Sequencing Batch Reactor Research Articles

Phenol and nitrogen removal in microalgal–bacterial granular sequential batch reactors

AbstractBACKGROUNDMicroalgal–bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. The ability of algal–bacterial photobioreactors for the treatment of wastewater containing ammonia and phenol has been poorly addressed. In this work a self‐sustaining synergetic microalgal–bacterial granular sludge process was thus developed to treatment of industrial wastewater based upon the low cost of photosynthetic oxygenation and the simultaneous phenol and nitrogen removal. The performance of a conventional sequential batch reactor (SBR) based on aerobic bacterial communities (SBRB) and a microalgal–bacterial granular SBR (SBRMB) were comparatively assessed. The major challenges associated with microalgal–bacterial systems were discussed.RESULTSA complete removal of phenol (100 mg L−1) was achieved in both reactors. The reactors SBRB and SBRMB showed similar performance in term of removal of inorganic nitrogen. Nitrogen mass balances estimated nitrogen assimilation, nitrification and denitrification. Higher simultaneous nitrification and denitrification (70% SND) occurred in SBRB as determined by mass balances. The higher nitrogen assimilation (17.9%) by the microalgal–bacterial biomass compensated the lower denitrifying activity in SBRMB (54% SND), resulting in a removal of inorganic nitrogen (61%) similar to that obtained in SBRB (66%). N2O was not detected in the headspace of any system.CONCLUSIONGranular microalgal–bacterial consortia implemented in SBR constitute an efficient method for industrial wastewater treatment achieving complete removal of ammonia and phenol. The application of SBRMB would be more cost effective than SBRB mainly due to the significant energy savings in SBRMB resulting in a sustainable system that contributes to the circular bioeconomy. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Exploiting Cheese Whey for Efficient Selection of Polyhydroxyalkanoates-Storing Bacteria

Agroindustrial by-products hold an enormous potential to be bioconverted into high-value-added products such as polyhydroxyalkanoates (PHA), a cost-effective alternative to conventional plastics. In this study, cheese whey, a highly abundant side stream of the cheese making process, was explored as a feasible substrate for the selection of a mixed culture highly enriched in PHA-storing bacteria using a sequencing batch reactor under an aerobic dynamic feeding regime. For that, the absence/presence of thiourea, magnesium and iron, as well as the application of two different organic loading rates (OLR), i.e., 60 and 80 CmM d−1, were tested. The results showed an improved culture selection when thiourea, magnesium and iron were added to the culture medium as well as when the highest OLR was applied. Under these conditions, the biomass achieved a maximum PHA storage of 54% and a PHA production rate of 4.81 Cmmol-PHA L−1 h−1. Additionally, the study of the microbial community showed that during this period of maximum productivity, the biomass was enriched in Azoarcus and Amaricoccus bacterial species. Conclusively, cheese whey can be considered a good feedstock to efficiently select a mixed culture with high potential to accumulate PHA and a good way to give this by-product added value.

Pilot-scale aerobic granular sludge reactors with granular activated carbon for effective nitrogen and phosphorus removal from domestic wastewater

