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The work presents the concept of aerobic granular sludge (AGS) and its potential for wastewater treatment. The work also evaluates the condition of the SBR (Sequencing Batch Reactor) type of municipal wastewater-treatment plant (WWTP) after its reconstruction into a system with AGS. The WWTP parameters achieved before and after reconstruction were compared. Operational measurements of the process during the individual phases of the treatment process showed a balanced concentration profile of the monitored parameters in the span of the semicontinuous cycle. Laboratory tests showed that the sludge from the WWTP has nitrification and denitrification rates comparable to the rates achieved for flocculent sludge, and it is also comparable to the nitrification and denitrification rates of AGS with size of granules below 400 µm. Despite the fact that complete sludge granulation was not achieved, the results measured at the WWTP confirmed the advantages of the AGS concept. Neither anaerobic nor anoxic conditions were identified in the SBR during the individual phases of operation, yet high removal efficiencies of ammonia and nitrate nitrogen and orthophosphate phosphorus were achieved. The concentration of ammonia and nitrate nitrogen at the WWTP effluent was below 5 mg/L, and the concentration of phosphorus was below 0.5 mg/L. [ABSTRACT FROM AUTHOR]

Abstract The sequencing batch reactor has emerged as a promising technology in treating wastewater; however, its application in the treatment of generated water still needs to be explored. This research gap led to the investigation of various carbon-to-nitrogen (C/N) ratios in a column-type sequencing batch reactor (cSBR). The resulting data and model demonstrated that augmenting the SND process with an external carbon source is effective until the C/N ratio reaches 15, ultimately eliminating nitrogen in the produced water. Conversely, a reduced C/N ratio can limit the ability of polyphosphate-accumulating organisms to incorporate carbon into polyphosphate synthesis, thereby decreasing phosphorus removal efficiency within the cSBR. When the C/N ratio ranged from 6 to 8, and the mixed liquor suspended solids concentration was high, the average phosphate removal was approximately 55%, compared to only around 25% when the C/N ratio was less than 6.

The soil surface in the southern Xinjiang region has a high salt content, and flooding water causes salt dissolution and pollutes surface water. Therefore, it is particularly important to study the technology of nitrogen and phosphorus removal in the degradation of high salt wastewater. Activated sludge was inoculated in an SBR system with a height to diameter ratio (RH/D) of 7.5, and synthetic wastewater (containing 0.25 mg/L Ni2+) was used as influent to analyze the changes in sludge morphology, pollutant removal performance, microbial community during the sludge granulation process, as well as the ability of granular sludge to remove pollutants from high salt wastewater under salinity stress. The results showed that the mature granular sludge was yellow in multiple forms, with an average particle size of 357 μm. The average removal rates of COD, TP, and NH4+-N in wastewater were 95%,91.27%,and 94.5%, respectively. The dominant bacterial genera were Zoogloea, Flavobacterium,and Unclassified_f_Comamonadaceae. The influent water quality would change the relative abundance of microorganisms, while there was no significant impact on the microbial community structure. When the salt application rate was 15 g/L, the removal rates of COD, TP, and NH4+-N were 86.7%, 67.2%, and 62.6%, respectively. The sludge maintained good carbon removal ability. When the salt application rate exceeded 15 g/L, the removal rates of all indicators showed a downward trend. The application of low concentrations of heavy metals accelerated the start-up of granular sludge and targeted microorganisms for nitrogen and phosphorus removal, which had reference for the treatment of pollutants in high salt wastewater.

To assess the possibility of using aerobic denitrification (AD) bacteria with high NO2−-N accumulation for nitrogen removal in wastewater treatment, conditional optimization, as well as sole and mixed nitrogen source tests involving AD bacterium, Comamonas sp. pw-6 was performed. The results showed that the optimal carbon source, pH, C/N ratio, rotational speed, and salinity for this strain were determined to be succinate, 7, 20, 160 rpm, and 0%, respectively. Further, this strain preferentially utilized NH4+-N, NO3−-N, and NO2−-N, and when NO3−-N was its sole nitrogen source, 92.28% of the NO3−-N (150 mg·L−1) was converted to NO2−-N. However, when NH4+-N and NO3−-N constituted the mixed nitrogen source, NO3−-N utilization by this strain was significantly lower (p < 0.05). Therefore, a strategy was proposed to combine pw-6 bacteria with traditional autotrophic nitrification to achieve the application of pw-6 bacteria in NH4+-N-containing wastewater treatment. Bioaugmented application experiments showed significantly higher NH4+-N removal (5.96 ± 0.94 mg·L−1·h−1) and lower NO3−-N accumulation (2.52 ± 0.18 mg·L−1·h−1) rates (p < 0.05) than those observed for the control test. Thus, AD bacteria with high NO2−-N accumulation can also be used for practical applications, providing a basis for expanding the selection range of AD strains for wastewater treatment. HIGHLIGHTS Optimal C source, pH, C/N ratio, and salinity for Comamonas sp. pw-6 were found.; Strain pw-6 preferentially utilized NH4+-N, NO3−-N, and NO2−-N, successively.; When NO3−-N was the sole nitrogen source, 92.28% of the NO3−-N converted to NO2−-N.; Addition of pw-6 into sequencing batch reactor can enhance NH4+-N and total inorganic nitrogen removal and reduce NO3−-N accumulation.;

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vertical oxidation pond operated in sequencing batch mode (HRT: 1.25 day) with duckweed as the vegetation was used to acclimatize with simulated agricultural wastewater. The maximum removal rate of urea [371 g/(m3.d)] and COD [222.4 g/(m3.d)] were observed at moderate concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L). Inhibition and toxicity posed by higher concentrations, decreased the removals of urea (83% to 61%), COD (81% to 51%), and TDS (76% to 50%) at the end of the acclimatization. Steady removal (> 99%) of PO43−-P was observed during acclimatization. Effluent pH increased due to the generation of NH4+-N (maximum 370 ± 5 mg/L) from the assimilation of urea. Oxidation of ammonia led to the maximum generation of NO2−-N and NO3−-N of 10 mg/L and 9 mg/L, respectively. Particles less than 300 μm increased, and both specific gravity (from 2.62 to 2.42) and maximum dry density (from 1.73 to 1.30 g/cm3) of the base soil decreased with an increase in urea, N-P-K, and pesticide. Reactor biomass increased (1.42 to 1.90 g/L) up to initial concentrations of urea (500 mg/L), N-P-K (60 mg/L), and pesticide (20 mg/L), then decreased (1.68 g/L) with an increase in concentration. [ABSTRACT FROM AUTHOR]

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.

