Simultaneous nitrification, denitrification, and phosphorus removal in a lab-scale sequencing batch reactor.

The potential for PHB (poly-beta-hydroxybutyrate) to serve as the electron donor for effective simultaneous nitrification and denitrification (SND) was investigated in a 2-L sequencing batch reactor (SBR) using a mixed culture and acetate as the organic substrate. During the feast period (i.e., acetate present), heterotrophic respiration activity was high and nitrification was prevented due to the inability of nitrifying bacteria to compete with heterotrophs for oxygen. Once acetate was depleted the oxidation rate of PHB was up to 6 times slower than that of soluble acetate and nitrification could proceed due to the decreased competition for oxygen. The slow nature of PHB degradation meant that it was an effective substrate for SND, as it was oxidised at a similar rate to ammonium and was therefore available for SND throughout the entire aerobic period. The percentage of nitrogen removed via SND increased at lower DO concentrations during the famine period, with up to 78% SND achieved at a DO concentration of 0.5 mg L(-1). However, the increased percentage of SND at a low DO concentration was compromised by a 2-times slower rate of nitrogen removal. A moderate DO concentration of 1 mg L(-1) was optimal for both SND efficiency (61%) and rate (4.4 mmol N x Cmol x(-1) x h(-1)). Electron flux analysis showed that the period of highest SND activity occurred during the first hour of the aerobic famine period, when the specific oxygen uptake rate (SOUR) was highest. It is postulated that a high SOUR due to NH(4) (+) and PHB oxidation decreases oxygen penetration into the floc, creating larger zones for anoxic denitrification. The accumulation of nitrate towards the end of the SND period showed that SND was finally limited by the rate of denitrification. As PHB degradation was found to follow first-order kinetics (df(PHB)/dt = -0.19 x f(PHB)), higher PHB concentrations would be expected to drive SND faster by increasing the availability rate of reducing power and reducing penetration of oxygen into the floc, due to the corresponding increased SOUR. Process control techniques to accumulate higher internal PHB concentrations to improve PHB-driven SND are discussed.

Discovery of a novel potential polyphosphate accumulating organism without denitrifying phosphorus uptake function in an enhanced biological phosphorus removal process

Can membrane aerated biofilm reactor (MABR) realize more efficient simultaneous partial nitrification and denitrification than conventional biofilm under low COD/N?

Nitrogen and phosphorus removal is necessary to avoid eutrophication of water bodies when treated wastewater is outlet to slowly flowing water bodies or recycled as technological water. The “BioBalance” technology as the latest way of nitrogen and phosphorus removal was applied at Utena Wastewater Treatment Plant. Composition of wastewater has an impact on biological phosphorus removal, particularly the ratio of biochemical oxygen demand and total phosphorus (BOD7/Total‐P) in wastewater after mechanical treatment. Nitrates in the anaerobic zone can have a negative effect on biological phosphorus removal. Consequently, it is necessary to evaluate the impact of the mentioned factors on biological nitrogen and phosphorus removal. Biological nitrogen and phosphorus removal was evaluated and compared by using the “BioBalance” technology for biological nitrogen and phosphorus removal and technology before reconstruction during this investigation. The correlation regressive analysis of the biochemical o...

In this study, a novel process combining partial denitrification (PD, NO3--N→NO2--N) and denitrifying phosphorus removal (DPR) in an anaerobic-anoxic-aerobic sequencing batch reactor (SBR) was developed. By comprehensively controlling the influent C/N ratio, anaerobic drainage ratio, and anoxic duration, the nitrite accumulation and phosphorus removal performance of a system treating high-strength nitrate and municipal wastewaters was investigated. The results showed that, after 140 days, the nitrate-to-nitrite transformation ratio (NTR) was 80.1%, and PO43--P removal efficiency was 97.64%. In the anaerobic stage (180 min), glycogen-accumulating organisms (GAOs) and phosphorus-accumulating organisms (PAOs) efficiently utilized the carbon source in municipal wastewater to enhance intracellular carbon storage. In the anoxic stage (150 min), denitrifying GAOs (DGAOs) and heterotrophic denitrifying bacteria (DOHOs) carried out endogenous and exogenous short-range denitrification, respectively, to achieve stable nitrite accumulation; simultaneously, denitrifying PAOs (DPAOs) carried out denitrifying phosphorus uptake to achieve efficient phosphorus removal. In the aerobic stage (10 min), without initiating ammonia/nitrite oxidation, PAOs absorbed excessive phosphorus, which improved the phosphorus removal performance of the system. The effluent NO2--N/NH4+-N of a ratio of 1.31:1 (close to the theoretical value of ANAMMOX process, 1.32:1), with little PO43--P and COD (0.30 and 12.94 mg·L-1), meets the requirements for deep-level nitrogen removal by coupling with ANAMMOX process.