Aerobic granular sludge (AGS) is a breakthrough biotechnology of 21st century and an innovative alternative to activated sludge for treating wastewater. Concerns on long-start up periods for development of AGS and stability of granules are impeding its widespread implementation for treating low-strength domestic wastewater especially in tropical climate conditions. Addition of nucleating agents have been shown to improve development of AGS while treating low-strength wastewaters. There are no previous studies on AGS development and biological nutrient removal (BNR) in the presence of nucleating agents during treatment of real domestic wastewater. This study investigated AGS formation and BNR pathways while treating real domestic wastewater in a 2 m3 pilot-scale granular sequencing batch reactor (gSBR) operated without and with granular activated carbon (GAC) particles. The gSBRs were operated under tropical climate (T ≈ 30 °C) for >4-years to evaluate the effect of GAC addition on granulation, granular stability and BNR at pilot-scale. Formation of granules was observed within 3 months. MLSS values of 4 and 8 g/L were recorded within 6 months in gSBRs without and with GAC particles, respectively. The granules had an average size of 1.2 mm and SVI5 of 22 mL/g. Ammonium was mainly removed through nitrate formation in the gSBR without GAC. But, ammonium was removed by short-cut nitrification via nitrite due to washout of nitrite oxidizing bacteria in the presence of GAC. Phosphorus removal was much higher in gSBR with GAC due to the establishment of enhanced biological phosphorus removal (EBPR) pathway. After 3 months, the phosphorus removal efficiencies were at 15 % and 75 %, respectively, without and with GAC particles. The addition of GAC led to moderation in bacterial community and enrichment of polyphosphate-accumulating organisms. This is the first ever report on pilot-scale demonstration of AGS technology in the Indian sub-continent and GAC addition on BNR pathways.

Fungal-Based Remediation in the Treatment of Anthropogenic Activities and Pharmaceutical-Pollutant-Contaminated Wastewater

Pharmaceutical personal care products (PPCPs) have increased in consumption due to the worldwide post-pandemic situation, marking them as chemical and pathogenic pollutants in significantly higher concentrations than ever in the ecosystem. Considering the inexplicable levels of these chemical residues discharged into the environment, concerns have been raised regarding their probable ecotoxicity to marine and terrestrial life. A further concern is the potential for developing and spreading antibiotic-resistant microorganisms and genes in aquatic ecosystems due to antibiotic exposure. Hence, knowing how these compounds impact aquatic ecosystem functioning is imperative, and thus is a critical area of research. The ecological risk analysis of PPCPs in aquatic ecosystems has been carried out using various strategies. Previous studies have reported numerous approaches for eliminating these PPCPs, including conventional treatment methods, activated sludge processes, generated wetlands, biological remediation, sequencing batch reactors, phytoremediation, and membrane bioreactors. In terms of green biotechnology approaches, the current research aims to discover effective procedures for removing PPCPs and their emerging resources as pollutants. Therefore, this review focuses on the over-extensive utilization of PPCPs and their emergent sources responsible for the contamination and environmental threat for future wastewater purposes. Further, as fungi and their enzymes and derivatives can remove pharmaceuticals and personal care products from wastewater through oxidation and several processes, they have attracted the attention of the scientific community due to their ability to remove PPCPs as pollutants and their status as emerging resources in wastewater. This review examines the fundamental approach and progress of the bioremediation of pharmaceutical- and personal-care-contaminated wastewater using fungal-based systems. It also discusses mechanistic approaches through hybridizing cultures and other biological systems with fungal strains, current technologies, and prospects for future research on PPCPs in wastewater treatment.

Reclamation Potential of Onsite Wastewater Post-Treatment with Microalgae: Chemical Elements Perspective

Algae-based wastewater treatment is a promising technology with various applications for excess biomass such as biofertilizer production or valuable elements extraction. The benefits of the technology have been discussed for larger wastewater treatment plants (WWTPs), but the use of microalgae in decentralized wastewater treatment has been barely reported. The current study screens the possible resource recovery potential of onsite technology, which adds algae-based post-treatment to the conventional biological treatment of domestic wastewater. The effluent from the onsite sequencing batch reactor (SBR) of a household was further processed in laboratory conditions using an SBR technology with two local monocultures of algae—Klebsormidium nitens (Kützing) Lokhorst and Tetradesmus obliquus (Turpin) M. J. Wynne. The decant and the generated algal biomass were analyzed in terms of their element content. The post-treated effluent has a slightly better quality for irrigation purposes than the effluent of the onsite treatment facility—up to 1.6 times increased concentration for macro-elements and up to 1.9 times for micro elements. However, the generated algal biomass shows promising potential for re-use as a fertilizing agent since it contains valuable macro- and micro-elements and the heavy (hazardous) metal content is considerably lower than the limiting values in the current European and national legislations. The K. nitens strain may attract interest since it accumulates valuable metals such as chromium (36 mg/kgDS), nickel (83 mg/kgDS), and silver (0.7 mg/kgDS) that can be derived from the biomass and turn the technology to a circular one.