Anaerobic oxidation of methane (AOM) is capable of coupling the reduction of various substrates, which plays a crucial role in accelerating the abatement of pollution. In this study, we employed a sequencing batch reactor (SBR) to enrich a mixed consortium that included AOM microbes and examined the ensuing microbial reduction of tellurate. To obtain the mixed consortium, we enriched AOM microbes in anaerobic conditions utilizing methane as the only electron donor, with nitrate serving as the electron acceptor. We evaluated the abundance of typical methane-oxidizing microbes and associated genes in the reactor using quantitative PCR. Notably, the enriched microbes were able to achieve microbial tellurate reduction and produce elemental tellurium. An analysis of community structure further indicated the vital roles of methanotrophs, denitrifiers, and other heterotrophs in the reactor, although their molecular mechanisms require further investigation. These findings underscore the role of enriched microbial communities in tellurate reduction using a lab-scale SBR, laying the groundwork for future studies into the mechanism of this process, which utilizes methane as an electron donor. [ABSTRACT FROM AUTHOR]

In this paper, the novelty consists of determining kinetic parameters for sequencing batch reactor (SBR) operated for the experimental design Nº1 (ED-1) under single (oxic) and combined biological sequences in two phases (anaerobic-oxic) treating a Chemical Oxygen Demand (COD) influent around 5,466 mg/L. ED-2 comprised three phases (anoxic I-oxic-anoxic II) with the influent containing COD (1,119-1,598 mg L−1), NH4+-N (63-94.5 mg L−1 and Total Kjeldahl Nitrogen (126 - 175 mg L−1). Kinetic parameters corresponded to the substrate maximum utilization rate r(m,S) and the half-saturation coefficient (Ks) The r(m,COD) and Ks was increased as the biological phases were increased from single oxic phase (−60 mg L−1 h−1; 2704 mg L−1), anaerobic-oxic phases (−100 mg L−1 h−1; 1,069.8 mg L−1) to the anoxic I –oxic-anoxic II phases (−250 mg L−1 h−1). The kinetic coefficients were significant in the first anoxic and the oxic phases of SBR, for conventional and simultaneous nitrification-denitrification. [ABSTRACT FROM AUTHOR]

As a typical representative of sulfonamides，sulfamethoxazole （SMZ） has a potential threat to biological phosphorus removal process. In order to explore its impact on biological phosphorus removal performance and its mechanism，a sequencing batch reactor was constructed to determine the impact of sulfamethoxazole on reactor performance，explore the impact of sulfamethoxazole on the content of microbial metabolic intermediates（poly-P，PHB and glycogen） and the activity of key enzymes（PPX，PPK）. Moreover， the micro mechanism of sulfamethoxazole on key enzymes were analyzed with molecular docking technology. The results showed that low concentrations of sulfamethoxazole（0.05 mg/L and 0.1 mg/L） had no significant effect on biological phosphorus removal performance，the content of metabolic intermediates and the activity of key enzymes. When the concentration of sulfamethoxazole increased to 1 mg/L，it began to inhibit biological phosphorus removal performance. With the increase of its concentration，the inhibition increased. Furthermore， the synthesis and degradation of poly-P and PHB in microbial cells decreased with the increase of the concentration of sulfamethoxazole， while the synthesis and degradation of glycogen will increase significantly. The inhibition rate of sulfamethoxazole on key enzyme activities increased with the rise of concentration. The molecular docking results showed that sulfamethoxazole combined with the amino acid residues in the enzyme activity center to form a complex，thus changing the structure of the enzyme.

Copyright of Industrial Water Treatment is the property of CNOOC Tianjin Chemical Research & Design Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The technological development for efficient nutrient removal from liquid dairy manure is critical to a sustainable dairy industry. A nutrient removal process using a two-step fed sequencing batch reactor (SBR) system was developed in this study to achieve the applicability of simultaneous removal of phosphorus, nitrogen, and chemical oxygen demand from anaerobically digested liquid dairy manure (ADLDM). Three operating parameters, namely anaerobic time:aerobic time (min), anaerobic DO:aerobic DO (mg L−1), and hydraulic retention time (days), were systematically investigated and optimized using the Taguchi method and grey relational analysis for maximum removal efficiencies of total phosphorus (TP), ortho-phosphate (OP), ammonia-nitrogen (NH3-N), total nitrogen (TN), and chemical oxygen demand (COD) simultaneously. The results demonstrated that the optimal mean removal efficiencies of 91.21%, 92.63%, 91.82%, 88.61%, and 90.21% were achieved for TP, OP, NH3-N, TN, and COD at operating conditions, i.e., anaerobic:aerobic time of 90:90 min, anaerobic DO:aerobic DO of 0.4:2.4 mg L−1, and HRT of 3 days. Based on analysis of variance, the percentage contributions of these operating parameters towards the mean removal efficiencies of TP and COD were ranked in the order of anaerobic DO:aerobic DO > HRT > anaerobic time:aerobic time, while HRT was the most influential parameter for the mean removal efficiencies of OP, NH3-N, and TN followed by anaerobic time:aerobic time and anaerobic DO:aerobic DO. The optimal conditions obtained in this study are beneficial to the development of pilot and full-scale systems for simultaneous biological removal of phosphorus, nitrogen, and COD from ADLDM. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the influencing factors and characteristics of granule morphology through approximately 500 d of long-term monitoring of two types of anaerobic–aerobic phosphorus-accumulating organism (PAO) and anaerobic–anoxic denitrifying PAO (DPAO) sequencing batch reactors (SBRs). The results show that granules were present in the DPAO SBR and PAO SBR after 200 d and 250 d of operation, respectively. The average diameters of the granules were 2.2 ± 0.7 mm in the DPAO SBR and 0.4 ± 0.3 mm in the PAO SBR, respectively. The DPAO granular sludge contained rod-shaped microorganisms, whereas the PAO granular sludge contained cocci-type microorganisms. A precipitated core consisting of hydroxyapatite was found in the DPAO granules. A comparative analysis conducted under various operating conditions revealed that the availability and type of the electron acceptors (EAs) may have a significant impact on granulation. This observation suggests that the presence and diversity of EAs are crucial factors for the development of different granule sizes and morphologies. [ABSTRACT FROM AUTHOR]

