Technological Conditions for the Coagulation of Wastewater from Cosmetic Industry

Coagulation is often used for the pre-treatment of industry wastewater, with effectiveness strictly dependent on technological conditions. This study aimed to determine what technological parameters of coagulation of cosmetic industry wastewater provided the highest efficiency of clarification. The dosages of reagents, the order of dosing, as well as the one- and two-stage processes were investigated. Samples of raw wastewater were collected from average daily effluent from a cosmetics manufacturing plant. Liquid coagulant PIX 111 (FeCl3) and NaOH as a pH-adjusting agent were used. Jar-test experiments were carried out to determine the optimum conditions for turbidity and total organic carbon (TOC) removal. The efficiency of clarification was high (90–99%) across a wide range of pH values (6–9) and coagulant doses (0.5–1.25 mL/L). What is important, the coagulant dose of 0.56 mL/L provided 97.6 % clarification efficiency without the addition of the alkali. The minimal stoichiometric excess of alkalinity for effective coagulation was 0.5 mmol/L. In all samples, the removal efficiency for TOC was lower than for turbidity, because some of the organic carbon forms were non-coagulating dissolved compounds. The wastewater from tonic and fluid production was very susceptible to coagulation. The addition of the coagulant before the alkali resulted in better wastewater treatment efficiency than the reverse order. Single-stage process with optimal doses of the reagents allowed to clarify wastewater to a level of 10 NTU. On the other hand, the two-stage process brought the turbidity down to 1 NTU level