Nitrogen removal performance and mechanism of low-carbon sewage by airlift internal loop sequencing batch bio-microcapsule reactor

In this study, bio-microcapsules (PSCF) embedded with corncobs, zero-valent iron (ZVI) and Acinetobacter pittii SY9 were prepared, and the airlift internal loop sequencing batch reactor (AILP-SBR) was constructed with PSCF as filler. Results showed that the TN removal ratios of AILP-SBR were affected by HRT, C/N ratio and NH4+-N concentration, the NH4+-N, TN and COD removal efficiency of AILP-SBR reached 97.46 ± 2.18%, 90.67 ± 3.53% and 76 ± 7.43%, respectively under appropriate conditions (HRT of 10–12 h, C/N of 2–3, the influent COD concentration of 162.75 ± 16.02 mg/L, influent NH4+-N of 50 ± 0.92 mg/L, and pH of 7.00 ± 0.02), and the maximum first-order rate constant of TN removal was 0.2563 h−1. Moreover, carbon and total Fe (TFe) release characteristics, enzyme activity, functional genes and microbial community structure were used to explore the mechanisms of PSCF to enhance nitrogen removal. These results indicated that PSCF could release 98.15 mg COD/g and 1.15 mg/g TFe, provide electron donors for denitrification, and improve enzyme activity of nitrogen conversion. In addition, the addition of zero-valent iron (ZVI) could promote the abundance of nitrogen removal genes and functional bacteria in the AILP-SBR. In AILP-SBR, the dominant genera for nitrogen removal included Acinetobacter (10.57%), Dechloromonas (4.09%) and Hydrogenophaga (4.09%).

Responses of activated sludge under a short-term exposure to facial scrub microbeads: implications from treatment performance and higher-life microbial population dynamics.

In this study, four identical laboratory-scale sequencing batch reactors (SBRs) were continuously operated with different concentrations of microbeads (MBs) (5,000-15,000 MBs/L) to investigate the stress-responses of activated sludge under the MB exposure. It was found that the overall treatment performance (organic removal) of SBRs was fairly affected by short-term exposure to low levels of MBs; however, it was adversely affected as the concentration of MBs increased. The average concentration of mixed liquor suspended solids and heterotrophic bacteria in the reactor fed with 15,000 MBs/L were 16 and 30% less than in the pristine control reactor, respectively. Batch experiments further demonstrated that fairly low concentrations of MBs favored the development of dense microbial structures. Further increasing the MB concentrations to 15,000 MBs/L, however, distinctly weakened the settling performance of sludge. Morphological observations revealed suppressed uniformity, strength, and integrity of flocs reactors with the addition of MBs. Microbial community analyses revealed that the abundance of protozoan species declined 37.5, 58, and 64%, respectively, when SBRs were exposed to 5,000; 10,000; and 15,000 MBs/L as compared with the control reactor. The present work provided new insight into the possible effects of MBs on the performances and operational parameters of activated sludge.

A novel experimental and machine learning model to remove COD in a batch reactor equipped with microalgae

