Granulation Time Research Articles

Thauera enriched granular activated carbon-assisted aerobic granular sludge performs enhanced biological nitrogen and phosphate removal via propionate utilization

Propionate constituting up to 25 % of volatile fatty acids in municipal wastewater, presents metabolic challenges for microorganisms. This study investigated the combined use of propionate along with granular activated carbon (GAC) for aerobic granular sludge (AGS) development and biological nutrient removal (BNR), particularly bio-P removal in granular reactors. GAC addition decreased granulation time and facilitated stable BNR pathways with propionate. AGS demonstrated robust settling properties (≥1 mm, 6 g/L MLSS, 40 mL/g SVI) with increased alginate-like exopolysaccharide (ALE) content up to 400 mgALE/gSS, indicating stable granule formation. Effective ammonium removal via simultaneous nitrification and denitrification was achieved. By day 90, phosphate removals reached 89 %, due to enrichment of polyphosphate accumulating organisms (PAOs) in GAC-containing AGS. The sludge fraction (>0.5 mm) comprised of granules and GAC-biofilms showed efficient phosphate removal through enhanced biological phosphate removal (EBPR). Enrichment of denitrifying PAO, Thauera sp., contributed to enhanced granulation, granular stability and nutrient removals.

Enhanced aerobic granular sludge by thermally-treated dredged sediment in wastewater treatment under low superficial gas velocity

The positive contributions of carriers to aerobic granulation have been wildly appreciated. In this study, as a way resource utilization, the dredged sediment was thermally-treated to prepared as carriers to promote aerobic granular sludge (AGS) formation and stability. The system was started under low superficial gas velocity (SGV, 0.6 cm/s)for a lower energy consumption. Two sequencing batch reactors (SBR) labeled R1 (no added carriers) and R2 (carriers added), were used in the experiment. R2 had excellent performance of granulation time (shortened nearly 43%). The maximum mean particle size at the maturity stage of AGS in R2 (0.545 mm) was larger compared to R1 (0.296 mm). The sludge settling performance in R2 was better. The reactors exhibited high chemical oxygen demand (COD) and ammonia nitrogen (NH3-N) removal rates. The total phosphorus (TP) removal rate in R2 was higher than R1 (almost 15% higher) on stage II (93-175d). R2 had a higher microbial abundance and dominant bacteria content. The relative abundance of dominant species was mainly affected by the carrier. However, the enrichment of dominant microorganisms and the evolution of subdominant species were more influenced by the increase of SGV. The results indicated that the addition of carriers induced the secretion of extracellular polymeric substances (EPS) by microorganisms and accelerated the rapid formation of initial microbial aggregates. This work provided a low-cost method and condition to enhance aerobic granulation, which may be helpful in optimizing wastewater treatment processes.

Enhanced AGS by granular activated carbon loaded with nano iron when treating low strength and low COD/TN ratio municipal wastewater: Microbial metabolism, electron transfer and enhancement mechanism

In order to accelerate aerobic granular sludge (AGS) formation and stabilization, four SBR reactors were used and labeled R1 (no added material), R2 (nano iron added, NI), R3 (granular activated carbon added, GAC) and R4 (GAC loaded with NI added, NI@GAC) to improve the granulation process when treating low strength and low COD/TN ratio municipal wastewater. R4 had excellent performance of granulation time (shortened nearly 40%), nitrogen removal performance (promoted the start-up and recovery time) and PO43--P removal efficiency (improved about 25%) compared with R1. The increased electron transport system activity (ETSA) and adenosine triphosphate (ATP) of R2 and R4 indicated that NI of NI@GAC is beneficial for promoting microbial metabolic activity and maintaining granules stability during granulation stage and famine recovery stage. Meanwhile, NI@GAC, acting as the core of AGS, stimulated the secretion of extracellular polymeric substances (EPS), which promoted AGS formation. Electrochemical analysis of R1-R4 showed that GAC of NI@GAC improved the electron transfer efficiency and maintained high electron transfer ability of EPS. In addition, NI@GAC promoted the enrichment of Bacteroidetes and Planctomycetes belonging to denitrifiers and nitrifiers genera, which is crucial for the nitrogen removal process. Combined with the above results, the enhancement mechanism of NI@GAC on AGS formation and granules stability was established through microbial metabolic activity, EPS secretion, electron transfer characteristic and bacterial community. This study provided a theoretical basis for rapid granulation and stability of AGS technology.

