Development of reactive iron-coated natural filter media for treating antibiotic residual in swine wastewater: Mechanisms, intermediates and toxicity

Application of heterogeneous Fenton-like reaction with modified zeolite for removal of antibiotics, antibiotic-resistant bacteria, and antibiotic-resistant genes from swine farm wastewater

The heterogeneous Fenton-like reaction with modified zeolite was introduced for the removal of antibiotics, antibiotic-resistant bacteria (ARB), and antibiotic-resistant genes (ARGs) to reduce environmental impact of the substance residues in swine farm effluent. The heterogeneous Fenton-like reaction with 100 g/L of the modified zeolite and 2 mM H2O2 could completely remove amoxicillin (AMX), tetracycline (TC), and tiamulin (TIA) in the swine farm effluent within 30 min. However, the antibiotic removal in the swine farm effluent was slower than in the ultrapure water. The heterogeneous Fenton-like reaction removed approximately 45-60% of dissolved organic carbon (DOC) and reduced the dissolved organic matter (DOM) sizes in the swine farm effluent. The large molecular size humic-like DOM co-existing in the swine farm effluent could probably decelerate the antibiotic removal via competitive adsorption and oxidation. To inactivate high-tolerant AMX-resistant E. coli, the heterogeneous Fenton-like reaction required 3-fold less exposure time than the H2O2 oxidation. No regrowth of the high-tolerant AMX-resistant E. coli was observed when the exposure time of the heterogeneous Fenton-like reaction was longer than 6 h. The heterogeneous Fenton-like reaction required the exposure time of 24 h to reduce the blaTEM genes, the AMX-resistant genes, of the high-tolerant AMX-resistant E. coli to the level of lower than the limit of detection. The results suggest that different reaction times are required for the removal of antibiotics (within 30 min), ARB (over 6 h), and ARGs (within 24 h). Furthermore, the heterogeneous Fenton-like reaction with the modified zeolite is a promising technology for sequential and efficient removal of antibiotics, ARB, and ARGs residues in swine farm effluent before being discharged into the environment.

Heterogeneous Fenton degradation of ciprofloxacin by RM-Co PBA prepared with red mud as iron source and carrier

Loading catalysts onto carriers to prepare supported catalysts is an important strategy for improving dispersion, stability and catalytic performance. In this study, we synthesized a supported red mud (RM)-based Fe-Co Prussian blue analogue (RM-Co PBA) catalyst using RM as iron source and carrier by acid dissolution-reduction-coprecipitation method to activate H2O2 for the degradation of ciprofloxacin (CIP). The RM-Co PBA obtained under the synthesis conditions of HCl concentration of 2.4 M and potassium cobalt cyanide addition of 4 mM exhibited the best dispersibility and regular shape, resulting in high catalytic performance. The degradation efficiency of RM-Co PBA/H2O2 system reached 75.79% in 10 min, which was 10.54 times and 1.21 times of that of RM/H2O2 system and Fe-Co PBA/H2O2 system, respectively. The RM-Co PBA/H2O2 system was almost unaffected by pH and was suitable for treating low concentration CIP wastewater. Additionally, the system can be reused well and possessed certain resistance to inorganic anions. The results showed that superoxide radical (⋅O2-) was the main ROS attacking CIP, which accumulated continuously in the cycling process of Co(III)/Fe(III) and Co(II)/Fe(II). On the other hand, the presence of a large number of oxygen vacancies in RM-Co PBA enhanced the production of ⋅O2- by endowing it with good electron transfer performance. Finally, we proposed possible CIP degradation pathways and demonstrated the toxicity reduction of each pathway by a quantitative structure-activity relationship analysis. This study provides guidance for the resource utilization of RM and the efficient treatment of antibiotic wastewater.

