Mixed Liquor Research Articles

Effect of Operating Conditions on Membrane Fouling in Pilot-Scale MBRs; Filaments Growth, Diminishing Dissolved Oxygen and Recirculation Rate of the Activated Sludge.

This is the first study that examines the effect of operating conditions on fouling of Membrane Bio-Reactors (MBRs), which treat municipal wastewater in field conditions, with specific regard to the controlled development of filamentous microorganisms (or filaments). The novelty of the present work is extended to minimize the dissolved oxygen (DO) in recirculated activated sludge for improving the process of denitrification. For this purpose, two pilot-scale MBRs were constructed and operated in parallel: (i) Filament-MBR, where an attempt was made to regulate the growth of filaments by adjustment of DO, the Food-to-Microorganisms (F/M) ratio and temperature, and (ii) Control-MBR, where a gentle stirring tank was employed for the purpose of zeroing the DO in the recycled sludge. Results showed that low temperature (<15 °C) slightly increased the number of filaments in the Filament-MBR which, in turn, decreased the Trans-Membrane Pressure (TMP). As the Soluble Microbial Products (SMP) and the colloids are considered to be the basic foulants of membranes in MBR systems, specific attention was directed to keep their concentration at low values in the mixed liquor. The low F/M ratio in the aeration tanks which preceded the membrane tank was achieved to keep the SMP proteins and carbohydrates at very low values in the mixed liquor, i.e., less than 6 mg/L. Moreover, as a result of the low recirculation rate (2.6∙Qin), good aggregation of the produced excess sludge was achieved, and low concentration of colloids with a size ≤50 nm (nearly the membranes’ pore size used for filtration/separation) was measured, accounted for maximum 15% of the total colloids. Additionally, the increase in filamentous population at the Filament-MBR contributed to the further reduction of colloids in the mixed liquor at 7.9%, contributing beneficially to the reduction of TMP and of membrane fouling. The diminishing of DO in the recirculated sludge improved denitrification, and resulted in lower concentrations of Ν-NO3− and TN in the effluent of the Control-MBR. Furthermore, the recirculation rate of Qr = 2.6∙Qin, in comparison with Qr = 4.3∙Qin, resulted in improved performance regarding the removal of N-NH4+. Finally, high organics removal and ammonium nitrification was observed in the effluent of both pilots, since COD and Ν-ΝH4+ concentrations were generally in the range of 10–25 mg/L and <0.1 mg/L, respectively.

Intoksikasi Alkohol Akibat Minuman Keras Oplosan

The incidence of alcoholic liquor poisoning (alcoholic liquor) in Indonesia shows a high number. One of the causes of alcohol poisoning is methanol. Methanol poisoning in Indonesia usually occurs as a result of drinking mixed alcohol liquor. It has been reported a male 23 years old with decreased consciousness after drinking oplosan alcohol suspected to contain methanol. The examination reveals that patients has metabolic acidosis, toxic optic neuropathy (TON) and erosive gastritis. Treatment was acidosis correction, prevent formation of metabolites, hemodialysis with supportive and symptomatic teraphy .Keywords: methanol, poisoning, alcohol mixed liquor

Performance evaluation of aerobic fluidized bed bioreactor coupled with tube-settler for hospital wastewater treatment

The need for wastewater treatment does not only arise from an environmental conservation point of view. But also, from the fact that it can be reused for secondary proposes. The most of hospitals being present in urban space, still their wastewater treatment are not fully explored. The Fluidized Aerobic Bed Bioreactor (FABB) treats wastewater in a liquid-solid phase among various wastewater treatment processes. This study employed a fluidized aerobic bed reactor coupled with a tube settler for hospital wastewater treatment. The treatment efficiency was evaluated based on the removal of pollutants and nutrients with associated parameters pH, Alkalinity, total suspended solids (TSS), and mixed liquor suspended solids (MLSS). The efficiency was determined by evaluating the influent and effluent quality of samples. The BOD5 was reduced at an average of 69% in FABB, and for tubesettler, it resulted in consumption of only 39%. Similar types of results were obtained when considering it for COD, i.e., 72% and 38%, respectively, for FABB and tube settler. The nitrification was observed in both nitrate accumulation by 103% and 3.65% in FABB and tube settler. In the absence of anaerobic conditions, the denitrification process could not be achieved. Hence the cycle was not completed. Lower phosphate reduction was achieved, 63% and 23%, however concentration in influent were below the permissible limit of 5 mgL−1. The study concludes that FABB can be successfully employed for hospital wastewater treatment. Additionally, tubesettler may be used in place of a secondary clarifier in the treatment of hospital wastewater.

