Development of an ensemble of machine learning algorithms to model aerobic granular sludge reactors.

Machine learning models provide an adaptive tool to predict the performance of treatment reactors under varying operational and influent conditions. Aerobic granular sludge (AGS) is still an emerging technology and does not have a long history of full-scale application. There is, therefore, a scarcity of long-term data in this field, which impacted the development of data-driven models. In this study, a machine learning model was developed for simulating the AGS process using 475 days of data collected from three lab-based reactors. Inputs were selected based on RReliefF ranking after multicollinearity reduction. A five-stage model structure was adopted in which each parameter was predicted using separate models for the preceding parameters as inputs. An ensemble of artificial neural networks, support vector regression and adaptive neuro-fuzzy inference systems was used to improve the models' performance. The developed model was able to predict the MLSS, MLVSS, SVI5, SVI30, granule size, and effluent COD, NH4-N, and PO43- with average R2, nRMSE and sMAPE of 95.7%, 0.032 and 3.7% respectively.

Augmentation of Biogranules for Enhanced Performance of Full-Scale Lagoon-Based Municipal Wastewater Treatment Plants.

This study investigated the treatment performance of lagoon-based municipal wastewater treatment plants (LWWTPs) inoculated by proprietary biogranules. Augmentation process included enhancing the microbial community of lagoon basins by weekly addition of biogranules over the treatment seasons (summer and fall). Effluent qualities before and after the augmentation process were compared, and the results were reported as "enhanced treatment efficiencies, EE". Very low concentrations of 5-day biochemical oxygen demand (BOD5), total nitrogen (TN), total Kjeldahl nitrogen (TKN), ammonium nitrogen (N-NH4), and total phosphorus (TP) were detected at discharge points after the augmentation process, which corresponded to enhanced treatment efficiencies of 86, 74, 72, 92.7, and 71%, respectively. Significant reduction in total coliform and E. coli concentrations in the effluents (91 and 98%, respectively) demonstrated the capability of granule-based lagoons in destroying pathogens. Adding biogranules to lagoons was an efficient remedy for excess sludge buildup in short and long runs. Hence, inoculating lagoon plants using biogranules was suggested as an effective technique to augment rural wastewater treatment facilities.

Effect of UV dose on degradation of venlafaxine using UV/H2O2: perspective of augmenting UV units in wastewater treatment.

Many water and wastewater treatment plants (WWTPs) are fitted with a UV system that provides post treatment disinfection before the water is released to receiving water. This paper presents a study on expected removal for the pharmaceutical venlafaxine (VEN) in a typical UV unit at a municipal WWTP with analysis of removal rates of an advanced oxidation process using UV irradiation with injection of H2O2. The study is supported by bench scale degradation experiments on VEN. Results demonstrated that UV can completely degrade VEN, but the addition of H2O2 increased pseudo first order rate constant by up to 2.5 times. Extrapolations of the lab data indicated that removal rates of VEN at the UV disinfection unit of a typical municipal WWTP are approximately 0.4% at standard operating conditions. With the addition of 10 mg/L of H2O2, degradation of VEN can be increased by ten times over existing UV treatment. By studying the impact of adjusting parameters such as UV intensity, UV dosage, and H2O2 dosage, a framework is set to allow researchers and engineers to move forward with developing UV/H2O2 systems that meet their future design needs for pharmaceutical removal.

Pilot-scale investigation on nutrient removal characteristics of mineral-rich aerobic granular sludge: Identification of uncommon mechanisms.

