Maximum Substrate Utilization Rate Research Articles

Ideal performance assessment of non-recirculating anaerobic fluidized bed reactors treating low to high strength organic loads with low retention time

This study investigated the ideal performance of non-recirculating Anaerobic Fluidized Bed Reactors (AnFBRs) for treating organic wastewater of varying strengths under low Hydraulic Retention Time (HRT). Four 4.58 L AnFBRs were used to treat synthetic wastewater with an Organic Loading Rate (OLR) ranging from 4.50 to 40.11 gCOD/L-d, and HRT between 1.1 and 4.4 hours. The AnFBRs achieved high removal efficiencies ranging from 83 % to 96 % at steady state, except during the organic shock load, which reduced removal performance to 12 %. Shortened HRT conditions led to a decreasing trend in reactor pH due to an incomplete anaerobic cycle. The modified Stover-Kincannon model estimated the maximum substrate utilization rate of AnFBR's to be 196.08 gCOD/L-d, with a correlation coefficient of 0.98. Under shortended HRT, microbial diversity analysis identified predominant non-filamentous bacterial families, such as Streptococcaceae and Veillonellaceae, which collaborate during biofilm development in anaerobic environments. It was suggested that the porous media provided secure attachment sites for the biomass growth and biofilm formation under shock load and high shear force conditions. While these results offer valuable insights, further studies are needed to confirm these findings and enhance the understanding of the use porous media in non-recirculating AnFBRs.

Kinetics of microbial cell growth, utilization of organic substrates and methane production in upflow anaerobic filters in two and three separated stages treating sanitary landfill leachates

AbstractThis paper deals with the kinetics of microbial cell growth, utilization of organic substrates and methane production in upflow anaerobic filters in two and three separated stages (UAF‐2SS and UAF‐3SS) treating sanitary landfill leachates, under three temperatures (20, 27, and 34°C), fed with volumetric organic loads (VOLs) for UAF‐2SS (1.8, 2.25, 2.76, 3.45, 3.71, 4.64 kgCOD (chemical oxygen demand)/m3/d) and UAF‐3SS (1.7, 2.25, 2.44, 2.6, 3.15, 3.45, 3.5, 4.57, 4.64, 6.31, 11.61, 14.18, 17.48 kgCOD/m3/d). Kinetic parameters were obtained at temperature (20–34°C), pH (8.8–9.1), each one of three stages within the UAF‐2SS and UAF‐3SS reactors containing methanogenic bacteria (Methanococcus sp., and Methanobacterium sp.) and Clostridium sp.: Maximum substrate utilization rate (rm,s) resulted in 102 mg COD/L/h, maximum microbial cell growth rate (μm) varied 102–103 CFU (colony forming units)/mL/h, methane (CH4) production rate (rm,CH4) tended to vary 100–101 mg CH4/d and the maximum production coefficient (Y) varied 0–102 CFU/mL/h/mgCOD/L/h.

Assessment of microbial population in integrated CW-MFC system and investigation of organics and fecal coliform removal pathway

The current study is focused on understanding the operational mechanism of an integrated constructed wetland-microbial fuel cell (CW-MFC) reactor emphasizing fecal coliform (FC) removal. Few studies are available in the literature investigating the inherent mechanisms of pathogen inactivation in a CW-MFC system. Raw domestic wastewater was treated in three vertical reactors, one planted constructed wetland (R1), one planted CW-MFC (R2), and one unplanted CW-MFC (R3). Spatial analysis of treated effluents showed a considerable amount of organics and fecal coliform removal at the vicinity of the anode in R2. Assessment of the microbial population inside all the reactors revealed that EABs (Firmicutes, Bacteroidetes, and Actinobacteria) were more abundant in R2 compared to R1 and R3. During the activity study, biomass obtained from R2 showed a maximum substrate utilization rate of 1.27 mg COD mgVSS−1 d−1. Kinetic batch studies were carried out for FC removal in all the reactors, and the maximum first order FC removal rate was obtained at the anode of R2 as 2.13 d−1 when operated in closed circuit mode. This value was much higher than the natural die-off rate of FCs in raw wastewater which was 1.16 d−1. Simultaneous bioelectricity monitoring inferred that voltage generation can be correlated to faster FC inactivation, which was probably due to EABs outcompeting other exogenous microbes in a preferable anaerobic environment with the presence of an anode. Reactor R2 was found to be functioning as a symbiotic bio-electrochemical mesocosm.

