Effluent Substrate Concentration Research Articles

MODEL ESTIMASI BIOKINETIKA UNTUK PROSES POST-DENITRIFIKASI AIR LIMBAH DOMESTIK PADA UNIT ANAEROBIC BAFFLED REACTOR

This study developed a combination of Continuous Stirred Tank Reactor (CSTR) for the acid fermentation and the Anaerobic Baffled Reactor (ABR) post-denitrification through high nitrite injection. Volatile Fatty Acids (VFAs) as a substrate for the post-denitrification process were optimally produced in the acid fermentation process. The aim of this study was to obtain the estimation of biokinetic values to predict the effluent wastewater quality in ABR post-denitrification process under unsteady state. The reactor was operated for HRT 7 days at temperature 25-28 ˚C and pH 6-7,2. The influent and effluent substrate concentration were monitored continuously for 160 days. Post-denitrification biokinetic from the Contois equation resulted in the value of hydrolysis rate (Kh) of 0.077 day-1, the substrate transport rate (k) of 4.364×10-6 Lmg-1day-1, maximum specific growth rate (μmax) of 0.559 day-1, half saturation constant (KS) of 0.209 mgL-1, microbial decay coefficient (b) of 0.0145 days-1; yield coefficient (Y) of 0.084 g-VSSg-COD-1. The validation of biokinetic parameters based on statistical analysis showed fairly precise results following the trend of experimental data to determine the substrate concentration in the effluent unit. Therefore, the biokinetic values can be applied in the design of ABR post-denitrification using primary sludge incorporation with high strength nitrate.Keywords: Anaerobic baffled reactor, biokinetics, Contois, hydrolysis, post-denitrification.

Calibration of model for the utilization rate of organic and nitrogenated substrates by the microorganism in a sequencing batch reactor

AbstractThis paper deals with the calibration of the model for the utilization rate of organic and nitrogenated substrates (URONS) by the microorganisms in a sequencing batch reactor. The URONS model parameterization was carried out using data obtained from two experimental designs (EDs) applied on tannery wastewater (TW), which included as factors: First ED (aeration sequence and cycle duration) reached a COD removal efficiency (RE) between 29% (cycle duration of 6 h) and 48% (cycle duration of 24 h). Second ED (aeration sequence and filling time) obtained COD‐RE (47–51%), NH4‐N–RE (71–91%), and TKN‐RE (50–67%). The URONS model was based on Monod's equation modification. For the first ED, the results of the maximum URONS parameter of 135–946 mg/L·h suggest the organic substrate accumulation due to a possible inhibition of the microorganisms by TW substances such as heavy metals and metal halides. For the second ED, the parameter values resulted negative and varying in the order of −10−2 to −10−4 mg/L·h with respect to for the first ED indicating that a better microorganism performance for URONS occurred in the second ED. For both EDs, the saturation parameter values compared to the effluent substrate concentration suggest that the primary substrate for biodegradation was present in the TW.

Specific affinity and relative abundance of methanogens in acclimated anaerobic sludge treating low-strength wastewater.

Kinetic parameters affecting effluent water quality including half saturation constant (Ks), maximum specific growth rate (μmax), and specific affinity ([Formula: see text], defined as μmax/Ks) were investigated using three types of anaerobic sludge (raw anaerobic digestion sludge referred to as unacclimated sludge, unacclimated sludge after endogenous decay, and sludge acclimated to low-strength wastewater in an anaerobic membrane bioreactor (AnMBR) for 360 days). Long-term acclimation to low-strength wastewater resulted in sludge with high specific affinity (1.6 × 10-3 L/mg COD/day for acclimated sludge compared to 4.1 × 10-4 L/mg COD/day for unacclimated sludge). The μmax values for unacclimated sludge and acclimated sludge were 0.08 and 0.07 day-1, respectively. The Ks values for unacclimated sludge and acclimated sludge were 194 ± 81 mg COD/L and 45 ± 13 mg COD/L, respectively. Although the Ks of unacclimated sludge after endogenous decay increased to 772 ± 74 mg COD/L, μmax increased to 0.35 day-1 as well, resulting in no statistically significant difference of [Formula: see text] between the two types of unacclimated sludge. Overall, [Formula: see text] is a better indicator than μmax or Ks alone for determining effluent water quality, as effluent substrate concentration is approximately inversely proportional to the specific affinity. 16S rRNA sequencing data analysis indicated a high abundance (85.8% of total archaea) of Methanosaeta in the microbial community after long-term acclimation. High [Formula: see text] associated with the enrichment of Methanosaeta appears to ensure successful anaerobic treatment of low-strength wastewater.