This study investigated nutrient removal characteristics and the related pathways in aerobic granular reactors using three pilot-scale granular sequencing batch reactors (GSBRs) treating wastewaters of diverse carbon and nutrient strength. The GSBRs were operated with alternating (AN/O/AX/O_SBR and AN/O_SBR) and purely-aerobic (O_SBR) operation modes. Mineral-rich aerobic granules with hydroxyapatite (HAp) core were cultivated in all the three GSBRs. The highest nitrogen removal efficiency (75%) was achieved in AN/O/AX/O_SBR and O_SBR and the lowest (22%) in AN/O_SBR, establishing a quasi-linear relationship with organic loading rate (OLR). Phosphorus removal efficiencies of 55-63% were achieved in the GSBRs despite different influent PO4-P concentrations. Heterotrophic nitrification and biologically-induced phosphate precipitation (BIPP) became the dominant nutrient depletion pathways, contributing 61-84% and 39-96% to overall ammonium nitrogen and phosphorus removal, respectively. A direct relation was noted between heterotrophic nitrification efficiency (ηHeterotrophic nitrification) and nutrient availability, as nitrification efficiencies of 18 and 64% were observed for COD:Ninf of 5 and 20, respectively. Whereas, BIPP efficiency (ηBIPP) established inverse relation with (COD:P)inf and (Ca:P)inf and direct relation with phosphorus concentration beyond microbial growth requirement. Core heterotrophic nitrifiers and bio-calcifying species were identified as {Thauera and Flavobacterium} and {Flavobacterium, Acinetobacter, Pseudomonas, and Corynebacterium}, respectively. Ca-P crystallization was proposed to be via phosphate precipitation on calcite surfaces. Granulation mechanism was proposed as crystallization on bio-aggregates' periphery and then crystal growth toward the core.

A sustainable strategy for effective regulation of aerobic granulation: Augmentation of the signaling molecule content by cultivating AHL-producing strains.

The positive roles of N-acyl homoserine lactone (AHL)-mediated quorum sensing (QS) in aerobic granular sludge (AGS) have been widely acknowledged. However, it is not feasible to manipulate granulation via direct addition of AHL chemicals or AHL-producing strains. Here, several strains with high AHL-producing capacity were successfully isolated from AGS. These QS strains were cultivated, mixed as a consortium, and then divided into two groups: AHLs supernatant and bacterial cells encapsulated in sodium alginate (CEBs). The potential of QS regulation, via doses of AHLs supernatant and CEBs, in accelerating granulation was evaluated. Results clearly indicated that short-term (days 21-70) addition of AHLs supernatant led to a rapid specific growth rate (0.08 d-1), compact structure without filamentous bacteria overgrowth, excellent settlement performance (SVI10 37.2 mL/g), and a high integrity coefficient (4.4%) of the granules. Sustainable release of AHLs (mainly C6- and C8-HSL) was induced by exogenous AHLs, possibly attributed to the enrichment of the genera Aeromonas and Pseudomonas. Further, tryptophan and aromatic protein substances were produced to maintain structural stability, suggesting that short-term QS regulation had long-term positive effects on the characteristics of AGS. By comparison, the addition of CEBs posed negligible or negative impact on the granulation, as evidenced by the rupture of smaller aggregates and poor characteristics of AGS. Overall, augmentation of the signaling content via addition of AHLs supernatant from QS strains is an economical and feasible regulation strategy to accelerate granulation and sustain long-term structural stability.

Impact of hydraulic retention time and organic matter concentration on side-stream aerobic granular membrane bioreactor.

This study investigated the effect of hydraulic retention time (HRT) and chemical oxygen demand (COD) concentration on membrane fouling in aerobic granular membrane bioreactor (AGMBR) in a systematic approach. Changes in HRT (7, 10, and 15 h) and COD (500, 1000 and 1500 mg/L) were applied in five operational phases, to determine the most significant parameters to control membrane fouling for enhanced AGMBR performance. Membrane permeability loss was dramatically intensified with increase in HRT from 7.5 to 15 h and COD from 500 to 1000 mg/L. The highest polysaccharide content of loosely bound EPS (0.41 mg PS/mg VSS) and soluble microbial products (SMPs) (27 mg PS/L) occurred alongside poor AGMBR performance. Variations in membrane fouling were accompanied with considerable changes in Flavobacterium, Thauera and Paracoccus populations. Analysis of variance (ANOVA) demonstrated that HRT and interaction between HRT and COD were the most significant parameters in controlling membrane fouling.

Coaggregation of bacterial communities in aerobic granulation and its application on the biodegradation of sulfolane.