Activated sludge filtration performance is a significant mean to evaluate membrane fouling trend for wastewater treatment. Here the impact of sunlight irradiation on activated sludge filtration performance and microbial communities in sequencing batch reactors (SBRs) when treating raw landfill leachate were studied. The sludge in photic SBR (i.e., SBR exposed to natural sunlight) exhibited better filtration performance compared to dark SBR (i.e., SBR unexposed to sunlight). The removal efficiency of COD and NH4+‐N in the photic SBR were slightly higher than those in the dark SBR. The contents of the extracellular polymeric substances (EPSs) of sludge in both SBRs initially increased and then decreased. However, in the later period, the sludge filtration performance worsened due to the fungal activity in the dark SBR. Natural sunlight irradiation promoted sludge filtration performance by affecting the microorganism structure in the photic SBR. The bacterial genus Thauera was dominant in the photic SBR (39.35%), whereas Planktosalinus and Ottowia were dominant in the dark SBR (16.84% and 12.55%, respectively). Natural sunlight irradiation had a prominent effect on the fungal diversity in the system, and filamentous bulking caused by the fungi genus Trichosporon's proliferation was observed in the dark SBR but not in the photic SBR, which also increased the polysaccharide content. [ABSTRACT FROM AUTHOR]

Coconut fiber waste has the potential to become a value-added product as a biofilm media and an adsorbent. The addition of biofilm media and adsorbent is important because it reduces the amount of sludge produced in wastewater. Furthermore, the quality of wastewater produced by the IASBR process with the addition of biofilm media and adsorbents can be used as clean water. The wastewater used comes from apartment wastewater. The IASBR was used to determine the optimal anoxic-aerobic processing time in a tropical climate. The study will further compare the efficiency of the two by using discarded coconut fiber as an additional adsorbent and biofilm media. The optimal adsorbent dose and weight of waste coconut fiber, and hydraulic retention time optimization were all examined. As a result, clean water was discovered to be the primary product after the addition of adsorbent and biofilm media made from waste coconut fiber.

In this article, the utilization rate of organic and nitrogenous substrates contained in tannery wastewater by a sequential batch reactor is evaluated. Two factorial experimental designs (FEDs) were implemented. FED1 (22) used granular biomass, the aeration sequence (oxic, anaerobic-oxic) and cycle duration (6 and 24 h). FED2 (4 x 3) included suspended biomass, reaction phases (anoxic I, oxic, anoxic II (CND: conventional nitrification-denitrification) and (SND: simultaneous nitrification-denitrification), filling time (fast, slow and in stages). The substrates examined were chemical oxygen demand (COD), ammonium (NH4+-N) and total nitrogen Kjeldahl (TKN). The utilization rates were COD (-100 and -200 mg l-1 h-1) (FED1) and (-48 and -75 mg l-1 h-1) (FED2), being 1.5 to 2 times higher in FED1 than FED2. In TKN (-5 mg l-1 h-1), and NH4+-N (-30 mg l-1 h-1), they were significant in the anoxic I and oxic phases.

This study quantifies the hydraulic performance of a pilot-scale ultrafiltration system integrated into a full-scale industrial aerobic granular sludge (AGS) plant. The treatment plant consisted of parallel AGS reactors, Bio1 and Bio2, with similar initial granular sludge properties. During the 3-month filtration test, a chemical oxygen demand (COD) overloading episode took place, affecting the settling properties, morphology, and microbial community composition in both reactors. The impact on Bio2 was more severe than on Bio1, with higher maximal sludge volume index values, a complete loss of granulation, and the excessive appearance of filamentous bacteria extending from the flocs. The membrane filtration properties of both sludges, with these different sludge qualities, were compared. The permeability in Bio1 varied between 190.8 ± 23.3 and 158.9 ± 19.2 L·m−2·h−1·bar−1, which was 50% higher than in Bio2 (89.9 ± 5.8 L·m−2·h−1·bar−1). A lab-scale filtration experiment using a flux-step protocol showed a lower fouling rate for Bio1 in comparison with Bio2. The membrane resistance due to pore blocking was three times higher in Bio2 than in Bio1. This study shows the positive impact of granular biomass on the long-term membrane filtration properties and stresses the importance of granular sludge stability during reactor operation. HIGHLIGHTS Well-filterable sludge was obtained by applying a feast (anaerobic)/famine (aerobic) feeding strategy.; The better the granules' properties, the lower the fouling rate and permeability loss.;

Distillery wastewater is a difficult type of wastewater to treat because of its low pH (pH = 3.3), high chloride and sulfate content, high organic matter concentrations (3.2 gTSS/L, 6.8 gBOD5/L and 14.6 gCOD/L). Moreover, the rum production is intermittent over the season (5 months per year). The acidity of this type of wastewater, combined with the relatively underbalanced nitrogen concentrations, requires the addition of specific chemicals such as soda solution and urea, when a biological treatment technology is envisioned. In this full scale experiment, located in a tropical zone (Martinique island), the objective was to demonstrate the ability of treatment chain composed of a sequencing batch reactor (SBR) followed by vertical flow treatment wetlands (VFTWs). The objective was to use VFTWs for treatment polishing as well as sludge/water separation and sludge treatment over years. The VFTWs are planted with Heliconia psittacorum and Cyperus papyrus. The monitoring occurred during three rum production seasons. The treatment chain allows an overall average removal of TSS of 92% and 96% for organic matter (COD and BOD5). The average annual load applied to the filter in operation was 32 kgTSS/m²/y, which is equivalent to 78 kgTSS/m²/y over the distillation period. The applied load was too high for the plants tested and lead to plant death and surface clogging of the filters. Nevertheless, this experiment allowed specifying the way to operate the whole treatment plant as well as acceptable daily loads that should be applied on the VFTWs. Even if the operation of the filters and the selection of plants in a tropical climate still need to be optimized, this combination of intensive and extensive processes is an effective and sustainable nature-based solution for rum distillery wastewater treatment.