Production of biohydrogen from waste wheat in continuously operated UPBR: The effect of influent substrate concentration

Utilization of waste materials is one of the most economical approaches to biohydrogen production. Continuous generation of biohydrogen in a bioreactor makes the process more economical with respect to the conventional physical and chemical method. The two main parameters that affect the biohydrogen production in a continuously operated bioreactor are hydraulic retention time (HRT) and influent substrate concentrations. The effect of influent substrate concentration on biohydrogen generation in an up-flow packed bed reactor (UPBR) at HRT = 3 h was investigated in this study. The substrate was waste wheat which was acid hydrolyzed in H2SO4 by adjusting the pH value to pH = 2, under high temperature as T = 90 °C in an autoclave to obtain fermentable sugar solution. A natural and porous support particle namely, aquarium biological sponge (ABS) was the microbial immobilization surface in the reactor. Total and hydrogen gas volumes, hydrogen percentage, influent and effluent substrate concentrations, VFA concentrations were monitored. The influent substrate concentration (TSo) was varied between TSo = 10 g/L and TSo = 35 g/L. The process performance was evaluated as biohydrogen volume, percentages, rate and yield under varying operating conditions. The production volume (4275 ml/day) and the rate (3.05 L H2/L day) were maximum at influent sugar concentration of TSo = 25 g/L, but the yield reached to its maximum value as Y = 1.22 mol H2/mol glucose at TSo = 19 g/L. Substrate limitation and inhibitions were observed at influent concentrations of TSo = 10 g/L and TSo = 35 g/L, respectively. The results indicated that ABS could be suggested as a microbial support particle for hydrogen generation in immobilized systems.

Substrate Inhibition and Kinetic Characteristics of Marine Anaerobic Ammonium Oxidizing Bacteria Treating Saline Wastewater

An anaerobic sequencing batch reactor (ASBR) was used to study substrate inhibition and kinetic characteristics of marine anaerobic ammonium oxidizing bacteria (MAAOB) treating saline wastewater. The results indicated that when ammonia increased to 1200 mg·L-1, the MAAOB still maintained good nitrogen removal capability, though there was a slight inhibitory effect. At the same time, nitrite nitrogen removal efficiency was stable at about 80.70%. When nitrite increased to 265.6 mg·L-1, the MAAOB were inhibited obviously, and ammonia nitrogen removal efficiency decreased to about 63.01%. When influent nitrite concentration increased to 305.6 mg·L-1, the removal rate of ammonia nitrogen further decreased to 43.93%. The kinetic characteristics resulting from inhibition of the MAAOB were simulated by the Haldane model and Aiba model. Three parameters, TNRRmax, KS, and Ki, and the relationship between effluent substrate concentration and total nitrogen loading (TNRR) were evaluated. Based on further analysis, the Haldane model was more suitable for describing dynamic characteristics resulting from NH4+-N inhibition, while the Aiba model was more suitable for describing the dynamic characteristics resulting from NO2--N inhibition. The predicted effluent inhibitory concentrations of NH4+-N and NO2--N were 3893.625 mg·L-1 and 287.208 mg·L-1, respectively. The results could provide a theoretical basis for saline wastewater treatment by MAAOB.

Light and Duty Cycle Optimization of a Photo-bioreactor in Batch Mode

Abstract This paper is focused on optimizing the amount of light duty cycle of a photo-bioreactor operating in batch mode. The mathematical model used is confined to one dissolved substrate, one biomass (algae), one internal cell quota, and the irradiance for photo-acclimated culture. The model has been previously published and validated with experimental data. The following optimization problem is studied: minimize the effluent substrate concentration subject to: maximum and minimum amount of light to be used, the time of the light/dark illumination and the total time of the batch experiment. Analytical solution for this optimization problem seems difficult to obtain. However, numerical results obtained from simulations show that it is possible to find solutions which satisfy the problem requirements.

