Sequencing Batch Reactor Research Articles

Effluent quality improvement in sequencing batch reactor-based wastewater treatment processes using advanced control strategies.

The treatment of wastewater is highly challenging due to large fluctuations in flowrates, pollutants, and variable influent water compositions. A sequencing batch reactor (SBR) and modified SBR cycle-step-feed process (SSBR) configuration are studied in this work to effectively treat municipal wastewater while simultaneously removing nitrogen and phosphorus. To control the amount of dissolved oxygen in an SBR, three axiomatic control strategies (proportional integral (PI), fractional proportional integral (FPI), and fuzzy logic controllers) are presented. Relevant control algorithms have been designed using plant data with the models of SBR and SSBR based on ASM2d framework. On comparison, FPI showed a significant reduction in nutrient levels and added an improvement in effluent quality. The overall effluent quality is improved by 0.86% in FPI in comparison with PI controller. The SSBR, which was improved by precisely optimizing nutrient supply and aeration, establishes a delicate equilibrium. This refined method reduces oxygen requirements while reliably sustaining important biological functions. Focusing solely on the FPI controller's performance in terms of total air volume consumption, the step-feed SBR mechanism achieves an excellent 11.04% reduction in consumption.

Semi‐continuous non‐sterile production of medium chain‐length polyhydroxyalkanoates from fatty acids

AbstractMedium chain‐length polyhydroxyalkanoates (mcl‐PHAs) are efficiently synthesized from fatty acids. It was hypothesized that under non‐axenic conditions, the anti‐microbial properties of fatty acids would reduce growth of microbial competitors and allow Pseudomonas putida LS46 to dominate the population resulting in non‐sterile mcl‐PHA production. Non‐sterile batch and fed‐batch cultures produced similar final mcl‐PHA content, monomer composition, and productivity during 24–27 h cultivations when compared to sterile control cultures for initial octanoic acid concentrations ranging from 5 to 40 mM at an initial pH of 6.5. In the absence of a P. putida inoculum, growth was eventually observed in non‐sterile medium after a lag period of up to 120 h, the length of which was dependent on the octanoic acid concentration. The efficacy of prolonged non‐sterile cultivation was tested using a sequential batch reactor (SBR). After 28 days (672 h), 1.62 g L−1 of total biomass was observed, of which the mcl‐PHA content was 47%. This resulted in a PHA titer of 0.77 g L−1, and a volumetric PHA productivity of 32 mg L−1 h−1. The polymer composition remained stable throughout at 87.0 ± 2.7% C8 monomers, and short‐chain length (scl‐) monomers were not detected. This study is the first of its kind to report that purely mcl‐PHAs were produced after prolonged periods in a non‐sterile environment and demonstrate that medium chain‐length fatty acids exert a strong selective pressure toward organisms that synthesize mcl‐PHA. This suggests an opportunity for mcl‐PHA production in open continuous cultivation, which could reduce both fixed and operating costs.

Quantitative image analysis for assessing extracellular polymeric substances in activated sludge under atrazine exposure

Extracellular polymeric substances (EPS) play a vital role in biological wastewater treatment systems. This study investigates the impact of herbicide atrazine (ATZ) on the overall performance, EPS yield, composition, and sludge morphology in an activated sludge (AS) system operated in a sequencing batch reactor (SBR). Since conventional methods for analyzing EPS are time-consuming and releases residues, a new approach was developed in this work to evaluate the EPS fractions and components, based on the morphological characterization of the biomass using quantitative image analysis (QIA) technique coupled with multivariate statistics.Results showed that exposure to ATZ inhibit biomass activity in terms of organic matter (COD) and nitrogen removal. Moreover, both tightly bound EPS (TB-EPS) and loosely bound EPS (LB-EPS) increased under ATZ, indicating that microorganisms release EPS as a defense mechanism against environmental changes. The PN/PS ratio also increases, indicating likely increased hydrophobicity in ATZ phases. Furthermore, ATZ phases exhibit a predominance of large aggregates compared to intermediate and small ones, indicating a change in aggregate morphological structure associated with EPS production. The new approach using QIA coupled with partial least squares (PLS) modeling provides accurate predictions of EPS content. The increase in TB-EPS is closely related to the rise of large aggregates in phases exposed to higher ATZ concentrations. The PLS models demonstrate high accuracy for EPS prediction (coefficients of determination, R2 above 0.86), showcasing the feasibility of using QIA for EPS assessment in AS systems. This approach offers significant potential for regular process monitoring and management, providing a more environmentally friendly methodology by eliminating the need for chemical usage.

