Bacterial Communities and Antibiotic Resistance Communities in a Full-Scale Hospital Wastewater Treatment Plant by High-Throughput Pyrosequencing

Degradation of Sulfonamides by UV/Electrochemical Oxidation and the Effects of Treated Effluents on the Bacterial Community in Surface Water

This study evaluated the effects of ultraviolet (UV) photolysis combined with electrochemical oxidation on sulfonamides (SAs) as well as its treated effluent on the bacterial community in surface water. In terms of degradation rate, the best anode material for electrochemical oxidation was Ti/RuO2-IrO2, which had the highest degradation kinetic constant compared to Ti/Ta2O5-IrO2 and Ti/Pt. Experiments showed the highest degradation rate of SAs at 8.3 pH. Similarly, increasing the current leads to stronger degradation due to the promotion of free chlorine production, and its energy consumption rate decreases slightly from 73 to 67 W h/mmol. Compared with tap water, the kinetic constants decreased by 20-62% for SAs in three different surface water samples, which was related to the decrease in free chlorine. When extending the reaction time to 24 h, the concentrations of chemical oxygen demand and total organic carbon decreased by approximately 30-40%, indicating that the SAs and their products could be mineralized. The diversity analysis showed that the effluents influenced the richness and diversity of the bacterial community, particularly in the 4 h sample. Additionally, there were 86 operational taxonomic units common to all samples, excluding the 4 h sample; significant differences were derived from changes in the Actinobacteriota and Bacteroidota phyla. The toxicity of the products might explain these changes, and these products could be mineralized, as observed in the 24 h sample. Therefore, the extension of treatment time would greatly reduce the ecological harm of treated effluent and ensure that the UV/electrochemical process is a feasible treatment option. Overall, this study provides valuable insight into the optimization and feasibility of UV/electrochemical processes as a sustainable treatment option for sulfonamide-contaminated water sources, emphasizing the importance of considering ecological impacts and the need for extended treatment times that address environmental concerns and ensuring improved water quality.

Enhanced biological phosphorus removal by high concentration powder carrier bio-fluidized bed (HPB): Phosphorus distribution, cyclone separation, and metagenomics

This study provides a comparative investigation of phosphorus removal between anaerobic-anoxic-oxic (AAO) and high-concentration powder carrier bio-fluidized bed (HPB) in the same full-scale wastewater treatment plant. The results showed that the total phosphorus removal of HPB was 71.45%-96.71%. Compared with AAO, the total phosphorus removal of HPB can be increased by a maximum of 15.73%. The mechanisms of enhanced phosphorus removal by HPB include the followings. Biological phosphorus removal was significant. The anaerobic phosphorus release capacity of HPB was enhanced and polyphosphate (Poly-P) in the excess sludge of HPB was 1.5 times higher than that of AAO. The relative abundance of Candidatus Accumulibacter was 5 times higher than that of AAO, and oxidative phosphorylation and butanoate metabolism were enhanced. The analysis of phosphorus distribution showed that cyclone separation increased the chemical phosphorus precipitation (Chem-P) in the excess sludge by 16.96% to avoid accumulation in the biochemical tank. The phosphorus adsorbed by extracellular polymeric substance (EPS) in the recycled sludge was stripped, and the EPS bound-P in the excess sludge increased by 1.5 times. This study demonstrated the feasibility of HPB to improve the phosphorus removal efficiency for domestic wastewater.

Cascade capture, oxidization and inactivation for removing multi-species pollutants, antimicrobial resistance and pathogenicity from hospital wastewater

As reservoirs of pathogens, antimicrobial resistant microorganisms and a wide variety of pollutants, hospital wastewaters (HWWs) need to be effectively treated before discharge. This study employed the functionalized colloidal microbubble technology as one-step fast HWW treatment. Inorganic coagulant (monomeric Fe(III)-coagulant or polymeric Al(III)-coagulant) and ozone were used as surface-decorator and gaseous core modifier, respectively. The Fe(III)- or Al(III)-modified colloidal gas (or, ozone) microbubbles (Fe(III)-CCGMBs, Fe(III)-CCOMBs, Al(III)-CCGMBs and Al(III)-CCOMBs) were constructed. Within 3 min, CCOMBs decreased COD_Cr and fecal coliform concentration to the levels meeting the national discharge standard for medical organization. Regrowth of bacteria was inhibited and biodegradability of organics was increased after the simultaneous oxidation and cell-inactivation process. The metagenomics analysis further reveals that Al(III)-CCOMBs performed best in capturing the virulence genes, antibiotic resistance genes and their potential hosts. The horizontal transfer of those harmful genes could be effectively hampered thanks to the removal of mobile genetic elements. Interestingly, the virulence factors of adherence, micronutrient uptake/acquisition and phase invasion could facilitate the interface-dominated capture. Featured as cascade processes of capture, oxidation and inactivation in the one-step operation, the robust Al(III)-CCOMB treatment is recommended for the HWW treatment and the protection of downstream aquatic environment.

