Abstract
Integration of sonication (US) with electrokinetic (EK) oxidation was studied for the treatment of a saline oily wastewater, as well as the effect of operating parameters, including pH, voltage, electrode distance (ED), sonication power, and reaction time on COD removal. A COD removal of 98 % was observed for the sono-electrokinetic (SEK) process with an applied voltage of 2.5 V, US power of 300 W, initial COD concentration of 3850 mg L–1, and reaction time of 9 h. The efficiency of SEK over sonication alone and EK oxidation alone was also confirmed with a higher pseudo-first-order reaction rate constant of 0.43 h–1, compared to values of 0.13 and 0.01 for alternative processes. In addition, the biodegradability of effluent was improved based on average oxidation state (AOS) and carbon oxidation state (COS) analysis. Oxygen consumption rate inhibition, dehydrogenase activity inhibition, and growth rate inhibition methods demonstrated the low toxicity of effluent (12–15 %) compared to influent. The current work indicated that SEK is a reliable and efficient technology for the treatment of saline oily wastewaters containing recalcitrant aromatic organics.
Highlights
Petroleum and fuel transportation in ports and the distribution of these hydrocarbon liquids via central terminals into cities, as well as storage of petroleum and its derivate in large tanks, produces a huge amount of oily and saline wastewater.[1]
In acidic conditions, due to existing chloride salts of sodium, the chloride ion in the wastewater with high total dissolved solids (TDS) is converted to chlorine which is further converted to hypochlorous acid in the aqueous solution, and the formed hypochlorite ions act as the main oxidizing agents in the pollutant degradation (Eqs. 5–7):[18]
An EK-based process enhanced by sonication was investigated for the treatment of a real saline oily wastewater containing different hydrocarbons with low biodegradability
Summary
Petroleum and fuel transportation in ports and the distribution of these hydrocarbon liquids via central terminals into cities, as well as storage of petroleum and its derivate in large tanks, produces a huge amount of oily and saline wastewater.[1] The presence of aromatic and aliphatic hydrocarbons, heavy metals, and high concentrations of minerals represent serious environmental and health risks, which necessitate the application of suitable technologies for the treatment of these flows before discharge into water bodies.[2]. Research has proved the carcinogenic and mutagenic effects of oily wastewater. Severe adverse effects on water quality, aquatic plants, birds, and. B. Darabi et al, Integrated Treatment of Saline Oily Wastewater... Ta b l e 1 – Characteristics of raw saline oily wastewater Parameter Mean STDEV Max Min COD (mg L–1).
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