Context. The performance of activated sludge systems is dependent on the growth kinetics of core microbial community (Saunders et al. 2016). To date, the design of many wastewater treatment plants (WWTPs) in the tropics are adopting default growth kinetic parameters from the temperate climate regions, which may be suboptimal for the WWTPs' operation.
Gap. Past study by Song et al. (2021) suggested that WWTPs in the tropics may harbor a diverse core nitrifying community, such as the presence of Nitrospira at higher relative abundances than WWTPs situated at higher latitudes. Yet, the significance of latitudinal diversity gradient is inconclusive (Wu et al. 2019). Further investigations are warranted to study the core nitrifying community in the tropics.
Aim. This study applied 16S rRNA amplicon sequencing to elucidate the core nitrifying community of activated sludge processes in the tropics.
Methods. We collected wastewater and sludge samples from eight WWTPs in the Greater Kuala Lumpur region, Malaysia, from December 2020 to January 2021. We extracted the DNA from the sludge and sequenced the 16S rRNA amplicons using IonTorrent Personal Genome Machine.
Findings. Most WWTPs removed the total chemical oxygen demand (TCOD) and ammoniacal nitrogen (NH4+-N) adequately (Table 1). Interestingly, WWTPs 3 and 6 operated at low-dissolved-oxygen (low-DO) condition (< 1 mg L-1) achieved low effluent NH4+-N and nitrate nitrogen (NO3--N). The active nitrification in low-DO condition may indicate a diverse core nitrifying community in the tropics. For instance, Nitrospira affiliated with complete ammonia oxidizers was previously reported in low-DO reactors below 1 mg L-1 at warm temperatures (How et al. 2020). The sequencing is ongoing to reveal the unique nitrifying community in the tropics.
Utilization. This study emphasizes that WWTPs in the tropics should adopt nitrifiers' growth parameters specific to their microbial assembly to achieve a more optimal operation.
