Abstract
Aerobic granular sludge technology has great potential for the treatment of petroleum refinery wastewater. However, strategies to shorten the granulation time and improvement the stability still need to be developed. In this work, biochar was prepared from waste petroleum activated sludge (biochar-WPS) and used in a sequencing batch reactor for the treatment of petroleum refinery wastewater. Biochar-WPS presented the surface area of 229.77 m2/g, pore volume of 0.28 cm3/g, H/C and O/C atomic ratios of 0.42 and 0.21, respectively. The porous structure and a high degree of hydrophilicity were found to facilitate microbial colonization and adhesion as well as particle aggregation. Application of biochar-WPS resulted in the formation of more substantial and stable aerobic granules (~ 66% of granules > 0.46 mm diameter) 15 days earlier compared with the control. The addition of biochar-WPS enhanced the average removal efficiency of chemical organic demand (~ 3%), oil (~ 4%) and total nitrogen (~ 10%) over the control. Increased microbial richness and diversity were observed within the formed granules and had an increased (~ 4%) proportion of denitrifying bacteria. These results indicate that an aerobic granulation mechanism using biochar-WPS is a feasible option for the treatment of petroleum refinery wastewater.
Highlights
Crude oil refining results in the generation of large quantities of wastewater (Petroleum Refinery Wastewater, Petroleum refinery wastewater (PRW)), often with a complex chemical compositions and poor biodegradability (Kaiser 2017)
The physiochemical properties of biochar-WPS were determined in order to evaluate its application potential in facilitating aerobic granulation during treatment of PRW
The scanning electron microscope (SEM) image revealed that the biochars had a rough and irregular surface area and a highly developed porous structure (Fig. 2a)
Summary
Crude oil refining results in the generation of large quantities of wastewater (Petroleum Refinery Wastewater, PRW), often with a complex chemical compositions and poor biodegradability (Kaiser 2017). The most common biological treatment processes utilize activated sludge (anoxic/ oxic process, anaerobic/anoxic/oxic process). These established processes are generally straightforward in operation but limited by low biomass retention, inefficient efficiency and significant space. Aerobic granular sludge (AGS) technology has been widely concerned in the treatment of industrial and municipal wastewaters (Rosman et al 2013; Cetin et al 2018). In comparison with conventional activated sludge, AGS exhibits enhanced settleability, higher biomass retention and improved resistance to shock loading of pollutants (Rosman et al 2013). Similar results were found in the treatment of oil wastewater. Granules were only observed after 110 days operation during the treatment of palm oil mill wastewater (Gobi et al 2011).
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