Aerobic granulation and bioresource production under intermittent saline stress

Aerobic Granular Sludge (AGS) systems have gained prominence for liquid waste treatment and bioresource recovery. In this regard, various strategies are employed to accelerate granulation processes in sequencing batch reactors (SBRs) and maximize stability and bioresource production. Intermittent stress supplementation can facilitate granule development, promoting slow-growth microorganisms. At the same time, osmotic stress may enhance bioresource production. In this study, an AGS reactor control with no saline stress (R1) was compared to two AGS systems operated under constant (R2) and intermittent (R3) saline stress in terms of efficiency, stability and bioresource productions (alginate-like exopolysaccharides-ALE and tryptophan). Granulation occurred around day 59 and 21 in R2 and R3, respectively, while complete granulation was not achieved in R1 within the 80-day operational period. However, SBRs performed well after 45 days, with 70% of the biomass being granular. The production of the biopolymer ALE remained more stable in reactors with osmotic stress compared to R1. The microbiological analysis revealed specific responses and adaptations to environmental factors, with genera such as Thauera and Pseudofulvimonas showing higher abundance in reactors with complete granulation, indicating a positive correlation with saline conditions (5 g/L). These insights are crucial for optimizing the performance of AGS systems in future applications, emphasizing the benefits of intermittent saline stress in promoting rapid granulation, stability in bioresource production, contaminant removal, and robust granule formation.

Tofu Liquid Waste Treatment Using Effective Volume of Anaerobic Sequencing Batch Reactor (ASBR)

The tofu industry produces liquid waste containing high organic compounds. Organic compounds in liquid waste can threaten aquatic ecosystems if discharged directly into water bodies. One of the most effective wastewater treatment systems is the treatment using Anaerobic Sequencing Batch Reactor (ASBR). Besides being able to reduce the content of organic compounds, ASBR can produce biogas, and its decomposing microorganisms do not flow into the effluent stream. The purpose of this study was to evaluate the performance of ASBR at an effective reactor volume according to the design. This is because the use of ASBR in previous studies had not reached the operational stage and did not use an effective volume reactor. The stages of waste treatment using ASBR include the seeding, acclimatization, and operation stages. Waste treatment took place at room temperature in the reactor with an effective volume of 6 L. The operating parameters tested were MLVSS, COD, BOD, pH, and cumulative biogas volume. The results obtained show that the seeding process took 56 days, acclimatization took 10 days, and the operation lasted for 17 days. The efficiency of reducing COD concentration was 60%, the efficiency of reducing BOD concentration was 35.65%, and the cumulative volume of biogas produced was 24,120 mL at the operating stage. The use of the ASBR system at an effective volume of 6 L resulted in the successful processing of tofu liquid waste.

Palm Oil Mill Effluent Treatment Technology using Sequencing Batch Reactor (SBR) with Oxidation Reduction Potential (ORP) Monitoring

Palm oil industries have products like Crude Palm Oil (CPO), and 70% of others contain waste. One of the wastes is the liquid waste known as Palm Oil Mill Effluent (POME). The potential of POME to be reprocessed into clean water will be profitable. One of POME's reprocessing methods is the Sequencing Batch Reactor with Aerobic Granulated Sludge (SBR-AGS), which has five main phases: filling, idling, aeration, settling, and discharge, with a cycle time of 360 minutes. The first step in using this reactor is the start-up process, a granule-forming process from some sludge that has already acclimatized. In one complete cycle, the Oxidation-Reduction Potential (ORP) parameter is used to observe the electron transfer process that shows the oxygen supply into the reactor, which enables the condition of each phase in the process to be analyzed. The trend of ORP value is constantly changing in every phase. For the idling phase, the ORP tends to decrease in a value of (-300)-(-400) mV, and for the aeration phase, it will increase in a value of (-100)-100 mV.