By using microorganisms and the microalgae Chlorella vulgaris in conjunction with sequencing batch reactors (SBRs), the performance of a wastewater treatment facility was studied. For this purpose, the effect of pH, temperature, {mathrm{COD}}_{mathrm{inlet}}, and air flowrate on COD removal rate and residual was investigated. A single-factorial optimization method is utilized to optimize the amount of COD removal, and the best result is obtained with a pH of 8, {mathrm{COD}}_{mathrm{inlet}}=600, mathrm{mg}/mathrm{l}, and an airflow rate of 55 l/min. Under optimal conditions, the amount of residual COD in the effluent reached 36 mathrm{mg}/mathrm{l}, showing an augmentation in the efficiency of the desired system. Moreover, empirical correlations are proposed for double-factorial optimization of residual COD and COD removal. Also, a multilayer perceptron artificial neural network is proposed to model the process and predict the residual COD concentration. The useful technique of hyperparameter tuning is utilized to obtain the best result for the predictions. All the effective parameters, including the number of hidden layers, neurons, epochs, and batch size, are adjusted. Data from the experiments agreed well with the artificial neural network modeling results. For this modeling, the values of the correlation coefficient ({R}^{2}) and mean absolute error (MAE) were obtained as 0.98 and 2%, respectively.

Enhanced ethanol-driven carboxylate chain elongation by Pt@C in simulated sequencing batch reactors: Process and mechanism

Carboxylate chain elongation can create value-added bioproducts from the organic waste. The effects of Pt@C on chain elongation and associated mechanisms were investigated in simulated sequencing batch reactors. 5.0 g/L of Pt@C greatly increased the synthesis of caproate, with an average yield of 21.5 g COD/L, which was 207.4% higher than the trial without Pt@C. Integrated metagenomic and metaproteomic analyses were used to reveal the mechanism of Pt@C-enhanced chain elongation. Pt@C enriched chain elongators by increasing the relative abundance of dominant species by 115.5%. The expression of functional genes related to chain elongation was promoted in the Pt@C trial. This study also demonstrates that Pt@C may promote overall chain elongation metabolism by enhancing CO2 uptake of Clostridium kluyveri. The study provides insights into the fundamental mechanisms of how chain elongation can perform CO2 metabolism and how it can be enhanced by Pt@C to upgrade bioproducts from organic waste streams.

Detection of microplastic traces in four different types of municipal wastewater treatment plants through FT-IR and TED-GC-MS

Large amounts of microplastics are discharged into wastewater treatment plants (WWTPs), from where some of them are released into natural waterbodies on account of their not being fully eliminated by WWTPs. To investigate the behavior and emission of microplastics from WWTPs, we selected four WWTPs with different treatment technologies, including anaerobic-anoxic-aerobic (A2O), sequence batch reactor (SBR), media, and membrane bioreactor (MBR). The number of microplastics detected using Fourier transform infrared (FT-IR) spectroscopy ranged from 520 to 1820 particles/L in influent and from 0.56 to 2.34 particles/L in effluent. The microplastic removal efficiencies of four WWTPs were over 99%, indicating that the type of treatment technologies did not significantly affect the removal rate of microplastics. In the unit process for each WWTP, the major stages relating to microplastic removal were the secondary clarifier and tertiary treatment processes. Most microplastics detected were categorized as fragments and fibers, while other types were hardly detected. The size of more than 80% of microplastic particles detected in WWTPs ranged between 20 and 300 μm, indicating that they were significantly smaller than the size threshold defined for microplastics. Therefore, we used thermal extraction-desorption coupled with gas chromatography-mass spectroscopy (TED-GC-MS) to evaluate the microplastic mass content in all four WWTPs, and the results were compared with those of the FT-IR analysis. In this method, only four components, namely polyethylene, polypropylene, polystyrene, and polyethylene terephthalate, were analyzed because of the analysis limitation, and the total microplastic concentration represented the sum of four components concentrations. The influent and effluent microplastic concentrations estimated by TED-GC-MS ranged from not detectable to 160 μg/L and 0.04–1.07 μg/L, respectively, indicating a correlation coefficient of 0.861 (p < 0.05) between the TED-GC-MS and FT-IR results, when compared to the combined abundance of the four microplastic components by FT-IR analysis.

