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

Abstract

Three constructed rapid infiltration (CRI) systems (C, C and C) 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) for C, C and C were 0.172 ± 0.008, 0.132 ± 0.009 and 0.128 ± 0.009 d, respectively, and those of NOB (k) were 0.159 ± 0.005, 0.152 ± 0.009 and 0.150 ± 0.005 d, respectively, implying that k was higher than k 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 C, C and C 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 C and C 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.

Study on the effect of corn cob biochar on the performance of constructed rapid infiltration systems

“…The CRI system was a typical push flow bioreactor. In the process of infiltration from top to bottom, pollutants could be adsorbed or trapped on the filter particles, and then be decomposed or transformed by microorganism in the biofilm that attached to the surface of filter particles, so as to realize the purification of wastewater [6].…”