Performance evaluation and kinetic modeling of the start-up of a UASB reactor treating municipal wastewater at low temperature

Biochar mediated high-rate anaerobic bioreactors: A critical review on high-strength wastewater treatment and management

Treatment of high-strength wastewater is critical for the aquatic environment and receiving water bodies around the globe. Untreated or partially treated high-strength wastewater may cause severe damage to the existing water bodies. Various high-rate anaerobic bioreactors have been developed in the last decades for treating high-strength wastewater. High-rate anaerobic bioreactors are effective in treating industrial wastewater and provide energy in the form of methane as well. However, the physical or chemical properties of high-strength industrial wastewater, sometimes, disrupt the functioning of a high-rate anaerobic bioreactor. For example, the disintegration of granular sludge in up flow anaerobic sludge blanket reactor or membrane blocking in an anaerobic membrane bioreactor are the results of a high-strength wastewater treatment which hamper the proper functioning and may harm the wastewater treatment plant economically. Biochar, if added to these bioreactors, may help to alleviate the ill-functioning of high-rate anaerobic bioreactors. The primary mechanisms by biochar work in these bioreactors are direct interspecies electron transfer, microbial immobilization, or gene level alternations in microbial structure. The present article explores and reviews the recent application of biochar in a high-rate anaerobic bioreactor treating high-strength industrial wastewater.

Biochemical potential evaluation and kinetic modeling of methane production from six agro-industrial wastewaters in mixed culture

Methane (CH₄) production from anaerobic digestion of solid and liquid agro-industrial wastes is an attractive strategy to meet the growing need for renewable energy sources and promote environmentally appropriate disposal of organic wastes. This work aimed at determining the CH₄ production potential of six agro-industrial wastewaters (AWW), evaluating the most promising for methanization purposes. It also aims to provide kinetic parameters and stoichiometric coefficients of CH₄ production and define which kinetic models are most suitable for simulating the CH₄ production of the evaluated substrates. The AWW studied were swine wastewater (SW), slaughterhouse wastewater (SHW), dairy wastewater (DW), brewery wastewater (BW), fruit processing wastewater (FPW), and residual glycerol (RG) of biodiesel production. RG was the substrate that showed the highest methanization potential. Exponential kinetic models can be efficiently applied for describing CH₄ production of more soluble substrates. On the other hand, logistic models were more suitable to predict the CH₄ production of more complex substrates.

Performance evaluation and substrate removal kinetics in an up-flow anaerobic hybrid membrane bioreactor treating simulated high-strength wastewater

The prime objective of the present study is to evaluate the performance of novel up-flow anaerobic hybrid membrane bioreactor (An-HMBR) treating high-strength wastewater (synthetic) using polyurethane foam as filter media. Treatment efficiency of the entire An-HMBR varied from 88-97% corresponding to 0.67-3.90 d of hydraulic retention time (HRT) with organic loading rate of 6.4-1.06 kg COD m^-3 d^-1. The modified Stover-Kincannon model was the most appropriate model for An-HMBR and anaerobic hybrid bioreactor (excluding membrane). The suspended growth system in An-HMBR could be described by both modified Stover-Kincannon and Grau second order model. The attached growth system in An-HMBR followed conventional Monod's kinetics. A novel combination of suspended, attached and membrane in single reactor increased the solid retention time to as high as 756 d at 3.9 d HRT which not only improved the COD removal efficiency but also enhanced the performance of the membrane.

Biological treatment of slaughterhouse wastewater: kinetic modeling and prediction of effluent

In this study three modeling approaches consisting Modified Stover-Kincannon, multilayer perceptron neural network (MLPANN) and B-Spline quasi interpolation were applied in order to predict effluent of up-flow anaerobic sludge blanket (UASB) reactor and also to find the reaction kinetics. At first run, the average total chemical oxygen demand (TCOD) removal efficiency was 48.3% with hydraulic retention time (HRT) of 26 h and 63.8% with HRT of 37 h, at OLR of 0.77-1.66 kg TCOD/m³ d. At the second run, UASB reactor operated with OLR of 1.94-3.1 kg TCOD/m³ d and achieved the average TCOD removal efficiency of 64.74 and 72.48% with HRT of 26 and 37 h, respectively. The Modified Stover-Kincannon performed well in terms of kinetic determination with a high value of regression coefficient over 0.98. The B-Spline quasi interpolation and MLPANN indicated a great fit for effluent prediction with average R of 0.9984 and 0.9986, and MSE of 157.6050 and 129.7796, respectively; however, they gave no information about reactions occurred in the system.

