Evaluation of a sequencing batch reactor sewage treatment rig for investigating the fate of radioactively labelled pharmaceuticals: Case study of propranolol

Tracking 14C-Labeled Organic Micropollutants to Differentiate between Adsorption and Degradation in GAC and Biofilm Processes

Granular activated carbon (GAC) filters can be used to reduce emissions of organic micropollutants via municipal wastewater, but it is still uncertain to which extent biological degradation contributes to their removal in GAC filters. 14C-labeled organic micropollutants were therefore used to distinguish degradation from adsorption in a GAC-filter media with associated biofilm. The rates and extents of biological degradation and adsorption were investigated and compared with other biofilm systems, including a moving bed biofilm reactor (MBBR) and a sand filter, by monitoring 14C activities in the liquid and gas phases. The microbial cleavage of ibuprofen, naproxen, diclofenac, and mecoprop was confirmed for all biofilms, based on the formation of 14CO2, whereas the degradation of 14C-labeled moieties of sulfamethoxazole and carbamazepine was undetected. Higher degradation rates for diclofenac were observed for the GAC-filter media than for the other biofilms. Degradation of previously adsorbed diclofenac onto GAC could be confirmed by the anaerobic adsorption and subsequent aerobic degradation by the GAC-bound biofilm. This study demonstrates the potential use of 14C-labeled micropollutants to study interactions and determine the relative contributions of adsorption and degradation in GAC-based treatment systems.

Adsorptive batch and biological treatments of produced water: Recent progresses, challenges, and potentials

Produced water is responsible for the largest contribution in terms of waste stream volume associated with the production of oil and gas. Characterization of produced water is very crucial for the determination of its main components and constituents for optimal selection of the treatment method. This review aims to review and critically discuss various treatment options that can be considered cost-efficient and environmentally friendly for the removal of different pollutants from produced water. Great efforts and progresses were made in various treatment options, including batch adsorption processes, membrane filtration, advanced oxidation, biological systems, adsorption, coagulation, and combined processes. Chemical precipitation, membrane filtration, and adsorption have high removal efficiencies that can reach more than 90% for different produced water components. The most effective method among these methods is adsorption using different adsorbents media. In this review, date-pits activated carbons, microemulsions-modified date pits, and cellulose nanocrystals as low-cost adsorbents were thoroughly reviewed and discussed. Moreover, the potential of using biological treatments in the removal of various pollutants from produced water such as conventional activated sludge, sequential batch reactor, and fixed-film biological aerated filter reactors were systematically discussed. Generally, produced water can be utilized in various fields including habitat and wildlife, agricultural and irrigation sector, energy sector, fire control, industrial use also power regeneration. The degree of treatment will depend on the application that produced water is being reused in. For instance, to use produced water in oil and gas industries, water will require minimal treatment while for agricultural and drinking purposes high treatment level will be required. It can also be concluded that one specific technique cannot be recommended that will meet all requirements including environmental, reuse, and recycling for sustainable energy. This is because of various dominant factors including the type of field, platform type, chemical composition, geological location, and chemical composition of the production chemicals.

Is sequential batch reactor an efficient technology to protect recipient against non-steroidal anti-inflammatory drugs and paracetamol in treated wastewater?

The tested facility was a wastewater treatment plant (WWTP) in Swarzewo, where the wastewater treatment takes place in aeration chambers with activated sludge using sequential batch reactors (SBRs). The concentration of the following pharmaceuticals: ibuprofen, paracetamol, flurbiprofen, naproxen, diclofenac, and its metabolites 5OH-diclofenac and 4OH-diclofenac was tested in influents and effluents. Simultaneously, the conventional parameters were characterised. The removal of conventional pollutants was high (94.4-99.5%). At the same time, the removal of pharmaceuticals was variable. In the case of diclofenac and its metabolites, the concentration in the effluent was higher than in the influents. The risk quotients (RQs) calculated for analyzed pharmaceuticals suggest low environmental risk for selected species. However, negative impact for the biota due to the chronic presence of diclofenac cannot be excluded. It can be concluded that the SBRs, similarly to traditional flow activated sludge technology, are not efficient in the removal of target pharmaceuticals.