Study on culture of stable aerobic granular sludge

In this study, three reactors were established with anaerobic plug-flow times of 1.5 hours, 1 hour, and 0.5 hours. The results indicated that the anaerobic plug-flow time of 1 hour constructed favorable "feast- famine" period ratio, promoting the enrichment of microorganisms that stored and utilized the internal carbon source, such as Phosphate and Glycogen Accumulating Organisms (PAO and GAO). This resulted in the formation of granular sludge with both short granulation time and structural stability. In contrast, shortening the anaerobic feed time to 0.5 hours was detrimental to the growth of GAO, leading to slow granularization of aerobic sludge. The anaerobic influent time of 1.5 h leads to the shortening of starvation period and poor stability of particle structure.

Development of a PAT platform for the prediction of granule tableting properties

In this work, the feasibility of implementing a process analytical technology (PAT) platform consisting of Near Infrared Spectroscopy (NIR) and particle size distribution (PSD) analysis was evaluated for the prediction of granule downstream processability. A Design of Experiments-based calibration set was prepared using a fluid bed melt granulation process by varying the binder content, granulation time, and granulation temperature. The granule samples were characterized using PAT tools and a compaction simulator in the 100-500kg load range. Comparing the systematic variability in NIR and PSD data, their complementarity was demonstrated by identifying joint and unique sources of variation. These particularities of the data explained some differences in the performance of individual models. Regarding the fusion of data sources, the input data structure for partial least squares (PLS) based models did not significantly impact the predictive performance, as the root mean squared error of prediction (RMSEP) values were similar. Comparing PLS and artificial neural network (ANN) models, it was observed that the ANNs systematically provided superior model performance. For example, the best tensile strength, ejection stress, and detachment stress prediction with ANN resulted in an RMSEP of 0.119, 0.256, and 0.293 as opposed to the 0.180, 0.395, and 0.430 RMSEPs of the PLS models, respectively. Finally, the robustness of the developed models was assessed.

Incremental nonlinear trend fuzzy granulation for carbon trading time series forecast

In addition to its important economic value, carbon trading is also an important tool in international politics and diplomacy. Carbon price forecast accuracy has far-reaching implications for economic development and the environment. Few existing studies have been more accurate in predicting carbon prices over longer periods. In this paper, the incremental Gaussian nonlinear trend fuzzy granulation method and the Gaussian nonlinear trend fuzzy granulation method are innovatively proposed to predict carbon prices. This study first converts carbon prices into incremental granulation time series. A time-varying core line is added to produce nonlinear trend granulation on the foundation of linear trend granulation. The nonlinear trend and residual information are then predicted using the DeeAR network, respectively, and the final prediction result is obtained by adding the predicted values for each. Moreover, a new evaluation index, the comprehensive evaluation of RMSE, MAE, and MAPE as three indicators, is proposed to consider the accuracy of the evaluation index more comprehensively and reliably. The results show that the prediction method has the smallest error in long-term prediction compared with other models. The daily closing price datasets of carbon exchanges published in Shenzhen and Beijing are used to validate the efficacy of this methodology.