The synthesis of polyhydroxyalkanoates (PHA) using mixed microbial cultures (MMC) has been studied in three stages: a sequencing batch reactor, a PHA accumulation reactor, and a pyruvate effect. Tainan pig farm, Chiayi pig farm, and Feng Chia University's sludge were the three seed sludges tested. Two distinct substrates are used, such as effluent from sucrose acidified fermenter and molasses waste acidified fermenter. Both substrates showed significant COD and VFA, but the effluent from molasses waste acidified fermenter had more significant acetic acid and butyric acid levels, with 4,087 ± 128 and 8,151 ± 152 mL/L, respectively. The propionic acid content in effluent from sucrose acidified fermenter is more significant (4,789 ± 36 mg/L). The highest PHA production yield in the three seed sludges was 26.88%, 22.88%, and 21.90%. Tainan pig farm sludge had the highest PHA accumulation of 26.88%. This study validated MMC's ability to produce PHA in 8 h using VFA efficiency. The present work employed the addition of pyruvate to enhance the MMC. The 1 g addition of pyruvate in a sequencing batch reactor (SBR) can increase the productivity of PHAs yielded 53.58 g PHAs/g VSS (%), respectively. Therefore, MMC boosted with pyruvate used in high organic wastewater to produce PHA could potentially further commercial activities. [ABSTRACT FROM AUTHOR]

Coconut fiber waste has the potential to become a value-added product as a biofilm media and an adsorbent. The addition of biofilm media and adsorbent is important because it reduces the amount of sludge produced in wastewater. Furthermore, the quality of wastewater produced by the Integrated Anoxic-Oxic Sequencing Batch Reactor (IASBR)process with the addition of biofilm media and adsorbents can be used as clean water. The wastewater used comes from apartment wastewater. The Integrated Anoxic-Oxic Sequencing Batch Reactor was used to determine the optimal anoxic-aerobic processing time in a tropical climate. The study will further compare the efficiency of the two by using discarded coconut fiber as an additional adsorbent and biofilm media. The optimal adsorbent dose and weight of waste coconut fiber, as well as hydraulic retention time optimization, were all examined. As a result, clean water was discovered to be the primary product after the addition of adsorbent and biofilm media made from waste coconut fiber. [ABSTRACT FROM AUTHOR]

Sequencing batch reactors (SBRs) are devices widely used in wastewater treatment, chemical engineering, and other areas. They allow for the sedimentation and compression of solid particles of biomass simultaneously with biochemical reactions with nutrients dissolved in the liquid. The kinetics of these reactions may be given by one of the established activated sludge models (ASMx). An SBR is operated in various stages and is equipped with a movable extraction and fill device and a discharge opening. A one-dimensional model of this unit can be formulated as a moving-boundary problem for a degenerating system of convection-diffusion-reaction equations whose unknowns are the concentrations of the components forming the solid and liquid phases, respectively. This model is transformed to a fixed computational domain and is discretized by an explicit monotone scheme along with an alternative semi-implicit variant. The semi-implicit variant is based on solving, during each time step, a system of nonlinear equations for the total solids concentration followed by the solution of linear systems for the solid component percentages and liquid component concentrations. It is demonstrated that the semi-implicit scheme is well posed and that both variants produce approximations that satisfy an invariant region principle: solids concentrations are nonnegative and less or equal to a set maximal one, percentages are nonnegative and sum up to one, and substrate concentrations are nonnegative. These properties are achieved under a Courant-Friedrichs-Lewy (CFL) condition that is less restrictive for the semi-implicit than for the explicit variant. Numerical examples with realistic parameters illustrate that as a consequence, the semi-implicit variant is more efficient than the explicit one. [ABSTRACT FROM AUTHOR]

Copyright of Tecnología y Ciencias del Agua is the property of Instituto Mexicano de Tecnologia del Agua (IMTA) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In 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 < 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. [ABSTRACT FROM AUTHOR]

This work deals with an approach for the water quality restoration with emphasis on the removal of organochlorine pesticides and eutrophic conditions in tropical rivers, causing influence on the management of the central‐regional aqueduct, as a source of water supply for human consumption (4 million people) and industrial production in the states of Carabobo, Cojedes and Aragua, Venezuela, testing the phytoremediation techniques through Vetiveria zizanioides (VZ) species and coupled bioreactors, Sequencing Batch Reactor (SBR) followed by an Upflow Anaerobic Filter in Three Separate Stages (UAF‐3SS). Five rivers are involved known as Chirgua, Paito Guacara, Ereigüe, and Tucutunemo, whose waters have been classified as hypereutrophic, and containing organochlorine pesticides (OCPs). As a sample, for Tucutunemo River, OCPs included to DDT (dichlorodiphenyltrichloroethane) and its isomers and DRINs (Aldrin, Endrin and Dieldrin) dissolved in water and sorbed on sediments, which were measured during the dry and rainy seasons in the period 2013 to 2016, in three monitoring stations distributed in a reach of 15 km. The results indicated that p.p′‐DDT concentration dissolved in water was increased up to 10 times from rainy to dry seasons, indicating that a permanent use of it is being carried out by farmers in the agricultural activity development. Steady concentrations of the DTT isomers (e.g., p.p′‐DDD and p.p′‐DDE) and Aldrin isomers (e.g., Dieldrin) demonstrated that the anaerobic and aerobic biodegradation processes occurred along the river and between climatic seasons. At experimental scale, VZ hydroponic system developed over a period of 6 months for the removal of nutrients demonstrated moderately low to high removal efficiencies. With respect coupled bioreactors, each bioreactor has been experimentally tested, demonstrating satisfactory performance in Chemical Oxygen Demand (COD) removal from industrial wastewater containing recalcitrant and inhibitory substances (46%–98%), which was estimated in the influent ranging from 3500 to 5500 mg/L, evidencing that coupling of bioreactors might lead to a effluent COD complying with environmental regulations. [ABSTRACT FROM AUTHOR]

Introduction: Landfill wastewater or leachate has unique characteristics. Several conventional methods need a few treatment tanks to cover the treatment process. A Sequencing Batch Reactor (SBR) is a biological treatment method that uses a single tank with few-cycle phases. This study aims to determine the potential of a Sequencing Batch Reactor (SBR) that can be used to treat landfill leachate. Methods: A Sequencing Batch Reactor (SBR) was used in this study. The characteristics of leachate served as the basis for the design of the SBR reactor. The synthetic leachate was used to create the reactor feed based on the actual landfill leachate compositions. The reactor's influent and effluent were analyzed based on a few parameter changes, such as Suspended Solid (SS), Chemical Oxygen Demand (COD), ammonia nitrogen (NH3-N), and Total Kjeldahl Nitrogen (TKN). Results and Discussion: While the experiment was running, 84% of SS were removed, 88% of COD were removed, a -28% efficiency rate for NH3-N removal, and a -172% efficiency rate for TKN removal. After the withdrawal phase, the supernatant showed promising results with 99% COD removal, 97% SS removal, and 65% TKN removal. Unfortunately, the removal of NH3-N reaches -130%. It indicates insufficient concentrations of MLSS and SRT, as well as the presence of a eutrophication process. Conclusion: SBR shows a promising result for leachate treatment. Few changes in the cycling process were needed for further study, so the treatment process becomes optimal to reach its full potential.

