Screening of physicochemical treatment processes for reducing toxicity of hair care products wastewaters

Toxicity reduction in wastewaters from small hair care products manufacturing companies using coagulation/flocculation/sedimentation or flotation, membrane separation and powdered activated charcoal adsorption was evaluated. Raw wastewater composition varied widely within and especially between companies, but all exhibited high acute toxicity to Daphnia similis (EC(I)50; 48 h < 0.02-0.33%). Coagulation with aluminum sulfate and polyaluminum chloride aided by cationic or anionic polymers, as well as filtration on ultra (UF) and nanofiltration (NF) membranes efficiently removed turbidity (>99%) and oil and grease (>99%) and all treated samples exhibited similar dissolved organic matter contents. However, elimination of acute toxicity was only achieved after UF on submerged hollow fiber membrane, while other membrane modules (tubular UF and NF) produced filtrates with residual toxicities equal to or higher than the wastewater samples treated by coagulation processes. Adsorption removed up to 90% of the soluble COD remaining after coagulation or membrane processes, but did not eliminate acute toxicity, possibly because of the presence of activated charcoal or substances leached from it in the treated samples. The results indicate the need for further studies to develop treatment strategies that can guarantee non-toxic effluents at costs compatible with those of the simple manufacturing processes used at small-scale cosmetics manufacturing plants.