Distribusi Ukuran Granul dari Tepung Singkong dengan Tepung Tapioka sebagai Pengikat pada Rotary Drum Granulator

Granulation is a process of monoparticle attachment with a particular mechanism to form a bigger and compact particle which is called granule. Granulation application has been used on many industries like pharmacy and agriculture industries. Research about granulation has been done continuously to get predictive models for various cases. The model which is only applicable to the specific material used in this research is expected to be useful to optimize the perfomances of the granulator in the industries. This research aims to develop the kinetics model of granule size distribution of cassava flour and its connection to granulation time by varying the mass of tapioca starch as the binder in rotary drum granulator. 2 grams of Cassava flour and tapioca starch were mixed in the rotary drum granulator and then water was sprayed during the granulation process. The duration of granulation were 5, 10, 15, 20, and 25 minutes. The variations of mass of the binder used in this research were 1, 1,5, and 2 gram. The granules were dried in the oven at 80°C until 30 minutes, and afterwards the granules were screened through various screen layers with different mesh size. The results of this research show that binder mass variations do not influence the layering rate of granule, and the increase of binder mass will decrease the birth rate.

Ball-milled magnetic sludge biochar enables fast aerobic granulation in anoxic/oxic process for the treatment of coal chemical wastewater

Coal chemical wastewater (CCW) containing toxic and hazardous matters requires to be treated prior to discharge. Promoting the in-situ formation of magnetic aerobic granular sludge (mAGS) in continuous flow reactor process has a great potential for CCW remediation. However, long granulation time and low stability limit the application of AGS technology. In this study, Fe3O4/sludge biochar (Fe3O4/SC) with biochar matrix derived from coal chemical sludge were applied to facilitate the aerobic granulation in two-stage continuous flow reactors, containing separated anoxic and oxic reaction units (abbreviated as A/O process). The performance of A/O process was evaluated at various hydraulic retention times (HRTs) (42 h, 27 h, and 15 h). Magnetic Fe3O4/SC with porous structures, high specific surface area (BET = 96.69 m2/g), and abundant functional groups was successfully prepared by ball-milled method. Adding magnetic Fe3O4/SC to A/O process could promote aerobic granulation (85 days) and the removal of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), and total nitrogen (TN) from CCW at all tested HRTs. Since the formed mAGS had high biomass, good settling ability, and high electrochemical activities, mAGS-based A/O process had high tolerance to the decrease of HRT from 42 h to 15 h for CCW treatment. The optimized HRT for A/O process was 27 h, at which Fe3O4/SC addition can result in the increase of COD, NH4+-N and TN removal efficiencies by 2.5 %, 4.7 % and 10.5 %, respectively. Based on 16S rRNA genes sequencing, the relative abundances of genus Nitrosomonas, Hyphomicrobium/Hydrogenophaga and Gaiella in mAGS accounting for nitrification, denitrification as well as COD removal were increased during aerobic granulation. Overall, this study proved that adding Fe3O4/SC to A/O process was effective for facilitating aerobic granulation and CCW treatment.

Research on the Particle Breakage Mechanism in High-Speed Shear Wet Granulation

During the operation of a high-speed shear wet granulator, the rotation of the granulation components leads to the emergence of the phenomenon of particle breakage, which results in changes in particle size. To simulate the breakage process of pharmaceutical powder particle agglomerates in a granulator, a Hertz–Mindlin with bonding contact model was designed in this study. The effects of impeller speed, chopper speed, and granulation time on particle breakage were then studied. The results show that the agglomerates formed by the powder particles are not only sheared and collided by the chopper at high speed but also squeezed by the impeller, which causes the powder particles to break. In this paper, 20 sets of case simulations were conducted, and it was found that the impeller significantly affected the fragmentation rate of particles. Increasing the speed of the impeller increases the particle breakage rate and reduces the mean particle size.

A Review on the Stability, Sustainability, Storage and Rejuvenation of Aerobic Granular Sludge for Wastewater Treatment

Aerobic granular sludge (AGS) is a recent innovative technology and is considered a forthcoming biological process for sustainable wastewater treatment. AGS is composed of the dense microbial consortium of aerobic, anaerobic, and facultative types of bacteria. The mechanism of AGS formation and its stability for long-term operation is still a subject of current research. On the other hand, AGS makes the treatment process sustainable in a cost-effective way. However, in order for AGS to be applied in a broader range of applications, there are several challenges to overcome, such as slow-speed granulation and the disintegration of AGS after granulation. Many factors play a role in the stability of granules. The storage of granules and the later use of them for granulation startup is a feasible method for reducing the time for granulation and maintaining stability. This review focuses on the granulation process and characteristics of AGS, granulation time and the stability of AGS under different conditions, the comparison of different storage methods of granules, and their recovery and rejuvenation. From this review, it is evident that additional research is required to assess the effectiveness of regenerated AGS after prolonged storage to promote AGS technology for commercial applications.