Anoxic granular activated sludge process for simultaneous removal of hazardous perchlorate and nitrate

An airtight, anoxic bubble-column sequencing batch reactor (SBR) was developed for the rapid cultivation of perchlorate (ClO4-) and nitrate (NO3-) reducing granular sludge (GS) in this study. Feast/famine conditions and shear force selection pressures in tandem with a short settling time (2-min) as a hydraulic section pressure resulted in the accelerated formation of anoxic granular activated sludge (AxGS). ClO4- and NO3- were efficiently (>99.9%) reduced over long-term (>500-d) steady-state operation. Specific NO3- reduction, ClO4- reduction, chloride production, and non-purgeable dissolved organic carbon (DOC) oxidation rates of 5.77 ± 0.54 mg NO3--N/g VSS·h, 8.13 ± 0.74 mg ClO4-/g VSS·h, 2.40 ± 0.40 mg Cl-/g VSS·h, and 16.0 ± 0.06 mg DOC/g VSS·h were recorded within the reactor under steady-state conditions, respectively. The AxGS biomass cultivated in this study exhibited faster specific ClO4- reduction, NO3- reduction, and DOC oxidation rates than flocculated biomass cultivated under similar conditions and AxGS biomass operated in an up-flow anaerobic sludge blank (UASB) bioreactor receiving the same influent loading. EPS peptide identification revealed a suite of extracellular catabolic enzymes. Dechloromonas species were present in high abundance throughout the entirety of this study. This is one of the initial studies on anoxic granulation to simultaneously treat hazardous chemicals and adds to the science of the granular activated sludge process.

Optimizing the efficiency of a three‐step fed anoxic/aerobic sequencing batch reactor using response surface methodology

AbstractIn this study, the removal of chemical oxygen demand (COD), ammonium nitrogen (NH4+‐N) and total inorganic nitrogen (TIN) in a three‐step fed anoxic/aerobic sequencing batch reactor was investigated. Response surface methodology (RSM) was used to determine and optimize the effect of operating parameters such as the ratio of aerobic/anoxic (Ae/Ax) phase durations, percentage of feeding to the first anoxic phase (R1) and ratio of feeding percentages to the third and second anoxic phases (R3:R2). The results of the analysis of variance (ANOVA) showed that the three independent variables were statistically highly significant (p &lt; 0.0001). The values of the determination coefficient (R2) for the removal efficiency of COD, NH4+‐N and TIN was 0.9558, 0.9334 and 0.9963, respectively, indicating a good agreement between the experimental results and the predicted values. The quadratic model was valid in predicting experimental results. The optimum conditions obtained using the desirability function were found to be 2.05 for the ratio of Ae/Ax phase durations, 43.09% for R1 and 0.86 for R3:R2, where the COD, NH4+‐N and TIN removal efficiency was 94.29, 97.83 and 86.86%, respectively. As a result of the evaluation of the interactive effect of the independent variables, it was determined that R1 was the most effective factor. The results showed that RSM could be used for optimization of operating parameters and improvement of efficiency in a three‐step fed anoxic/aerobic sequencing batch reactor.

Simultaneous dissolved methane and nitrogen removal from low-strength wastewater using anaerobic granule-based sequencing batch reactor

Anaerobic treatment of mainstream wastewater has been proposed as a promising solution to enhance bioenergy recovery for wastewater treatment plants (WWTPs). However, the limited organics for downstream nitrogen removal and emissions of dissolved methane into the atmosphere are two major barriers to the broad application of anaerobic wastewater treatment. This study aims to develop a novel technology to overcome these two challenges by achieving simultaneous removal of dissolved methane and nitrogen, and unravel the microbial competitions underpinning the process from the microbial and kinetic perspectives. To this end, a laboratory granule-based sequencing batch reactor (GSBR) coupling anammox and nitrite/nitrate-dependent anaerobic methane oxidation (n-DAMO) microorganisms was developed to treat wastewater mimicking effluent from mainstream anaerobic treatment. The GSBR achieved high-level nitrogen and dissolved methane removal rates (> 250 mg N/L/d and > 65 mg CH4/L/d) and efficiencies (> 99% total nitrogen removal and > 90% total methane removal) during the long-term demonstration. The availability of different electron acceptors (nitrite or nitrate) imposed significant effects on the removal of ammonium and dissolved methane, as well as on the microbial communities, and the abundance and expression of functional genes. The analysis of apparent microbial kinetics showed that anammox bacteria had a higher nitrite affinity than n-DAMO bacteria, while n-DAMO bacteria had a higher methane affinity than n-DAMO archaea. These kinetics underpin the observation that nitrite is a preferred electron acceptor for removing ammonium and dissolved methane than nitrate. The findings not only extend the applications of novel n-DAMO microorganisms in nitrogen and dissolved methane removal, but also provide insights into microbial cooperation and competition in granular systems.

