main Authors: Rigobello, Eliane Sloboda, Dantas, Angela Di Bernardo, Di Bernardo, Luiz, Vieira, Eny Maria
• Format: Article
• Language: English
• Subjects: Alum Compounds - chemistry; Aluminium sulfate; aluminium sulphate; apparent molecular size; Applied sciences; aquatic humic substances; Benzopyrans - analysis; Chemical engineering; Chlorides - chemistry; Coagulation; Color; Color removal; Colour; colour removal; Exact sciences and technology; Ferric chloride; Ferric Compounds - chemistry; Filtration; Humic Substances - analysis; Liquid-liquid and fluid-solid mechanical separations; Molecular Weight; Pollution; Sand; Spectrophotometry, Ultraviolet; Waste Disposal, Fluid - methods; Water treatment
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330.2011.555423

This study aims to verify the influence of the apparent molecular size of aquatic humic substances (AHSs) on the effectiveness of coagulation with aluminium sulphate and ferric chloride. Coagulation-filtration tests using the jar test and bench-scale sand filters were carried out with water samples having a true colour of approximately 100 Hazen units and prepared with AHSs of different molecular sizes. Stability diagrams are presented showing regions of≥90% and≥95% apparent colour removal delineated for each water sample using plots of total metal ion concentration (Al 3+ and Fe 3+ ) versus coagulation pH. To achieve the same degree of colour removal, the water samples with smaller apparent molecular sizes and a higher percentage of fulvic acids required higher dosages of both aluminium sulphate and ferric chloride.