A Hybrid Ultrasonic Membrane Anaerobic System (UMAS) Development for Palm Oil Mill Effluent (POME) Treatment

The high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) levels in palm oil mill effluent (POME) wastewater make it an environmental contaminant. Moreover, conventional POME wastewater treatment approaches pose economic and environmental risks. The present study employed an ultrasonic membrane anaerobic system (UMAS) to treat POME. Resultantly, six steady states were procured when a kinetic assessment involving 11,800–21,700 mg·L−1 of mixed liquor suspended solids (MLSS) and 9800–16,800 mg·L−1 of mixed liquor volatile suspended solids (MLVSS) was conducted. The POME treatment kinetics were explained with kinetic equations derived by Monod, Contois and Chen and Hashimoto for organic at loading rates within the 1–11 kg·COD·m−3·d−1 range. The UMAS proposed successfully removed 96.6–98.4% COD with a 7.5 day hydraulic retention time. The Y value was 0.67 g·VSS/g·COD, while the specific micro-organism decay rate, b was 0.24 day−1. Methane (CH4) gas production ranged from 0.24 to 0.59 litres per gram of COD daily. Once the initial steady state was achieved, the incoming COD concentrations increased to 88,100 mg·L−1. The three kinetic models recorded a minimum calculated solids retention time of 12.1 days with maximum substrate utilization rate, K values ranging from 0.340 to 0.527 COD·g−1·VSS·d−1 and maximum specific growth rate, µmax from 0.248 to 0.474 d−1. Furthermore, the solids retention time (SRT) was reduced from 500 to 12.1 days, resulting in a 98.4% COD level reduction to 1400 mg·L−1.

Microbial Reductive Dechlorination by a Commercially Available Dechlorinating Consortium Is Not Inhibited by Perfluoroalkyl Acids (PFAAs) at Field-Relevant Concentrations.

Perfluoroalkyl acids (PFAAs) have been shown to inhibit biodegradation (i.e., organohalide respiration) of chlorinated ethenes. The potential negative impacts of PFAAs on microbial species performing organohalide respiration, particularly Dehalococcoides mccartyi (Dhc), and the efficacy of in situ bioremediation are a critical concern for comingled PFAA-chlorinated ethene plumes. Batch reactor (no soil) and microcosm (with soil) experiments, containing a PFAA mixture and bioaugmented with KB-1, were completed to assess the impact of PFAAs on chlorinated ethene organohalide respiration. In batch reactors, PFAAs delayed complete biodegradation of cis-1,2-dichloroethene (cis-DCE) to ethene. Maximum substrate utilization rates (a metric for quantifying biodegradation rates) were fit to batch reactor experiments using a numerical model that accounted for chlorinated ethene losses to septa. Fitted values for cis-DCE and vinyl chloride biodegradation were significantly lower (p < 0.05) in batch reactors containing ≥50 mg/L PFAAs. Examination of reductive dehalogenase genes implicated in ethene formation revealed a PFAA-associated change in the Dhc community from cells harboring the vcrA gene to those harboring the bvcA gene. Organohalide respiration of chlorinated ethenes was not impaired in microcosm experiments with PFAA concentrations of 38.7 mg/L and less, suggesting that a microbial community containing multiple strains of Dhc is unlikely to be inhibited by PFAAs at lower, environmentally relevant concentrations.

Screening and evaluation of phenol utilization and growth in Acinetobacter baumannii W29 of wastewater

Phenols are ubiquitous pollutants, mainly from industrial effluent, causing pollution of natural water resources. The research focused on screening efficient phenol-degrading bacteria and kinetic modelling of phenol biodegradation and growth. Membrane filtration was used for the isolation of bacteria from the wastewater sample. The screening of phenol-degrading bacteria was based on the efficiency of phenol utilization. The strain with efficient phenol degradation capacity was characterized by 16S rDNA sequencing and designated Acinetobacter baumannii W29. Biomass growth and phenol utilization rate of the strain were evaluated at different initial phenol concentrations (100-800 mgL-1). Specific growth rate data were fitted to five models, i.e. Monod, Haldane, Aiba, Teisser, and Webb model. The yield coefficient at different initial phenol concentrations was calculated from the slope of the specific growth rate (μ) versus the specific phenol utilization rate (q). The strain showed complete phenol degradation potential up to 1000 mgL-1. The maximal growth rate was achieved at 400 mgL-1 , which coincided with the maximum substrate utilization rate at the same concentration. The specific growth rate showed the best fit with the Haldane model. The strain had a yield coefficient of 0.70 (mg cell mg-1 phenol). The value of µ and Ks revealed the affinity of the strain for high-concentration phenol and the its ability to withstand high phenol concentrations. The kinetic growth behaviour of the strain fitted well with the Haldane model. The findings of the study could be applied to wastewater treatment with a high phenol load.