Determination of Kinetic Parameters in Integrated Fixed Film Activated Sludge for Amol's Industrial Park Wastewater Treatment Plant

In this study the performance of integrated fixed film activated sludge system (IFAS) in Amol industrial wastewater treatment plant (Amol, Iran) in treatment of food industrial wastewater was investigated. In addition, kinetic coefficients were evaluated for the system. The capacity of this system was 1700 cubic meters per day; that includes different process comprising physical and biological treatment, disinfection, sludge thickening, digestion and dewatering. COD removal efficiency and kinetic coefficients including yield coefficient (Y), half saturation coefficient (Ks), maximum substrate utilization rate constant (k) and endogenous decay coefficient (kd) were evaluated. The obtained results demonstrated that except Ks other coefficient were in the normal range that was frequently reported for conventional activated sludge in the literature. The COD removal efficiency was about 98 to 99 percent. The results indicated that there is a direct relationship between the variation of kd and Ks with effluent substrate concentration; while, the relationship between rate constant (k) and effluent COD is reversed. Finally, the effect of increasing sludge retention time (SRT) on COD removal was also studied. It was concluded that COD removal increased with an increase active solid retention time to a certain point, behind that point there was no significant changes observed.

Modelling Continuous Anaerobic Digestion of Municipal Solid Waste in Biogas Production

In this study, mathematical models were developed for the anaerobic biodegradation of municipal solid waste (MSW) in Port Harcourt metropolis, Nigeria, in a continuously stirred tank bioreactor. The MSW in Port Harcourt is presently not treated before final disposal. The need to incorporate a treatment element into the management scheme has elicited various treatment proposals, including the anaerobic digestion of the waste in a continuous processing system, in order to generate biogas in the process. Bench-scale experimentation was conducted to investigate the behavior of the waste when subjected to anaerobic decomposition in a continuous reactor, leading to the formulation of process models. The development of the models was based on a material balance analysis of the continuous anaerobic biodegradation processes. The models were simulated over a range of fractional conversion (α) of 0.2-0.8 and percentage Total Solids (TS) concentration of 4-10 using the Microsoft Visual Basic Version 6.0 computer programming language. The results of the simulation were further analyzed with the Microsoft Chart Editor, which was used to establish relationships between the various process parameters, including the fractional conversion, time of digestion, effluent substrates and microbial concentrations, volume of gas produced and effluent substrates stabilization. It was found that, whereas the effect of 'α' on the time of digestion is a logarithmic function of the 'α', it is linear for the effluent substrate and microbial concentrations and a power function for the total volume of biogas produced.

Steady-state analyses of activated sludge processes with plug-flow reactor

Activated sludge processes (ASPs) consisting of a plug-flow reactor (PFR) and a settler are analyzed in steady-state operation using a reduced model consisting of one soluble substrate and one particulate biomass component modelling the dominating biological process. Monod biomass growth rate is assumed. Two settler models are studied. One is the commonly used ideal settler, or point settler, which is assumed to never be overloaded and to have unlimited flux capacity. The other recently published steady-state settler model includes hindered and compressive settling, and models a realistic limiting flux capacity. Generally, the steady-state concentration profiles within the PFR and the settler are governed by nonlinear ordinary differential equations. It is shown that the steady-state behaviour of the ASP can, however, be captured by equations without derivatives. New theoretical results are given, such as conditions by means of inequalities on input variables and parameters for a steady-state solution to exist. Another novel finding is that, if the incoming substrate concentration is increased from a low or moderate stationary value and the solids residence time is kept fixed, then this results in a lower effluent concentration in the new steady state. The steady-state equations are solved numerically for different operating conditions. For common parameter values, numerical solutions reveal that an ASP having a PFR, instead of a continuously stirred tank reactor, is far more efficient in reducing the effluent substrate concentration and this can be obtained for much lower recycle ratios, which reduces the pumping energy considerably.

