Evaluating Pre- and Post-Coagulation Configuration of Dissolved Air Flotation Using Response Surface Methodology

Emmanuel Kweinor Tetteh,Sudesh Rathilal

doi:10.3390/pr8040383

Abstract

The effects of coagulation-dissolved air flotation (DAF) process configuration was studied on oil refinery wastewater. The configuration was done in two ways: acid-coagulation-DAF (pre-treatment) and acid-DAF-coagulation (post-treatment). Two different cationic and polymeric organic coagulants were employed in this study to compare their treatability performance with the two aforementioned configurations. All the coagulants applied before the DAF were found to be effective, with over 85% more contaminant removal efficiency than their post-treatment. Alum, being the most cost-effective coagulant, was then employed with response surface methodology (RSM) to obtain the optimum conditions. These include a coagulant dosage of 100 mg/L, air saturator pressure of 375 kPa and air–water ratio of 10% vol/vol corresponding to a desirability of 92% for the removal of oily pollutants from a local South Africa oil refinery’s wastewater. With the response quadratic models that were developed, the optimum conditions were tested experimentally, which were consistent with the models predicted results at a 95% confidence level.

Highlights

Energy demand is escalating with the production of petrochemical products, which ends up generating high amounts of wastewater due to its complex process
It was deduced that the pre-treatment was more the dissolved air flotation (DAF) were to be more effective for the removal of the residual contaminants under study
This study presents coagulation before DAF as the better configuration option compared to coagulation after DAF

Summary

Introduction

Energy demand is escalating with the production of petrochemical products, which ends up generating high amounts of wastewater due to its complex process This creates a global problem of contaminated oily wastewater which needs to be decontaminated [1]. Coagulation and dissolved air flotation (CDAF) systems have been the most widely used physio-chemical processes in the water and wastewater treatment settings [2,3] Of these processes, the DAF can be operated alone or combined with other processes at different stages of the WWTPs for primary, secondary or tertiary treatment purposes [4]. Turbidity, total suspended solids (TSS), chemical oxygen demand (COD), SOG and other organic compounds’ derivatives [7,9,10] These contaminants are not just detrimental to the environment, and to aquatic life and human health [8]

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Methods

Discussion

Conclusion