IntroductionNowadays, with the increasing urban population on the one hand and growing water consumption per capita on the other, the use of treated wastewater has been the subject of much attention, especially in arid and semi-arid areas. The city of Yazd, in central Iran, with its hot and dry climate, is the driest major city in Iran, with annual precipitation of 50–60 mm. Since there is no surface water, the city has relied on its groundwater system. In past decades, underground aqueducts, called Qanats (a series of well-like vertical shafts, connected by gently sloping tunnels) were used to irrigate farmland in this area. Over the past few decades, the qanats have experienced decline and deletion due to low rainfall and the excessive use of groundwater resources. Considering that the qanats are failing, water shortage is a critical challenge in this area. Therefore, treated wastewater is a good alternative, especially in agricultural applications. In the Yazd municipal wastewater treatment plant (YMWTP), the stabilization ponds had been used for sewage treatment until 2013, but after that, the advanced sequencing batch reactors (SBRs) became operational, and treated wastewater and sludge are used in agricultural applications. The most important aspect of wastewater application is a concern for public health. Therefore, the main objectives of the present study are: 1) risk assessment of the SBRs effluent in agricultural irrigation based on the comprehensive pollution index (CPI) and 2) evaluation of SBRs performance and comparison with the efficiency of stabilization ponds and artificial wetlands. Material and methodsThe YMWTP is located in northern Yazd, close to the main road of Yazd airport. In the YMWTP, wastewater passes two initial treatment units including a screening and grit chamber and is then discharged into the SBRs. In the YMWTP, six SBRs are employed. The dimension of each reactor in meters is as follow length 40, width 23.7, and depth 6.6. In the SBR process, five stages including filling, reaction (mixing and aeration), settling, effluent, and idle are conducted in each reactor. The treated WW is decanted from SBR units to the disinfection section and then transferred to irrigate the green space. It should be noted that extra sludge is also discharged from the system in other treatment processes including digestion, dewatering, and drying to use in farmlands. All of these phases plus the total retention time is 4.9 h. For sample collection, composite sampling was carried out daily (every four hours) from October (2018) to September (2019). In this regard, special polyethylene bottles (1 L) for wastewater sampling were utilized to collect samples from the influent and effluent of the SBR system in the YMWTP. The American Public Health Association (APHA) method was applied To the measurement of turbidity, biological oxygen demand (BOD), total suspended solids (TSS), chemical oxygen demand (COD), ammonia (NH3), total phosphorus (TP), electrical conductivity (EC), total dissolved solids (TDS), and power of hydrogen (pH). The Statistical Package for the Social Sciences (SPSS) was also used for data analysis. This study adopted a simplified approach to risk assessment named CPI. The CPI was evaluated by using the measured concentration of parameters concerning their permissible limit in irrigation wastewater quality prescribed by the department of environment of Iran (DOE) and the United States environmental protection agency (USEPA). Results and discussionBased on our results, the annual average of the studied parameters in the influent, effluent, and also the percent of removal efficiency were; turbidity 173.5, 7.59, 96%, BOD 325.6, 14.9, 95%, TSS 293.7. 17.4, 94%, COD 650.2, 43.5, 93%, NH3 44.6, 5, 88%, TP 5.6, 2.6, 52%, EC 1881.1, 1463.1, 22%, TDS 981.5, 825.5, 16%, and pH 7.65, 7.27 and 5%. The results also indicated that the efficiency of SBR is higher than the stabilization ponds and artificial wetlands. Considering the DOE limits, the results of the calculation of CPI showed that the effluent from the SBR units of the YMWTP is suitable for agricultural purposes and irrigation of green spaces because the CPI rate was less than 0.5 in all months; and according to the annual average CPI (0.17), the effluent quality is in the clean category. But considering the limits set by the USEPA and the obtained average annual CPI (1.63), the quality of effluent from the YMWTP SBR units is placed in the category of medium pollution. It should be mentioned that in some months, such as Bahman and Farvardin, the monthly average of the CPI index exceeded the number of 2, and the quality of effluent was placed in the category of severe pollution. It was also found that the most effective parameters in increasing CPI are turbidity and TDS parameters. Our results revealed that the annual average of EC in the YMWTP SBRS was 1601 ± 196 µS/cm, which according to the Wilcox classification, the quality of the effluent is placed in the high salinity category; therefore, it is at the medium level for agricultural uses. According to the correlation analysis, a positive significant relationship was found between the EC and TDS and also turbidity and TSS in the influent. There was a negative significant correlation between the TSS, turbidity, and NH3 in the influent, while it was positive in the effluent. Our data showed a negative significant correlation between the TP, TDS, and NH3 in the effluent. ConclusionAccording to our results, the highest efficiency of the SBR units is in removing turbidity, BOD, TSS, and COD, respectively. Although according to the USEPA limits, the quality of the effluent from the SBR units of the YMWTP is in the medium pollution category and it is risky to use YMWTP effluent for agricultural purposes, according to the DOE limits, the quality of the effluent is in the clean category and it is suitable for agricultural use. Considering the characteristics of the treated wastewater of this city and considering the presence of many industries in the Yazd-Ardakan plain and the lack of water in this area, it is suggested that in future research, the feasibility of using treated wastewater for industrial purposes such as cooling towers, steam boilers, product production process, fire extinguishing, dust control, construction industry and artificial feeding of underground water should also be investigated.

This study proposed an AO-SBR (Anaerobic Aerobic Sequencing Batch Reactor) combined with iron-carbon micro-electrolysis (ICME) particles system for sewage treatment at low temperature and explored the dephosphorisation mechanism and microbial community structure. The experimental results illustrated that ICME particles contributed to phosphorus removal, metabolic mechanism of poly-phosphorus accumulating organism (PAO) and microbial community structure in the AO-SBR system. The optimal treatment effect was achieved under the conditions of pH 7, DO 3.0 mg/L and particle dosage of 2.6 g Fe-C/g MLSS, and the removal rates of COD, TP, NH4+-N and TN reached 80.56%, 91.46%, 69.42% and 57.57%. The proportion of phosphorus accumulating organisms (PAOs) increased from 4.54% in the SBR system to 10.89% in the ICME-SBR system at 10°C. Additionally, the metabolic rate of PAOs was promoted, and the activities of DHA and ETS both reached the maximum value of 13.34 and 102.88 μg·mg−1VSS·h−1. These results suggest that the ICME particles could improve the performance of activated sludge under low-temperature conditions. This technology provides a new way for upgrading the performance of sewage treatment in the cold area. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate bis(2-ethylhexyl) phthalate (DEHP) inhibition in the flocculent and granular sludge sequencing batch reactors (GSBRs) used for the treatment of landfill leachate. Three columns of laboratory-scale sequencing batch reactors were utilized to evaluate the inhibition of the suspended flocs and aerobic granular sludge. The inhibitory concentrations of DEHP were detected as the purpose of the specific oxygen uptake rate, soluble chemical oxygen demand (SCOD), and DEHP removal function. In addition, glucose was used as the main biogenic substrate to dilute landfill leachate at 20% ratios. The GSBRs reveald a high performance in the SCOD and DEHP removal at the concentrations of up to 200 µg/L though the process ceased at 200 and 400 µg of DEHP/L in the suspended flocs sequencing batch reactors (FSBRs). At different dosing concentrations of DEHP in the reactor, short and suitable time led to the gradual accumulation of inhibitory compounds. At the inhibitory concentrations, only limited degradation of DEHP occurred. Although the assimilatory removal of DEHP was low at the normal efficiency of the FSBR, it reached significant values in the GSBRs. [ABSTRACT FROM AUTHOR]