SUBSTRATE REDUCTION KINETICS AND PERFORMANCE EVALUATION OF FLUIDIZED-BED REACTOR FOR TREATMENT OF BREWERY WASTEWATER

pilot scale anaerobic fluidized-bed reactor was operated for treating brewery wastewater at nine different hydraulic retention time (HRTs) of 2, 3, 4, 5, 6, 7, 8, 9, and 10hr. The COD reduction efficiencies increased from 9.8% to 74.1% with increasing HRT from 2 to 10hr.Similarly, the corresponding BOD 5 reduction efficiencies increased from 38.0% to 92.9% with the same increase in HRT. The predicted effluent substrate concentration values of Modified Stover–Kincannon model were found to be in strong agreement with the experimental values. This is due to proper solubilization and consumption of entrapped substrates in the fluidized-bed reactor since the microbial cells have maximum opportunity to interact with the entrapped substrates in the reactor. The kinetic parameters were determined using existing linear models with experimental data. Modified Stover-Kincannon model showed high correlation coefficient (R 2 = 0.9996) only in predicted effluent concentration of wastewater. This shows that this model can be best used to predict effluent COD concentration in a fluidized bed reactor treating brewery wastewater. Similarly, FIRST ORDER MODEL has the highest correlation coefficient in the plot using experimental data. This means that first order model can be used to represent the real biological degradation that takes place during the treatment of waste water by microorganisms in a fluidized-bed reactor system treating brewery wastewater. This model and kinetic parameters obtained in this work can be employed in the design of industrial size- fluidized bed reactor for treatment of brewery waste water. Maximum utilization rate constant (U max ) determined is 11.75g COD/l.hr and the saturation value constant (K B ) 131.41g COD/l.hr was also determined. The values of kinetic constants were also used to predict the effluent COD concentration. It was observed that the simulated data (predicted data) were in good harmony with the experimental data counterpart in modified Stover –Kicannon model, The strength of the above-mentioned model can be observed from the correlation coefficient obtained from the model asR 2 =0.9996 in modified Stover-kicannon model. http://dx.doi.org/10.4314/njt.v35i1.15

Optimal steady-state design of zone volumes of bioreactors with Monod growth kinetics

This paper deals with steady-state analysis and design of bioreactors consisting of a number of completely stirred tank reactors (CSTRs) in series. The study is confined to one consumed (substrate) and one consuming constituent (biomass). The specific microbial growth rate is assumed to be described by Monod kinetics. The death of biomass is assumed to be negligible. Two optimal design problems for a large number of CSTRs in series are studied: to minimize the effluent substrate concentration for a given total volume, and to minimize the total volume for a given effluent substrate concentration. As an appealing alternative to solve these problems numerically, it is proposed to consider the asymptotic case where the number of CSTRs tends to infinity. This is shown to correspond to one CSTR in series with a plug flow reactor (PFR). A CSTR with a sufficient large volume is needed to avoid wash-out of the biomass. The main result is that both design problems for the CSTR+PFR configuration have the same solution with respect to the optimal volume of the CSTR, which is given as an explicit function of the incoming substrate concentration, the volumetric flow rate and the coefficients of the Monod growth rate function. Numerical results indicate that the plug flow approach may be used as a feasible design procedure even for a reasonably low number of CSTRs in series.

Determination of biokinetic coefficients for an adsorption/bio-oxidation process on municipal wastewater in pilot-scale

Aims: The present study was carried out to determine biokinetic coefficients of a pilot-scale adsorption-bio-oxidation process. Materials and Methods: The pilot plant was simulated North wastewater treatment plant, Isfahan, Iran. The pilot plant was operated 135 days under different mixed liquor suspended solids (MLSS) concentrations in aeration tank. In each phase, MLSS value was kept constant to reach a steady state condition. B-stage has a higher hydraulic retention time and SRT than A-stage. Also, in order to determine influence of biokinetic parameters on the effluent substrate concentration, a sensitivity analysis was performed. Results: The coefficients Y, K d , K S , and μmax of A-stage were 1.34 mg VSS/mg sCOD, 0.17 d−1 , 8.61 mg/L, and 2.78 d−1 , respectively. Also, Y, K d , K S , and μmax of B-stage were 0.74 mg VSS/mg sCOD, 0.12 d−1 , 3.34 mg/L, and 71.94 d−1 , respectively. Sensitivity analysis showed that in the A-stage, all coefficients are directly proportional to the effluent sCOD concentration. In the B-stage, K d and K S are directly proportional, but μmax was inversely proportional to the effluent sCOD concentration. Conclusions: All coefficients were in the range of activated sludge coefficients that are mentioned in the literature, except μmax and K S of B-stage. However, K S value of B-stage was close to the desired range. Sensitivity analysis showed that μmax and K S have the most influence on effluent substrate concentration (sCOD).

