Impact of aerobic famine and feast condition on extracellular polymeric substance production in high-rate contact stabilization systems

- Switching from aerobic famine to aerobic feast condition increases EPS response.
- Carbon harvesting efficiency increased with increased EPS response in contactor.
- F/M ratio play vital role to increase EPS in contactor for high-strength wastewater.
- Optimum starvation time is required for EPS response at low-strength wastewater system.
- Higher SRT sludge requires higher starvation time and vice versa for short SRT sludge.

The high-rate contact stabilization (CS) system is gaining back its popularity for recovering carbon from wastewater. This study investigated the role of extracellular polymeric substance (EPS) on bioflocculation improvement and carbon capture from municipal wastewater in pilot-scale and bench-scale CS systems. Results showed that a rapid increase in EPS was established from the famine stabilizer to the aerobic feast contactor, and this mechanism was responsible for improved bioflocculation, carbon capture efficiency (linear function) and effluent quality in CS systems. In contrast, these improvements were not observed under anaerobic contactor conditions, thus favoring application of aerobic contactor. The EPS production was driven by the high organic loading rate for high-strength wastewater and minimum stabilization time required to induce starvation condition for low-strength wastewater systems. Mechanistic understanding of the feast-famine regimes in CS system through this study, will aid future design and operation of CS systems for enhanced carbon recovery.

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