Thermodynamic approach to simulate current densities of energy-harvesting microbial electrochemical systems fed with human urine

Different theoretical models have been addressed to simulate electricity generation of microbial electrochemical systems (MESs) fed with a variety of organics. In the case of urine-fed MESs (u-MESs), the lack of input parameters to feed current bio-physical models has somehow restrained their theoretical approach. This study introduces a model, based on microbial energetics, to simulate current generation of u-MESs without the need of resorting to parameters typically used as simulation entries in bio-physical approaches (e.g., maximum substrate-utilization rates (qmax), Monod half-saturation coefficients (KS)). The strategy consisted in linking the catabolic energy density available in the urine medium to the specific electro-active microbial growth-rate, the latter calculated from metabolic thermodynamics (Gibbs free-energy changes for the catabolic/anabolic reactions, and Gibbs energy dissipation). Calculated growth rates were used to compute specific substrate-utilization rates, the effective flux of electrons into the anode biofilm and the resulting current densities as a function of urine concentration.

A New Model for Microbial Desalination Cells: Model Formulation and Validation under Different Operating Conditions

In this paper, a dynamic mathematical model was developed to simulate the processes in Microbial Desalination Cells (MDCs) operated in cyclic batch flow mode using ordinary differential equations found in the literature. In contrast to previous models, the proposed model was developed for fed-batch operations and considers the effects of temperature and substrate inhibition using simple equations for quick simulation. Local sensitivity analysis was performed to determine the parameters with the least impact on current, COD, and salt removal, which were then eliminated from the simplified model. These parameters were found to be the decay rates of anodophilic and methanogenic microorganisms ( k d , a and k d , m ) and the internal resistance parameters ( R anolyte and R membrane ). In addition, the best-performing parameters based on the sensitivity analysis results were selected for reestimation for model fitting. The reestimated parameters were mediator yield ( Y ), membrane salt transfer coefficient ( d ), maximum substrate utilization rate by methanogenic microorganisms ( μ s , m , max), and maximum anodophilic growth rate ( μ a , max). The predictions of the model were consistent with both our previous experimental data and experimental studies found in the literature and can be easily used by experimentalists for the rapid simulation and prediction of an MDC’s performance under different operating conditions.

Kinetic models evaluation for chemical organic matter removal prediction in a full-scale primary facultative pond treating municipal wastewater

Abstract This study focuses on determining the bio-kinetic coefficients of chemical oxygen demand (COD) removal in full-scale primary facultative ponds (PFPs) system on the basis of 3-year continuous operation. The mean removal of chemical oxygen demand (COD), total suspended solid (TSS) and volatile suspended solid (VSS) were 80, 59 and 49%, respectively. The first-order model paired with continuous stirred-tank reactor (CSTR) and plug flow (PF) regimes, PF k–C*, Stover-Kincannon and Grau second-order models were applied to link COD concentrations at the inlet and outlet of the system and to compare the predictive power of models for the estimation of effluent COD concentrations. The Stover-Kincannon model showed the best adaptability (r2 = 0.9294) with the maximum substrate utilization rate (Umax) of 79.14 g/L· d and saturation constant (KB) of 80.65 g/L· d, whereas the Grau second-order model was the best model to predict outlet COD concentrations (r2 = 0.6925). The computed constants, m and n, of the Grau second-order model were 0.6725 and 15.867 d−1, respectively. While the Stover-Kincannon kinetic rates obtained in this study can be used to design the PFP systems in similar operational conditions, the appropriate prediction of pond behavior can be achieved using the Grau model.