Assessing the impact of increasing phenol loads on the performance and stability of an aerobic granular sludge system

This work evaluated the impact of phenol on the performance and stability of an aerobic granular sludge (AGS) sequencing batch reactor (SBR) operated under alternating anaerobic-aerobic conditions for simultaneous organic matter, nitrogen, and phosphorus removal. The reactor was fed with synthetic wastewater whose phenol concentration was gradually increased from 2 to 200 mg L−1, while the other carbon source (acetate) was reduced proportionally to keep the organic loading rate invariable. Up to 20 mg L−1 of phenol, the average COD removal was above 90%, while practically full ammonium, phosphorus, and phenol removal was achieved. However, at higher phenol concentrations, the activity of polyphosphate-accumulating organisms and nitrifiers was affected. Although the overall COD removal was only slightly affected by increasing phenol loads, replacing the main carbon source from acetate to phenol changed the organic matter removal profile over the cycle, with the latter being converted mainly within the aerated stage of the SBR. As a result, there was filamentous growth that deteriorated the settling properties of the granules. The establishment of an anaerobic feast-aerobic famine regime over the non-aerated and aerated phases of the AGS SBR and the presence of a readily biodegradable substrate (such as acetate) proved to be crucial for maintaining granules stability. Having phenol as the sole organic carbon source led to complete process failure regarding nutrient removal capability.

Bioaugmentation of Cd(II) removal in high-salinity wastewater by engineered Escherichia coli harbouring EC20 and irrE genes

Wild strain generally can remove heavy metals but cannot tolerate high-salinity. In this study, Cd(II) adsorption protein EC20 on the cell surface and global regulator irrE in the cytoplasm of Escherichia coli were expressed to adsorb Cd(II) in high-salinity conditions. The maximum adsorption amount was 30.79 mg/g at 30.84 mg/L Cd(II) and 2% NaCl of E. coli (EC20/irrE), which was higher than E. coli (p23), E. coli (EC20) and E. coli (irrE). The adsorption kinetics fitted well with the Elovich model. And Redlich-Peterson model was used to describe the adsorption process successfully. Transcriptome data analysis showed that the overexpression of irrE in E. coli significantly increased high-salinity tolerance, because of trehalose accumulation and exopolysaccharide export. Subsequently, a bioaugmentation sequencing batch reactor was adopted for treating the actual Cd(II) contained high-salinity petrochemical wastewater. The results showed that the chemical oxygen demand and Cd(II) removal reached up to 96.17% and 97.60%, higher than the control group of 79.15% and 92.09%, under the influent chemical oxygen demand of 1715 mg/L, Cd(II) of 4.63 mg/L and salinity of 3.0% in bioaugmented system. 16S rRNA analysis revealed that the microbial community in the bioaugmented system adapted to the high-salinity and Cd(II) stress which proved the superiority of bioaugmentation. Finally, a mechanism for high-salinity tolerance in sequencing batch reactor was revealed and provides a basic foundation for the engineered strain to treat Cd(II) containing high-salinity wastewater. This study will promote the understanding of the effect of engineered strains bioaugmentation on the treatment of heavy metals and other pollutants in high-salinity wastewater.