Inhibiting effect of textile wastewater on the activity of sludge from the biological treatment process of the activated sludge plant

Textile industry represents an important source of toxic substances rejected in environment. Indeed, effluent of these industries contains dyes and chemicals. They are rejected in environment without any treatment. The aim of this work is to evaluate ecotoxicological effect of industrial textile effluents on the sludge harvested from activated sludge treatment plant of Marrakech city (Morocco). For this, we are interested in determining the inhibition condition that corresponds to 50% decrease of bacterial activity in sludge. Obtained results showed that inhibition percentage of bacterial activity depends narrowly on contact time and on added effluent volume, until a limit concentration where there is no degradation of substratum. In fact, substratum degradation speed shows about 65 times decrease when 80% (v/v) of textile wastewater is added, in comparison with the controlled one. Consequently the inhibition constant (Ki) that corresponds to 50% of bacterial inhibition activity is estimated to 0.65 mg l^-1 of dye. These studies confirm a real ecotoxicological risk of these effluents. Therefore, a treatment is mandatory before their rejection in environment.

Anaerobic treatment of chocolate-processing industry wastewater at different organic loading rates and temperatures

The objective of the present study was to determine the optimum operating temperature of laboratory-scale upflow anaerobic sludge blanket (UASB) reactors during the treatment of a chocolate-processing industry wastewater at medium applied organic loading rates (OLR_appl). Four UASB reactors were operated at different temperature (15, 20, 25 and 30 °C) and three OLR_appl (2, 4 and 6 kg soluble chemical oxygen demand (COD_s)/(m³ d)). The flowrate and the hydraulic retention time were constant (11.5 L/d and 6 h, respectively). The monitored parameters were pH, temperature, COD_s, and total and volatile suspended solids. The COD_s removal efficiency (RE) and biogas production rate (BPR) were calculated. The 15 °C UASB reactor had the lowest RE (39 to 78%) due to the low operating temperature. Regardless of the OLR_appl, the RE of the 20, 25 and 30 °C reactors was high and similar to each other (between 88 and 94%). The BPR of the four UASB reactors had the same behaviour as the RE (BPR of 15 °C: 0.3 to 0.5 L_biogas/(L_reactor d) (L_b/(L_r d)) and BPR of 20, 25 and 30 °C: 0.5 to 1.9 L_b/(L_r d)).

Modelling anaerobic, aerobic and partial nitritation-anammox granular sludge reactors - A review

Wastewater treatment processes with granular sludge are compact and are becoming increasingly popular. Interest has been accompanied by the development of mathematical models. This contribution simultaneously reviews available models in the scientific literature for anaerobic, aerobic and partial nitritation-anammox granular sludge reactors because they comprise common phenomena (e.g. liquid, gas and granule transport) and thus pose similar challenges. Many of the publications were found to have no clearly defined goal. The importance of a goal is stressed because it determines the appropriate model complexity and helps other potential users to find a suitable model in the vast amount of literature. Secondly, a wide variety was found in the model features. This review explains the chosen modelling assumptions based on the different reactor types and goals wherever possible, but some assumptions appeared to be habitual within fields of research, without clear reason. We therefore suggest further research to more clearly define the range of operational conditions and goals for which certain simplifying assumptions can be made, e.g. when intragranule solute transport can be lumped in apparent kinetics and when biofilm models are needed, which explicitly calculate substrate concentration gradients inside granules. Furthermore, research is needed to better mechanistically understand detachment, removal of influent particulate matter and changes in the mixing behaviour inside anaerobic systems, before these phenomena can be adequately incorporated in models. Finally, it is suggested to perform full-scale model validation studies for aerobic and anammox reactors. A spreadsheet in the supplementary information provides an overview of the features in the 167 reviewed models.

Modified kinetic-hydraulic UASB reactor model for treatment of wastewater containing biodegradable organic substrates

This paper addresses a modified kinetic-hydraulic model for up-flow anaerobic sludge blanket (UASB) reactor aimed to treat wastewater of biodegradable organic substrates as acetic acid based on Van der Meer model incorporated with biological granules inclusion. This dynamic model illustrates the biomass kinetic reaction rate for both direct and indirect growth of microorganisms coupled with the amount of biogas produced by methanogenic bacteria in bed and blanket zones of reactor. Moreover, the pH value required for substrate degradation at the peak specific growth rate of bacteria is discussed for Andrews' kinetics. The sensitivity analyses of biomass concentration with respect to fraction of volume of reactor occupied by granules and up-flow velocity are also demonstrated. Furthermore, the modified mass balance equations of reactor are applied during steady state using Newton Raphson technique to obtain a suitable degree of freedom for the modified model matching with the measured results of UASB Sanhour wastewater treatment plant in Fayoum, Egypt.

