Removal of organic compounds in the pretreatment of a brackish industrial waste stream

The paper discusses the treatment of brackish wastewater (1,000 mg Cl-/L), which also contained a high concentration of organic compounds (1,576 mg O2/L as COD) and was characterized by high toxicity. Wastewater treatment was carried out in the following systems: microfiltration (MF), coagulation, coagulation/ultrafiltration (UF), coagulation/UF/nanofiltration (NF). Flat polymer membranes with PES and polyamide-TFC were used in the tests. The removal of impurities was as follows: The pre-treatment carried out by MF or by coagulation was to protect the next stages of treatment, i.e. UF and NF. In both cases, similar effectiveness were obtained, respectively: 33.3% (TOC), 33.9% (COD), 66.9% (colour) and 26.6% (TOC), 21.7% (COD), 41.4% (BOD), 64.2% (colour). Due to the decrease in flux during MF, coagulation was used as the first stage of brackish waste-water treatment. This process was carried out with the use of aluminum compounds at a dose of 1.5 g/L and the following parameters: rapid mixing (2 min), slow mixing (20 min), and sedimenta-tion (20 min). The wastewater pre-treated in this way was treated in UF followed by NF, achieving high efficiency: 93.7% (TOC), 83.7% (COD), 98.3% (BOD), 99.24% (colour), and 79.8% (IC).