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a b s t r a c tThe combination of coagulation/flocculation and ultrafiltration in the process of drinking water treatment was investigated using natural (chitosan) and chemical (aluminum sulfate) coagulants. A 0.1 m singlechannel membrane was applied at pressures of 1 bar and 2 bar, using the principle of crossflow filtration. The final produced water quality was assessed considering the efficiency of removal of color, turbidity, COD, and compounds that absorb UV at 254 nm, among other physico-chemical and microbiological parameters. The coagulation/flocculation with chitosan as coagulant (CFQ) was efficient in removing compounds that add color and turbidity and that absorb UV at 254 nm, with levels that were very similar to those obtained with the coagulation/flocculation process with aluminum sulfate as coagulant (CFS). Performance evaluation of the hybrid systems (CFS-UF and CFQ-UF) showed that the permeate quality was increased when compared with individually operated systems (UF, CFS, and CFQ). The CFQ-UF process caused higher membrane fouling (79% at 2 bar), but yielded a higher stabilized permeate flux, which was approximately twice that achieved with CFS-UF. Based on the results, one can say that chitosan has a potential application as natural coagulant in CF-UF hybrid processes for treating drinking water with relatively high turbidity.

Methylene blue is a cationic dye used for dyeing cotton, wool, and silk. This dye can cause impacts when reaching water resources due to the reduction of sunlight infiltration, besides the health problems if ingested. Therefore, the complete removal of this contaminant in industrial effluents is indispensable. Currently, soybean hulls residues are used in animal feed supplementation; however, since soybean oil production is large, expressive quantities is discarded in landfills. Thus, the present study aim is to evaluate the adsorption capacity of methylene blue onto soybean hulls as an alternative use of this agroindustrial residue. The material was characterized through morphological and chemical analysis which showed porosity, heterogeneity, and functional groups that favor the adsorption. Due to the mainly negative charge of the surface, the pH did not affect the cationic dye uptake, enabling a wide pH range. After the adsorption studies, the best experimental conditions were at temperatures of 298 K, mass of 0.025 g, and contact time of 180 min, resulting in the maximum adsorption capacity of 169.90 mg g−1. When compared with other low‐cost biosorbent and activated carbons, it can be perceived a potential applicability of soybean hulls in wastewater treatment as an alternative use.

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