Stages Of Wastewater Treatment Plant Research Articles

Bacterial resistome in different stages of wastewater treatment plant is highly impacted by the abundance of the Pseudomonadota community

Wastewater treatment plants (WWTPs) are significant sources of antimicrobial resistance (AMR). We studied bacterial communities and antibiotic-resistance genes (ARGs) in different stages of a WWTP in the UAE. We found high levels of extended-spectrum beta-lactamase bacteria in the returned activated sludge (RAS) stage, including Escherichia coli and Aeromonas sobria, resistant to ESBL, ampicillin, and fosfomycin. Bacterial richness was highest in the primary effluent (PE) stage, with distinct community structures influenced by environmental factors. Pseudomonadota dominated across all stages, with Bacteroidota and Bacillota in PE, and Actinomycetota and Pseudomonadota in AS and RAS. Acidovorax sp. showed strong connections with ARGs in PE and RAS, while Delftia acidovorans had the most associations with ARGs in AS. These findings underscore the role of WWTP stages in shaping bacterial communities and ARG abundance, highlighting the potential of certain bacteria in AMR development and dissemination.

Impacts of Polylactic Acid Microplastics on Performance and Microbial Dynamics in Activated Sludge System

A large number of microplastics (MPs) have been found in various stages of wastewater treatment plants, which may affect the functional microbial activity in activated sludge and lead to unstable pollutant removal performance. In this study, the effects of different concentrations of polylactic acid microplastics (PLA MPs) on system performance, nitrification and phosphorus (P) removal activities, and extracellular polymeric substances (EPS) were evaluated. The results showed that under the same influent conditions, low concentrations (50 particles/(g TS)) of PLA MPs had no significant effect on effluent quality. The average removal efficiencies of chemical oxygen demand, phosphate, and ammonia were all above 80%, and the average removal efficiencies of total nitrogen remained above 70%. High concentrations (200 particles/(g TS)) of PLA MPs inhibited the activities of polyphosphate-accumulating organisms (PAOs) and nitrifying bacteria. The specific anaerobic P release rate decreased from 37.7 to 23.1 mg P/(g VSS·h), and the specific aerobic P uptake rate also significantly decreased. The specific ammonia oxidation rate decreased from 0.67 to 0.34 mg N/(g VSS·h), while the change in the specific nitrite oxidation rate was not significant. The dosing of PLA MPs decreased the total EPS and humic acid content. As the concentration of PLA MPs increased, microbial community diversity increased. The relative abundance of potential PAOs (i.e., Acinetobacter) increased from 0.08 to 12.57%, while the relative abundance of glycogen-accumulating organisms (i.e., Competibacter and Defluviicoccus) showed no significant changes, which would lead to improved P removal performance. The relative abundance of denitrifying bacteria (i.e., Pseudomonas) decreased from 95.43 to 58.98%, potentially contributing to the decline in denitrification performance.

Synthesis, Characterization and Performance Evaluation of Burmese Grape (Baccaurea ramiflora) Seed Biochar for Sustainable Wastewater Treatment

Biochar prepared from different bio-sources serves as a feasible solution for the decontamination of dye-contaminated wastewater. In this study, biochar was synthesized from a sustainable source, i.e., local fruit waste, Burmese grape seeds (BGSs). The seeds were collected from a local market, washed, pre-teated and finally converted into biochar by pyrolysis in a N2 furnace. The removal efficiency of the synthesized biochar was evaluated towards a cationic industrial azo dye, methylene blue (MB). The phosphoric acid (H3PO4) and potassium hydroxide (KOH) pretreated BGS were pyrolized at 500 °C for 3 h in a N2 furnace at a heating rate of 10 °C/min. The spectroscopic analysis confirmed the presence of multiple surface functional groups, e.g., R-OH, OH, -C=O, -COOH, etc. The surface of the biochar was randomized with porous tunnel-like structures. The specific surface area and pore volume obtained from BET analysis were 19.90 ± 1.20 m2/g and 5.85 cm3/g. The MB concentration (mg/L), contact duration (min) and pH were varied to assess the MB sorption phenomena. The optimum pH was found to be 8. During the first 20 min of contact time, adsorption was rapid and equilibrium was reached after 75 min. The adsorption was best described by pseudo-first-order kinetics with a good fit (R2 = 0.99). The maximum removal percentage was ~85%, and per gram of BGS can adsorb 166.30 mg of MB, which supports the Langmuir adsorption isotherm model. The obtained results were compared with the reported literature, and BGS showed its excellent candidacy to be industrially utilized in the tertiary stage of wastewater treatment plants.