Understanding the role of polyurethane sponges on rapid formation of aerobic granular sludge and enhanced nitrogen removal

Long formation time and limited simultaneous nitrification–denitrification (SND) are still the problems for aerobic granular sludge (AGS) application. This study presents a novel strategy to simultaneously promote sludge granulation and enhance nitrogen removal. This new approach consists of adding polyurethane sponges (PUS) and applying intensive aeration periodically. To demonstrate the effectiveness of this strategy and understand the role of PUS, two sequencing batch reactors (R1: without PUS; R2: PUS addition) were used. The results show that the granulation time in R2 (14 days) was much shorter and the nitrogen removal (80.7 %) was much higher when compared to the R1 (75 days and 64.8 %). Biofilm was rapidly formed on PUS because of the porous network structure, resulting in the low suspended biomass concentration. Thus, a close to discrete non-flocculent settling type was created, which promoted the selection of well-settling aggregates rapidly and efficiently. Meanwhile, biofilm was detached from PUS by intensive aeration, providing the nucleus (fragments of biofilm) in-suit for microbial adhesion. Under the combined effects, the aerobic granulation process was significantly accelerated. The total biomass amount was maintained during initial granulation because of the rapid biofilm formation, resulting in the stable removal of NH4+-N at a rapid start-up period. The rapid formation of biofilm and fast granulation created more anoxic zones during aeration and thereby enhanced SND. The biofilm formation also increased the relative abundances of aerobic denitrifiers (Dokdonella and Denitratisoma), autotrophic denitrifiers (Sulfuritalea), and hydrolytic/fermentativebacteria (Ferruginibacter, Opitutus, and Lactobacillus), which enhanced the SND performance and endogenous denitrification.

Effect of Various Binders on the Properties of Microalgae-Enriched Urea Granules.

As the human population grows and the demand for food grows with it, the recycling, or containment of materials is important for resource consumption. Nitrogen is one of the main plant nutrients, most commonly used as the chemical substance urea. Because urea is very soluble and at a relatively low temperature (50-60 °C) it hydrolyses easily (releases N2 and CO2) in soil solutions; this is why very large amounts of nitrogen are lost and greenhouse gases are released and this causes serious environmental problems. Therefore, the aim of this study was to create microalgae-enriched nitrogen fertilizers with different binders that inhibit nitrogen leaching from the soil. Binders such as water (W), polyvinyl acetate dispersion (PVAD), molasses (M), potato starch (S), and carboxymethyl cellulose (CMC) were used in this study and their influence on leaching was analysed. Granular fertilizers were produced in a drum granulator and dryer under equal conditions: granulation time was 7 min, granulation took place at a temperature of 50-60 °C, at a drum rotation speed of 26 rpm, with a 5° inclination angle of the drum. The results show that the highest quantity of the marketable fraction was 43.01 (±3.068%) and it was obtained using urea, with 10% (w/w) microalgae additive, and 11.4% (w/w) of 5% concentration molasses solution. The granules of the fertilizer marketable fraction are similar in size because the size guide number (SGN) of the granules vary in a narrow range and fall within the interval of 287 to 304; this means that the average particle size is ~3 mm. When different binders were used, the average static crushing strength of the granulated fertilizers was lower (approximately 6-12 MPa) than using water alone (approximately 12-16 MPa), but the lower values still fell into the required range. Additives of PVAD solutions and molasses solutions have been found to retain nitrogen in sand. The method of one-way analysis of variance (ANOVA) was used to evaluate the results.

