Degradation of Chloroquine by Ammonia-Oxidizing Bacteria: Performance, Mechanisms, and Associated Impact on N₂O Production

Since the mass production and extensive use of chloroquine (CLQ) would lead to its inevitable discharge, wastewater treatment plants (WWTPs) might play a key role in the management of CLQ. Despite the reported functional versatility of ammonia-oxidizing bacteria (AOB) that mediate the first step for biological nitrogen removal at WWTP (i.e., partial nitrification), their potential capability to degrade CLQ remains to be discovered. Therefore, with the enriched partial nitrification sludge, a series of dedicated batch tests were performed in this study to verify the performance and mechanisms of CLQ biodegradation under the ammonium conditions of mainstream wastewater. The results showed that AOB could degrade CLQ in the presence of ammonium oxidation activity, but the capability was limited by the amount of partial nitrification sludge (∼1.1 mg/L at a mixed liquor volatile suspended solids concentration of 200 mg/L). CLQ and its biodegradation products were found to have no significant effect on the ammonium oxidation activity of AOB while the latter would promote N2O production through the AOB denitrification pathway, especially at relatively low DO levels (≤0.5 mg-O2/L). This study provided valuable insights into a more comprehensive assessment of the fate of CLQ in the context of wastewater treatment

Efficient Chloroquine Removal by Electro-Fenton with FeS₂‑Modified Cathode: Performance, Influencing Factors, Pathway Contributions, and Degradation Mechanisms

The application of chloroquine (CLQ) due to its antibacterial/antiviral nature and high potential of being persistent and bioaccumulative poses a significant environmental threat. In this study, the electro-Fenton (EF) process with pyrite (FeS2)-modified graphite felt (FeS2/GF) as the cathode (EF-FeS2/GF), capable of providing a stable acidic environment with a solution pH of 3.0 was constructed and found to (i) achieve 83.3 ± 0.4% 60 min CLQ removal and (ii) maintain about 60.0% CLQ removal during consecutive batch tests. FeS2 loading amount, current density applied, and spacing between electrodes all influenced the efficacy of EF-FeS2/GF, with the optimum CLQ removal obtained at 10 mg, 150 mA, and 2.0 cm, respectively. Adsorption and electrocatalysis were both observed to contribute to the CLQ removal while the EF process with the verified functioning of ·OH played a dominant role. Based on the detected intermediates with identified ecotoxicities, two main paths were postulated to describe the degradation processes which led to the mineralization of CLQ. These findings supported that the EF-FeS2/GF could be an efficient technology to treat wastewater contaminated with CLQ

Modeling of Simultaneous Anaerobic Methane and Ammonium Oxidation in a Membrane Biofilm Reactor

Nitrogen removal by using the synergy of denitrifying anaerobic methane oxidation (DAMO) and anaerobic ammonium oxidation (Anammox) microorganisms in a membrane biofilm reactor (MBfR) has previously been demonstrated experimentally. In this work, a mathematical model is developed to describe the simultaneous anaerobic methane and ammonium oxidation by DAMO and Anammox microorganisms in an MBfR for the first time. In this model, DAMO archaea convert nitrate, both externally fed and/or produced by Anammox, to nitrite, with methane as the electron donor. Anammox and DAMO bacteria jointly remove the nitrite fed/produced, with ammonium and methane as the electron donor, respectively. The model is successfully calibrated and validated using the long-term (over 400 days) dynamic experimental data from the MBfR, as well as two independent batch tests at different operational stages of the MBfR. The model satisfactorily describes the methane oxidation and nitrogen conversion data from the system. Modeling results show the concentration gradients of methane and nitrogen would cause stratification of the biofilm, where Anammox bacteria mainly grow in the biofilm layer close to the bulk liquid and DAMO organisms attach close to the membrane surface. The low surface methane loadings result in a low fraction of DAMO microorganisms, but the high surface methane loadings would lead to overgrowth of DAMO bacteria, which would compete with Anammox for nitrite and decrease the fraction of Anammox bacteria. The results suggest an optimal methane supply under the given condition should be applied not only to benefit the nitrogen removal but also to avoid potential methane emissions