Anticancer Drugs Gemcitabine, Letrozole, and Tamoxifen in Municipal Wastewater and Their Photodegradation in Laboratory-Scale UV Experiments

The occurrence of three anticancer drugs (gemcitabine, letrozole, tamoxifen) was studied in wastewater samples from two local wastewater treatment plants (WWTPs) in Finland. Studied pharmaceuticals were selected, as anticancer drugs are potential to cause adverse effects on organisms even at low concentrations, but they are seldom included in the analysis of emerging contaminants. The concentration of anticancer drugs was determined by liquid chromatography-triple quadrupole mass spectrometer (LC–MS/MS). Tamoxifen and letrozole were detected from influent samples ranging from 0.5 to 5.0 ng/L, respectively. Letrozole was detected from effluent samples at a concentration up to 2.4 ng/L. Letrozole has been detected in wastewater effluent only once before, at a lower concentration of 0.28 ng/L. Gemcitabine was not detected in any of the samples. UV irradiation is used in many wastewater treatment plants to disinfect the effluent. Such tertiary treatment might degrade also these potentially harmful drugs and, therefore, photodegradation of the chosen pharmaceuticals was studied in laboratory-scale experiments. Tamoxifen showed high degradation rates, 94% in spiked wastewater with UV fluence 4830 mJ/cm2 and 98% in pure water with UV fluence 2520 mJ/cm2, respectively. Letrozole showed the lowest degradation rates of 24% in wastewater and 34% in pure water, respectively. The degradation rate at the fluence level typical for UV disinfection stage of wastewater treatment plants was 37% for tamoxifen but only 5% for letrozole. To the best of the authors’ knowledge, this is the first report to show the effectiveness of UV irradiation to degrade letrozole.

Effects of Seasonal Variation on Performance of Conventional Wastewater Treatment System

The study was to determine the seasonal differences of conventional wastewater treatment process. This was done by sampling and analyses of wastewater samples from four different points during the dry and wet seasons of the year 2019. Water samples were taken from influent point, primary effluent, trickling filter effluent and final effluent. Gravimetric method was used in determining Total Suspended Solids (TSS) and Total Dissolved Solids (TDS). The BOD 5 technique was used for determination of Biological Oxygen Demand (BOD) and the digestion method was used for determination Chemical Oxygen Demand (COD). Temperature, pH and conductivity were measured using respective meters. Analysis of Variance showed that there was significant difference (p < 0.05) in all the parameters quantified at all the points of treatment during the two seasons. The results showed that BOD and COD both reduced from one point to the next during the two seasons of study. The TSS levels increased after primary pond effluent undergoing treatment at the trickling filter and the temperature also increased after the trickling filter effluent undergoing treatment at oxidation ponds. The levels of conductivity and TDS decreased from one treatment stage to the next during dry season but during the wet season the levels of these parameters increased from one stage to the next except that the levels reduced after the primary pond effluent underwent treatment at the trickling filter. The various stages of wastewater treatment plant under were effective during the two seasons however, wet season recorded lower figures for most of the parameters. Keywords: effluent, influent, wastewater, seasonal variation, ponds DOI: 10.7176/JEES/11-7-06 Publication date: July 31 st 2021

Applications of Extended Ozonation at Different Stages of A Full Scale Municipal Wastewater Treatment Plant

ABSTRACT Removal of micropollutants in wastewaters has gained importance in recent years. Advanced treatment processes such as ozone oxidation, activated carbon adsorption, and membrane filtration are required to remove the micropollutants from wastewaters. In this study, extended ozonation was applied at different stages of a wastewater treatment plant (WWTP) to determine its effect on the removal efficiencies of both macro and micropollutants. At the first experimental study, wastewater that was obtained from the effluent of the aerated grit chamber of a conventional full-scale municipal WWTP, was treated with a concentration of 30 mg/L FeCl3 through a laboratory scale jar test system followed by a laboratory-scale ozonation unit. According to the results, chemically enhanced primary treatment (CEPT) achieved removal efficiencies over 75% for chemical oxygen demand (COD), 50% for total phosphorus (TP) and 90% for total-suspended solids (TSS), while ozonation followed by the CEPT resulted with an overall COD removal efficiency up to 93%. As a second experimental study, effluent of the overloaded conventional activated sludge (CAS) system of the same WWTP was solely post ozonated. 90 min of post-ozonation resulted with a decrease by 70% and an increase by 50% in ammonium and nitrate concentration, respectively. Over 99% removal efficiency of diclofenac was achieved in each experimental study (CEPT+O3 and CAS+O3). Results of each experimental study were evaluated in terms of both efficiency and feasibility. Since the ozonation results with an increase in the concentration of oxidized nitrogen; applying ozonation to a preliminary-treated wastewater after CEPT can be advantageous in some cases, where nitrate can be used as electron acceptor in anoxic environments for deep-sea discharges.