Aerobic granulation is regarded as the future technology for wastewater treatment that can replace conventional activated sludge. In this study, two approaches of forming sulfolane degrading aerobic granules (SDAG) were successfully developed and evaluated. These include adaptation of pre-grown granules to sulfolane environment and coaggregation of pre-grown granules with bacterial culture native to sulfolane contaminated site. The adaption method required a longer period to form robust SDAG compared to coaggregation method where degradation of sulfolane was observed within 24 h. Electronic images revealed dominant filamentous bacteria on the surface of granules while DNA analysis unveiled the complexity of the dynamic change of microbial community during aerobic granule formation. The rate of sulfolane degradation by coaggregated granules reduced as the concentration of carbon source increased, nevertheless, the rate increased with increased biomass. In addition, the presence of co-contaminants can slightly impact the ability of newly cultivated granules to degrade sulfolane. Finally, the stability and settleability of the new aerobic granules was investigated under different environmental conditions. About 30% of the aerobic granules were lost after 14 d of operation without any continuous supply of carbon sources. The surviving SDAGs continued to display an intact structure coupled with good settleability.

Influence of operation mode and wastewater strength on aerobic granulation at pilot scale: Startup period, granular sludge characteristics, and effluent quality.

This study attempted to investigate the influence of operation mode and wastewater strength on startup period, aerobic granular sludge (AGS) characteristics, and system effluent quality at pilot scale. Granulation was monitored in three pilot-scale granular sequencing batch reactors (GSBRs). Comparative evaluation of AN/O/AX/O_SBR and O_SBR, fed with wastewater of the same composition but run with completely different SBR reaction phase arrangements (alternating vs. purely aerobic), revealed the effect of SBR operation mode. Comparative study of the GSBRs operated with alternating SBR reaction phases (AN/O/AX/O_SBR and AN/O_SBR) and fed with wastewater of different strength (high- vs. medium-strength) determined the effect of wastewater composition. Granulation time and granule size were regulated by wastewater strength and the resulting organic and sludge loading conditions. Whereas, AGS morphology, granule structure, and floccular proportion of AGS were attributed to SBR operation mode. Effluent clarity in terms of suspended solid concentration depended on wastewater strength. Subtle but distinct microbial selection strategies were in effect during granulation which were also imposed by wastewater strength. Due to strong correlation between the effluent and AGS microbial structures, demonstrated by biodiversity analysis, differences in the microbial composition of effluent biomass and washout patterns of the GSBRs could be explained by wastewater strength as well. Limited nutrient removal efficiencies, restricted by organic matter concentration, could be due to involvement of unorthodox nutrient removal pathways which warrants further investigation.

Adsorption of anion polyacrylamide from aqueous solution by polytetrafluoroethylene (PTFE) membrane as an adsorbent: Kinetic and isotherm studies.

In this study, the kinetic and isothermal behaviors of anion polyacrylamide (APAM) on a polytetrafluoroethylene (PTFE) microfiltration membrane were investigated to better understand the adsorption mechanism. A series of adsorption experiments were conducted to determine the effects of the initial APAM concentration, contact time, solution pH and temperature on the adsorption performance. The results showed that the three isotherm models (Langmuir equation, Freundlich equation and Temkin equation) favorably fit the adsorption process with R2 values of 0.98957, 0.90721 and 0.96321, respectively. The adsorption rate of APAM onto the PTFE membrane increased with increasing temperature, and the adsorption reaction reached equilibrium at 20 h. The values of thermodynamic adsorption parameters (ΔrGmθ, ΔrHmθ, and ΔrSmθ) suggested that the adsorption process was not spontaneous but endothermic. In addition, high temperatures favored adsorption, and the adsorption can be categorized as physisorption. Specifically, the main physisorption force was hydrogen bonding. The adsorption process consisted of two phases: rapid adsorption and stable adsorption. The three kinetic equations provided a good fit according to the R2 values and were applicable in the following order: pseudo-first-order > pseudo-second-order > Elovich.

Aerobic granular sludge membrane bioreactor (AGMBR): Extracellular polymeric substances (EPS) analysis.