Hospital wastewater treatment methods and its impact on human health and environments

The scientific development and economic advances have led to the identification of many pathogenic agents in hospital effluents. Hospital wastewaters are qualitatively similar to municipal wastewaters, with the difference that these wastewaters contain toxic and infectious substances and compounds that can be dangerous for the health of the environment, employees of these centers, and the entire community. Therefore, in the last few years, it has been emphasized that all hospitals and medical and health centers should have a treatment facility for their produced wastewater so that the health of the society and people is not threatened. An issue that is not paid attention to has become one of the environmental problems and concerns of the world today. The present study focused on the investigate hospital wastewater treatment methods and its impact on human health and the environment. In this narrative study, the first literature search was performed with four hundred and twenty-three articles were retrieved based on PubMed, Elsevier, Web of science, Spring, and Google Scholar databases. The results of this study showed that wastewater from hospitals and medical centers can play a significant impress in polluting soil and aquatic environments and spreading infectious diseases. According to the mentioned contents, collection and treatment of hospital wastewater is essential. In addition, if hospital wastewater enters the wastewater collection network without knowing its characteristics or with incomplete treatment and finally enters the municipal wastewater treatment plant. It causes many problems, including disturbing the balance of the biological system of the treatment plant. Purification and disposal of hospital wastewater is considered a vital action based on environmental standards. The results of this study also showed that the treatment methods of this type of hospital wastewater can play a significant role in reducing the spread of diseases caused by hospital wastewater treatment, including infectious diseases. The results of this study can be very useful for politicians, the managers of the Ministry of Energy and Health and the Environmental Organization in choosing the appropriate methods and process to reduce hospital wastewater and increase the efficiency of hospital wastewater treatment plants.

Long-read metagenomic sequencing reveals shifts in associations of antibiotic resistance genes with mobile genetic elements from sewage to activated sludge

BACKGROUND

There is concern that the microbially rich activated sludge environment of wastewater treatment plants (WWTPs) may contribute to the dissemination of antibiotic resistance genes (ARGs). We applied long-read (nanopore) sequencing to profile ARGs and their neighboring genes to illuminate their fate in the activated sludge treatment by comparing their abundance, genetic locations, mobility potential, and bacterial hosts within activated sludge relative to those in influent sewage across five WWTPs from three continents.

RESULTS

The abundances (gene copies per Gb of reads, aka gc/Gb) of all ARGs and those carried by putative pathogens decreased 75-90% from influent sewage (192-605 gc/Gb) to activated sludge (31-62 gc/Gb) at all five WWTPs. Long reads enabled quantification of the percent abundance of ARGs with mobility potential (i.e., located on plasmids or co-located with other mobile genetic elements (MGEs)). The abundance of plasmid-associated ARGs decreased at four of five WWTPs (from 40-73 to 31-68%), and ARGs co-located with transposable, integrative, and conjugative element hallmark genes showed similar trends. Most ARG-associated elements decreased 0.35-13.52% while integrative and transposable elements displayed slight increases at two WWTPs (1.4-2.4%). While resistome and taxonomic compositions both shifted significantly, host phyla for chromosomal ARG classes remained relatively consistent, indicating vertical gene transfer via active biomass growth in activated sludge as the key pathway of chromosomal ARG dissemination.

CONCLUSIONS

Overall, our results suggest that the activated sludge process acted as a barrier against the proliferation of most ARGs, while those that persisted or increased warrant further attention. Video abstract.

