Application of Adsorption and Ultrafiltration Processes for the Pre-treatment of Several Industrial Wastewater Streams

In this work ultrafiltration (UF) was coupled with suitable minerals and dried activated sludge for the pre-treatment of several industrial wastewater streams. The aim was to decrease heavy metal concentrations to low levels so that wastewater can be safely discharged into municipal sewers or biological wastewater treatment can take place without biomass inhibition problems. Industrial wastewater originating from metal plating, chemical and textile industries was employed. The experiments were conducted in a reactor where the UF membrane module was immersed. UF reduced the amount of heavy metals, but the performance was variable with removal efficiencies ranging from 20 to 99.7 %, depending on the metal type and on the wastewater initial characteristics. The prevailing wastewater characteristics were the pH, the presence of certain anions, the suspended solids concentration and the presence of competing cations. The addition of activated sludge and/or minerals could further increase heavy metal removal through the process of sorption. UF assisted by minerals could achieve variable colour and COD removal ranging from 22 to 94 % and 58 to > 99.9 % respectively. Minerals resulted in membrane fouling mitigation, while sludge adversely impacted on fouling.