To optimize sequencing batch reactor (SBR) and monitor aerobic granular sludge (AGS) development for domestic wastewater treatment

Abstract

The aim of this study is to determine design and process parameters of the aerobic granular sludge system to treat actual domestic wastewater. The aerobic granular sludge was developed in a 2.5 L lab-scale bioreactor which uses the operational system based on the sequencing batch reactor (SBR). The bioreactor was fed with influent from local sewerage treatment plant and seeding with fresh inoculums (seed sludge) from activated sludge tank. The operation of the reactor was based on the SBR system with a complete cycle time of 4 hours and specifically designed to be operated for 24 hours continuously. Two sets of experiments were carried out in a single-walled cylindrical glass column bioreactor. These two sets of experiments are referred to as SBRA and SBRB with different time setting. SBR systems have four stages which is feeding, aeration, settling and decant. It was carried out in sequence: (1) 'feeding with aeration' for SBRA (feed and aerate pumps operated simultaneously); 'feeding without aeration' for SBRB (feed and aerate pumps operated separately), (2) 'aeration only', (3) 'settling', and (4) 'discharge'. Removal performance of the SBR such as BOD, COD, AMN, NO3−, TSS, VSS and TP along with the other several parameters of the SBR such as DO, SOUR, ORP and settling profile are monitored daily. Starting from day 1 until day 26 the average DO values were around 1 - 2 mg/l but after 1.5 hours the DO values increased drastically. It shows that the microbe did not consumed air during the process. Day 13 onwards SOUR profiles show that the microbe consumed oxygen slowly. These results suggest that low amount of readily oxidized organic available in the bioreactor. The SVI reading shows good settling performance which is less than 100 mL/g. The settling profile shows the sludge has been further compact day by day. From the finding, it is suggested that it would be better for feed and aerate pumps to be operated separately.