Shotgun metagenomic analysis reveals the prevalence of antibiotic resistance genes and mobile genetic elements in full scale hospital wastewater treatment plants

Wastewater treatment plants are considered as hotspots of emerging antimicrobial genes and mobile genetic elements. We used a shotgun metagenomic approach to examine the wide-spectrum profiles of ARGs (antibiotic resistance genes) and MGEs (mobile genetic elements) in activated sludge samples from two different hospital trains at the wastewater treatment plants (WWTPs) in Daegu, South Korea. The influent activated sludge and effluent of two trains (six samples in total) at WWTPs receiving domestic sewage wastewater (SWW) and hospital wastewater (HWW) samples collected at multiple periods were subjected to high throughput 16S rRNA metagenome sequencing for microbial community diversity. Cloacibacterium caeni and Lewinella nigricans were predominant in SWW effluents, while Bacillus subtilis and Staphylococcus epidermidis were predominant in HWW effluents based on the Miseq platform. Totally, 20,011 reads and 28,545 metagenomic sequence reads were assigned to 25 known ARG types in the SWW2 and HWW5 samples, respectively. The higher abundance of ARGs, including multidrug resistance (>53%, MDR), macrolide-lincosamide-streptogramin (>9%, MLS), beta-lactam (>3.3%), bacitracin (>4.4%), and tetracycline (>3.4%), confirmed the use of these antibiotics in human medicine. In total, 190 subtypes belonging to 23 antibiotic classes were detected in both SWW2 and HWW5 samples. RpoB2, MacB, and multidrug (MDR) ABC transporter shared the maximum matched genes in both activated sludge samples. The high abundance of MGEs, such as a gene transfer agent (GTA) (four times higher), transposable elements (1.6 times higher), plasmid related functions (3.8 times higher), and phages (two times higher) in HWW5 than in SWW2, revealed a risk of horizontal gene transfer in HWW. Domestic wastewater from hospital patients also influenced the abundance of ARGs and MGEs in the activated sludge process.

Taxonomic and Functional Distribution of Bacterial Communities in Domestic and Hospital Wastewater System: Implications for Public and Environmental Health

The discharge of untreated hospital and domestic wastewater into receiving water bodies is still a prevalent practice in developing countries. Unfortunately, because of an ever-increasing population of people who are perennially under medication, these wastewaters contain residues of antibiotics and other antimicrobials as well as microbial shedding, the direct and indirect effects of which include the dissemination of antibiotic resistance genes and an increase in the evolution of antibiotic-resistant bacteria that pose a threat to public and environmental health. This study assessed the taxonomic and functional profiles of bacterial communities, as well as the antibiotic concentrations in untreated domestic wastewater (DWW) and hospital wastewater (HWW), using high-throughput sequencing analysis and solid-phase extraction coupled to Ultra-high-performance liquid chromatography Mass Spectrometry (UHPLC–MS/MS) analysis, respectively. The physicochemical qualities of both wastewater systems were also determined. The mean concentration of antibiotics and the concentrations of Cl⁻, F⁻ and PO₄³ were higher in HWW samples than in DWW samples. The phylum Firmicutes was dominant in DWW with a sequence coverage of 59.61% while Proteobacteria was dominant in HWW samples with a sequence coverage of 86.32%. At genus level, the genus Exiguobacterium (20.65%) and Roseomonas (67.41%) were predominant in DWW and HWW samples, respectively. Several pathogenic or opportunistic bacterial genera were detected in HWW (Enterococcus, Pseudomonas and Vibrio) and DWW (Clostridium, Klebsiella, Corynebacterium, Bordetella, Staphylocccus and Rhodococcus) samples. Functional prediction analysis indicated the presence of beta-lactam resistance, cationic antimicrobial peptide (CAMP) resistance and vancomycin resistance genes in HWW samples. The presence of these antibiotic resistance genes and cassettes were positively correlated with the presence of pathogens. These findings show the risk posed to public and environmental health by the discharge of untreated domestic and hospital wastewaters into environmental water bodies.