High frequency of gram-negative bacilli harboring blaKPC-2 in the different stages of wastewater treatment plant: A successful mechanism of resistance to carbapenems outside the hospital settings

Wastewater treatment plants (WWTPs) are considered to be a reservoir and a source of bacterial resistance. Worryingly, the presence of carbapenem-resistant Gram-negative bacilli (CRGNB) in WWTPs has recently been reported, but there are still many research gaps regarding its emergence and impact. The distribution of CRGNB in the different stages of a WWTP in Colombia and the relationship between the physicochemical factors involved with their presence are described in this paper. Additionally, given the impact on public health, the CRGNB detected were compared with isolates previously found in hospital patients. Residual water samples were taken from five different stages of a WWTP between January and July 2017. A total of 390 GNB were isolated, and a significant frequency of CRGNB harboring blaKPC-2 (38.2%, n = 149/390) was detected, of which 57% were Enterobacteriaceae, 41.6% Aeromonadaceae, and 1.3% Pseudomonadaceae. The Enterobacteriaceae were more frequent in the raw effluent compared to the Aeromonadaceae, which in turn were more prevalent in the recycled activated sludge and final effluent. Environmental variables such as pH, oxygen, chemical oxygen demand, and temperature were significantly correlated with the quantification of carbapenem-resistant Enterobacteriaceae (CRE) at specific points in the WWTP. Interestingly, isolated K. pneumoniae harboring blaKPC-2 from the WWTPs were diverse and did not relate genetically to the hospital strains with which they were compared. In conclusion, these results confirm the worrying scenario of the dissemination and persistence of emerging contaminants such as CRGNB harboring blaKPC-2, and reinforce the need to establish strategies aimed at containing this problem using multifocal interventions.

Sand Content Prediction in Urban WWTPs Using MARS

The pre-treatment stage of wastewater treatment plants (WWTP), where most of the larger waste, including sand and fat, is removed, is of great importance for the performance and durability of these plants. This work develops a model that predicts the sand content that reaches the plant. For this purpose, data were collected from one operation year of the Villapérez Wastewater Treatment Plant located in the northeast of the city of Oviedo (Asturias, Spain) and the MARS (Multivariate Adaptive Regression Splines) method was used for modelling. The accuracy of the MARS model developed using the determination coefficient is R2 = 0.74 for training data and R2 = 0.70 in validation data. These results indicate that it is possible to predict trend changes in sand production as a function of input variables changes such as flow rate, pH, ammonia, etc. This will prevent the plant from possible operational problems, as actions could be taken, such as starting up more pre-treatment lines or emptying the containers, so that the arrival of the sand can be assumed without any problem. In this way, the possibility of letting sand contents over the established limits pass that could affect the following processes of the treatment plant is avoided.

Automated SPE-HPLC-UV methodology for the on-line determination of plasticisers in wastewater samples

ABSTRACT An automated methodology (SPE-HPLC-UV) is proposed in this work for the determination of plasticisers in water samples collected at different stages of two wastewater treatment plants (WWTPs). Bisphenol A (BPA) and 4-tert-butylphenol (4tBP) were chosen as model pollutants. The 33−1 fractional factorial experimental design (FFED) was used to determine more significant variables associated with the preconcentration procedure. The factors studied were the adsorbent composing the SPE membrane disk, sample volume and pH of the sample. Three SPE membranes disks were evaluated: (1) C18 octadecyl bonded silica (C18), (2) styrenedivinylbenzene‐extra clean (SDB‐XC) copolymer, and (3) styrenedivinylbenzene‐reversed-phase sulphonated (SDB‐RPS) copolymer. The preconcentration conditions selected were the SDB-RPS membrane disk as the sorbent, a sample volume of 30 mL and a solution pH of 7. HPLC-UV analysis was achieved isocratically using a C18 column with CH3CN:H2O, 60:40% v v−1, at a flow rate of 1.0 mL min−1. The linearity range was between 5 and 80 μg L−1 with determination coefficients (R2) higher than 0.9989. The limits of detection (LODs) were 0.77 and 1.46 μg L−1 for BPA and 4tBP, respectively. Furthermore, the intraday and interday precisions expressed in terms of relative standard deviation (RSD) were found between 2.5–5.0% and 4.6–6.0%, respectively. Excellent recovery rates (72.2–99.8%) were demonstrated by spiking known concentrations of BPA and 4tBP in the WWTP samples. The proposed methodology was successfully applied to determine BPA and 4tBP in water samples of two WWTPs from the metropolitan area of Monterrey, Mexico. BPA was found in wastewater influent ranging from 5.9 to 16.6 μg L−1, while 4tBP was detected in samples from different stages of WWTPs in concentrations ranging from 4.9 to 21.5 μg L−1.