Aerobic granular sludge membrane bioreactor (AGMBR) has emerged with strong potential to overcome membrane fouling. There have been no extensive studies on extracellular polymeric substances (EPS) in AGMBR. The present work aimed at conducting an in-depth study of EPS and monitoring fouling development in AGMBR using a 22 factorial design having hydraulic retention time (HRT) and total organic carbon (TOC) as independent variables. HRT was tested at three levels of 6, 8 and 10 h while the TOC levels were 104 ±â€¯13, 189 ±â€¯17, and 266 ±â€¯27 mg/L. AGMBR exhibited high proteins (PN) in the tightly-bound EPS (TB-EPS) resulting in high proteins/polysaccharides (PN/PS) ratios of 2-16. The PN in the LB-EPS was low, ranging from 0.01 to 1.92 mg/g MLVSS, but the range of PN/PS ratio was also of 2-16. Despite the high PN/PS ratio, TMP rise was low. Water jet easily sloughed off the developed membrane cake layer. The elimination of chemicals for membrane cleaning has significant cost savings. TOC had a significant main effect on both the PN and PS components of TB-EPS at α < 0.05. TB-EPS PN increased with increase in TOC. TB-EPS PN decreased as HRT increased from 6 h to 10 h at 104 ±â€¯13 mg/L TOC but the change of HRT from 10 h to 6 h at 266 ±â€¯27 mg/L TOC did not affect TB-EPS PN. The TMP increased with increasing HRT at 104 ±â€¯13 and 266 ±â€¯27 mg/L TOC. An increase in sEPS PN correlated well with increase in membrane fouling (r = 0.581). Three runs performed best: 266 ±â€¯27 mg/L TOC and 10 h HRT; 104 ±â€¯13 mg/L TOC and 6 h HRT; and 266 ±â€¯27 mg/L TOC and 6 h HRT as TMP was below the 50 kPa threshold. AGMBR achieved 98 ±â€¯1%, 99 ±â€¯1%, 52 ±â€¯33% organics degradation, NH3-N removal, total nitrogen removal, respectively.

Denitrification performance and microbial versatility in response to different selection pressures.

This study investigated functional dynamics of microbial community in response to different selection pressures, with a focus on denitrification. Suspended-biomass experiments demonstrated limited aerobic and relatively higher anoxic nitrate and nitrite reduction capabilities; the highest NO2-N and NO3-N removal rates were 1.3 ±â€¯0.1 and 0.74 ±â€¯0.01 in aerobic and 1.4 ±â€¯0.05 and 3.4 ±â€¯0.1 mg/L.h in anoxic media, respectively. Key potential denitrifiers were identified as: (i) complete aerobic denitrifiers: Dokdonella, Flavobacterium, and Ca. Accumulibacter; (ii) complete anoxic denitrifiers: Acinetobacter, Pseudomonas, Arcobacter, and Comamonas; (iii) incomplete nitrite denitrifier: Diaphorobacter (aerobic/anoxic), (iv): incomplete nitrate denitrifiers: Thauera (aerobic/anoxic) and Zoogloea (strictly-aerobic). Granular biomass removed 72 mg/L NH4-N with no NOx- accumulation. Heterotrophic nitrification and aerobic denitrification were proposed as the principal nitrogen removal pathway in granular reactors, potentially performed by two key organisms Thuaera and Flavobacterium. Biodiversity analysis suggested that the selection pressure of nourishment condition was the decisive factor for microbial selection and nitrogen removal mechanism.

Degradation of sulfolane in aqueous media by integrating activated sludge and advanced oxidation process.

In this study, the performance of an integrated technology, combining biological treatment with advanced oxidation process in sequence, was evaluated for the degradation of sulfolane in aqueous media. In addition, the impact of biological process on AOP was also studied by assessing residual sulfolane, nutrient and total suspended solids (TSS) concentrations. The integration of activated sludge process with UVC/H2O2 resulted in more than 81% of sulfolane degradation in less than 24 h. It was observed that mineralization was much faster in biological system compared to AOP. Mechanistically, the process of degradation is different in the two processes as various by-products were identified during UVC/H2O2 but not during the biological process. The impact of residual sulfolane concentration on UVC/H2O2 was significant beyond a concentration of 30 mg L-1, while below 30 mg L-1 the rate of degradation was independent of sulfolane concentration. Residual nutrients from biological systems did not impact AOP performance. Nevertheless, presence of TSS >44 mg L-1 had a negative impact on the performance of UVC/H2O2 by reducing UV transmittance which led to retardation of sulfolane degradation. The application of UVC/H2O2 after biological treatment was an advantage as UVC/H2O2 could perform dual roles of oxidant and disinfectant.

