Oil removal from industrial wastewater using flotation in a mechanically agitated flotation cell

Abstract

This paper investigates the flotation of oil from wastewater in a laboratory-scale mechanically agitated flotation cell. Mechanical flotation cells are used commercially for oil flotation but, to the authors' best knowledge, there are no studies on their flotation performance in the literature. Some researchers have suggested that mechanically agitated systems are inappropriate for oil flotation as the high shear rates may break up the fragile organic flocs. The chemical pretreatment operating factors of pH and type of acid adjustor, coagulant type and dosage and flocculant dosage were firstly investigated. When using H 3 PO 4 for pH adjustment, a preferential pH of 5.5 was identified. When using H 2 SO 4 , a pH of 5.5 was not optimal. The acid type was subsequently the determining factor. Al 2 (SO 4 ) 3 was a more effective coagulating agent than lime, based on coagulant and flocculant dosages required (0.5mg/ℓ when using Al 2 (SO 4 ) 3 and 1.5 mg/ℓ when using lime). The flotation cell operating factors of aeration rate and impeller speed were subsequently investigated. Oil removal rates were found to increase at higher levels of aeration and agitation. This suggests that oil flotation is both possible and beneficial in high-shear turbulent environments. However, residual oil concentrations could not be reduced to below 50 to 100 mg/ℓ which is higher than the desired target of 50 mg/ℓ.

The Effect of Temperature and Impeller Speed on Mechanically Induced Gas Flotation (IGF) Performance in Separation of Oil from Oilfield-Produced Water

“…In IGF, gas bubbles are mechanically generated or hydraulically induced in the oily wastewater. The size of the gas bubbles in DGF range from 30 to 100 m. In IGF the bubbles will be larger and usually range from 500 to 2,000 m (Bradley, 1990;Casaday, 1993;Berne and Cordonnier, 1995;Zlokarnik, 1998;Jameson, 1999;Rubio et al, 2002;Welz et al, 2007).…”

Bio-treatment and water reuse as feasible treatment approaches for improving wastewater management during flotation of copper ores

“…In this field, flotation could be practiced like conventional or as dissolved air flotation (DAF) mode (Otadi et al 2011). Welz et al (2007) have investigated conventional flotation at a laboratory scale for removal of oils from wastewaters using aluminium sulphate as coagulant at pH 5.5. After the treatment, oil concentration has been found slightly above the targeted level for industrial wastewaters (50 mg/L) safe release to the environment.…”

Application of Response Surface Methodology (Rsm) - Reduction of Industrial Wastewater Chemical Oxygen Demand

“…About 50-60% of the oil recovered can be used as base oil or lubricants (Tetteh et al, 2017). The conventional treatment of industrial wastewater involves processes such as membrane technology, chemical and electrochemical oxidation, filtration, adsorption, and biological and various floatation methods (Welz et al, 2007;Diya'uddeen et al, 2011). However, there are certain limitations of each technique in industrial oil wastewater treatment.…”

“…For this purpose, a combination of different operational units is required to enhance treatment efficiency (Welz et al, 2007;Maksimov et al, 2015). Similarly, the available crude quality and demand for petroleum products, as well as strict environmental regulations, affect the processing, operation, and configuration of the refinery and wastewater treatment plants (Vasseghian, 2016).…”