Quantification and characterisation of activated carbon in activated sludge by thermogravimetric and evolved gas analyses

Advanced wastewater treatment with powdered activated carbon (PAC) leads to a spread of PAC into different purification stages of wastewater treatment plants (WWTP) due to recirculation and filter back-wash. Currently, no methods for quantification of PAC in activated sludge are available. In this study, PAC containing activated sludge from four WWTP were examined by two-step thermogravimetric analysis (TGA) with heating up to 600°C in N2 and subsequently in synthetic air. Direct quantification of PAC according to temperature specific weight losses was possible for one WWTP. Quantification by combining specific mass losses was found to be an alternative direct method, with a detection limit of 1.2% PAC in dry sample mass.Additionally, evolved gas analysis (EGA) by infrared-spectroscopy (FTIR) during TGA revealed interaction mechanisms between PAC and activated sludge. Aliphatic compounds from activated sludge were identified as major substances influenced by PAC. In derivative thermogravimetry (DTG), a typical double peak at approximately 300°C was found to be related to carbonylic species with increased evolution of acetic acid in aged activated sludge. TGA and EGA are promising tools to understand, control and optimise the application of PAC in advanced wastewater treatment.

Assessment of the Fate of Escherichia coli in Different Stages of Wastewater Treatment Plants

Seven full-scale wastewater treatment plants were investigated to highlight the effectiveness of each treatment stage on removing Escherichia coli. The primary sedimentation achieved an average E. coli removal efficiency of 30.5% which was much lower than the suspended solids (58%), thus, revealing the absence of a linear relationship between the two parameters. Biological processes proved to be very important in the removal of E. coli through adsorption inside the sludge flocs and complex decay (mortality). In biological processes with a long retention time, such as activated sludge denitrification-nitrification, the decay was very important, whereas in the more traditional activated sludge process, without nitrification, the contribution of adsorption and mortality was quite balanced. Overall, the mechanical-biological treatment achieved a removal efficiency of 91.8–96.5% depending on the process. Additional removal can be achieved by disinfection. The effectiveness of E. coli removal with sodium hypochlorite was strictly depended on the product of residual chlorine (C R) with the contact time (t). The experimental curve fitted the Collins model well, with a standard deviation of less than 7%.

Utilization of Fenton-like reaction for antibiotics and resistant bacteria elimination in different parts of WWTP

Utilization of relatively low-cost modification of Fenton reaction for the elimination of selected antibiotics and resistant coliforms in different part of wastewater treatment plant (WWTP) was studied. The concentration of antibiotics and occurrence of resistant gems in different stages of WWTP in the capital city of Slovakia – Bratislava was analyzed by LC–MS/MS technique. Consequently, Fenton-like reaction was applied for the elimination of chemical and biological contaminants. Comparative study with classical Fenton reaction was also done. Very high concentrations of clarithromycin, ciprofloxacin and azithromycin in influent water were found. Coliform bacteria were predominantly resistant to ampicillin, ciprofloxacin and gentamicin. After the mechanical stage, the concentration of antibiotics in water was significantly decreased because of the sorption during this step. Biological step degraded 12 types of antibiotics. Analyses of effluent water showed very bad elimination of azithromycin (919ng/L) and clarithromycin (684ng/L). Contrary, ciprofloxacin was removed with very high efficiency (95%). The number of resistant bacteria was also significantly decreased in effluent water. In the case of Escherichia coli only ampicillin and gentamicin resistance bacteria were detected. Our results show that antibiotics as well as resistant bacteria were eliminated by the modification of classical Fenton reaction with high efficiency. The modification of the Fenton reaction can decrease the process wages, environmental impact. Moreover, the degradation process was easily controlled, monitored and tuned.

