Pilot Study of Oxic–Anoxic Process under Low Dissolved Oxygen for Nitrogen Removal from Low COD/N Tropical Wastewater

Abstract

Conventionally, nitrification in biological nitrogen removal (BNR) requires high dissolved oxygen (DO) concentrations (>2 mg L−1), making the process energy intensive. Recent studies have shown that efficient ammonium removal and energy reduction can be realized by operating the nitrification at low DO concentrations (<1 mg L−1). In this study, the low-DO oxic anoxic (low-DO OA) process was operated in a pilot-scale sequencing batch reactor (SBR) over 218 days to evaluate the feasibility of nitrogen removal from low chemical oxygen demand-to-nitrogen ratio (COD/N) tropical municipal wastewater. The results revealed that the low-DO OA process attained high removal efficiency for ammonium (97%) and total nitrogen (TN) (80%) under an average DO concentration of 0.6 mg L−1. The effective TN removal efficiency is attributed to the occurrence of simultaneous nitrification–denitrification (SND) under low DO conditions. Further batch tests revealed that slowly biodegradable COD (sbCOD) in tropical wastewater can support denitrification in the post-anoxic phase, resulting in a high TN removal rate. Compared with high DO concentrations (2 mg L−1), low DO conditions achieved 10% higher TN removal efficiency, with similar ammonium and COD removal efficiency. This study is crucial in promoting the energy efficiency and sustainability of wastewater treatment plants treating low COD/N wastewater.

Wastewater Treatment System Optimization for Sustainable Operation of the SHARON–Anammox Process under Varying Carbon/Nitrogen Loadings

“…The influent is described for three conditions of influent variation: low C/N ratio (below 1), intermediate C/N ratio (equal to 1), and high C/N ratio (above 1). The ratio value was defined considering previous studies conditions for WWTPs [1,5,25,26]. The low-strength stream data from [28] and high-strength stream data adapted from [4] were used in this study.…”

“…Water 2023, 15, 4015 2 of 20 Novel technologies have been studied over the years to overcome the effects of nitrogen overloads, such as the configurations of oxic-anoxic treatment process [5], the combined nitrification/denitrification and deammonification process, complete autotrophic nitrogen removal over nitrite (CANON) [6], single reactor system for high-activity ammonia removal over nitrite (SHARON), and the anaerobic ammonium oxidation (Anammox) [7][8][9][10]. The combined SHARON-Anammox process has been reported to present a substantial advantage in nitrogen removal, reducing operational costs and benefiting resource recovery [4,7,11].…”

“…Few studies have presented the effects of varying effluent from the anaerobic digester, which can present a different C/N ratio as the influent to the partial nitritation process [1] and an inappropriate NO 2 /NH 4 ratio as the influent to the Anammox process [24]. An optimal and low C/N ratio, for nitrogen removal, has the potential to completely convert ammonium to nitrogen gas (N 2 ) in ammonium-rich wastewater [1,5,25,26]. The NO 2 /NH 4 ratio is an underlying condition for the correct operation of the Anammox process.…”

The Inhibition of Engineered Nano-ZnO in the Biological Nitrogen Removal Process: A Review

“…Anammox technology, which has garnered significant attention in recent years, employs anammox bacteria to transform ammonium nitrogen and nitrite nitrogen into nitrogen under anaerobic conditions [18]. However, these nitrogen-removal bacteria are all sensitive to environmental factors such as dissolved oxygen (DO) [19][20][21], the C/N ratio [22,23], temperature [24][25][26], pH [27,28], and so on. Numerous studies have confirmed the negative impact of nano-ZnO on the biological nitrogen removal (BNR) process in wastewater due to its antibacterial properties [29][30][31].…”