Kinetics of substrate utilization and bacterial growth of crude oil degraded by Pseudomonas aeruginosa

Pollution associated with crude oil (CO) extraction degrades the quality of waters, threatens drinking water sources and may ham air quality. The systems biology approach aims at learning the kinetics of substrate utilization and bacterial growth for a biological process for which very limited knowledge is available. This study uses the Pseudomonas aeruginosa to degrade CO and determines the kinetic parameters of substrate utilization and bacterial growth modeled from a completely mixed batch reactor. The ability of Pseudomonas aeruginosa can remove 91 % of the total petroleum hydrocarbons and 83 % of the aromatic compounds from oily environment. The value k of 9.31 g of substrate g(-1) of microorganism d(-1) could be far higher than the value k obtained for petrochemical wastewater treatment and that for municipal wastewater treatment. The production of new cells of using CO as the sole carbon and energy source can exceed 2(3) of the existing cells per day. The kinetic parameters are verified to contribute to improving the biological removal of CO from oily environment.

Identical full-scale biogas-lift reactors (Blrs) with anaerobic granular sludge and residual activated sludge for brewery wastewater treatment and kinetic modeling

Two identical full-scale biogas-lift reactors treating brewery wastewater were inoculated with different types of sludge to compare their operational conditions, sludge characteristics, and kinetic models at a mesophilic temperature. One reactor (R1) started up with anaerobic granular sludge in 12 weeks and obtained a continuously average organic loading rate (OLR) of 7.4 kg chemical oxygen demand (COD)/(m3 x day), COD removal efficiency of 80%, and effluent COD of 450 mg/L. The other reactor (R2) started up with residual activated sludge in 30 weeks and granulation accomplished when the reactor reached an average OLR of 8.3 kg COD/(m3 x day), COD removal efficiency of 90%, and effluent COD of 240 mg/L. Differences in sludge characteristics, biogas compositions, and biogas-lift processes may be accounted for the superior efficiency of the treatment performance of R2 over R1. Grau second-order and modified StoverKincannon models based on influent and effluent concentrations as well as hydraulic retention time were successfully used to develop kinetic parameters of the experimental data with high correlation coefficients (R2 > 0.95), which further showed that R2 had higher treatment performance than R1. These results demonstrated that residual activated sludge could be used effectively instead of anaerobic granular sludge despite the need for a longer time.

Antibiotic Fermentation Broth Treatment by a pilot upflow anaerobic sludge bed reactor and kinetic modeling

In this study, an upflow anaerobic sludge blanket (UASB) mesophilic reactor was used to remove antibiotic fermentation broth wastewater. The hydraulic retention time was held constant at 13.3 days. The volumetric organic loading value increased from 0.33 to 7.43 kg(COD)m(-3)d(-1) using antibiotic fermentation broth wastewater gradually diluted with various ratios of domestic wastewater. A COD removal efficiency of 95.7% was obtained with a maximum yield of 3,700 L d(-1) methane gas production. The results of the study were interpreted using the modified Stover-Kincannon, first-order, substrate mass balance and Van der Meer and Heertjes kinetic models. The obtained kinetic coefficients showed that antibiotic fermentation broth wastewater can be successfully treated using a UASB reactor while taking COD removal and methane production into account.

Integration of kinetic modeling and desirability function approach for multi-objective optimization of UASB reactor treating poultry manure wastewater

An integrated multi-objective optimization approach within the framework of nonlinear regression-based kinetic modeling and desirability function was proposed to optimize an up-flow anaerobic sludge blanket (UASB) reactor treating poultry manure wastewater (PMW). Chen-Hashimoto and modified Stover-Kincannon models were applied to the UASB reactor for determination of bio-kinetic coefficients. A new empirical formulation of volumetric organic loading rate was derived for the first time for PMW to estimate the dimensionless kinetic parameter (K) in the Chen-Hashimoto model. Maximum substrate utilization rate constant and saturation constant were predicted as 11.83 g COD/L/day and 13.02 g COD/L/day, respectively, for the modified Stover-Kincannon model. Based on four process-related variables, three objective functions including a detailed bio-economic model were derived and optimized by using a LOQO/AMPL algorithm, with a maximum overall desirability of 0.896. The proposed optimization scheme demonstrated a useful tool for the UASB reactor to optimize several responses simultaneously.