Effect of light intensity on the characteristics of algal-bacterial granular sludge and the role of N-acyl-homoserine lactone in the granulation.

The effects of light intensity on the development of algal-bacterial granular sludge (ABGS) were investigated over a period of 12 weeks. The ABGS developed at low light intensity (142 ±â€¯10 µmol m-2·s-1) exhibited excellent settling ability (SVI30 of 30.9 mL/g), COD and TN removal efficiencies (97.6% and 60.4%, respectively). High light intensity (316 ±â€¯12 µmol m-2·s-1) accelerated granular biomass growth (5.3 g/L) and enhanced the TP removal efficiency (83.7%). Extracellular polymeric substance (EPS) analysis revealed that low light intensity induced more large weight distribution protein production (9-12 kDa and 50-150 kDa), predominantly tryptophan and aromatic proteins. Furthermore, N-acyl-homoserine lactones (AHLs) with a side chain ≤ C10 were commonly shared in the ABGS, and the ABGS developed at low light intensity had a higher C6- and 3OC8-HSL content, which effectively promoted the biofilm formation. The add-back studies showed that the AHLs facilitated the regulation of EPS synthesis. Statistical analysis indicated that the AHLs content had a close correlation with the EPS production, the 50th percentile of the particle size distribution and microbial community assembly, suggesting that AHLs-mediated quorum sensing have an important ecological role in EPS expression and algal-bacterial granulation. Overall, this study describes the ABGS development at different light intensities and the mechanisms of ABGS formation treating synthetic domestic wastewater.

Efficiencies and mechanisms of the chemical cleaning of fouled polytetrafluoroethylene (PTFE) membranes during the microfiltration of alkali/surfactant/polymer flooding oilfield wastewater.

The chemical cleaning of fouled polytetrafluoroethylene (PTFE) membranes with different reagents after the microfiltration of alkali/surfactant/polymer (ASP) flooding oilfield wastewater was examined in this study. Foulant analyses, cleaning efficiencies of different reagents and conditions and cleaning mechanisms were investigated. The results showed that anionic polyacrylamide (APAM) and crude oil were the main membrane foulants accompanied by organic-inorganic-organic/membrane aggregate foulants formed by bridging inorganic ions and organic species. Cleaning efficiency of 93% was acquired through mixed cleaning with 0.04 N NaClO + 200 mg L-1 NaOH, which was found to be better than individual cleaning. Moreover, consecutive cleaning with NaClO + NaOH-HCl restored 98% of the membrane flux, suggesting that HCl cleaning contributed to flux recovery. Additionally, the cleaning temperature and time were set as 40 °C and 3 h, respectively, considering economy and membrane lifespan. Finally, the mechanism of membrane cleaning and analyses of membrane properties were described in this paper, aiming to provide a future direction for production practices. Considering that the cleaning reagents used in this study are easy to obtain and use, consecutive cleaning with NaClO + NaOH-HCl is recommended to clean the PTFE membranes fouled by ASP flooding oilfield wastewater.

Influence of UV dose on the UV/H2O2 process for the degradation of carbamazepine in wastewater.

This study evaluates the influence of UV dose on degradation of carbamazepine (CBZ) in wastewater under UV-C (λ = 254 nm) photolysis with and without H2O2. The rate of degradation of CBZ exhibited a direct dependence on the intensity of incident UV irradiation as the rate of degradation was observed to increase linearly (R2 = 0.98) with UV intensity between 1.67 and 8.95 × 1017 photons/s. More than 95% of the CBZ that spiked in wastewater rapidly degraded within 4 min with a first-order rate constant of 1.2 min-1 for an optimum H2O2 dose of 100 mg/L. Bench-scale continuous flow reactor experiments also showed that CBZ degraded with first-order kinetics at a rate constant of 1.02 min-1. The kinetic parameters obtained for a continuous bench-scale reactor were in good agreement with the relationships developed through batch experiments with only a marginal deviation of ± 6.5%. The relationship between UV intensity and CBZ degradation rate obtained in this study was extrapolated to the UV disinfection unit of a wastewater treatment plant to predict possible degradation of CBZ during UV disinfection. The addition of 100 mg/L of H2O2 to the secondary-treated effluent entering the UV disinfection unit is predicted to achieve over 60% degradation of CBZ. Abbreviations: CBZ carbamazepine; AOPs advanced oxidation processes; UV ultraviolet radiation; UV-C ultraviolet C (λ = 254 nm) radiation; NZVI non-zerovalent iron; WWTP wastewater treatment plant; HPLC high-performance liquid chromatography.