Modeling and optimization of bioenergy production from co-digestion of poultry litter with wheat straw in anaerobic sequencing batch reactor: Response surface methodology and artificial neural network

This study investigated the sequencing batch co-digestion (Co-AD) of poultry litter (PL) and wheat straw (WS) for continuous methane production as a renewable bioenergy resource. Response surface methodology (RSM) and artificial neural network (ANN) were both used to model the methane content (MC, %) in the produced biogas and daily methane yield (DMY, mL CH4/g VS added) from the Co-AD process. The RSM models (R2 = 0.9554, RMSE = 0.813; R2 = 0.9618, RMSE = 4.940) were more accurate than the ANN models (R2 = 0.9163, RMSE = 1.114; R2 = 0.9037, RMSE = 7.847) in predicting MC and DMY, respectively. The optimal conditions for maximum DMY obtained by RSM were a C/N ratio of 22.73 (a mixing ratio of 0.46 g PL to 1.00 g WS on dry matter basis), total solids of 2.27%, and hydraulic retention time of 11.45 days, under which the validation trials showed MC of (58.37 ± 0.25)% and DMY of (184.36 ± 0.51) mL CH4/g VS added with the prediction errors by RSM (1.07% and 1.87%) being relatively lower than that by ANN (4.21% and 4.35%). The models and optimized parameters results could provide support for the operation and prediction of the continuous Co-AD of PL with WS for real bioenergy production applications.

Performance of short-cut denitrifying phosphorus removal and microbial community structure in the A2SBR process

ABSTRACT Acclimatization of short-cut denitrifying polyphosphate accumulating organisms (SDPAOs), metabolic mechanism, and operating parameters were analyzed to investigate the performance of the anaerobic/anoxic sequencing batch reactor (A2SBR) process. The high-throughput sequencing technology was employed to explore the microbial community structures of activated sludge systems. The experimental results illustrated that SDPAOs were successfully enriched with three-phase inoculation for 36 days. The removal rates of TP and NO2 −-N were 93.22% and 91.36%, respectively, under the optimal parameters of a pH of 7.5, an SRT of 26 days, a temperature of 24 ℃ and a COD of 200.00 mg·L−1 using acetate as the carbon source. In the anaerobic stage, 82.20% external carbon source was converted into 88.78 mg·g−1 PHB, and the removal rate of NO2 −-N in the anoxic stage was characterized by ΔNO2 −-N/ΔPHB, anoxic ΔP/ΔPHBeffective was 0.289, which was higher than anaerobic ΔP/ΔCODeffective of 0.203. Ignavibacterium and Povalibacter with significant phosphorus removal ability were the dominant bacterial genera. The nitrogen and phosphorus removal could be realized simultaneously in an anaerobic/anoxic sequencing batch reactor. Therefore, this study provided an important understanding of the removal of nitrogen and phosphorus from low-carbon nitrogen wastewater.

Development and application of random forest regression soft sensor model for treating domestic wastewater in a sequencing batch reactor

Small-scale distributed water treatment equipment such as sequencing batch reactor (SBR) is widely used in the field of rural domestic sewage treatment because of its advantages of rapid installation and construction, low operation cost and strong adaptability. However, due to the characteristics of non-linearity and hysteresis in SBR process, it is difficult to construct the simulation model of wastewater treatment. In this study, a methodology was developed using artificial intelligence and automatic control system that can save energy corresponding to reduce carbon emissions. The methodology leverages random forest model to determine a suitable soft sensor for the prediction of COD trends. This study uses pH and temperature sensors as premises for COD sensors. In the proposed method, data were pre-processed into 12 input variables and top 7 variables were selected as the variables of the optimized model. Cycle ended by the artificial intelligence and automatic control system instead of by fixed time control that was an uncontrolled scenario. In 12 test cases, percentage of COD removal is about 91. 075% while 24. 25% time or energy was saved from an average perspective. This proposed soft sensor selection methodology can be applied in field of rural domestic sewage treatment with advantages of time and energy saving. Time-saving results in increasing treatment capacity and energy-saving represents low carbon technology. The proposed methodology provides a framework for investigating ways to reduce costs associated with data collection by replacing costly and unreliable sensors with affordable and reliable alternatives. By adopting this approach, energy conservation can be maintained while meeting emission standards.