In this study, it was aimed to determine the change in the toxic effect of copper (Cu2+) and tetracycline (TC) on biological treatment by sludge disintegration application. For this purpose, two labscale reactors, sequencing batch reactor (SBR) and sludge disintegration applied sequencing batch reactor (SBR-SD), were used. In the control stage of SBR and SBR-SD, namely SBR-C and SBR-SD-C, the chemical oxygen demand (COD) and NH4 +-N removal efficiency was 93% and 95%, respectively. While reductions were observed in the COD and NH4 +-N removal efficiency from the 66th day in SBR, stable treatment efficiency was obtained in SBR-SD throughout the operation. While sludge volume index value increased to 175 mL/g in SBR, it remained stable between 78-85 mL/g in SBR-SD. While the decrease in the specific oxygen consumption rate value in SBR was 55% on the 90th day due to the toxicity of Cu2+ and TC, it was 29% in SBR-SD. In SBR, PN and PS content in tightly bound extracellular polymeric substances (TB-EPS) and loosely bound extracellular polymeric substances (LB-EPS) increased due to resistance to the toxic effects of Cu2+ and TC. The protein (PN) and polysaccharide (PS) content in TB-EPS and LB-EPS remained the same as the control stage values since the toxic effect of Cu2+ and TC in SBR-SD was relatively eliminated by sludge disintegration. The toxic effect of Cu2+ and TC on biological treatment was prevented by sludge disintegration and stability was ensured during long-term operation. [ABSTRACT FROM AUTHOR]

Aerobic granular sludge (AGS) technology offers several benefits, such as simultaneous removal of nutrients and organic matter from wastewater, stronger granule structure, excellent settleability, and high resistance to toxicity. However, the formation of granules can take a long time and needs to be dense and stable. In this study, the formation of aerobic granules in sequencing batch reactors (SBRs) using a granular activated carbon (GAC) and aluminium sulphate coagulant were evaluated for the simultaneous removal of nutrient (phosphorus (TP) and nitrogen (TN)) and organic matter (chemical oxygen demand (COD)) from wastewater. The reactors were continuously operated for 107 days and were fed with synthetic media and real domestic sewage. However, adaptation process with the synthetic wastewater led to relatively slow granulation process (sedimentation rate of sludge flocks was 3 m h-1). During the experiments, there was no visible formation of granules in SBRs based on the analysis of the sludge samples, only the formation of aggregate structures similar to flocks. However, the results showed that total phosphorus (TP) removal efficiency was over 90% in SBR operated with aluminium sulphate. However, COD and total nitrogen (TN) removals were higher in GAC SBR, 75% and 10%, respectively. Thus, even if granules are not developed yet, the system is working efficiently. The results of this study could be useful in the development of AGS technology for full-scale wastewater treatment plant. [ABSTRACT FROM AUTHOR]

This study evaluates the performance of a simple sequencing batch reactor (SBR) with conical geometric configuration in terms of aerobic granulation and simultaneous removal of COD, nitrogen, and phosphorous from synthetic wastewater. The reactor was operated for 328 days in 3 different phases. Stable granules measuring around 0.9±0.3 mm with good settling properties were formed in phase III of operation. Optimum removals of COD (90%), NH4+-N (91%), total nitrogen (87%), and PO43--P (83%) were achieved in phase III, while the influent concentrations were COD (640±32 mg/L), NH4+-N (53±2.5 mg/L), and PO43--P (9±0.6 mg/L). Mixed liquor suspended solids increased from 0.26 g/L to 2.3 g/L while sludge volume index (SVI30) decreased from 380 mL/g to 65 mL/g during start-up to end of the study, respectively. The conical geometry induces an effective velocity gradient along with aeration in the reactor for better flocculation of biomass which has a good impact on the formation of stable and resistant aerobic granules. This system in conical SBR is advantageous as it attains simultaneous nutrient removal (CNP) with effective biomass retention without automatic process control. This treatment system has the potential to employ in low volume wastewater treatment in many decentralized applications. [ABSTRACT FROM AUTHOR]

Biogranulation has emerged as a viable alternative biological wastewater treatment approach because of its strong biodegradability potential, toxicity tolerance, and biomass retention features. However, this process requires a long duration for biogranules formation to occur. In this study, magnetic powder activated carbon (MPAC) was used as support material in a sequencing batch reactor to enhance biogranules development for wastewater treatment. Two parallel SBRs (designated R1 and R2) were used, with R1 serving as a control without the presence of MPAC while R2 was operated with MPAC. The biodegradability capacity and biomass properties of MPAC biogranules were compared with a control system. The measured diameter of biogranules for R1 and R2 after 8 weeks of maturation were 2.2 mm and 3.4 mm, respectively. The integrity coefficient of the biogranules in R2 was higher (8.3%) than that of R1 (13.4%), indicating that the addition of MPAC improved the structure of the biogranules in R2. The components of extracellular polymeric substances were also higher in R2 than in R1. Scanning electronic microscopy was able to examine the morphological structures of the biogranules which showed there were irregular formations compacted together. However, there were more cavities situated in R1 biogranules (without MPAC) when compared to R2 biogranules (with MPAC). Dye removal reached 65% and 83% in R1 and R2 in the post-development stage. This study demonstrates that the addition of MPAC could shorten and improve biogranules formation. MPAC acted as the support media for microbial growth during the biogranulation developmental process. [ABSTRACT FROM AUTHOR]