Anaerobic Treatment for Palm Oil Mill Effluent Using Covered In-the Ground Anaerobic Reactor (CIGAR)

Wastewater from crude palm oil mills contains high organic matter, which potentially produces biogas through anaerobic digestion processes. The design and operation of an anaerobic bioreactor require a good understanding of the reaction kinetic in the bioreactor. This study aimed to evaluate the biogas production from POME and to determine the kinetic parameters of microbial growth and the substrate utilization rates in a CIGAR. An experiment was conducted using a 5-m3 bioreactor with a working volume of 4.4 m3. Wastewater from the Bekri palm oil mill was stored in a 5-m3 tank. After stabilization, the wastewater was loaded into the reactor at a rate of 100 to 250 L/d, corresponding to a COD loading rate of 1.373-3.097 kg·m-3.d-1, and an HRT of 18-44 days. Monod, Contois, Moser, and Shuler kinetic models were evaluated. The results showed that the Shuler model performed best for microbial activities, while the first order reaction model performed best for the substrate utilization kinetic. The maximum specific growth rate (μmax) for the Shuler model was 0.052 d-1 and the saturation constant (Kso) was 0.119. The maximum substrate utilization rate constant (ks) was 2.183 d-1 and biomass yield (Yx/s) 0.024 kg/kg. The maximum average efficiency of anaerobic degradation (34.4%) occurred at a feeding rate of 100 L/d with methane yield of 0.120 Nm3/kg of removed COD. This value is relatively low compared to the maximum potential of 0.350 Nm3/kg CODr.

Performance evaluation and substrate removal kinetics in a thermophilic anaerobic moving bed biofilm reactor for starch degradation

Abstract A laboratory-scale anaerobic moving bed biofilm reactor (AnMBBR) was installed and operated at various hydraulic retention times (HRTs) of 20 to 1.5 d with surface area loading rate (SALR) of 0.86 to 11.43 gCOD/m2/d. Synthetic starch containing desizing wastewater with chemical oxygen demand (COD) of 12.75 g/L was prepared and fed into the reactor. Monod, modified Stover-Kincannon, Grau second-order and First-order substrate removal models were used to evaluate the results of AnMBBR. COD removal efficiency of bioreactor was dwindled by increasing the SALR or reducing the HRT. Decay coefficient (Kd) and yield coefficient (Y) for the Monod model were 0.027 1/d and 1.01 mgVSS/mgCOD, respectively. Maximum substrate utilization rate (Umax) and kinetic constant (Kb) for the Modified Stover-Kincannon model were estimated as 12.57 and 15.22 g/L/d, respectively. The constants (a and b) for the Grau second-order model were found to be 1.09 and 1.31 whilst kinetic coefficient for the Second-order model and First-order substrate removal model were 1.62 and 1.55 1/d, respectively. Modified Stover-Kincannon model and Grau second-order model were found to be the best fit for experimental data with R2 value of 0.99. The findings suggest that these models can be applied to predict the behaviour of AnMBBRs on various scales.

Testing an aerobic fluidized biofilm process to treat intermittent flows of oil polluted wastewater

An aerobic fluidized biofilm process of treating oil-polluted wastewater has been studied. A series of batch experiments were conducted using synthetic wastewater and the kinetic coefficients were evaluated. The maximum rate of substrate utilization per unit mass microorganisms (K) was 1.6 days-1, the substrate concentration at one-half the maximum growth rate (Ks) was 26 mg/L, the maximum specific growth rate (m) was 1.0 days-1, the ratio of the mass cells formed to the mass of substrate consumed (Y) was 0.61, and the endogenous decay coefficient (Kd ) was 0.044 days-1. The kinetic coefficients obtained were within the range of municipal wastewater. It was observed that up to 1500 mg/L oil (Motor oil SAE–40) could be degraded in a fluidized bed bioreactor (FBBR). The experiments, however, were limited to the oil concentration within a range of 1000-2600 mg/L. Average biofilm thickness () under specific conditions was found to be 22 m and average oil degradation rate of 0.053 mg oil/mg biomass/hour was measured in the FBBR. The results also support that the increase in the concentration of oil in the treatment process reduced significantly the degradation rate of non-oil carbon.

A Model for Optimal Treatment of Cassava Wastewater Using Anaerobic Baffled Reactor

The major components of the effluents from cassava processing industries are cyanide and starch. However it is suspected that cyanide inhibits the treatment of cassava wastewater. The experimental data were successfully fitted to a polynomial model which was used to optimize the treatment processes at a laboratory scale. The Monod and Michealis-menten models for cassava wastewater treatment was successfully calibrated and validated in an ABR system. For Michealis-Menten model, the maximum substrate utilization rate is estimated in the range: 2866.88 to 1432.84 mgl-1 and for Monod’s model, it is estimated in the range: 493 to 1242 mgl-1, which is more realistic, hence validating the empirical model as more accurate than the former, which is theoretical. The result revealed that the inhibitor constant decreased from 9.9989 to 1.6101mgl-1 as the number of baffles increased from 3 to 10. To reach a maximum COD removal efficiency of 99%, it was found that the aspect ratio of 10, 20 baffles, cyanide inhibition constant of 30 mg/l and influent flow rate of 0.8 l/min, are the required optimum operating conditions of the anaerobic baffled reactors.

