Flocculants in produced water

Abstract

Produced water as the major by-product of oil and gas explorations contains high amounts of oil that are not safe for disposal into aquatic environment. With the increasing need for oil and gas across the globe, one of the major problems encountered is developing effective measures to properly treat and meet the regulation for reuse or disposal of produced water. Flocculation is an essential process in the treatment of produced water and involves the addition of flocculants during treatments to enhance effective separation of oil drops from water. Flocculation is however affected by the molecular weight of the flocculants, pH and salinity of the water. This work studied the effects of these factors on aggregation of flocculants in water.

Different concentrations of four flocculants of Polydiallyldimethylammonium chloride (PolyDADMAC) F100k, F200k, F350k and F500k having different molecular weights were prepared in varying pH and salt concentrations and tested. The aggregate size distribution, Polydispersity Index (PDI) and Zeta potential (ZP) were characterized with a zeta sizer. Adsorption to Silica surfaces using Quartz Crystal Microbalance with Dissipation (QCM-D) was also determined. It was found that the aggregate size distribution, PDI and ZP varied from one flocculant to another at different concentrations, indicating that the choice of flocculants for produced water treatment depends specifically on the water pH and salinity in addition to the flocculant’s molecular weight. More mass was adsorbed at higher salinities and pH values and also depended on the type and concentration of the flocculant.