Aerobic Granulation Stability and Microbial Diversity of Filamentous Bulking Sludge

Filamentous bacteria, as one of the common bacteria types in wastewater biological treatment, are considered to be the main factor to induce sludge bulking. However, because of its special filamentous shape, it plays a crucial role in the formation of sludge particles. Taking filamentous bulking sludge as the research object, the effect of filamentous bacteria on the sludge granulation process and maintaining the stability of sludge granules was studied, and the microbial diversity of the sludge system was analyzed. Filamentous bulking sludge (SVI=241.56 mL·g-1) and flocculated sludge (SVI=64.22 mL·g-1) were respectively inoculated to carry out granulation culture. The results showed that the time of particle appearance of bulking sludge and flocculated sludge was 20 days and 40 days, respectively; the mature particle sizes were 650 μm and 700 μm, respectively; and the granulation time of bulking sludge was only half that of flocculated sludge. After adding the anoxic zone, the granules were broken to differing degrees, but the SV30/SV5 value of mature granules recovered to 1 after short-term fluctuation, and the stability of the mature granules was stronger. The analysis of microbial community structure showed that the relative abundance of norank_o__Saccharimonadales, unclassified_o__Saccharimonadales, and unclassified_f__Saccharimonadaceae increased from 0.05%, 0.01%, and 0.01% to 4.09%, 3.15%, and 1.12%. The existence and accumulations of these hydrophobic bacteria were important for rapid granulation. The removal rates of COD, NH4+-N, and TN were 94%, 99%, and 35% and 92%, 97%, and 30%, respectively, in SBR1 of bulking sludge and SBR2 of flocculated sludge, and the removal rates of TP were 60% and 30%, respectively.

Manufacture and characterization of carbonated lightweight aggregates from waste paper fly ash

The combustion of biomass and waste paper sludge in a fluidized bed is ecologically profitable. However, a large amount of by-product with high hydraulic reactivity is produced and is considered as wastes. Most of the time the waste paper fly ash (WPFA) goes to landfills, therefore new utilization methods are necessary. In some countries, the high content of metallic and metalloids trace elements (MMTE) in WPFA, more specifically Barium (Ba) and Lead (Pb) makes its valorization difficult. In this paper, the Lightweight Aggregates (LWA) was produced from WPFA by granulating with water in high-intensity granulator. Since WPFA is rich in CaO, the addition of water promotes rapid setting and hydration compared to other types of ash. In this study, different granulation parameters were investigated, such as the rotation modes between the steel pan and the impeller, the rotation speed of the steel pan, the granulation time, in order to improve the mass percentage of the targeted LWA (2–16 mm). In order to evolve the immobilization potential of Ba and Pb, a carbonation process was performed, exposing the manufactured LWA to pure carbon dioxide (CO2) gas at laboratory scale. The physical, morphological, thermal and mechanical characterizations were performed on LWA for use in mortars, concretes or civil engineering constructions.Results have demonstrated the influence of the rotation mode between the steel pan and the on the distribution of WPFA inside the steel pan and the change in the growth rate of the granules can be observed. Increased density and improved compressive strength with low porosity and water absorption were also found in LWA after carbonation. This was due to the occurrence of both a carbonation reaction and a hydration reaction. Furthermore, the results of thermogravimetry and SEM-EDS confirmed the formation of hydrated phases (ettringite, carboaluminates), also the formation of calcite in the pores and the external surface of the LWA. Regarding environmental aspects, the results have revealed that Ba and Pb were well immobilized in the solid matrix after carbonation.

Coupling of sponge fillers and two-zone clarifiers for granular sludge in an integrated oxidation ditch