Biosorption and biotransformation behaviours of veterinary antibiotics under aerobic livestock wastewater treatment processes

To study the fate of veterinary antibiotics released from swine wastewater treatment plants (SWTP), 10 antibiotics were investigated in each unit of a local SWTP periodically. Over a 14-month period of field investigation into target antibiotics, it was confirmed that tetracycline, chlortetracycline, sulfathiazole, and lincomycin were used in this SWTP, with their presence observed in raw manure. Most of these antibiotics could be effectively treated by aerobic activated sludge, except for lincomycin, which was still detected in the effluent, with a maximum concentration of 1506 μg/L. In addition, the potential for removing antibiotics was evaluated using lab-scale aerobic sequencing batch reactors (SBRs) that were dosed with high concentrations of antibiotics. The SBR results, however, showed that both sulfonamides and macrolides, as well as lincomycin, can achieve 100% removal in lab-scale aerobic SBRs within 7 days. This reveals that the potential removal of those antibiotics in field aeration tanks can be facilitated by providing suitable conditions, such as adequate dissolved oxygen, pH, and retention time. Furthermore, the biosorption of target antibiotics was also confirmed in the abiotic sorption batch tests. Biotransformation and hydrolysis were identified as the dominant mechanism for removing negatively charged sulfonamides and positively charged antibiotics (macrolides and lincomycin) in SBRs. This is due to their relatively low sorption affinity (resulting in negligible to 20% removal) onto activated sludge in abiotic sorption tests. On the other hand, tetracyclines exhibited significant sorption behavior both onto activated sludge and onto soluble organic matters in swine wastewater supernatant, accounting for 70%–91% and 21%–94% of removal within 24 h, respectively. S-shape sorption isotherms with saturation were observed when high amounts of tetracyclines were spiked into sludge, with equilibrium concentrations ranging from 0.4 to 65 mg/L. Therefore, the sorption of tetracyclines onto activated sludge was governed by electrostatic interaction rather than hydrophobic partition. This resulted in a saturated sorption capacity (Qmax) of 17,263 mg/g, 1637 mg/g, and 641.7 mg/g for OTC, TC, and CTC, respectively.

A Mathematical Study of Metal Biosorption on Algal–Bacterial Granular Biofilms

A multiscale mathematical model describing the metals biosorption on algal–bacterial photogranules within a sequencing batch reactor (SBR) is presented. The model is based on systems of partial differential equations (PDEs) derived from mass conservation principles on a spherical free boundary domain with radial symmetry. Hyperbolic PDEs account for the dynamics of sessile species and their free sorption sites, where metals are adsorbed. Parabolic PDEs govern the diffusion, conversion and adsorption of nutrients and metals. The dual effect of metals on photogranule ecology is also modelled: metal stimulates the production of EPS by sessile species and negatively affects the metabolic activities of microbial species. Accordingly, a stimulation term for EPS production and an inhibition term for metal are included in all microbial kinetics. The formation and evolution of the granule domain are governed by an ordinary differential equation with a vanishing initial value, accounting for microbial growth, attachment and detachment phenomena. The model is completed with systems of impulsive differential equations describing the evolution of dissolved substrates, metals, and planktonic and detached biomasses within the granular-based SBR. The model is integrated numerically to examine the role of the microbial species and EPS in the adsorption process, and the effect of metal concentration and adsorption properties of biofilm components on the metal removal. Numerical results show an accurate description of the photogranules evolution and ecology and confirm the applicability of algal–bacterial photogranule technology for metal-rich wastewater treatment.