Biological mechanism of alleviating membrane biofouling by porous spherical carriers in a submerged membrane bioreactor

In this study, porous spherical carriers were fixed around the hollow fiber membrane module to mitigate membrane biofouling. Two MBRs (R1 without carriers, R2 with carriers) were operated for 31 days under identical operating conditions to investigate the effects of the carriers on the reactor performances, the production of extracellular polymeric substances (EPS), the level of N-acyl-homoserine lactones (AHLs), and the microbial communities. The results showed that the presence of carriers in MBR was conducive to nitrogen removal and decreased the total membrane filtration resistance by about 1.7 times. Slower transmembrane pressure (TMP) rise-up, thinner bio-cakes, lower EPS production, and fewer tryptophan and aromatic proteins substances on the membrane surface were observed in R2. The polysaccharides secretion of EPS in bio-cakes was mainly regulated by C4-HSL and 3OC6-HSL in the presence of carriers. The microbial community analysis revealed that carriers addition reduced the relative abundance of EPS and AHL producing bacteria in the membrane bio-cakes and enriched the accumulation of functional bacteria conducive to nutrient removal in the mixed liquor. This study provided an in-depth understanding for the application of porous spherical carriers to alleviate membrane biofouling.

Co-optimization of wastewater treatment plants interconnected with smart grids

Wastewater treatment plants (WWTPs) and smart grids of urban systems are in a strong nexus. Energy consumption of WWTPs will directly impact the economy of the smart grids, while the energy forecast, marketing, and resource allocation of smart grids will affect the economy of WWTPs. As such, these two critical infrastructures need to be operated and managed cooperatively to maximize the mutual economic benefits. In this paper, a mixed integer nonlinear programming (MINLP) co-optimization model is developed to address the day-ahead economic dispatch problem of smart grids embedded with interdependent links among wastewater treatment plants and smart grids. The energy demand of WWTPs is optimized by minimizing the energy consumption of the aeration module, mixed liquor pumping, primary clarifier’s influent pumping, secondary clarifier’s sludge pumping, and mixing devices that are integrated in the dynamic economic dispatch problem of smart grid. Additionally, biochemical oxygen demand (BOD) and total Kjedhal nitrogen (TKN) concentrations of the treated wastewater is also incorporated in the economic dispatch problem to ensure of the high quality of the WWTP’s effluent. Electricity consumption of the buildings is also added as a constraint to the economic dispatch, serving as a dynamic load for smart grid. Case studies are conducted to examine the impact of wastewater flow rate, influent BOD and TKN concentrations, battery efficiency, and end-of-day battery’s state of the charge constraints on economic dispatch of the smart grid. The results show that total operational cost and energy consumption of the integrated WWTP-smart grid is increased only by 3.4% and 1.75%, respectively, as the daily influent flow rate and BOD & TKN concentrations are increased from their minimum to maximum thresholds.

Microbial community structure analysis in a hybrid membrane bioreactor via high-throughput sequencing

Compared to the suspended culture (sludge) of a conventional bioreactor, hybrid membrane bioreactors (HMBRs) are more effective at removing pollutants owing to the addition of fillers addition of fillers that facilitate biofilm formation. However, the microbial community structure and composition in an HMBR remain unclear. We ran three laboratory-scale HMBRs at room temperature under different sludge retention times (SRTs; 10d, 20d, and 30d) to compare the microbial diversity and community structure among the membrane surface, suspended filler surface, and mixed liquor using high-throughput sequencing. The results showed that SRT can markedly affect microbial community structure in the HMBR, and different trends appeared in the three functional units. The largest number of mutual operational taxonomic units was found in the activated sludge mixture and suspended carrier with an SRT of 20d and 30d. Species belonging to Proteobacteria in the 10d SRT group had the greatest contribution to between-group differences. A longer SRT could mitigate membrane fouling by decreasing the relative abundance of Thauera and Sphaerotilus attached on the membrane surface. Comamonadaceae, a family of denitrifying bacteria, offer high denitrification potential for bioreactors operating under a long SRT.