Diversity among activated sludge in vacuum degassed laboratory systems

Vacuum degassing of activated sludge is a technology used to improve sludge settling. By improving the settling ability of the sludge, a higher amount of biomass can be kept in the bioreactor, which further results in better wastewater treatment results. However, the momentaneous vacuum exposition has been found a stress agent for activated sludge flocs and bacteria and may cause changes in sludge activity. However, no biological studies on the long-term intermittent application of vacuum to activated sludge have been published so far. The question arises whether the improvement in the degree of wastewater treatment results from an increase in the amount of biomass involved in the treatment process or does the change in pressure stimulate bacteria to increased activity? The study aimed to examine whether and how cyclic pressure reduction in the biological system affects the activity and composition of bacterial biocenosis of activated sludge. Three sequencing batch reactors were operated for almost three months. The work cycle of two of them included a vacuum degassing stage inserted between reaction and settling stage. Degassing was obtained with a pressure of 300 or 30 hPa. In addition to the wastewater quality analyzes, the microbial activity, number and variety of activated sludge bacteria and the characteristics of activated sludge flocs were determined. There were no significant differences between the reactors in the obtained effects of nutrient removal. All reactors showed organic compounds removal around 93%, and 40% and 58% of nitrogen and phosphorus removal, respectively. Obtained differences in respiratory and dehydrogenase activity were not significant. The biodiversity assessed with DNA sequencing revealed sludge enrichment with unclassified bacteria. Moreover, vacuum degassing caused flocs disintegration. In both the vacuum degassing reactors, the floc size range was much narrower than that of the control sludge. In the sludge degassed with a pressure of 30 hPa, the flocs were 25-80% smaller than in the sludge without the influence of a vacuum. The total number of bacteria was comparable among the reactors, however, in the reactor with degassing pressure of 30 hPa, the share of dead bacteria in the activated sludge (11%) was significantly lower than in other reactors (about 16%). The concentration of extracellular polymers in activated sludge was up to 87% higher when using vacuum degassing of 30 hPa than in other reactors. The results of the presented research show that the changes in the activated sludge occurring under the influence of vacuum degassing do not change the effectiveness of wastewater treatment, but may alter the community composition.

Antibiotic resistance in wastewater treatment plants: understanding the problem and future perspectives

Antibiotics residues (AR), antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARG) are a new class of water contaminants, due to their adverse effects on aquatic ecosystems and human health. Contamination of water bodies occurs mainly by the excretion of antibiotics incompletely metabolized by humans and animals and is considered the main source of contamination of antibiotics in the environment. Given the imminent threat, the World Health Organization (WHO) has categorized the spread of antibiotics as one of the top three threats to public health in the twenty-first century. The Urban Wastewater Treatment Plants (UWWTP) bring together AR, ARB, ARG, making the understanding of this peculiar environment fundamental for the investigation of technologies aimed at combating the spread of bacterial resistance. Several methodologies have been employed focusing on reducing the ARB and ARG loads of the effluents, however the reactivation of these microorganisms after the treatment is widely reported. This work aims to elucidate the role of UWWTPs in the spread of bacterial resistance, as well as to report the efforts that have been made so far and future perspectives to combat this important global problem.

Evidence of mutations conferring resistance to clarithromycin in wastewater and activated sludge

The occurrence of clarithromycin in wastewater samples and of the activated sludge bacteria possibly resistant to this pharmaceutical was the object of the study. Samples of wastewater or activated sludge were taken from a municipal wastewater treatment plant in summer and winter and characterised regarding their clarithromycin concentrations and the presence of nucleic acid fragments (Cla-sequences) known to be responsible for clarithromycin resistance in Helicobacter pylori. The concentrations of clarithromycin in raw wastewater were about 1086-2271 ng/L. Around 50-60% less of the pharmaceutical was found in treated wastewater. The concentrations were much higher in winter samples, as compared to summer samples. The clarithromycin resistance markers in H. pylori were detected by fluorescence in situ hybridisation in activated sludge bacterial cells. Cla-sequences were found in all the detected Proteobacteria, independently of the sampling season. Among nitrifying or phosphate or glycogen accumulating bacteria only Nitrosomonas spp. revealed presence of the clarithromycin sequences.

Hospital wastewater treatment scenario around the globe

Wastewaters generated from hospitals contain pharmaceuticals residues, pathogens, chemical reagents, radionuclide, and other harmful matter. The wastewater characteristics, quantity, and handling methods have not only variations among countries but also within a country. Some hazardous substances of hospital wastewaters (HWWs) may have a regulatory status and should be treated accordingly while others have characteristics similar to that of domestic sewage. At a global level, guidelines do exist for treatment of these HWWs. But literatures have shown that legislation has various loopholes in implementation. This chapter outlines the current status of management and handling of HWWs around the major industrial hubs of worlds in two categories of developed (the United States, United Kingdom, and Europe) and developing (India, China, Iran, and Bangladesh) countries. Various literatures and guidelines of these countries have been referred which mainly highlight different treatment scenarios and status of coverage of HWW management guidelines.

