Effect of starvation on the nitrification performance of constructed rapid infiltration systems

ABSTRACT

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 (k_AOB) 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 (k_NOB) were 0.159 ± 0.005, 0.152 ± 0.009 and 0.150 ± 0.005 d⁻¹, respectively, implying that k_AOB was higher than k_NOB 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.

KEYWORDS:

• Starvation
• nitrification
• decay
• recovery
• constructed rapid infiltration system

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was financially supported by the National Natural Science Foundation of China [grant number 41502333], the Research Fund for the Doctoral Program of Higher Education of China [grant number 20130184110027], the Science and Technology Project of Sichuan Province-China [grant number 2017GZ0375]; and the Technology Research and Development Project of Chengdu-China [grant number 2015-HM01-00333-SF].