Promoting mechanism of nitrogen removal by Fe3O4 magnetic particles during the start-up phase in sequencing batch reactor.

In this paper, a magnetic sequencing batch reactor (SBR) was constructed, and the influence rule of magnetic particle dosing performance of denitrification was investigated. The diversity, structure, and potential functions of the microbial community were comprehensively explored. The results showed that the particle size and the dosage of Fe3O4 magnetic particles were the main parameters affecting the sedimentation performance of activated sludge. The start-up phase of the SBR reactor with Fe3O4 magnetic particles was 5days less than the control. Moreover, total nitrogen removal efficiency during the start-up phase was improved, with the maximum value reaching 91.93%, surpassing the control by 9.7% with the Fe3O4 dosage of 1.2g L-1. In addition, the activated sludge concentration and dehydrogenase activity were improved, compared to the control. High-throughput sequencing showed that the denitrifying bacterium Saccharimonadales dominated the reactor and was enriched by magnetic particles. According to predicted functions, the abundance of genes for denitrification increased with the addition of magnetic particles, suggesting the capacity of nitrogen removal was enhanced in the microbial community. Overall, the Fe3O4 magnetic particles provide great potential for enhanced wastewater nitrogen removal.

A Study of the System Performance and the Microbial Community Composition of Chemical Wastewater in an AO-MBBR Treatment Process

To improve the nitrogen removal and reduce the chemical oxygen demand (COD) of a full-scale wastewater treatment plant, two sequential batch reactor devices were used to treat chemical wastewater with biocarriers in low carbon-to-nitrogen (C/N) ratio conditions. The results showed that the addition of biocarriers to the anoxic tank reduced the average concentration of COD in the effluent from 98.1 mg/L to 80.7 mg/L and increased total nitrogen (TN) removal by 9.4%. Metagenomic sequencing was performed to study the composition and function of microbial community samples taken from anoxic sludge and anoxic-carrier biofilms in this wastewater treatment plant. The results showed that Proteobacteria and Actinobacteria were the dominant phyla in the two samples, ensuring their capability for organic matter removal. The anoxic-carrier biofilms were mainly enriched with denitrifying bacteria such as Thauera (10.7%) and Comammonas (2.2%) and the anammox bacteria Candidatus Kuenenia (0.03%). Meanwhile, the nitrogen metabolism pathway was elaborated and the abundance of the functional genes involved in the nitrogen metabolism pathway was quantified. In addition, results from qPCR showed increased copy numbers of denitrification and anammox genes in the anoxic-carrier biofilms compared to those in the anoxic sludge, further confirming the enrichment of functional bacteria.

Reduction of greenhouse gas emissions from closed activated sludge- to aerobic granular sludge-based biosystems via gas circulation

Greenhouse gas (GHG) emissions from biological treatment units are challenging wastewater treatment plants (WWTPs) due to their wide applications and global warming. This study aimed to reduce GHG emissions (especially N2O) using a gas circulation strategy in a closed sequencing-batch reactor when the biological unit varies from activated sludge (AS) to aerobic granular sludge (AGS). Results show that gas circulation lowers pH to 6.3 ± 0.2, facilitating regular granules but elevating total N2O production. From AS to AGS, N2O emission factor increased (0.07–0.86 %) due to decreasing ammonia-oxidizing rates while the emissions of CO2 (0.3 ± 0.1 kg-CO2/kg-chemical oxygen demand) and CH4 remained in the closed biosystem. The gas circulation decreased N2O emission factor by 63 ± 15 % after granulation higher than 44 ± 34 % before granulation, which is implemented by heterotrophic denitrification. This study provides a feasible strategy to enhance heterotrophic N2O elimination in the biological WWTPs.