Nitrogen and phosphorus removal is necessary to avoid eutrophication of water bodies when treated wastewater is outlet to slowly flowing water bodies or recycled as technological water. The “BioBalance” technology as the latest way of nitrogen and phosphorus removal was applied at Utena Wastewater Treatment Plant. Composition of wastewater has an impact on biological phosphorus removal, particularly the ratio of biochemical oxygen demand and total phosphorus (BOD7/Total-P) in wastewater after mechanical treatment. Nitrates in the anaerobic zone can have a negative effect on biological phosphorus removal. Consequently, it is necessary to evaluate the impact of the mentioned factors on biological nitrogen and phosphorus removal. Biological nitrogen and phosphorus removal was evaluated and compared by using the “BioBalance” technology for biological nitrogen and phosphorus removal and technology before reconstruction during this investigation. The correlation regressive analysis of the biochemical oxygen demand and total phosphorus (BOD7/Total‐P) after mechanical treatment and the total phosphorus concentration in the effluent was evaluated. The correlation regressive analysis of nitrates in an anaerobic zone on the aeration tank and the efficiency of phosphorus removal was also evaluated.

In high-altitude regions, a diminished atmospheric oxygen content significantly impairs the aeration efficiency of municipal wastewater, posing a challenge to sustainable wastewater management. Consequently, conventional biological wastewater treatment methods necessitate elevated energy consumption in high-altitude areas, rendering them economically and environmentally unsustainable. The simultaneous nitrification and denitrification (SND) process, owing to its minimal oxygen requirements, emerges as a promising and sustainable solution in low-pressure environments. Additionally, owing to the unique lifestyle and natural conditions in plateau regions, the organic loading in municipal wastewater is often low. To comprehensively assess the impact of low pressure and organic loading on the SND process, three laboratory-scale reactors were implemented. This study revealed that low pressure and the introduction of organic matter enhanced both nitrogen removal performance and SND efficiency. The sludge volume index decreased by 93.5%, indicating a substantial improvement in the microbial aggregation ability and the formation of a more favorable SND sludge structure. 16S rRNA sequencing results demonstrated alterations in the microbial community structure due to low pressure and the addition of organic matter, leading to a substantial increase in the abundance of nitrifying and denitrifying bacteria. Furthermore, the prediction results of functional genes indicated the upregulation of genes related to the nitrification and denitrification processes with decreasing pressure and the addition of organic matter. This enhancement underlines the improved microbial nitrogen removal function. This study underscores the positive influence of low pressure and organic loading on the SND system, thereby substantially enhancing the economic and environmental sustainability of the SND process in plateau regions.

