Effects of influent DO/COD ratio on the performance of an anaerobic fluidized bed reactor fed low-strength synthetic wastewater

► Influent dissolved oxygen (DO) affects the anaerobic treatment of dilute wastewaters. ► An adverse effect was dependent upon the influent DO/COD ratio. ► A rapid growth of zoogloeal-like organisms resulted at high influent DO/COD ratio. ► The influent DO increased the time for recovery of methanogenic activity. ► Control of the influent DO/COD ratio is important.