Effect of influent C/N ratios on high-concentration powder carrier bio-fluidized bed (HPB) process: Performance, sludge characteristics, and microbial community

High concentration powder carrier bio-fluidized bed (HPB) process has demonstrated significant advantages in municipal wastewater treatment. However, the influent C/N ratio as an important factor has not yet been explored in HPB system. In this study, eight parallel sequential batch reactors (SBR) were established to investigate the effect of influent C/N ratio on HPB process, using diatomite powder and FeC powder as carriers, respectively. Process performance, sludge characteristics, and functional microbes under different C/N ratio (2–8) were explored. Results showed that TN removal efficiency reached 48.2 %, 64.3 %, 76.8 %, and 83.3 %, respectively, in diatomite group, and it was stable at 64.0 %, 73.6 %, 80.2 %, and 83.1 %, respectively, in FeC group. The increase in influent C/N ratio improved the denitrification in anoxic period while also enhancing the simultaneous nitrification and denitrification in aerobic period. A higher sludge concentration and a bigger particle size were observed under a higher C/N ratio. EPS content also showed an upward tread with increase in C/N ratio, and EPS content in biofilm was always higher than that in floc sludge in both diatomite and FeC groups. Microbial analysis suggested the activity rate and abundance of denitrifying bacteria was enhanced with increase in C/N ratio, while it declined in nitrifying and anammox bacteria. The rich pore and groups of diatomite promoted the enrichment of nitrifying bacteria. And denitrification process was enhanced by FeC carrier as electron donors and its micro-electrode functions. These results will provide a theoretical basis for operation optimization and engineering practice of the HPB process.

Phosphate recovery from urban sewage by the biofilm sequencing batch reactor process: Key factors in biofilm formation and related mechanisms

The biofilm sequencing batch reactor (BSBR) technique has been deployed in the laboratory to enrich phosphorus from simulated wastewater, but it is still not clear what its performance will be when real world sewage is used. In this work, the effluent from the multi-stage anoxic-oxic (AO) activated sludge process at a sewage plant was used as the feed water for a BSBR pilot system, which had three reactors operating at different levels of dissolved oxygen (DO). The phosphorus adsorption and release, the biofilm growth, and the extracellular polymeric substances (EPS) components and contents were examined. The microbial communities and the signaling molecules N-acyl-l-homoserine lactones (AHLs) were also analyzed. Gratifyingly, the BSBR process successfully processed the treated sewage, and the biofilm developed phosphorus accumulation capability within 40 days. After entering stable operation, the system concentrated phosphate from 2.59 ± 0.77 mg/L in the influent to as much as 81.64 mg/L in the recovery liquid. Sludge discharge had profound impacts on all aspects of BSBR, and it was carried out successfully when the phosphorus absorption capacity of the biofilm alone was comparable to that of the reactor containing the activated sludge. Shortly after the sludge discharge, the phosphate concentration of the recovery liquid surged from 50 to 140 mg/L, the biofilm thickness grew from 20.56 to 67.32 μm, and the diversity of the microbial population plunged. Sludge discharge stimulated Candidatus competibacter to produce a large amount of AHLs, which was key in culturing the biofilm. Among the AHLs, both C10-HSL and 3OC12-HSL were significantly positively correlated with EPS and the abundance of Candidatus competibacter. The current results demonstrated BSBR as a viable option to enrich phosphorus from real world sewage with low phosphorus content and fluctuating chemistry. The mechanistic explorations also provided theoretical guidance for cultivating phosphorus-accumulating biofilms.

The combination of ciprofloxacin and dialkyldimethyl ammonium compound synergistically proliferated intracellular resistance genes in nitrifying system

Antibiotics and quaternary ammonium compounds (QACs) usually co-exist in wastewater treatment plants. Hence, three sequencing batch reactors were established and named as R1, R2 and R3, to investigate the effects of individual and combined exposure of different concentrations of ciprofloxacin (CIP) (0.2, 1.0 and 2.0 mg/L) and dialkyldimethyl ammonium compound (DADMAC) (0.4, 2.0 and 4.0 mg/L) on the performance, microbial community structures and resistance genes (RGs) in nitrifying system during 150 days. Results showed that CIP had a slight effect on ammonia oxidation activity, while 2.0 and 4.0 mg/L DADAMAC could obviously inhibit it, and the combination of CIP and DADMAC had a synergistic inhibitory effect. Besides, both CIP and DADMAC caused partial nitrification, and the order of nitrite accumulation rate was ranked as R3 > R2 > R1. The combination of CIP and DADMAC had an antagonistic effect on the increase of sludge particle size and α-Helix/(β-Sheet + Random coil) was lowest in R3 (0.40). The combination of CIP and DADMAC synergistically stimulated most intracellular RGs in sludge, and the relative abundances of target RGs (e.g., qacEdelta1-01, qacH-01 and qnrS) at the end of operation in R3 were increased by 4.61–18.19 folds compared with those in CK, which were 1.34–5.57 folds higher than the R1 and R2. Moreover, the combination of CIP and DADMAC also promoted the transfer of RGs from sludge to water and enriched more potential hosts of RGs, further promoting the spread of RGs in nitrifying system. Thus, the combined pollution of CIP and DADMAC in wastewaters should attract more attentions.