Biokinetic Coefficients Determination for the Biological Treatment of Langat River

River basin areas often associated with agriculture, industry and housing are the major source of pollution. This paper was conducted to determine biokinetic coefficients of pilot scale biofilm reactor. The biofilm reactor system (BRS) was installed on Langat River; Malaysia. The system was operated 65 days with different concentrations of mixed liquor suspended solid (MLSS), chemical oxygen demand (COD), and total suspended solids (TSS).Parameters in the influent and effluent of biofilm reactor were determined and biokinetic coefficients of maximum substrate utilization rate (K), half velocity constant (KS), cell yield coefficients (Y), decay coefficient (Kd), and maximum specific growth rate (µmax) were evaluated by Monod equations. Results showed that; the coefficients K, Ks, Y,Kd , and µmax were 1.39 day-1, 53.22 mg/L, 0.302 day-1,0.067 day-1 , and 1.936 day-1. It be can conclude that, all coefficients were in the range of active sludge coefficients that are mentioned in the literature.

A Study on the Reaction Kinetics of Anaerobic Microbes Using Batch Anaerobic Sludge Technique for Beverage Industrial Wastewater

In this study, a low-cost, efficient, and environmentally friendly anaerobic sludge process for the treatment of industrial beverage wastewater was investigated to analyze the effect of bacteria growth on the degradation of organic matter (chemical oxygen demand). Additionally, the mechanism, interactions between the microbe’s growth, and operating conditions of an anaerobic batch reactor along with the wastewater treatment efficiency were evaluated via microbial kinetics. The kinetic coefficients based on chemical oxygen demand (COD) by conventional techniques such as kinetic coefficients growth yield (0.46 mg VSS/mg COD), saturation coefficient (3500 mg/L COD), the maximum rate of substrate utilization per unit mass of biomass (0.0066 mg/L COD), growth rate by Monod equation, M (0.03833 L/h), and maximum growth rate, μm (0.03672 L/h) were calculated. The results show a higher rate of substrate degradation (0.54 day−1) due to the high COD removal efficiency (CRE) of 99.31% during 13 days that was achieved, which can be attributed to the active involvement of anaerobic microbes in the process of degradation. Based on these results, it can be concluded that the current study can be used as an effective way to analyze the industrial beverage wastewater at commercial levels.

Kinetics of Anaerobic Digestion of Unripe Plantain Peels

This study was carried out to investigate the biogas production obtained from anaerobic digestion of unripe plantain peels (PP) and the kinetics of the digestion process. 400 g of dried and shredded unripe plantain peels were mixed with 200 ml of water and put into 1 L digester and observed for biogas for hydraulic retention time (HRT) of 15 days by the method of downwards displacement. The cumulative biogas volume obtained after digestion was 285 ml. The COD removal efficiency of 72.5% was achieved. The kinetics of PP digestion was evaluated using first order, Monod, Contois and, Grau second-order models. Results showed that the kinetics of anaerobic digestion of PP followed the first-order model with a constant (K) of 0.095 day-1. Monod kinetics was evaluated and the maximum rate of substrate utilization (K), the half velocity constant (KS), endogenous decay coefficient (Kd), biomass growth yield (Y) and, maximum specific microorganism growth rate (µmax) obtained were 0.7615 day-1, 16.20 mg/l, 0.0047 day-1, 0.0112 mgVSS mgCOD-1 and, 0.009 day-1 respectively. These results revealed that inoculation would be required to increase the rate and volume of biogas production. Both first-order and Monod models gave a high coefficient of determination indicating that first order and Monod models can be used to model the digestion of PP. Contois model gave values of µmax and β as 0.011 day-1 and 0.644 mgCOD mgVSS-1 respectively. The result obtained has shown that the digestion of PP did not follow second-order kinetics.

Direct and Indirect Effects of Increased CO2 Partial Pressure on the Bioenergetics of Syntrophic Propionate and Butyrate Conversion.