Removal of antibiotics, bacterial toxicity, and occurrence of antibiotic resistance genes in secondary hospital effluents treated with granular activated carbon and the impact of preceding chlorination

This comprehensive investigation highlighted the complex adsorption behaviors of antibiotics onto granular activated carbon (GAC), the effectiveness of this adsorption in reducing bacterial toxicity, and the reduction of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) in hospital wastewater (HWW) effluents. Six GACs were characterized for their physicochemical properties, and their ability to adsorb six antibiotics in the background matrix of actual HWW was evaluated. Coconut shell-derived GAC (Co-U), which had the highest hydrophobicity and lowest content of oxygen-containing acidic functional groups, demonstrated the highest adsorption capacities for the tested antibiotics. Bacterial toxicity tests revealed that GACs could eliminate the bacterial toxicity from antibiotic intermediates present in chlorinated HWW. By contrast, the bacterial toxicity could not be removed by GACs in non-chlorinated HWW due to the greater presence of intermediate components identified by LC-MS/MS. The intraparticle diffusion coefficient of antibiotics adsorbed onto Co-U could be calculated by adsorption kinetics derived from the linear driving force model and the homogenous intraparticle diffusion model associated with the linear adsorption isotherms (0-150 μg/L). Meropenem and sulfamethoxazole exhibited the highest adsorption capacities in a single-solute solution compared to penicillin G, ampicillin, cetazidime, and ciprofloxacin. However, the greater adsorption capacities of meropenem and sulfamethoxazole disappeared in mixed-solute solutions, indicating the lowest adsorption competition. GAC can eliminate most ARGs while also promoting the growth of some ARB. Chlorination (free chlorine residues at 0.5 mg Cl2/L) did not significantly affect the overall composition of ARGs and ARB in HWW. However, the accumulation of ARGs and ARB on GAC in fixed bed columns was lower in chlorinated HWW than in non-chlorinated HWW due to an increase in the adsorption of intermediates.

Degradation of veterinary antibiotics by Fenton process: Products identification and toxicity assessment

The aim of the work was primarily to determine the relationship between the doses of Fenton's reagents and the effectiveness of the ecotoxicity removal of aqueous solutions containing selected antibiotics. The degradation process of ampicillin, doxycycline, and tylosin in an acidic environment in the presence of H2O2 and FeSO4 was studied. The effect of reagent doses on the degree of degradation and identification of antibiotic transformation products was measured by the UPLC qTOF method. The degree of mineralisation was determined based on changes in the concentration of total organic carbon. The ecotoxicity of products was determined with commercial MARA® and MICROTOX® bioassays, as well as against unselected microorganisms from polluted rivers and wastewater treatment plant effluent. It was found that the complete degradation of antibiotics and the simultaneous elimination of the toxicity of the Fenton process products required the use of a precisely defined amount of reagents. When an insufficient dose of reactants was used, the post-reaction solutions contained antibiotic derivatives showing antimicrobial activity. On the other hand, the toxicity of the post-reaction solution against to microbiocenoses was observed when too high doses of H2O2 were used in the process. This effect resulted from the presence of unreacted reagent or other unidentified peroxides.

Wastewater reclamation trends in Thailand

Thailand constantly faces the problem of water scarcity, resulting from an imbalance between available water supply and increasing water demand for economic and community expansion, as well as climate change. To address this shortage, wastewater reclamation is being planned and implemented throughout the country, along with a 20-year, long-term integrated water resource management plan. Significant opportunities from municipal wastewater treatment plants (WWTPs) are dependent on the following factors: the establishment of a reuse water framework and a tangible target for treated wastewater set by local government authorities; widespread recognition and adaptation of wastewater reuse measures in the agriculture, industry, tourism and service sectors regarding climate change and water stress; and the implementation of joint investment water reuse projects between private and government agencies. However, wastewater reclamation faces some significant challenges, specifically: the limitations of regulation and monitoring for specific reuse purposes; a lack of public confidence in the water quality; the limited commercial development of reclaimed wastewater research; and difficulties in self-sustaining business models through adapting circular economy principles. This study aims to provide an overview of the wastewater reclamation, present research trends, currently operating WWTPs as well as opportunities and challenges to speed up water reuse activities in Thailand.