Considering that aerobic granular sludge (AGS) exhibits a long granulation time in continuous flow and that the poor removal effects on N and P have severely restricted its large-scale application, a novel strategy was developed involving sponge fillers to construct an anoxic zone coupling two-zone clarifiers to promote granulation in an integrated oxidation ditch. The different pores in the sponge fillers were used to accelerate the accumulation and formation of aggregates under the impetus of water flow, meanwhile, the A/O operation mode and the formation of AGS were also improved the denitrification and phosphorus removal capacity of the reactor. The experimental results indicated that AGS was shaped in the anoxic and aerobic zones on day 30 and on day 43, respectively. When running for 90 days, the mixed liquor suspended solids (MLSS), sludge volume index (SVI5) and average particle size in the anoxic zone and aerobic zone were 5848 mg/L and 4812 mg/L, 31.2 mL/g and 35.8 mL/g, and 329.2μm and 362.3μm, respectively. During the granulation process, the EPS content in the anoxic zone was significantly higher than that in the aerobic zone, indicating that the sponge fillers played a dominant role in granulation. After the reactor reached steady conditions, the removal efficiencies of COD and N were 87.29%±2.61% and 60.11%±4.68%, respectively. The TP removal efficiency gradually increased from 26.90% on day 1 to 77.54% on day 90. Moreover, the microbial community transformed conspicuously throughout granulation, including an enrichment of microorganisms exhibiting EPS secretion and pollutants degradation.

Enhanced aerobic granular sludge formation by applying Phanerochaete chrysosporium pellets as induced nucleus.

The long start-up period is a major challenging issue for the widespread application of aerobic granular sludge (AGS). In this study, a novel rapid start-up strategy was developed by inoculating Phanerochaete chrysosporium (P. chrysosporium) pellets as the induced nucleus in a sequencing batch airlift reactor (SBAR) to enhance activated sludge granulation. The results demonstrated that P. chrysosporium pellets could effectively shorten the aerobic granulation time from 32 to 20days. The AGS promoted by P. chrysosporium pellets had a larger average diameter (2.60-2.74mm) than that without P. chrysosporium pellets (1.78-1.88mm) and had better biomass retention capacity and sedimentation properties; its mixed liquor suspended solids (MLSS) and sludge volume index (SVI30) reached approximately 5.2g/L and 45mL/g, respectively. The addition of P. chrysosporium pellets promoted the secretion of extracellular polymeric substances (EPS), especially protein (PN). The removal efficiencies of chemical oxygen demand (COD), ammonia nitrogen (NH4+-N), total nitrogen (TN), and total phosphorus (TP) in P. chrysosporium pellets reactor were 98.91%, 89.17%, 64.73%, and 94.42%, respectively, which were higher than those in the reactor without P. chrysosporium pellets (88.73%, 82.09%, 55.75%, and 88.92%). High throughput sequencing analysis indicated that several functional genera that were responsible for the formation of aerobic granules and the removal of pollutants, such as Acinetobacter, Pseudomonas, Janthinobacterium, and Enterobacter, were found to be predominant in the mature sludge granules promoted by P. chrysosporium pellets.

Numerical study of the dynamic behaviour of iron ore particles during wet granulation process using discrete element method

Iron ore granulation process is simulated by the discrete element method to understand the dynamic behaviour of iron ore particles. The results show that the macroscopic particle flow transits from rolling regime to cascading regime after water addition, with the angle of repose of particles increasing and the level of particle size segregation decreasing. The moisture distribution becomes more uniform through particle tumbling, which improves the granule growth. The microdynamic behaviours of the fines, intermediates and nuclei during the auto-layering process have been studied respectively. The variations in the average contact number, kinetic and rotational energy per particle with granulation time are analysed. The optimal moisture contents for Ores N, M and Y are estimated as 6.46 wt%, 9.12 wt% and 8.70 wt%, respectively. The numerical results are generally in accordance with the corresponding experimental ones, which basically validates the DEM modelling of iron ore granulation presented in this paper.

Effect of magnetic field intensity on aerobic granulation and partial nitrification-denitrification performance

Magnetic field, acknowledged as a sustainable approach, is a promising method to improve the formation, stability and treatment performance of aerobic granular sludge (AGS). In this study, partial nitrification-denitrification was achieved in three AGS sequencing batch reactors (SBRs), and the effect of magnetic field intensity on AGS formation and partial nitrification-denitrification performance were investigated. 50 mT magnetic field could accelerate complete granulation time from 45 d (0 mT) to 30 d (50 mT) by promoting the settling ability of AGS and stimulating the secretion of extracellular polymeric substances (EPS). With 50 mT magnetic field, partial nitrification-denitrification in AGS was enhanced, and the removal efficiency of chemical oxygen demand (COD), NH4+-N and TN increased by 7.6%, 26.2% and 41.5% comparing with the control (0 mT). Magnetic field balanced the dominant genera Thauera, Flavobacterium, Chryseobacterium and Meganema, which further enhanced the aerobic granulation and partial nitrification-denitrification in AGS. Thus, the application of magnetic field is reliable for accelerating aerobic granulation and enhancing partial nitrification-denitrification process.