Fate of psychoactive compounds in wastewater treatment plant and the possibility of their degradation using aquatic plants

In this study we analyzed and characterized 29 psychoactive remedies, illicit drugs and their metabolites in single stages of wastewater treatment plants in the capital city of Slovakia. Psychoactive compounds were present within all stages, and tramadol was detected at a very high concentration (706ng/L). Significant decreases of codeine, THC-COOH, cocaine and buprenorphine concentration were observed in the biological stage. Consequently, we were interested in the possibility of alternative tertiary post-treatment of effluent water with the following aquatic plants: Cabomba caroliniana, Limnophila sessiliflora, Egeria najas and Iris pseudacorus. The most effective plant for tertiary cleansing was I. pseudacorus which demonstrated the best pharmaceutical removal capacity. After 48h codeine and citalopram was removed with 87% efficiency. After 96h were all analyzed compounds were eliminated with efficiencies above 58%.

Metagenomic analysis of DNA viruses in a wastewater treatment plant in tropical climate

Viruses have been detected in the different stages of wastewater treatment plants (WWTPs) at concentrations of 10(8) -10(10) ml(-1) of virus-like particles (VLPs), 10-1000 times higher than in natural aquatic environments, suggesting that WWTPs can be considered as an important reservoir and source of viruses. This study revealed novel diversity and function with the DNA viral communities in the influent, activated sludge, anaerobic digester, and effluent of a domestic WWTP using metagenomics. WWTP was a very specific environment, with less than 5% of the > 936 000 metagenomic sequences obtained (∼70-119 Mbp per sample) similar to sequences present in other environmental viromes. Many viruses found in the WWTP were novel, resulting in only < 5-20% of the reads being phylogenetically or functionally assigned. DNA metabolism was observed as the most abundant function with DNA methylase detected at levels 4.2-fold higher than other published viromes, while carbohydrate and amino acids metabolisms were 3.7- and 4.2-fold less abundant respectively. These specific aspects of the WWTP community functions are likely due to high biomass concentration, turnover rate and microbial activity in WWTPs, and likely include mechanisms that help viruses increase their infectivity. Among ∼500 genotypes estimated in individual WWTP viromes, > 82% were shared. These data suggested that VLPs of most viral types could be present between 1 and 30 days in the process before they were discharged. Viruses in WWTP and the discharged ones can have potential impacts on the functioning of the wastewater treatment system and on the dynamics of microbial community in the surrounding aquatic environments respectively.

Removal of hardness and COD from retanning treated effluent by membrane process

The use of membrane separation process integrated with conventional tannery wastewater treatment was studied in order to reuse the treated effluent in the retanning process. Laboratory scale tests were performed to find a suitable membrane for the process and to define pretreatment, fluid dynamic conditions and membrane cleaning procedures. Hardness levels restrict effluent reutilization on the process. The effects of the addition of lime, soda, Na 2CO 3 and EDTA to the primary stage of wastewater treatment plant to reduce hardness levels were presented in a previous work. The results obtained are reported and discussed. It was observed that the membrane MX07 (Osmonics) reached hardness retention values of 54%, obtaining soft permeate which is suitable to the process. The permeate will be used in retanning, partially closing the water cycle, and after that, the exhausted baths will be sent to the wastewater treatment plant.

Early warning-system for operation-failures in biological stages of WWTPs by on-line image analysis

By the observation and evaluation of the microscopic picture of activated sludge samples it is possible to introduce another biological parameter additional to conventional physico-chemical parameters for the control of biological stages of waste water treatment plants. Considering the fact that parameters like floc size and floc size distribution, structure of the flocs (compact/open), shape of the flocs (round/irregular) allow perceptions of the adjusted operation conditions of the biological stages, evidence for changing operation conditions or threatening operation disturbances can be recognised. This recognition takes place at a very early phase, because the morphology of activated sludge flocs reacts very fast to changing conditions. An automatic image analysis of activated sludge floc pictures would enable the introduction of a new sum parameter to enhance operation control of aeration tanks. By a statistical evaluation of the processed sludge images several parameters can be used to describe the alteration of activated sludge flocs characteristics. With these biological parameters it is possible to detect altered operation conditions or threatening or existing operation problems at an early phase. Thus it is possible to plan suitable countermeasures. Furthermore, the microscopic picture is the only parameter, that gives important information about the structure of the activated sludge flocs and the biozenosis. In comparison with the mainly used physico-chemical parameters, that just give information about the inlet and outlet of the wastewater treatment plants, the microscopic picture is the only parameter that gives information about the biology of the wastewater treatment process. By means of this biological parameter an improved control and regulation of the biological stages of wastewater treatment plants can be obtained.