Influence of cell lysis by Fenton oxidation on cryptic growth in sequencing batch reactor (SBR): Implication of reducing sludge source discharge

The cell lysis-cryptic growth was implemented by Fenton oxidation in sequencing batch reactor. Optimizing sludge lysis condition could maximize the release of nutrients and sludge disintegration degree. After Fenton oxidation, the extracellular polymeric substance was obviously destroyed with the sludge average particle decreased from 64 μm to 36 μm. After 5% of the settled sludge in sequencing batch reactor (SBR) was oxidized by Fenton and then returned to SBR, the mixed liquor suspended solids (MLSS) decreased by 19.3% at the end of 35 days operation, the average mixed liquor volatile suspended solids/mixed liquor suspended solids (MLVSS/MLSS) was promoted by 13.3% during the entire operation. Returning lysed sludge had no significant influence on the organics and nitrogen removal, but the total phosphorus removal was distinctly enhanced by generating FePO4 precipitate. Additionally, returning lysed sludge suppressed nitrifying bacteria and promoted denitrifying bacteria slightly. Consequently, the cell lysis-cryptic growth for reducing sludge source discharge from wastewater biological treatment could be achieved on the premise of ensuring effluent quality.

Delivery and effects of proton pump inhibitor on anaerobic digestion of food and kitchen waste under ammonia stress

Ammonia stress changes microbial metabolism of anaerobic digestion and decreases methane yield, where proton pump overactivated by free ammonia suggested to be the centre of the metabolism changes in anaerobic digestion under ammonia stress. The work demonstrated that proton pump inhibitor (PPI) could alleviate the overactivated proton pump and mitigate ammonia inhibition. Its impacts on iron transporter, substrates uptake, and energy conservation were investigated in anaerobic digestion treating food and kitchen waste. The PPI formed a stimuli-responsive drug delivery system driven by pH for the more inhibited microbe (p < 0.01), confirmed by FE-SEM/EDS and high throughput sequencing, implying the PPI was activated at inhibited microbe more than mixed liquor. Consistent microbial population increase observed in syntrophs and methanogens, who utilized the substrates for high yielding pathway and facilitated the energy sharing by direct interspecies electron transfer. These results demonstrated PPI could recovery methane production and could mitigate fatty-acid accumulation under high ammonia stress by delivery and activation in acetoclastic methanogen.

Screening cost effectiveness and salinity build up control in osmotic membrane bioreactors for refinery wastewater treatment: A draw solute with lower diffusivity and ultrafiltration implementation

Two strategies were investigated for salinity build up prevention in osmotic membrane bioreactors (OMBR) treating a real refinery wastewater. Firstly, a solute with lower diffusivity (MgCl2, for 102 days) was used. The impact on the microbiological activity was lower, which favored the recalcitrant compounds degradation. However, without salinity relief, the mixed liquor (ML) salinity increased, impacting the forward osmosis (FO) flux (0.18 L/m2h). Secondly, an ultrafiltration (UF) membrane was submerged within the ML and the draw solution (DS) replaced to NaCl. The ML conductivity was stable along 330 days without a severe flux decay (1.07 L/m2h). Nonetheless, the reverse NaCl flux had a higher impact on the microbiological activity and the concentration of dissolved organic carbon and ammoniacal nitrogen started to increase in the UF permeate. Due to the lower permeate flux, the OMBR had a higher membrane area requirement which represented the main contributor for the total operating costs.

Artificial intelligence modeling to predict transmembrane pressure in anaerobic membrane bioreactor-sequencing batch reactor during biohydrogen production

The complex nature of wastewater treatment has led to search for alternative strategies such as different artificial intelligence (AI) techniques to model the various operational parameters. The present work is aimed at predicting the transmembrane pressure (TMP) as a key operational parameter in the case of anaerobic membrane bioreactor-sequencing batch reactor (AnMBR-SBR) during biohydrogen production using the adaptive neuro-fuzzy inference systems (ANFIS) and artificial neural network (ANN). In both the models, organic loading rates (OLR) ranging from 0.5 to 8.0 g COD/L/d, effluent pH (3.6–6.9), mixed liquor suspended solid (4.6–21.5 g/L) and mixed liquor volatile suspended solid (3.7–15.5 g/L) were used as the input parameters to test TMP as an output parameter. The ANFIS model was trained using the hybrid algorithms for TMP prediction. The higher prediction performance was obtained by using the Gauss membership function with four membership numbers. A back-propagation algorithm was also employed for the feed forward training of ANN model; the best structure was a Levenberg-Marquardt training algorithm with nine neurons in the hidden layer. By employing ANFIS and ANN models, relatively a good prediction of TMP was obtained with the R2 values of 0.93 and 0.88, respectively while the calculated mean square error for TMP in the ANFIS model (7.3 × 10−3) was lower than that of ANN model (8.02 × 10−3). The higher R2 and lower MSE values for the ANFIS model exhibited a better TMP prediction performance than the ANN model. Finally, it was observed that in the sensitivity analysis of ANN model, OLR was the most important input parameter on the variation of TMP.