Influence of operation sequences on phosphorus recovery by polyphosphate-accumulating organisms biofilm: Performance, kinetics and metabolic response

Two biofilm sequencing batch reactors (BSBRs) were conducted under alternating aerobic/anaerobic (Ae/An) sequence and alternating anaerobic/aerobic (An/Ae) sequence to investigate the effects of operation sequences on phosphorus removal and recovery performance. The Ae/An BSBR had advantages in phosphate enrichment, phosphorus concentration of enrichment solution can reach 99.08 mg/L. While An/Ae BSBR exhibited a higher kinetic rate for phosphate uptake and release up to 0.48 mmol/gVSS. In An/Ae BSBR, the remarkable increase of phosphate concentration in aerobic stage put a great strain on the phosphate uptake of biofilms that led to an increase of phosphorus accumulation in the biofilm (Pbiofilm). However, the poly-P proportion in TPbiofilm decreased which triggered the metabolisim of polyphosphate accumulating organisms (PAOs) shifting from polyphosphate accumulating metabolism (PAM) to glycogen accumulating metabolism (GAM) and suppressed the phosphorus enrichment performance of the An/Ae BSBR. The phosphate uptake rate (PUR) of biofilms was in alignment with the bulk phosphate concentration. PAOs were dominated by Rhodoplanes and Saprospiraceae in the Ae/An BSBR, whereas Thiothrix was predominant in the An/Ae BSBR. Notably, the Candidatus Competibacter, considered as a denitrifying glycogen accumulating organisms (DGAOs), showed a dominant proportion in the microbial community of both BSBRs. The higher expression of actP in the An/Ae system indicated a greater capacity for the uptake of acetate, while the Ae/An system was is more adept for degrading acetate represented by the higher relative abundance of ackA, pta and acsA genes The high phosphorus loading in the An/Ae system suppressed the ppk expression but enhanced the ppx expression.

Case Study of Deterioration of Mansar Lake and Comparative Study of FAB and SBR Technologies in Sewage Treatment Plant

The deterioration of Mansar Lake, a significant tourist attraction and a vital water resource in India, has become a matter of concern due to the discharge of untreated sewage and industrial effluents. The present study aims to investigate the factors leading to the degradation of Mansar Lake and the effectiveness of two advanced sewage treatment technologies, Fixed Activated Beds (FAB) and Sequencing Batch Reactors (SBR), in treating sewage waste. The study begins with a comprehensive analysis of the factors contributing to the degradation of Mansar Lake, including the inflow of untreated sewage, industrial effluents, and agricultural runoff, as well as the impact of climate change and anthropogenic activities. The research then moves on to the comparative study of FAB and SBR technologies, evaluating their performance in terms of pollutant removal efficiency, energy consumption, and operational costs. The results of the study show that both FAB and SBR technologies are effective in treating sewage waste, with SBR technology having a slight edge in terms of pollutant removal efficiency. However, FAB technology is more cost-effective and energy-efficient, making it a more viable option for developing countries with limited resources. The study concludes with recommendations for the implementation of FAB technology in the sewage treatment plant serving Mansar Lake, as well as the need for stricter regulations and enforcement to prevent the inflow of untreated sewage and industrial effluents into the lake. The study also emphasizes the importance of public awareness and education in preserving the lake's ecological balance and promoting sustainable tourism practices. Mansar Lake, sewage treatment, FAB technology, SBR technology, pollutant removal efficiency, cost-effectiveness, energy efficiency, sustainable tourism.

