Green chemistry for treatment of liquid discharges from a dyeing industry: bio coagulation and flocculation

Abstract

Textile industry is among the highly polluting industries in water effluent. It consumes large quantities of water and chemicals compounds. These releases can have varying characteristics regarding their volumes and pollutants concentrations. Therefore, adverse effects can be observed as consequence on environment and biodiversity. According to the environmental protection regulations in Morocco, the treatment of this water before discharge is compulsorily to avoid pollution of surface and ground water.

The aim of our study is the treatment of these effluents by a physicochemical process using coagulation / flocculation.  Two coagulants of different type and purity are used. The first one “aluminum sulfate” is a pure coagulants used on industrial scale. The second “alum stone” is excerpt from the nature of Moroccan desert. Beside, two flocculants are compared, a natural extract from cactus and a polymer synthesized (polyacrylamide).

The comparative study between a pure coagulant and a biocoagulant, with the two flocculants, showed a very good absorbency rate of reduction (ABS), turbidity (T), chemical oxygen demand (DCO), dry matter (DM) and chemical elements (sodium, lithium, nitrogen, phosphorus, boron, and silicon). By the jar test treatment process, the optimal dose of coagulants and flocculants to use in the neutral pH treatment was identified. The optimal dose used gives 85% of abatement efficiency absorbance, 90 % for turbidity and 80% for the chemical oxygen demand. Moreover, the dry matter content is over 25% and over 90% for some chemical elements.