Abstract
A system consisting of six SBR units was operated in parallel for three phases to investigate the impacts of salinity shock and anaerobic and aerobic starvation on the activated sludge process stability and effects of various recovery stimulation methods on the subsequent recovery period. Different recovery strategies were applied in each SBR unit, including natural recovery, adding bio-accelerators, a stepwise increase feed strategy, a stepwise strategy coupled with bio-accelerators dosing, extended aeration time, and extended aeration time coupled with bio-accelerators dosing. It was concluded that the combination of stepwise strategy and dosing bio-accelerators showed the most efficiency in boosting system recovery after being subjected to NaCl shock and starvation. The boosting effect of the stepwise strategy alone was slightly better in recovery after NaCl shock. Furthermore, extending the aeration rate could bring more positive effects when resuscitating the system after long-term anaerobic starvation. For the unit that only received dosing of bio-accelerators during the recovery period, it could be concluded that there was a specific time requirement for the bio-accelerators to take effect significantly, as the impact of bio-accelerators on the beginning days of recovery periods was very slight. In contrast, adjusting operational regimes such as stepwise increased feed volume or extending aeration time could significantly boost the SBRs from the first recovery days. Hence, highly effective recovery efficiency could be achieved by coupling dosing bio-accelerators with other operational adjustment methods, especially stepwise strategies.
Highlights
In water and wastewater treatment, there are strict regulations imposed on the quality of effluent water applied by most regions in the world
The average SOURAOB and SOURNOB in the sequencing batch reactor (SBR) dropped to 0.0187 ± 0.0016 and
There were five different recovery stimulation methods, including dosing bio-accelerators, stepwise increase feed flowrate, stepwise increase feed flowrate coupled with dosing bio-accelerators, extended aeration time, and extended aeration time coupled with dosing bio-accelerators, proposed to boost the recovery process of the SBRs system
Summary
In water and wastewater treatment, there are strict regulations imposed on the quality of effluent water applied by most regions in the world. High stability is required in water/wastewater treatment units to maintain the overall process’s high treatment efficiency. In some developed countries such as Australia or America, implementing the wastewater treatment process for recycling requires validation or verification to test whether the technology can achieve the required water quality [1]. The US EPA requires records of upset condition occurrences in its verification report protocol [2]. Hazardous events such as sudden changes in inlet water composition, extreme weather events, operational error, and mechanical malfunctions can negatively affect the overall treatment efficiency of the technology [1], posing a potential risk of
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