Treatment of industrial mineral oil wastewater – effects of coagulant type and dosage

Abstract

The use of coagulants is essential in the diverse disciplines of conventional water and wastewater treatment. This work aimed to select an economic and effective coagulant, to minimize the cost of treatment and the oil droplet content of the water, thus enhancing the efficiency of a local South African oil refinery effluent plant recovering water and oil for reuse by treating the industrial mineral oil wastewater. A standard dissolved air flotation jar test preceded evaluation of four coagulants, viz. aluminum sulfate (Alum), aluminum chloride, ferric sulfate and ferric chloride. Chemical oxygen demand, soap oil and grease, total suspended solids and turbidity were determined as water quality parameters to check coagulant efficiency. Removal of over 70% was achieved for each parameter. The results obtained at pH 5 and coagulant dose of 50 mg/L showed that alum was the best pretreatment coagulant for destabilizing and minimizing oil droplets in water, due to its trivalent cationic nature. It was also economically viable.

Investigating Dissolved Air Flotation Factors for Oil Refinery Wastewater Treatment

“…Figure 3, shows that increasing the coagulant dosage had a significant change in the contaminants removal. This led to good agglomeration and floatability of the oil droplets, and clarification of the treated water (Tetteh et al 2017). The correlation between the coagulant dosage and the contaminant removal were well fitted with R 2 values of 96.91% and 86.67% for SOG and TSS respectively.…”

“…Oil refinery effluent obtained from a local South African oil refinery plant was used for this study. The ORW sample was characterised in accordance with methods by Tetteh et al, (2017)and the American Public Health Association (APHA) standard method of examining wastewater(APHA, 2012). The initial chemistry of the ORW obtained werea pH-7, SOG-1320 mg/L and TSS-1035 mg/L.…”

Effects of a polymeric organic coagulant for industrial mineral oil wastewater treatment using response surface methodology (RSM)

“…The principal focus of addition of coagulant chemicals to physical separation processes is to effectively reduce the workload for downstream treatment. However, this has its own limitations, with high sludge production and a high cost of operational chemical procurement (Hosny et al, 2016;Kweinor Tetteh et al, 2017). The selection of the right type of polymeric coagulant for application depends on its sensitivity and operating conditions, applied in the right proportion to initiate neutralization, stability and mobility of the colloidal oil droplets in order to enhance treatment effectiveness (Hosny et al, 2016).…”

“…There are some drawbacks to conventional wastewater treatment associated with the use of inorganic coagulants (e.g. aluminium and iron salts), such as high volumes of sludge generation, and high pH and dosage requirements (Hosny et al, 2016;Kweinor Tetteh et al, 2017;Yu et al, 2017). Therefore, application of polymeric organic coagulants has become the alternative method to reduce the high sludge volumes generated when utilising inorganic coagulants.…”

“…In general, the main mechanism of coagulation is charge neutralisation and bridging of the oil micro-droplet flocs to produce macro-droplet flocs, which depends on the molecular charge and the charge density. Some of the polymers used for coagulation are of low molecular weight with high cationic charge density, for example, hydrolysed polyaluminium sulphate (PAS), polyacrylamide, melamine formaldehydes, polyamine, polyacrylamides (Zetag-FS/A50) and polydiallydimethyl ammonium chloride (polyDADMAC) (Zouboulis and Avranas, 2000;Bolto and Gregory, 2007;Li et al, 2008;Guan et al, 2014;Oliveira et al, 2014;Kweinor Tetteh et al, 2017). There has recently been extensive and ongoing work looking for an alternative coagulant for chemical treatment that is capable of meeting more stringent treatment standards.…”