Aerobic granular sludge and naphthenic acids treatment by varying initial concentrations and supplemental carbon concentrations.

Aerobic granular sludge (AGS) has previously been utilized in the treatment of toxic compounds due to its diverse and dense microbial structure. The present study subjected mature AGS to model naphthenic acids (NAs) representative of the Canadian oil sands. To this effect, three NA concentrations (10, 50 and 100 mg/L) and three supplemental carbon source concentrations (600, 1200 and 2500 mg/L) were studied in batch reactors for 5 days. The responding variables were chemical oxygen demand (COD), NA concentrations and nutrients. Cyclohexane carboxylic acid (CHCA), cyclohexane acetic acid (CHAA) and 1-adamantane carboxylic acid (ACA) were chosen to study structure-based degradation kinetics. The optimal COD according to the runs was 1200 mg/L. CHCA was removed completely with biodegradation rate constants increasing with lower NA concentrations and lower COD concentrations. CHAA was also removed completely, however, an optimal rate constant of 1.9 d-1 was achieved at NA and COD concentrations of 50 mg/L and 1200 mg/L, respectively. ACA removal trends did not follow statistically significant regressions; however, degradation and sorption helped remove ACA up to 19.9%. Pseudomonas, Acinetobacter, Hyphomonas and Brevundimonas spp. increased over time, indicating increased AGS adaptability to NAs.

Reactivation and pilot-scale application of long-term storage denitrification biofilm based on flow cytometry.

The work provides a method on the basis of flow cytometry to evaluate the performance of denitrification biofilm during the preservation, reactivation and pilot-scale operation process. The viable cell ratio of denitrification biofilm significantly reduced and further led to the decrease of denitrification capacity after long-term preservation for 5 months. Protein component in tightly bound extracellular polymeric substances (TB-EPS) could serve to enhance microbial adhesion and promote denitrification biofilm formation. With the significant correlation of viable cell ratio and microbial characteristics, 4 °C was more appropriate for preserving denitrification biofilm and conducive to maintain the relatively high denitrification capacity. A maximum denitrification rate of 5.80 gNO3--N/m2·d was obtained in pilot-scale anoxic-oxic (AO) process and Dechloromonas became greater prevalence in denitrification suspended carriers. Furthermore, the enrichment of Pseudomonas, Parcubacteria, Acidovorax, Aquabacterium and Unclassified_Flavobacteriaceae enhanced biofilm formation and nutrient conservation. The significantly positive correlation between viable cell ratio and the ratio of nitrate reduction to COD consumption was discovered, and the indices of Chao, ACE, Shannon and Simpson of denitrification biofilm were positively correlated with viable cell ratio, meaning that flow cytometry analysis was reasonable and suitable to evaluate the performances of denitrification biofilm.

Piggery wastewater treatment by aerobic granular sludge: Granulation process and antibiotics and antibiotic-resistant bacteria removal and transport.

The aim of this work was to study the responses of aerobic granulation process to antibiotics and investigate the antibiotics and antibiotic-resistant bacteria (ARB) removal and transport. Results showed that aerobic granular sludge (AGS) was dominant in the bioreactor at day 45, and the relatively high protein content from tightly bound extracellular polymeric substances (TB-EPS) facilitated aerobic granulation and maintained biomass stabilization. The protein contents in EPS and TB-EPS were positively correlated with relative hydrophobicity, thereby improving the adsorption capacity among hydrophobic particles. The chemical oxygen demand (COD), NH3-N, and total N removal efficiencies were 98.0%, 97.0%, and 92.4%, respectively. Five antibiotics, including kanamycin, tetracycline, ciprofloxacin, ampicillin, and erythromycin, were examined in piggery wastewater, with concentrations up to the concentration range of 29.4-44.1 µg/l, and the total antibiotics removal rate reached up to 88.4% ±â€¯4.5%. A total of 5.2% of the total antibiotics were discharged from bioreactor, and 62.5% of the total antibiotics were degraded, and 32.3% of total antibiotics were adsorbed by aerobic granules. The presence of antibiotics rarely exhibited an influence on AGS formation, and the relatively high microbial activity of aerobic granules was beneficial to antibiotics removal. The ARB removal rate increased up to 89.4% ±â€¯3.3%, but a large amount of ARB was enriched in aerobic granules.