Switching from batch to continuous granulation: A case study of metoprolol succinate ER tablets

Continuous manufacturing (CM) has been used to produce several immediate release drug products. No extended-release (ER) product manufactured employing CM technology has been approved yet. This study investigated the critical aspects of switching from the batch mode of high shear granulation to the continuous operation of twin-screw granulation for extended-release tablets. Metoprolol succinate ER tablets was used as a model ER formulation for this purpose. A central composite design (CCD) was employed to determine the effects of high shear granulator (HSG) parameters, namely impeller speed, granulation time, and binder liquid feeding rate, on the critical granulation characteristics important for product performance. These critical granulation characteristics served as a guide for switching from the batch processing to the continuous operation for achieving the same breaking strength and dissolution for this ER metoprolol tablets.The granulation time was the most critical factor affecting the bulk properties of granules which contributed to tablet dissolution. The higher density and lower compressibility of granules were attained at the longest granulation time of 5.4 min with the fastest liquid feeding rate of 75 g/min. The granules’ density was the primary factor negatively affecting the dissolution of metoprolol tablets. However, the breaking strength of tablets confounded the effect of granules density on metoprolol dissolution. Switching the processing parameters of high shear granulation to twin-screw granulation achieved similar dissolution profiles (F2 greater than 50). The screw speed was not found to affect bulk properties of granules. The root cause of granulation failures in twin-screw granulation, such as premature consolidation, excessive swelling, poor cohesion, inconsistent shearing effects, and formation of deformed agglomerates, were identified. In conclusion, the use of critical granulation characteristics through a performance-based approach of ER tablets facilitated the switching of manufacturing of an ER formulation form batch to continuous operation.

Enhancing robustness of halophilic aerobic granule sludge by granular activated carbon at decreasing temperature

High salinity seriously inhibits the growth and metabolism of microorganisms, resulting in poor settleability, excessive biomass loss and low treatment efficiency of biological wastewater treatment systems. The development of halophilic aerobic granular sludge (HAGS) is a feasible strategy for addressing this challenge. However, there are problems with the granulation of HAGS and the stability of granules at decreasing temperatures. In this study, granular activated carbon (GAC) with a large specific surface area and good biocompatibility was used to enhance the robustness of HAGS. The results showed that the addition of GAC shortened the granulation time from 60 d (control system) to 35 d (GAC-addition system). The proteins contents of extracellular polymeric substances (EPS) in the GAC-addition system was significantly higher (p < 0.05) than that in the control system during granulation. Satisfactory NH4+-N and chemical oxygen demand (COD) removal efficiencies reached more than 96% in both systems at 18–26 °C. When the operating temperature was lower than 15 °C, the GAC-addition system exhibited better NH4+-N removal performance (>80%) than the control system (<60%). Moreover, the abundance of almost all nitrogen metabolism-related genes in the GAC-addition system was higher than that in the control system. During the granulation process, the enrichment of functional microorganisms, including family Flavobacteriaceae, Rhodobacteraceae, and Cryomorphaceae, may promote the production of EPS by significantly upregulating (p < 0.05) the metabolic pathway “Signaling Molecules and Interaction” in the GAC-addition system. The overexpression of the nitrogen assimilation gene glnA in heterotrophic bacteria (Halomonas and Marinobacterium) may promote the conversion of inorganic nitrogen to extracellular proteins to adapt to the decreased operational temperature. Our findings confirm that GAC addition is a simple but effective strategy to accelerate granulation and enhance the robustness of HAGS in saline wastewater treatment.