Insitu kinetics of human pharmaceutical conjugates and the impact of transformation, deconjugation, and sorption on persistence in wastewater batch bioreactors

The fate of selected common pharmaceuticals and four of their major conjugates in wastewater batch bioreactors was evaluated to determine how treatment plant parameters such as addition of air, and the presence of waste activated sludge (WAS) could influence the removal of parent compounds and conjugates. Under a realistic hydraulic residence time (HRT) for each treatment sub-process of approximately 2 h, acetaminophen and its sulfate metabolite were both rapidly degraded (>99%). Propranolol was sulfated and concurrently removed. Deconjugation of N-acetylsulfamethoxazole and sulfamethoxazole-glucuronide contributed to increases of the parent sulfamethoxazole. Thyroxine was resistant to degradation, while thyroxine-glucuronide was rapidly deconjugated (>90% in <2 h). In the absence of WAS, sorption to suspended solids was another major removal mechanism for acetaminophen, propranolol, sulfamethoxazole, and thyroxine. However, with WAS, concentrations associated with suspended solids decreased for all analytes within 24 h. These results indicate that both conjugation and back-transformation are compound-specific and dependent on parameters such as HRT, addition of microbial content, and suspended solids levels. Therefore, conjugation-deconjugation processes may strongly influence the speciation of pharmaceuticals and their fate in wastewater treatment plant effluents.

A sustainable strategy for effective regulation of aerobic granulation: Augmentation of the signaling molecule content by cultivating AHL-producing strains

The positive roles of N-acyl homoserine lactone (AHL)-mediated quorum sensing (QS) in aerobic granular sludge (AGS) have been widely acknowledged. However, it is not feasible to manipulate granulation via direct addition of AHL chemicals or AHL-producing strains. Here, several strains with high AHL-producing capacity were successfully isolated from AGS. These QS strains were cultivated, mixed as a consortium, and then divided into two groups: AHLs supernatant and bacterial cells encapsulated in sodium alginate (CEBs). The potential of QS regulation, via doses of AHLs supernatant and CEBs, in accelerating granulation was evaluated. Results clearly indicated that short-term (days 21-70) addition of AHLs supernatant led to a rapid specific growth rate (0.08 d^-1), compact structure without filamentous bacteria overgrowth, excellent settlement performance (SVI₁₀ 37.2 mL/g), and a high integrity coefficient (4.4%) of the granules. Sustainable release of AHLs (mainly C₆- and C₈-HSL) was induced by exogenous AHLs, possibly attributed to the enrichment of the genera Aeromonas and Pseudomonas. Further, tryptophan and aromatic protein substances were produced to maintain structural stability, suggesting that short-term QS regulation had long-term positive effects on the characteristics of AGS. By comparison, the addition of CEBs posed negligible or negative impact on the granulation, as evidenced by the rupture of smaller aggregates and poor characteristics of AGS. Overall, augmentation of the signaling content via addition of AHLs supernatant from QS strains is an economical and feasible regulation strategy to accelerate granulation and sustain long-term structural stability.