Synergistic degradation efficiency of nitrogen, phosphorus and microbial dynamic succession driven by a novel strain Gordonia sp. D4 during synthetic wastewater treatment

Nitrogen (N) and phosphorus (P) coexist in the industrial and domestic wastewater posed a pressing challenge for synergistic removal of N and P by bioenhancement. In this study, a novel denitrifying phosphorus-accumulating organism (DPAO) of Gordonia sp. D4, exhibited peak NO3--N, NO2--N, NH4+-N and TP removal efficiencies of 98.11%, 65.02%, 85.34% and 100%, corresponding to 9.30 mg/(L·h), 6.08 mg/(L·h), 3.63 mg/(L·h) and 0.47 mg/(L·h) removal rates, respectively. Strain D4 contained the nitrogen cycling genes narK, narI, narJ, narH, narG, nirB and nirD, as well as the phosphorus cycling genes ppk1, ppk2 and ppx-gppA, which contributes to its excellent simultaneous removal of N and P. More importantly, the addition of D4 into the sequencing batch reactor (SBR) significantly improved the P, TN and NO3--N removal efficiencies by 18.91%, 7.35%, and 18.55%, respectively. This was closely related to the clear enrichment of Gordonia and its contribution to the increasing abundances of Pararhodobacter, unclassified_f_Cyclobacteriaceae, unclassified_o_Rhodospirillales, Thauera and Candidatus Promineofilum and their associated functional genes that drive P or N removal, thereby enhancing the N and P synergistic degradation efficiency. This study provides a valuable strain resource and process reference for the simultaneously removing N and P from the wastewater.

Response of nitrification system to co-exposure of sucralose and single or combined disinfectants: Reducing damage to nitrification performance and aggravating the spread of intracellular resistance genes

Sucralose (SUC) is an artificial sweetener for everyday consumption and often co-exists with disinfectants such as triclosan (TCS) and dialkyldimethyl ammonium compound (DAC) in sewage. Considering their continuous accumulation in sewage, it is essential to understand the impacts of their single and combined stress on the evolution of resistance genes (RGs) and microorganisms. In this study, three sequencing batch reactors (SBRs) were established, which were added with SUC, disinfectant, SUC and disinfectant, respectively, and named SSBR, DSBR and SDSBR in turn. There were four stages in total, the first two stages and the latter two stages were set to explore the effects of co-exposure of SUC and single disinfectant (TCS), SUC and combined disinfectants (TCS and DAC) on nitrification system, respectively. SSBR showed excellent ammonia oxidation performance in the whole operation stages. Compared with DSBR, the microorganisms in SDSBR under the combined stress of SUC and TCS were less inhibited. TCS and DAC destroyed the ammonia oxidation performance of DSBR and SDSBR. Within 120 days, the removal efficiency of TCS reached 90 %. In SSBR, 1 mg/L SUC promoted the proliferation of RGs, especially induced free RGs in water (w-RGs) to maintain high abundance and persistence. Compared with single stress, the abundances of intracellular RGs in sludge were higher under the combined stress of SUC and TCS, and the risk of RGs transmission was greater. The combined stress of SUC and disinfectants (TCS and DAC) led to a higher enrichment of w-RGs, exacerbating the risk of w-RGs transmission.

Comparison of nitrification performance in SBR and SBBR with response to NaCl salinity shock: Microbial structure and functional genes

Ammonia removal by nitrifiers at the extremely high salinity poses a great challenge for saline wastewater treatment. Sequencing batch reactor (SBR) was conducted with a stepwise increase of salinity from 10 to 40 g-NaCl·L−1, while sequencing batch biofilm reactor (SBBR) with one-step salinity enhancement, their nitrification performance, microbial structure and interaction were evaluated. Both SBR and SBBR can achieve high-efficiency nitrification (98% ammonia removal) at 40 g-NaCl·L−1. However, SBBR showed more stable nitrification performance than SBR at 40 g-NaCl·L−1 after a shorter adaptation period of 4–15 d compared to previous studies. High-throughput sequencing and metagenomic analysis demonstrated that the abundance and capability of conventional ammonia-oxidizing bacteria (Nitrosomonas) were suppressed in SBBR relative to SBR. Gelidibacter, Anaerolineales were the predominant genus in SBBR, which were not found in SBR. NorB and nosZ responsible for reducing NO to N2O and reducing N2O to N2 respectively had s strong synergistic effect in SBBR. This study will provide a valuable reference for the startup of nitrification process within a short period of time under the extremely high NaCl salinity.