The kinetic model derived in this study was able to adequately predict the simultaneous oxidation of ammonia, nitrite, and m-cresol and microbial growth using nitrifying sludge in a sequencing batch reactor. Time-varying inhibition and inactivation effects were successfully incorporated in the process kinetics to account for the past cell exposure history to m-cresol increasing concentrations (up to 150 mg C L−1). The initial concentration of the microbial species (ammonia and nitrite oxidizers, heterotrophs) was evaluated using pyrosequencing of DNA samples of the consortium. These measurements allowed to establish a model that explicitly handles specific reaction rates and to enhance the practical identifiability of the model parameters. A single simulation run was used to adequately predict the kinetic behavior of the main variables throughout the 242 cycles using a single set of initial conditions in the first cycle. This kind of dynamic model may be used as a helpful predictive tool to improve nitrification by avoiding the occurrence of severely repetitive inhibitive conditions due to the presence of inhibitive/toxic aromatic compounds. [ABSTRACT FROM AUTHOR]

Objective: The objective of the present work was to reduce the start-up time of aerobic granular sludge (AGS) formation using medium-strength sewage and to find the most effective anaerobic, aerobic (oxic), and anoxic (A/O/A) cyclic time distribution over the 6 h cycle time for the removal of nutrients. Methods: A rectangular sequencing batch reactor (SBR) operated systematically in A/O/A cycle was designed for AGS formation. In order to achieve complete nutrient removal, the anoxic phase (5% of the total cycle duration) was introduced in the SBR cycle. Results: Growth in the biomass profile was observed after 20 days of operation, and complete granulation was achieved within 35 days of operational studies. Regular-shaped, compact granules with visible outlines and clear boundaries predominate inside the system, with an average particle size of 220.19 µm. The A/O/A system achieved average removal efficiencies of 70.02±5.98%, 78.21±18.66%, 60.62±9.69%, and 53.49±8.14% for COD, NH4+-N, TN, and PO43--P, respectively. The reasons for poor COD and PO43--P removal performance were the short anaerobic phase (25% of total cycle duration of 6 h) and higher biomass concentration. However, the long aerobic phase (60% of total cycle duration of 6 h) with the anoxic phase achieved outstanding (100%) NH4+-N removal efficiency after the system reached a steady state. SEM results inferred that Rod-shaped bacteria, Cocci, and Filamentous fungi were the dominant microorganisms found within the cultivated granules. Conclusions: Sewage with a high COD loading rate accelerates AGS formation and development within an A/O/A cycle SBR reactor. The rapid granulation and simultaneous removal of organics and nutrients by the A/O/A mode SBR without any support materials provide an alternative for wastewater treatment. [ABSTRACT FROM AUTHOR]

Enhanced biological phosphorus removal (EBPR) is an obscure but economical and helpful technology for removing phosphorus biologically from wastewater. A 3-MLD capacity pre-anoxic selector-attached sequencing batch reactor (SBR) treated municipal wastewater from the residents of IIT Roorkee. The treatment in the plant satisfied the effluent discharge standards in all respects except phosphorus, observed during an intensive two-year study. An elaborated 80-day study was performed to enhance and improve the plant's performance in terms of phosphorus removal specifically, with run 1: solid retention times (SRT) reduced from 56 to 20 days (t = 35 d), run 2: lowering the diffuser's running time from 15 min to 10 min in anoxic cum anaerobic selector chambers (dissolved oxygen (DO) concentration reduced to <0.15 mg/L) along with reducing SRT to 15 days (t = 25 d), and run 3:intensive reduction in SRT to ≤10 days (t = 20 d). During run 3, the increment in the enhanced biological phosphorus removal (EBPR) efficiency was three times that of the initial run (ηmax~65%) with a readily biodegradable chemical oxygen demand to total phosphorus ratio (rbCOD/TP) of 7.8. The 16SrRNA sequencing revealed the microbial community structure before and after the changes in SRT and EBPR efficiencies, to correlate the biochemical processes and functional organisms. [ABSTRACT FROM AUTHOR]

Although wastewater treatment plants are considered hotspots for the spread of antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs), few studies have explored the mechanisms underlying the emergence of multidrug-resistance. Using four sequencing batch reactors under fluctuating concentrations of levofloxacin (LVX), we isolated 440 isolates, which were identified based on the sequence of the 16 S rRNA gene and growth at 37 ºC, focusing on potential human pathogens. We then evaluated the multidrug-resistance of 62% of these isolates by determining the minimum inhibition concentration (MIC) of erythromycin, tetracycline, chloramphenicol, and LVX in the emergence of ARB. The average MIC was increased more than 100-fold in the first exposure, whereas did not show the same response after re-exposure due to different LVX concentrations between the 2 conditions. We identified 33 Acinetobacter baumannii isolates that emerged only during re-exposure, especially in R-2 and R-3, in which the LVX concentration was changed from 4 and 16 mg/L, respectively, to 128 mg/L. Moreover, we assessed the disinfection efficiency of chlorine/UV treatment against pathogenic ARB. The growth of multidrug-resistant A. baumannii isolates was decreased by 0.9–7.4 log 10 following disinfection treatment with > 0.5 mg /L Cl 2 or > 30 min UV irradiation. [Display omitted] [ABSTRACT FROM AUTHOR]

This study aims to investigate, the effect of organic loading rates (OLRs), nutrient ratio addition, and sludge retention time (SRT) on treating dairy wastewater in a sequencing batch reactor (SBR) system. This investigation is verified by experiments conducted in 3 phases at 3 different OLRs (1.8, 1.2, and 0.9 kg/m³d, respectively). Urea ((NH2)2CO) is added to make a suitable (COD:N:P) ratio of (100:5:1) in dairy wastewater. The SRT is adjusted from 50 days to an appropriate value of 18 days. The obtained results show that the COD, TN, and TP removal efficiencies are increased with decreasing OLRs. Sludge concentration in the SBR tank is stable at 1100 mg/L after adding (NH2)2CO. In addition, the SBR operated at a suitable SRT (i.e. 18 days) helps the biomass stably, resulting in enhancement of COD, TN, and TP removal. The results are helpful to the design of SBR for treating dairy wastewater. [ABSTRACT FROM AUTHOR]

