Critical design factors for polyvinyl alcohol hydrogel entrapping ammonia-oxidizing bacteria: biomass loading, distribution of dissolved oxygen, and bacterial liability

In order to achieve an appropriate effluent ratio of ammonium and nitrite as an influent of the anaerobic ammonium oxidation process, the optimum conditions for the partial nitritation in a continuous stirred tank reactor (CSTR) were investigated using real reject water. Hydraulic retention time (HRT) and influent alkalinity (HCO3-)/NH4+-N ratio were major factors that greatly influenced the partial nitritation. As a result of continuous operation, ammonium conversion efficiency (ACE) and effluent nitrite to ammonium ratio (NAR) could be achieved at the HRT of 19 h corresponding to 0.71 kg/m3/d of nitrogen loading rate (NLR). Thereafter, the influent HCO3-/NH4+-N ratio was adjusted from 0.5 to 2, and as a result, the optimum partial nitritation efficiency was maintained when the influent HCO3-/NH4+-N ratio was one. The suitability of the determined operating conditions was verified in a CSTR over 30 d of operation time.

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“…This is a mechanism of selective inhibition of NOB [27]. This has already been verified in many studies [28,29].…”

Section: Adaptation Of Bacteria To New Operation Conditionssupporting

confidence: 65%

Effect of nitrogen loading rate and alkalinity on partial nitritation in a continuous stirred tank reactor

Choi

Yun

et al. 2021

Environmental Engineering Research

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“…In the event of hydrogel surface clogging, the hindered in ltration of substrates into the hydrogel's interior precludes any reactions from occurring. Therefore, it is crucial to increase the speci c area per volume, and the simplest and most effective way to achieve this objective is by reducing the thickness of the hydrogel 13 . To address this issue, reducing the size of the hydrogel can increase the external surface area, thereby enhancing the probability of contact between the substrate and the carrier per unit volume 14 .…”

Section: Introductionmentioning

confidence: 99%

Thickness of hydrogel for nitrifying biomass entrapment determines the free ammonia susceptibility differently in batch and continuous modes

Song

Jeong

et al. 2023

Preprint

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Hydrogels immobilizing nitrifying bacteria with different thicknesses of 0.55 and 1.13 cm (HG-0.55 and HG-1.13, respectively) were produced. It was recognized that the thickness of media is a crucial process parameter that affects both the stability and efficiency of wastewater treatment. Batch mode experiments were conducted to quantify specific oxygen uptake rate (SOUR) values at various total ammonium nitrogen (TAN) concentrations and pH levels. In the batch test, HG-0.55 exhibited 2.4 times higher nitrifying activity than HG-1.13, with corresponding SOUR values of 0.00768 and 0.00317 mg-O2/L·mL-PVA·min, respectively. However, HG-0.55 was more susceptible to free ammonia (FA) toxicity than HG-1.13, resulting in a reduction of 80% and 50% in SOUR values for HG-0.55 and − 1.13, respectively, upon increasing the FA concentration from 15.73 to 118.12 mg-FA/L. Continuous mode experiments were conducted to assess the partial nitritation (PN) strategy's efficiency in practical applications, where continuous wastewater inflow maintains low FA toxicity through high ammonia-oxidizing rates. With step-wise TAN concentration increases, HG-0.55 experienced a gentler increase in FA concentration compared to HG-1.13. At a nitrogen loading rate of 0.78–0.95 kg-N/m3·day, the FA increase rate for HG-0.55 was 0.0179 kg-FA/m3·day, while that of HG-1.13 was 0.0516 kg-FA/m3·day. Despite its sensitivity to FA toxicity, the thinner HG-0.55 can enhance PN performance owing to its higher ammonia-oxidizing activity. FA susceptibility depends on hydrogel thickness in batch and continuous modes, with continuous mode favoring thin gel with high ammonia-oxidizing activity due to the decrease in FA accumulation.

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Thickness of hydrogel for nitrifying biomass entrapment determines the free ammonia susceptibility differently in batch and continuous modes

Song

Jeong

et al. 2023

Sci Rep

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Hydrogels immobilizing nitrifying bacteria with different thicknesses of 0.55 and 1.13 cm (HG-0.55 and HG-1.13, respectively) were produced. It was recognized that the thickness of media is a crucial parameter that affects both the stability and efficiency of wastewater treatment. Batch mode experiments were conducted to quantify specific oxygen uptake rate (SOUR) values at various total ammonium nitrogen (TAN) concentrations and pH levels. In the batch test, HG-0.55 exhibited 2.4 times higher nitrifying activity than HG-1.13, with corresponding SOUR values of 0.00768 and 0.00317 mg-O2/L mL-PVA min, respectively. However, HG-0.55 was more susceptible to free ammonia (FA) toxicity than HG-1.13, resulting in a reduction of 80% and 50% in SOUR values for HG-0.55 and -1.13, respectively, upon increasing the FA concentration from 15.73 to 118.12 mg-FA/L. Continuous mode experiments were conducted to assess the partial nitritation (PN) efficiency in practical applications, where continuous wastewater inflow maintains low FA toxicity through high ammonia-oxidizing rates. With step-wise TAN concentration increases, HG-0.55 experienced a gentler increase in FA concentration compared to HG-1.13. At a nitrogen loading rate of 0.78–0.95 kg-N/m3 day, the FA increase rate for HG-0.55 was 0.0179 kg-FA/m3 day, while that of HG-1.13 was 0.0516 kg-FA/m3 day. In the batch mode, where wastewater is introduced all at once, the high accumulation of FA posed a disadvantage for the FA-susceptible HG-0.55, which made it unsuitable for application. However, in the continuous mode, the thinner HG-0.55, with its larger surface area and high ammonia oxidation activity, proved to be suitable and demonstrated its effectiveness. This study provides valuable insights and a framework for the utilization strategy of immobilized gels in addressing the toxic effects of FA in practical processes.

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Critical design factors for polyvinyl alcohol hydrogel entrapping ammonia-oxidizing bacteria: biomass loading, distribution of dissolved oxygen, and bacterial liability

Cited by 5 publications

References 45 publications

Effect of nitrogen loading rate and alkalinity on partial nitritation in a continuous stirred tank reactor

Effect of nitrogen loading rate and alkalinity on partial nitritation in a continuous stirred tank reactor

Thickness of hydrogel for nitrifying biomass entrapment determines the free ammonia susceptibility differently in batch and continuous modes

Thickness of hydrogel for nitrifying biomass entrapment determines the free ammonia susceptibility differently in batch and continuous modes

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