For economic and efficient nitrogen removal from wastewater treatment plants via simultaneous nitrification and denitrification the nitrification process should stop at the level of nitrite such that nitrite rather than nitrate becomes the substrate for denitrification. This study aims to contribute to the understanding of the conditions that are necessary to improve nitrite reduction over nitrite oxidation. Laboratory sequencing batch reactors (SBRs) were operated with synthetic wastewater containing acetate as COD and ammonium as the nitrogen source. Computer controlled operation of the reactors allowed reproducible simultaneous nitrification and denitrification (SND). The oxygen supply was kept precisely at a low level of 0.5 mgL(-1) and bacterial PHB was the only electron donor available for denitrification. During SND little nitrite or nitrate accumulated (< 20% total N), indicating that the reducing processes were almost as fast as the production of nitrite and nitrate from nitrification. Nitrite spiking tests were performed to investigate the fate of nitrite under different oxidation (0.1-1.5 mgL(-1) of dissolved oxygen) and reduction conditions. High levels of reducing power were provided by allowing the cells to build up to 2.5 mM of PHB. Nitrite added was preferentially oxidised to nitrate rather than reduced even when dissolved oxygen was low and reducing power (PHB) was excessively high. However, the presence of ammonium enabled significant reduction of nitrite under low oxygen conditions. This is consistent with previous observations in SBR where aerobic nitrite and nitrate reduction occurred only as long as ammonium was present. As soon as ammonium was depleted, the rate of denitrification decreased significantly. The significance of the observed strongly stimulating effect of ammonium on nitrite reduction under SND conditions is discussed and potential consequences for SBR operation are suggested.

An investigation into the optimal granular sludge size for simultaneous nitrogen and phosphate removal

Nitrogen and phosphorus removal in pilot-scale anaerobic-anoxic oxidation ditch system

Aeration control strategy design based on dissolved oxygen and redox potential profiles for nitrogen and phosphorus removal from sewage in a sequencing batch reactor

Two feeding ratios, 3:1 (RUN I) and 2:1 (RUN II), were experimented to investigate their effect on removal of nitrogen, phosphorus, organic matter, and on the trends of oxidization-reduction potential (ORP) and pH in sequencing batch reactors (SBR) with dual anoxic feedings of swine wastewater. Results showed for both runs, the feeding ratio had a more significant effect on the removal of phosphorus and nitrogen than on COD in the operating cycle. As compared to RUN I, the removal of nitrogen and phosphorus was enhanced in RUN II. In addition, the optimal feeding ratio greater than 1:1 for SBR with dual anoxic feedings can be determined with reference to the decreasing range of ORP following the primary feeding, and the denitrification-associated ORP bending point in the second non-aeration phase.

Aerobic N2O emission for activated sludge acclimated under different aeration rates in the multiple anoxic and aerobic process

In traditional biological phosphorus removal (BPR), phosphorus release in anaerobic stage is the prerequisite of phosphorus excessive uptake in aerobic conditions. Moreover, when low molecular weight of the organic substance such as volatile fatty acids (VFAs) is scarce in bulk liquid or anaerobic condition does not exist, phosphate accumulating organisms (PAOs) have difficulty removing phosphorus. However, in this work, phosphorus removal in two anoxic-aerobic sequencing batch reactors (SBRs) was observed when starch was supplied as a sole carbon source. The relations of the BPR with idle period were investigated in the two identical SBRs; the idle times were set to 0.5 hr (R1) and 4 hr (R2), respectively. Results of the study showed that, in the two SBRs, phosphorus concentrations of 0.26-3.11 mg/L in effluent were obtained after aeration when phosphorus concentration in influent was about 8 mg/L. Moreover, lower accumulations/transformations of polyhydroxyalkanoates (PHAs) and higher transformation of glycogen occurred in the SBRs, indicating that glycogen was the main energy source that was different from the traditional mechanism of BPR. Under the different idle time, the phosphorus removal was a little different. In R2, which had a longer idle period, phosphorus release was very obvious just as occurs in a anaerobic-aerobic regime, but there was a special phenomenon of chemical oxygen demand increase, while VFAs had no notable change. It is speculated that PAOs can assimilate organic compounds in the mixed liquor, which were generated from glycolysis by fermentative organisms, coupled with phosphorus release. In R1, which had a very short idle period, anaerobic condition did not exist; phosphorus removal rate reached 63%. It is implied that a new metabolic pathway can occur even without anaerobic phosphorus release when starch is supplied as the sole carbon source.

Chapter 17 - Role of ammonia oxidizers in performing simultaneous nitrification and denitrification process in advanced SBR plants