Effect of starvation on the nitrification performance of constructed rapid infiltration systems
2019
Chen, Jiao | Lü, Yixin | Zheng, Run | Zhang, Jianqiang
Three constructed rapid infiltration (CRI) systems (C¹, C² and C³) were operated under 7, 14 and 21 days of continuous starvation, respectively. The effect of starvation on the ammonia removal efficiency (ARE), nitrite accumulation rate (NAR), bioactivity of nitrifiers and content of extracellular polymeric substances (EPS) was investigated. The results showed that the activity of nitrite-oxidizing bacteria (NOB) was higher than that of ammonia-oxidizing bacteria (AOB) in stabilization periods, leading to a complete nitrification in CRI systems. During starvation periods, the activity decay rates of AOB (kAOB) for C¹, C² and C³ were 0.172 ± 0.008, 0.132 ± 0.009 and 0.128 ± 0.009 d⁻¹, respectively, and those of NOB (kNOB) were 0.159 ± 0.005, 0.152 ± 0.009 and 0.150 ± 0.005 d⁻¹, respectively, implying that kAOB was higher than kNOB in a 7-day starvation period, while showing a contrasting result in a 14- or 21-day starvation period. When resuming wastewater supply, AOB activity as well as the ARE in C¹, C² and C³ gradually restored to their initial levels within 6, 10 and 23 days, respectively. However, NOB activity was unable to fully restore after a 14- or 21-day starvation period, causing the final NAR of C² and C³ to remain at 25% and 60%, respectively. Furthermore, EPS could be used as the source of carbon and energy for hungry microorganisms to guarantee the metabolic activity of living cells in a starvation environment. These findings could provide a theoretical foundation for operational optimization of CRI systems under starvation conditions.
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