Microbiology of hospital wastewater

The study of hospital wastewater (HWW) microbiology is important to understand the pollution load, growth of particular pathogenic microbes, shift and drift in microbial community, development and spread of antibiotic resistance in microbes, and subsequent change in treatment efficiencies. This chapter investigates the potential microbes such as bacteria, viruses, fungi, and parasites present in HWW along with the diseases associated and methods of treatment used. Due to the indiscriminate release of antibiotics from hospitals, HWW serves as a hotspot for emergence of antibiotic-resistance genes (ARGs) and antibiotic-resistance bacteria. This chapter discusses the ARGs occurrence in HWW, their prevalence in the environment, the molecular tools used for identification, and different mechanisms of horizontal gene transfer. Thus better understanding of the microbiology of HWW could further help in development of advanced treatment technologies for effective removal of microbes and their bioproducts (toxins and infectious nucleic acid) from HWW and contaminated water.

Impacts of solids retention time and antibiotic loading in activated sludge systems on secondary effluent water quality and microbial community structure

Solids retention time (SRT) is one of the most important factors in designing and operating activated sludge systems for biological wastewater treatment. Longer SRTs have been shown to alter the structure and function of microbial communities, thereby leading to improved treatment efficacy with respect to bulk and trace organics, nutrient removal, and membrane fouling. Research has also shown that longer SRTs and/or higher influent antibiotic concentrations may lead to increased prevalence of antibiotic resistance. However, it is unclear whether elevated, yet subclinical, concentrations of antibiotics also impact the overall microbial community. The purpose of this study was to characterize changes in microbial community structure in a laboratory-scale activated sludge system as a function of SRT (2-20 days) and influent concentrations (1×-100× ambient) of ampicillin, sulfamethoxazole, tetracycline, trimethoprim, and vancomycin. Changes in microbial community structure were evaluated based on 16S rRNA gene sequencing, and microbial community function was evaluated based on changes in effluent water quality, including attenuation of bulk and trace organics. The results confirmed that longer SRTs-but not antibiotic loadings-had a significant impact on microbial community structure and effluent water quality. Therefore, moderate spikes in influent antibiotic concentrations are not expected to adversely impact biological wastewater treatment. PRACTITIONER POINTS: Longer SRTs lead to changes in microbial community structure, including alpha and beta diversity and relative abundance of various taxa. Enhanced TOrC attenuation at longer SRTs may be linked to biomass abundance rather than changes in microbial community structure. Moderate spikes in influent antibiotic concentrations do not impact activated sludge performance or microbial community structure. The phyla Proteobacteria and Bacteroidetes comprise a majority of the microbial community in primary effluent and mixed liquor.

Relationship between modification of activated sludge wastewater treatment and changes in antibiotic resistance of bacteria

Biological treatment processes at wastewater treatment plants (WWTPs), which are the most common methods of sewage treatment, could cause selective elimination and/or changes in the proportions of phenotypes/genotypes within bacterial populations in effluent. Therefore, WWTPs based on activated sludge used in sewage treatment constitute an important reservoir of enteric bacteria which harbour potentially transferable resistance genes. Together with treated wastewater, these microorganisms can penetrate the soil, surface water, rural groundwater supplies and drinking water. Because of this, the aim of this study was to determine the impact of various modification of sewage treatment (the conventional anaerobic/anoxic/oxic (A2/O) process, mechanical-biological (MB) system, sequencing batch reactors (SBR), mechanical-biological system with elevated removal of nutrients (MB-ERN)) on the amount of antibiotic resistant bacteria (ARB) (including E. coli) and antibiotic resistance genes (ARGs) in sewage flowing out of the 13 treatment plants using activated sludge technology. There were no significant differences in ARB and ARGs regardless of time of sampling and type of treated wastewater (p > 0.05). The highest percentage of reduction (up to 99.9%) in the amount of ARB and ARGs was observed in WWTPs with MB and MB-ERN systems. The lowest reduction was detected in WWTPs with SBR. A significant increase (p < 0.05) in the percentage of bacteria resistant to the new generation antibiotics (CTX and DOX) in total counts of microorganisms was observed in effluents (EFF) from WWTPs with A2/O system and with SBR. Among all ARGs analyzed, the highest prevalence of ARGs copies in EFF samples was observed for sul1, tet(A) and qepA, the lowest for bla_TEM and bla_SHV. Although, the results of presented study demonstrate high efficiency of ARB and ARGs removal during the wastewater treatment processes, especially by WWTPs with MB and MB-ERN systems, EFF is still an important reservoir of ARGs which can be transferred to other microorganisms.