Efficacy and mechanism of enhanced Sb(V) removal from textile wastewater using ferric flocs in aerobic biological treatment

Antimony contamination from textile industries has been a global environmental concern and the existing treatment technologies could not reduce Sb(V) to meet the discharge standards. To overcome this shortcoming, ferric flocs were introduced to expedite the biological process for enhanced Sb(V) removal in wastewater treatment plant (WWTP). For this purpose, a series of laboratorial-scale sequential batch reactor activated sludge processes (SBRs) were applied for Sb(V) removal with varied reactor conditions and the transformation of Fe and Sb in SBR system was investigated. Results showed a significant improvement in Sb(V) removal and the 20 mg L−1 d−1 iron ions dosage and iron loss rate was found to be only 15.2%. The influent Sb(V) concentration ranging 153–612 μg L−1 was reduced to below 50 μg L−1, and the maximum Sb(V) removal rate of the enhanced system reached about 94.3%. Furthermore, it exhibited high stability of Sb(V) removal in the face of antimonate load, Fe strike and matrix change of wastewater. Sludge total Sb determination and capacity calculation revealed decreasing in Sb adsorption capacity and desorption without fresh Fe dosage. While sludge morphology analysis demonstrated the aging and crystallization of iron hydroxides. These results verify the distinct effects of fresh iron addition and iron aging on Sb(V) removal. High-throughput gene pyrosequencing results showed that the iron addition changed microbial mechanisms and effect Fe oxidized bacterial quantity, indicating Sb(V) immobilization achieved by microbial synergistic iron oxidation. The present study successfully established a simple and efficient method for Sb(V) removal during biological treatment, and the modification of biological process by iron supplement could provide insights for real textile wastewater treatment.

Effects and mechanisms of oxytetracycline and norfloxacin on microbial extracellular polymeric substances (EPS) in biological denitrification of aquaculture wastewater

The direct equalizing ray method was employed to design three groups of mixtures of oxytetracycline(OTC) and norfloxacin(NOR) with varying proportions(Group R1 had a higher proportion of OTC, while R2 had similar concentrations of both antibiotics, and R3 had a higher proportion of NOR).The effects of these mixtures on the content and properties of extracellular polymeric substances (EPS) in the biological denitrification process were investigated using an sequencing batch reactor activated sludge reactor (SBR). The results revealed that the removal rates of ammonia nitrogen(NH3-N) decreased in all three groups with the addition of antibiotics. As the antibiotic concentration increased, the EPS content decreased by 68.46%, 55.53%, and 65.03% in R1, R2, and R3, respectively. To understand the interaction mechanism of mixed antibiotics on EPS in activated sludge, Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) techniques were employed. The findings demonstrated significant effects of mixed antibiotics on functional groups such as C-O, CO, and C-O-C. Specifically, hydrogen bonding was found to be the primary influencing factor in the R1 ratio, while Π-Π conjugation played a major role in the R3 ratio.

Nutrient removal and emission of nitrous oxide and methane by a sequencing batch reactor treating wastewater with and without landfill leachate

Wastewater and landfill leachate treatment processes have the potential to generate nitrous oxide (N2O) and methane (CH4), both significant greenhouse gases (GHG). However, little is known about these emissions when a combined treatment approach (wastewater with leachate) is utilized. This study aimed to assess the emissions of these gases and nutrient removal in an anaerobic/aerobic/anoxic sequencing batch reactor (SBR) employed for treating wastewater with landfill leachate (1% v/v). Leachate contributes significantly to the removal of organic matter and nutrients, primarily phosphorus. The production and emission of N2O occurred during the aerobic phase, whereas CH4 was produced in the anaerobic and anoxic phases. This gas was emitted at the beginning of the aerobic phase and in the end of anoxic phase. The emission factors obtained in this work were 0.0108 and 0.0119 kg N2O-N per kg TNinfluent and 0.000225 and 0.000253 kg CH4-C per kg CODinfluent with and without landfill leachate, respectively. Regarding CO2-equivalent, the N2O was the major contributor, accounting for 99% of the emitted GHG by the process. Further studies are required; however, the main findings of this study suggest that this system may be appropriate when lower GHG emissions are required.