Biochemical Kinetics of Cross flow Membrane Bioreactor Processes in the Treatment of Refinery Wastewater

A lab-scale cross flow membrane bioreactor (CF-MBR) was operated to determine the biokinetic coefficients under MLSS concentrations of 5000 and 3000 mg/L. The investigation showed that the yield (Y), the endogenous decay coefficient (kd), the maximum specific growth rate (μm) and the saturation constant (KS) were 0.276 mg/mg, 0.07 /day, 0.653 /day, and 396.62 mg COD/L respectively for MLSS 5000 mg/L, and 0.222 mg/mg, 0.09 /day, 1.2 /day, and 659.45 mg COD/L for MLSS 3000 mg/L. The values of kinetic coefficients were within the normal range of the activated sludge process found in the literature, except the values of Y. However, value of Y increased with the increase of MLSS. Kinetic parameters determined from CF-MBR process were used to simulate the effluent COD. The simulation study showed good agreement between model prediction and experimental data. Sensitivity analysis was carried out to determine influence of biokinetic parameters on the effluent substrate concentration. From the analysis, it was evident that kd and KS were directly proportional to the effluent substrate concentration, while μm was inversely proportional.

Fundamental nonlinearities of the reactor-settler interaction in the activated sludge process

The activated sludge process can be modelled by ordinary and partial differential equations for the biological reactors and secondary settlers, respectively. Because of the complexity of such a system, simulation models are most often used to investigate them. However, simulation models cannot give general rules on how to control a complex nonlinear process. For a reduced-order model with only two components, soluble substrate and particulate biomass, general results on steady-state solutions have recently been obtained, such as existence, uniqueness and stability of solutions. The aim of the present paper is to utilize those results to formulate some implications of practical importance. In particular, strategies are described for the manual control of the effluent substrate concentration subject to the constraint that the settler is maintained in normal operation (with a sludge blanket in the thickening zone) in steady state. Such strategies contain how the two control parameters, the recycle and waste volumetric flow ratios, should be chosen for any (steady-state) values of the input variables.

Optimal control of hydrogen production in a continuous anaerobic fermentation bioreactor

This paper addresses the problem of optimization of hydrogen production in continuous anaerobic digesters using a model predictive control (MPC) strategy. The process is described by a dynamic nonlinear model. The influent concentration of molasses together with the effluent substrate and product concentrations of acetate, propionate, butyrate and biomass were estimated by an asymptotic online observer from measurements of gas composition in H 2 and CO 2 and gas flow rate. The observer was tested experimentally before to apply MPC online. The combined strategy (MPC and observer) was used in order to optimize a bioreactor of 2 L. The hydrogen production was increased by 75% up to 8 . 27 mL H 2 L − 1 min − 1 , using the influent flow rate as the main control variable while keeping the conversion of the influent concentration higher than 95% and maintaining the temperature at 37 °C and pH at 5.5.

Metaheuristic control of substrate concentration for an activated sludge process

In this paper, a two-stage linear dynamic control scheme, using a metaheuristic approach, will be developed to control the effluent substrate concentration of an ASP. In the first stage, a static output feedback controller will be designed, using only measurements of the oxygen concentration. In the second stage, an asymptotic non-linear estimator of the substrate concentration will be used and the estimate will be fed back through a PI controller. In particular, the model of the ASP will be presented both in its non-linear and linearised form. Based on the linearised approximation, a static inner loop controller will be designed using a metaheuristic search algorithm for the computation of the controller parameters. Following, an outer PI controller will be designed based on the linearised model, again using a metaheuristic search algorithm in order to compensate the influence of the non-linearities when the static controller is applied to the non-linear model. The performance of the overall closed loop system will be illustrated through simulation experiments.

Two-stage robust control of substrate concentration for an activated sludge process

A two-stage robust control scheme improving the performance of an Activated Sludge Process is proposed. In the first stage, asymptotic command following the substrate concentration with simultaneous attenuation of the fluctuations of the dissolved oxygen concentration is assured. The first stage is a pure dynamic controller. The second stage is a PID controller. Good performance of the proposed control scheme on the corresponding nonlinear ASP model is illustrated through extensive simulation experiments. The contribution of the paper can be summarized to the derivation of the following two results: An accurate to a wide range of inputs and disturbances, linearized generic model of the ASP and, most important, a linear robust controller that controls accurately the effluent substrate concentration without using measurements of it.