Optimization of organics to nutrients (COD:N:P) ratio for aerobic granular sludge treating high-strength organic wastewater.

The present study attempted to optimize the nutrients required for biological growth and biomass synthesis in the treatment of high-strength organics wastewater using aerobic granular sludge (AGS). Three identical sequencing batch reactors (SBRs) were used to cultivate aerobic granules at COD concentration of ~5000 mg/L at COD:N:P ratios of 100:2.8:0.4, 100:4.4:0.5, and 100:5:0.7. Results indicated that the amount of nutrients needed for biomass growth does not follow the conventional organics to nutrients ratio (COD:N:P) of 100:5:1 when dealing with high-strength organics wastewater. The highest removal efficiency was achieved at COD:N:P ratio of 100:2.8:0.4, where COD, TN, and P removal was 98.8 ±â€¯0.3%, 100.0 ±â€¯0.0%, and 99.3 ±â€¯1.0%, respectively. Moreover, the presence of high amounts of organics led to the dominance of the fast-growing heterotrophs in all SBRs, with the genus Thauera identified as the most abundant genera (23-40%), while autotrophic nitrifiers disappeared. The observed biomass yield at COD:N ratio of 100:2.8 suggested that heterotrophic nitrification may have occurred, while at COD:N ratios of 100:4.4 and 100:5, all the nitrogen was used for biomass synthesis. Moreover, at COD:N ratio of 100:5, almost 1/5 of the organics were utilized by the biomass cells to produce EPS as defensive action against the effects of free ammonia. Batch optimization experiments showed that the fastest rate of removal occurred at COD:N:P ratio of 100:1.1:0.4. After 4 h, the COD, TN, and P removal efficiencies were 95%, 99%, and 96%, achieving overall removal efficiencies of 98%, 100%, and 97% respectively, at HRT of 8 h. The bacterial behavior in consuming the organics was altered under nutrient-deficient conditions, where faster degradation rates were observed as the amounts of nutrients decreased, with higher relative abundance of heterotrophs and diazotrophic bacterial populations.

Treatment of 17α­ethinylestradiol, 4­nonylphenol, and carbamazepine in wastewater using an aerobic granular sludge sequencing batch reactor.

This study quantifies the removal of a mixture of commonly detected emerging contaminants, 17α­ethinylestradiol (EE2), 4­nonylphenol (NP), and carbamazepine (CBZ) from synthetic wastewater using aerobic granular sludge in a sequential batch reactor. The emerging contaminant concentration in the influent wastewater was maintained near 500 µg/L for the duration of the experiment. Removal of EE2, NP, and CBZ is comprised of both adsorption and degradation. In general, the main removal mechanism for the emerging contaminants was initially adsorption, however it transitions to degradation as the adsorption capacity is saturated. The stabilized degradation for EE2 and NP in the SBR, was 16.09 µg/g and 20.05 µg/g, respectively. There was limited degradation of CBZ during the anaerobic phase. Both the Langmuir and Freundlich adsorption isotherms fit the data well and constants for the equations are calculated. The constants for the Langmuir Isotherm are found to be (X/m)max = 36.23, b = 0.0019 for EE2 and (X/m)max = 44.25, b = 0.0004 for CBZ. None of the tested compounds were found to be detrimental to the performance of the aerobic granules, and high macronutrient removal efficiency was maintained. The granule sludge bed and particle size were not negatively affected by EE2 and NP, however, carbamazepine appeared to interfere with the mechanism of granule formation resulting in a decrease in particle size during the experiment.