Development of a Kinetically Engineered Microbial Community for Nitrite Shunt as a B-Stage Process Using Different Aeration Strategies

Nowadays, depleted energy resources, increasing worldwide energy demand and global climate change has been witnessed. In accordance, wastewater treatment plants (WWTPs) have prioritized minimizing its energy use, maximizing resources recovery, while efficiently treating the received wastewater. Shortcut BNR (SBNR) has been proposed as an energy-efficient nutrients removal process towards lowering the energy use of the current WWTPs.

Nonetheless, full-scale implementation of SBNR in mainstream conditions has been hindered by the major challenge of nitrite oxidizing bacteria (NOB out-selection. To address such a key bottleneck, this dissertation proposes, for the first time, a novel kinetic-adaptation based strategy to engineer the microbial community to maintain NOB out-selection at mainstream conditions. The successful implementation of such a strategy and its underlying mechanisms was demonstrated and investigated for more than 400 days. In result, an ammonia removal efficiency of 99.4±0.4% and nitrite accumulation rate of 87.4±0.6% under low DO levels of 0.1–0.2 mg/L was reached.

Afterwards, the potential to employ the developed strategy to perform mainstream nitrite shunt was investigated considering the limited carbon availability in the A-stage effluent, its fractionation, and the applied aeration strategy. At carbon to nitrogen (C:N) ratio as low as 6.0, ammonia, COD and total inorganic nitrogen (TIN) removal efficiencies of 99.2±0.7, 94.0±0.1 and 93.2±1.6% were successfully achieved under continuous low DO aeration strategy. Investigations revealed that maintaining NOB suppression played a key role in achieving high TIN without the need for external carbon addition. Two more aeration strategies were investigated, low DO intermittent aeration and high DO intermittent aeration. At C:N ratio as low as 6, higher TIN removal of 95.8±0.9% was achieved at low DO compared to high DO which achieved a TIN removal of 73.8±1.7%. Therefore, it was concluded that the developed kinetic-adaptation strategy can be utilized along with different aeration strategies with slight advantage to low DO intermittent aeration for its higher TIN removal with limited carbon.

The findings of this dissertation present a novel strategy that blaze a trail to overcome the major bottleneck of NOB out-selection to implement nitrite shunt at mainstream as energy and resources efficient B-stage process.