Short- and long-term effects of manganese, zinc and copper ions on nitrogen removal in nitritation-anammox process

This study provided a deep insight into the impacts of trace elements (Mn2+, Zn2+ and Cu2+) on nitritation-anammox process. For short-term exposure, all the three elements could improve the nitrogen removal rate (NRR) and the optimal concentrations were 2.0 mg/L, 2.0 mg/L and 0.5 mg/L for Mn2+, Zn2+ and Cu2+, respectively. Accordingly, the NRR were enhanced 54.62%, 45.93% and 44.09%. The long-term experiments were carried out in lab-scale sequencing batch reactors. The surprising results showed that only Mn2+ addition could enhance the long-term nitritation-anammox process, and the NRR increased from 0.35 ± 0.01 kg N/m3/d (control, no extra trace element addition) to 0.49 ± 0.03 kg N/m3/d. Vice versa, the amendment of Zn2+ reduced the NRR to 0.28 ± 0.02 kg N/m3/d, and Cu2+ had no significant effect on the NRR (0.36 ± 0.01 kg N/m3/d). From the analysis of microbial community structure, it was explained by the increasing abundance of anaerobic ammonium oxidizing bacteria (AnAOB) only in Mn2+ treatment, whereas Zn2+ predominantly promoted ammonium oxidizing bacteria (AOB). Additionally, the majority of Mn2+ was identified inside AnAOB cells, and Zn2+ and Cu2+ were mainly located in AOB. Our results indicated the synergistic effects of trace elements on nitritation-anammox, both short-term encouraging activities of AnAOB and long-term altering microbial community structure. This work implies the importance of trace elements addition in nitritation-anammox process

Nitrogen Removal Efficiency for Pharmaceutical Wastewater with a Single-Stage Anaerobic Ammonium Oxidation Process

A single-stage anaerobic ammonium oxidation (ANAMMOX) process with an integrated biofilm–activated sludge system was carried out in a laboratory-scale flow-through reactor (volume = 57.6 L) to treat pharmaceutical wastewater containing chlortetracycline. Partial nitrification was successfully achieved after 48 days of treatment with a nitrite accumulation of 70%. The activity of ammonia oxidizing bacteria (AOB) decreased when the chemical oxygen demand (COD) concentration of the influent was 3000 mg/L. When switching to the single-stage ANAMMOX operation, (T = 32–34 °C, DO = 0.4–0.8 mg/L, pH = 8.0–8.5), the total nitrogen (TN) removal loading rate and efficiency were 1.0 kg/m3/d and 75.2%, respectively, when the ammonium concentration of the influent was 287 ± 146 mg/L for 73 days. The findings of this study imply that single-stage ANAMMOX can achieve high nitrogen removal rates and effectively treat pharmaceutical wastewater with high concentrations of COD (1000 mg/L) and ammonium

The application of glycine betaine to alleviate the inhibitory effect of salinity on one-stage partial nitritation/anammox process

One-stage partial nitritation/anammox (PN/A) has been proposed as a sustainable method for removing nitrogen from various wastewater. However, the activities of ammonium-oxidizing bacteria (AOB) and anammox bacteria are often inhibited by the exposure to salinity, thereby hindering their wide application in treating industrial wastewater with high salinity. This study reports that the addition of glycine betaine (GB), which is a compatible solute, could alleviate the inhibitory effects of salinity on both AOB and anammox, thereby improving nitrogen removal performance in a one-stage PN/A system. Short-term tests showed that with an addition of GB higher than 1\ua0mM, the activity of AOB and anammox under salinity of 30\ua0g/L could be increased by at least 45% and 51%, respectively. The half-inhibitory concentration of AOB and anammox rose with increasing GB concentration, with 1\ua0mM\ua0GB being the optimal cost-effective dosage. Long-term experiments also demonstrated that 1\ua0mM\ua0GB addition could enhance nitrogen removal performance and shorten recovery time by 42.9% under a salinity stress of 30\ua0g/L. Collectively, GB addition was found to be a feasible and effective strategy to the counteract adverse effects of salinity on PN/A process. Practitioner points: Glycine betaine (GB) could improving performance of the PN/A process by alleviating the inhibitory effects of salinity on both AOB and anammox bacteria. A GB concentration of 1\ua0mM was found to be optimum in terms of effectiveness and cost. GB addition was a feasible and effective strategy to remain stabilized in the community structure of PN/A sludge. GB could optimize the nitrogen removal performance and shorten the recovery time of PN/A process under saline stress