Effect of light intensity on the characteristics of algal-bacterial granular sludge and the role of N-acyl-homoserine lactone in the granulation

The effects of light intensity on the development of algal-bacterial granular sludge (ABGS) were investigated over a period of 12 weeks. The ABGS developed at low light intensity (142 ± 10 μmol m^-2·s^-1) exhibited excellent settling ability (SVI₃₀ of 30.9 mL/g), COD and TN removal efficiencies (97.6% and 60.4%, respectively). High light intensity (316 ± 12 μmol m^-2·s^-1) accelerated granular biomass growth (5.3 g/L) and enhanced the TP removal efficiency (83.7%). Extracellular polymeric substance (EPS) analysis revealed that low light intensity induced more large weight distribution protein production (9-12 kDa and 50-150 kDa), predominantly tryptophan and aromatic proteins. Furthermore, N-acyl-homoserine lactones (AHLs) with a side chain ≤ C₁₀ were commonly shared in the ABGS, and the ABGS developed at low light intensity had a higher C₆- and 3OC₈-HSL content, which effectively promoted the biofilm formation. The add-back studies showed that the AHLs facilitated the regulation of EPS synthesis. Statistical analysis indicated that the AHLs content had a close correlation with the EPS production, the 50th percentile of the particle size distribution and microbial community assembly, suggesting that AHLs-mediated quorum sensing have an important ecological role in EPS expression and algal-bacterial granulation. Overall, this study describes the ABGS development at different light intensities and the mechanisms of ABGS formation treating synthetic domestic wastewater.

Sorption and biodegradation of six pharmaceutically active compounds under four different redox conditions

This study explored the removal of six pharmaceutically active compounds (PhACs) in lab-scale experiments with sediments under four redox conditions, namely aerobic, nitrate reducing, sulfate reducing, and methanogenic conditions using batch and column set-ups. Redox conditions were found to influence PhAC removal by sorption and biodegradation. The most optimal PhAC removal was observed at the outer ranges of the redox spectrum, i.e. either aerobic or deep anaerobic (sulfate reducing and methanogenic conditions), whereas nitrate reducing conditions were found least effective for PhACs biodegradation and sorption. For instance, sorption coefficient K_d values for metoprolol in column experiments were 90, 65, 42 and 11 L/kg for sulfate reducing, methanogenic, aerobic and nitrate reducing conditions, respectively. For the same conditions K_d values for propranolol were 101, 94, 55 and 55 L/kg, respectively. As expected, biodegradation efficiencies were highest under aerobic conditions, showing >99% removal of caffeine and naproxen, but no removal for propranolol and carbamazepine. The adaptive capacity of sediment was demonstrated by pre-exposure to PhACs leading to improved PhAC biodegradation. The results of this study indicate the necessity to combine diverse redox conditions, including aerobic conditions, for maximizing PhAC removal by sorption and biodegradation. Furthermore, our findings stress the need for additional treatment measures as recalcitrant PhACs are not effectively removed under any redox condition.

Antibiotic Concentrations Decrease during Wastewater Treatment but Persist at Low Levels in Reclaimed Water

Reclaimed water has emerged as a potential irrigation solution to freshwater shortages. However, limited data exist on the persistence of antibiotics in reclaimed water used for irrigation. Therefore, we examined the fate of nine commonly-used antibiotics (ampicillin, azithromycin, ciprofloxacin, linezolid, oxacillin, oxolinic acid, penicillin G, pipemidic acid, and tetracycline) in differentially treated wastewater and reclaimed water from two U.S. regions. We collected 72 samples from two Mid-Atlantic and two Midwest treatment plants, as well as one Mid-Atlantic spray irrigation site. Antibiotic concentrations were measured using liquid-chromatography- tandem mass spectrometry. Data were analyzed using Mann-Whitney-Wilcoxon tests and Kruskal Wallis tests. Overall, antibiotic concentrations in effluent samples were lower than that of influent samples. Mid-Atlantic plants had similar influent but lower effluent antibiotic concentrations compared to Midwest plants. Azithromycin was detected at the highest concentrations (of all antibiotics) in influent and effluent samples from both regions. For most antibiotics, transport from the treatment plant to the irrigation site resulted in no changes in antibiotic concentrations, and UV treatment at the irrigation site had no effect on antibiotic concentrations in reclaimed water. Our findings show that low-level antibiotic concentrations persist in reclaimed water used for irrigation; however, the public health implications are unclear at this time.