Effect of the organic loading rate on the performance of anaerobic acidogenic fermentation of two-phase olive mill solid residue

A study of the effect of the organic loading rate (OLR) on the anaerobic acidogenic fermentation of two-phase olive mill solid residue (OMSR) derived from fruits with a low ripening index was carried out in a laboratory-scale completely stirred tank reactor at mesophilic temperature (35 degrees C). Eight experimental runs were carried out at OLRs of 3.2, 5.6, 7.4, 9.6, 11.0, 12.9, 14.0 and 15.1g T-COD/ld, which were equivalent to hydraulic retention times of 50.0, 28.8, 21.8, 16.9, 14.7, 12.4, 11.5 and 10.7d, respectively. The experimental results obtained demonstrated that the optimum value of OLR for the acidogenic fermentation process was 12.9 g T-COD/ld, for which a maximum production of acetic acid was achieved. It was found that inhibition of the process occurred at OLRs higher than 12.9 g T-COD/ld. This was characterized by a significant decrease in the acetic acid concentration in the effluent and an increase in the concentration of other volatile acids that may affect the methanogenic step. The process inhibition was also characterized by the plateau in the curves of the effluent substrate concentration versus the OLR applied. It was found that a first-order kinetics satisfactorily described the influence of non-acetic acid soluble organic matter concentration (S-COD( *)) on the rate of soluble organic matter conversion to acetic acid (R(S-COD)( *)), and the influence of acetic acid concentration (AcH) on the rate of acetic acid production (R(AcH)), while a potential equation type adequately described the influence of acetic acid concentration on the volumetric hydrogen production (R(ACH) ). The kinetic constant for soluble organic matter removal was 0.145 d(-1), while the constant for acetic acid formation was found to be 0.075 d(-1).

Biodegradation of distillery spent wash in anaerobic hybrid reactor

A lab-scale anaerobic hybrid (combining sludge blanket and filter) reactor was operated in a continuous mode to study anaerobic biodegradation of distillery-spent wash. The study demonstrated that at optimum hydraulic retention time (HRT), 5 days and organic loading rate (OLR), 8.7 kg COD / m 3 d , the COD removal efficiency of the reactor was 79%. The anaerobic reduction of sulfate increases sulfide concentration, which inhibited the metabolism of methanogens and reduced the performance of the reactors. The kinetics of biomass growth i.e. yield coefficient ( Y , 0.0532 ) and decay coefficient ( K d , 0.0041 d - 1 ) was obtained using Lawrence and McCarty model. However, this model failed in determining the kinetics of substrate utilization. Bhatia et al. model having inbuilt provision of process inhibition described the kinetics of substrate utilization, i.e. maximum rate of substrate utilization ( R , 1.945 d - 1 ) and inhibition coefficient values ( K i , 0.032 L / mg ) . Modeling of the reactor demonstrated that Parkin and Speece, and Bhatia et al. models, both, could be used to predict the effluent substrate concentration. However, Parkin and Speece model predicts effluent COD more precisely (within ± 2 % ) than Bhatia et al. model (within ± 5 – 20 % ) of the experimental value. Karhadkar et al. model predicted biogas yield within ± 5 % of the experimental value.

Evaluation of a laboratory-scale stabilization pond for tertiary treatment of distillery waste previously treated by a combined anaerobic filter–aerobic trickling system

Distillery waste tertiary treatment in a laboratory stabilization pond was evaluated. Effluents from a combined laboratory-scale anaerobic filter–aerobic trickling filter process were used as the influent. The effect of the hydraulic retention time (HRT) in the range of 5–30 days was evaluated at influent total chemical oxygen demand (TCOD) in the range of 271–5286 mg/l (BOD 5 in the range of 66–1212 mg/l). TCOD and BOD 5 removals of up to 54% and 74%, respectively, were obtained for the most concentrated influent used at 30 days of HRT. The effect of the HRT on TCOD and BOD 5 removal efficiencies followed an exponential relationship. An empirical equation adequately described the effect of the organic surface-loading rate on the process efficiency. The pond acted as an intermediate flow pattern between completely mixed flow and plug-flow. It was found that a second-order model fit in well with the experimental results of organic matter removal rate and effluent substrate concentration. The second-order kinetic constant was found to be K S = 0.23 mg BOD 5/mg TSS day. The proposed model accurately predicted the behaviour of the pond showing deviations between the experimental and theoretical values of effluent substrate concentrations equal to or lower than 11%.