Introduction: Landfill wastewater or leachate has unique characteristics. Several conventional methods need a few treatment tanks to cover the treatment process. A Sequencing Batch Reactor (SBR) is a biological treatment method that uses a single tank with few-cycle phases. This study aims to determine the potential of a Sequencing Batch Reactor (SBR) that can be used to treat landfill leachate. Methods: A Sequencing Batch Reactor (SBR) was used in this study. The characteristics of leachate served as the basis for the design of the SBR reactor. The synthetic leachate was used to create the reactor feed based on the actual landfill leachate compositions. The reactor's influent and effluent were analyzed based on a few parameter changes, such as Suspended Solid (SS), Chemical Oxygen Demand (COD), ammonia nitrogen (NH3-N), and Total Kjeldahl Nitrogen (TKN). Results and Discussion: While the experiment was running, 84% of SS were removed, 88% of COD were removed, a -28% efficiency rate for NH3-N removal, and a -172% efficiency rate for TKN removal. After the withdrawal phase, the supernatant showed promising results with 99% COD removal, 97% SS removal, and 65% TKN removal. Unfortunately, the removal of NH3-N reaches -130%. It indicates insufficient concentrations of MLSS and SRT, as well as the presence of a eutrophication process. Conclusion: SBR shows a promising result for leachate treatment. Few changes in the cycling process were needed for further study, so the treatment process becomes optimal to reach its full potential. [ABSTRACT FROM AUTHOR]

Introduction Nowadays, with the increasing urban population on the one hand and growing water consumption per capita on the other, the use of treated wastewater has been the subject of much attention, especially in arid and semi-arid areas. The city of Yazd, in central Iran, with its hot and dry climate, is the driest major city in Iran, with annual precipitation of 50–60 mm. Since there is no surface water, the city has relied on its groundwater system. In past decades, underground aqueducts, called Qanats (a series of well-like vertical shafts, connected by gently sloping tunnels) were used to irrigate farmland in this area. Over the past few decades, the qanats have experienced decline and deletion due to low rainfall and the excessive use of groundwater resources. Considering that the qanats are failing, water shortage is a critical challenge in this area. Therefore, treated wastewater is a good alternative, especially in agricultural applications. In the Yazd municipal wastewater treatment plant (YMWTP), the stabilization ponds had been used for sewage treatment until 2013, but after that, the advanced sequencing batch reactors (SBRs) became operational, and treated wastewater and sludge are used in agricultural applications. The most important aspect of wastewater application is a concern for public health. Therefore, the main objectives of the present study are: 1) risk assessment of the SBRs effluent in agricultural irrigation based on the comprehensive pollution index (CPI) and 2) evaluation of SBRs performance and comparison with the efficiency of stabilization ponds and artificial wetlands. Material and methods The YMWTP is located in northern Yazd, close to the main road of Yazd airport. In the YMWTP, wastewater passes two initial treatment units including a screening and grit chamber and is then discharged into the SBRs. In the YMWTP, six SBRs are employed. The dimension of each reactor in meters is as follow length 40, width 23.7, and depth 6.6. In the SBR process, five stages including filling, reaction (mixing and aeration), settling, effluent, and idle are conducted in each reactor. The treated WW is decanted from SBR units to the disinfection section and then transferred to irrigate the green space. It should be noted that extra sludge is also discharged from the system in other treatment processes including digestion, dewatering, and drying to use in farmlands. All of these phases plus the total retention time is 4.9 h. For sample collection, composite sampling was carried out daily (every four hours) from October (2018) to September (2019). In this regard, special polyethylene bottles (1 L) for wastewater sampling were utilized to collect samples from the influent and effluent of the SBR system in the YMWTP. The American Public Health Association (APHA) method was applied To the measurement of turbidity, biological oxygen demand (BOD), total suspended solids (TSS), chemical oxygen demand (COD), ammonia (NH3), total phosphorus (TP), electrical conductivity (EC), total dissolved solids (TDS), and power of hydrogen (pH). The Statistical Package for the Social Sciences (SPSS) was also used for data analysis. This study adopted a simplified approach to risk assessment named CPI. The CPI was evaluated by using the measured concentration of parameters concerning their permissible limit in irrigation wastewater quality prescribed by the department of environment of Iran (DOE) and the United States environmental protection agency (USEPA). Results and discussion Based on our results, the annual average of the studied parameters in the influent, effluent, and also the percent of removal efficiency were; turbidity 173.5, 7.59, 96%, BOD 325.6, 14.9, 95%, TSS 293.7. 17.4, 94%, COD 650.2, 43.5, 93%, NH3 44.6, 5, 88%, TP 5.6, 2.6, 52%, EC 1881.1, 1463.1, 22%, TDS 981.5, 825.5, 16%, and pH 7.65, 7.27 and 5%. The results also indicated that the efficiency of SBR is higher than the stabilization ponds and artificial wetlands. Considering the DOE limits, the results of the calculation of CPI showed that the effluent from the SBR units of the YMWTP is suitable for agricultural purposes and irrigation of green spaces because the CPI rate was less than 0.5 in all months; and according to the annual average CPI (0.17), the effluent quality is in the clean category. But considering the limits set by the USEPA and the obtained average annual CPI (1.63), the quality of effluent from the YMWTP SBR units is placed in the category of medium pollution. It should be mentioned that in some months, such as Bahman and Farvardin, the monthly average of the CPI index exceeded the number of 2, and the quality of effluent was placed in the category of severe pollution. It was also found that the most effective parameters in increasing CPI are turbidity and TDS parameters. Our results revealed that the annual average of EC in the YMWTP SBRS was 1601 ± 196 µS/cm, which according to the Wilcox classification, the quality of the effluent is placed in the high salinity category; therefore, it is at the medium level for agricultural uses. According to the correlation analysis, a positive significant relationship was found between the EC and TDS and also turbidity and TSS in the influent. There was a negative significant correlation between the TSS, turbidity, and NH3 in the influent, while it was positive in the effluent. Our data showed a negative significant correlation between the TP, TDS, and NH3 in the effluent. Conclusion According to our results, the highest efficiency of the SBR units is in removing turbidity, BOD, TSS, and COD, respectively. Although according to the USEPA limits, the quality of the effluent from the SBR units of the YMWTP is in the medium pollution category and it is risky to use YMWTP effluent for agricultural purposes, according to the DOE limits, the quality of the effluent is in the clean category and it is suitable for agricultural use. Considering the characteristics of the treated wastewater of this city and considering the presence of many industries in the Yazd-Ardakan plain and the lack of water in this area, it is suggested that in future research, the feasibility of using treated wastewater for industrial purposes such as cooling towers, steam boilers, product production process, fire extinguishing, dust control, construction industry and artificial feeding of underground water should also be investigated. [ABSTRACT FROM AUTHOR]