Advanced removal of organics and nitrogen in upgraded anaerobic-aerobic slaughterhouse wastewater treatment process.

Slaughterhouse wastewater (SWW) is one of the most harmful agriculture and food industrial wastewaters because of rich impurities, particularly organic matter, suspended solids, oil, grease, and nitrogen (N) nutrients. This study investigated organics and N nutrients removal performance in the developed upgraded anaerobic-aerobic slaughterhouse wastewater treatment process (U-AASWWTP). The supernatant reflux position, ratio and dissolved oxygen (DO) in the aerobic units play key roles, and the optimized solutions were 300% reflux to the second compartment at DO of 4.64-4.90 mg/L. Under such conditions, chemical oxygen demand (COD) removal efficiency only decreased from 98.14% to 95.94% when the loading rates increased from 500 to 2,000 g·COD/(m³·d) gradually, whereas total nitrogen (TN) showed a different removal trend. Effluent TN was the lowest at 1,500 g·COD/(m³·d) and the corresponding effluent COD, TN and NH₄⁺-N all satisfied with the Chinese upcoming discharge standard. Therefore, U-AASWWTP can effectively remove COD and N from SWW and would become the main direction of traditional treatment processes upgrading to addressing the issue of upcoming stricter effluent standard. This study holds significant importance in ensuring the sustainable development of slaughtering industry in China. Additionally, this study enhances the understanding of the synergy relationship between anaerobic digestion and Anammox microorganisms, thereby promoting the intelligent application in SWW treatment processes. [ABSTRACT FROM AUTHOR]