Simultaneous digestion and in situ biogas upgrading in high-pressure bioreactors will result in elevated CO2 partial pressure (pCO2). With the concomitant increase in dissolved CO2, microbial conversion processes may be affected beyond the impact of increased acidity. Elevated pCO2 was reported to affect the kinetics and thermodynamics of biochemical conversions because CO2 is an intermediate and end-product of the digestion process and modifies the carbonate equilibrium. Our results showed that increasing pCO2 from 0.3 to 8 bar in lab-scale batch reactors decreased the maximum substrate utilization rate (rsmax) for both syntrophic propionate and butyrate oxidation. These kinetic limitations are linked to an increased overall Gibbs free energy change (ΔGOverall) and a potential biochemical energy redistribution among syntrophic partners, which showed interdependence with hydrogen partial pressure (pH2). The bioenergetics analysis identified a moderate, direct impact of elevated pCO2 on propionate oxidation and a pH-mediated effect on butyrate oxidation. These constraints, combined with physiological limitations on growth exerted by increased acidity and inhibition due to higher concentrations of undissociated volatile fatty acids, help to explain the observed phenomena. Overall, this investigation sheds light on the role of elevated pCO2 in delicate biochemical syntrophic conversions by connecting kinetic, bioenergetic, and physiological effects.

Characteristics and metabolic pathway of the bacteria for heterotrophic nitrification and aerobic denitrification in aquatic ecosystems

The present study investigated the nitrogen removal characteristics and metabolic pathway of bacteria in aquatic ecosystem, with a focus on heterotrophic nitrification and aerobic denitrification. The bacteria demonstrated significant heterotrophic nitrification and aerobic denitrification capacity. The highest ammonium-N, nitrate-N, and nitrite-N removal efficiencies were 95.31 ± 0.11%, 98.91 ± 0.05%, and 98.79 ± 0.09%, respectively. The Monod model was used to estimate the maximum rate of substrate utilization (Rmo) and the half-saturation concentration (Ks) for the two substrates, i.e., ammonium and nitrate. The kinetic coefficients were 3.34 mg/L/d (Rmo) and 30.59 mg/L (Ks) for ammonium-N, respectively, and 14.23 mg/L/d (Rmo) and 215.24 mg/L (Ks) for nitrate-N, respectively. The effects of initial nitrogen (ammonium-N or nitrate-N) concentration, temperature, and dissolved oxygen (DO) on nitrogen removal rate were investigated using response surface methodology (RSM), and the optimal conditions for nitrogen removal were determined. The principal nitrogen removal pathway of the bacteria was proposed as complete heterotrophic nitrification and aerobic denitrification, which was performed by six key genera: Arthrobacter, Pseudomonas, Rhodococcus, Bacillus, Massilia, and Rhizobium. Chryseobacterium and other denitrifying species may also reduce nitrification products (NOX−) via aerobic denitrification.

Kinetic Evaluation of Two-Phase Anaerobic Treatment of Slaughterhouse Wastewater

Two-phase anaerobic treatment by a continuously stirred tank reactor (CSTR) and an upflow anaerobic sludge blanket (UASB) system was applied to treat slaughterhouse wastewater at ambient temperature, non-pH adjustment, at five different organic loading rates (OLR) of 1.39-2.60 kg COD/m3.d with the hydraulic retention time (HRT) in the range of 14.1-26.4 hr. The kinetic evaluation of the experimental data was carried out using a kinetic model derived from Michaelis-Menten and Monod equation. The maximum substrate utilization rate (kmax) and the half velocity constant (Ks) were 0.252 d−1 and 586.5 mg/l, respectively. The results indicated that the applied kinetic model is capable of explaining the bio-kinetic behaviour of the CSTR-UASB system and can be used as a design criteria for two-phase anaerobic treatment treating other fat-containing wastewater.

Performance of a high-rate anammox reactor under high hydraulic loadings: Physicochemical properties, microbial structure and process kinetics

In this study, a lab-scale upflow anaerobic sludge blanket (UASB) reactor was applied to studying the high-rate nitrogen removal of granule-based anammox process. The nitrogen removal rate (NRR) finally improved to 15.77 kg/m3/d by shortening hydraulic retention time (HRT) to 1.06 h. Well-shaped red anammox granules were extensively enriched inside the reactor. The results of nitrogen removal kinetics indicated that the present bioreactor has great nitrogen removal potential, because the maximum rate of substrate utilization (Umax) predicted by Stover-Kincannon model is suggested as 55.68 kg/(m3·d). Analysis of the microbial community showed that the anammox genus Candidatus Kuenenia dominated the bacterial communities. The relative abundance of Candidatus Kuenenia rose from 12.29% to 36.95% after progressively shorter HRT and higher influent substrate concentrations, illustrating the stability of nitrogen removal performance and biomass enrichment offered by the UASB in carrying out high-rate anammox process.