Design of the Reactor and the Clarifier of an Activated Sludge Water Resource Recovery Facility, AS WRRF

Metcalf & Eddy´s formula that gives the mixed liquor volatile suspended solids, MLVSS= Xv, produced in the aeration tank, from hereon called Reactor, will be used giving it the parameters for AS WRRFs shown in Table 10-5 of its 3rd Edition placing values of hydraulic retention time, HRT, in the first column and values of solids retention time, SRT, in the first row. Many solutions are found that solve the formula. Some will be studied, using the flux graph, to check if they comply with other requirements as moderate volume, V, of Reactor, small surface, S, of Clarifier, ample range of return flow percentages, R, and admissible relation F/M. A solution will then be chosen.

Investigation of operational parameters for retaining properties of micro-plastics for typical aerobic wastewater treatment unit

Given the large number of existing wastewater treatment plants (WWTPs), this paper investigates the effects of routine operational factors on retaining the properties of the microplastics (MPs) of a typical aerobic bioreactor, which is widely adopted in both municipal and industrial WWTPs. The three most detected plastics, namely, polyethylene, polypropylene, and polyvinyl chloride, are pulverized and injected into an anoxic–oxic configured laboratory facility to explore the size distribution and removal efficiency of the MPs in the effluent. A laser particle analyzer is used for the continuous particle size distribution testing, which indicates that nearly all the particles whose diameters exceed 35 μm are retained. This phenomenon poses a threat to mammal health for particles less than 20 μm in diameter that dominate the effluent’s abundance. Comprehensive discussions and comparisons with existing works in terms of how the three operational factors affect the bioreactor’s retaining properties significantly are presented. The moderate mixed liquor suspended solids and short hydraulic retention time of the bioreactor are beneficial to the MPs removal based on the in-depth analysis of variance of the limited experiment runs. Furthermore, the sludge in the bioreactor renders an adsorption–desorption pathway in retaining the MPs.

Understanding the role of in-situ ozonation in Fe(II)-dosed membrane bioreactor (MBR) for membrane fouling mitigation

Inorganic salts (e.g., FeCl3 and FeSO4) are typically added to membrane bioreactor (MBR) for achieving improved total phosphorus (TP) removal and hydraulic performance. However, at the iron dose (e.g., Fe to P molar ratio of 1–4) required for effective TP removal, severe irreversible membrane fouling could become a significant concern. In this context, intermittent in-situ ozonation was provided for the first time directly in the membrane tank of Fe(II)-dosed membrane bioreactor, and its effect on membrane fouling mitigation was assessed and elucidated. The basic effluent quality remained unaffected, indicating that in-situ ozonation had no detrimental effects. In addition, concentration of foulants and the relative abundance of biofilm-forming microbes were comparable in both the Fe-MBR and Fe/O3-MBR. Importantly, as compared to the Fe-MBR, a 33% reduction in membrane fouling was achieved in the Fe/O3-MBR. The enhanced filterability of mixed liquor and the scrubbing of the membrane surface by ozone with the direct/indirect oxidation of the deposited foulants contributed to membrane fouling mitigation in the Fe/O3-MBR. Meanwhile, trans-membrane pressure profiles of MBRs followed cake-intermediate fouling mechanism. This study demonstrates that provision of intermittent in-situ ozonation is a simple and attractive approach to extend the operation of iron-dosed MBR.

Parameters to characterize the internal recirculation of an oxidation ditch

Mixed liquor circulates ceaselessly in the closed-loop corridor in an oxidation ditch (OD), which is significantly different from other wastewater treatment processes. The internal recirculation ratio (IRR), i.e., the ratio between circulation flow rate (QCC) and influent flow rate (QIn), and the circulatory period (T), i.e. the time consumed for the mixed liquor to complete one lap in the circular corridor, was used to quantify the internal recirculation characteristics of the OD system. In order to elucidate the characteristics and applicability of IRR and T, this study obtained the numerical relationship between IRR and T by formula derivation. It also discusses the factors influencing IRR and analyses the applications of IRR and T. The results showed that IRR = QCC/QIn = HRT/T = HRT ž IRF (HRT = hydraulic retention time of the mixed liquor in the circular corridor; IRF = internal recirculation frequency). Moreover, three kinds of parameters had an effect on IRR: QIn; reactor dimensions, i.e., length (Lmid), width (B), and height (H) of the circular corridor; and horizontal velocity of the mixed liquor in the circular corridor (v). QIn changed IRR by altering HRT. However, B, H, Lmid, and v changed IRR by altering IRF and T. Furthermore, the same IRR corresponded to many different HRT and IRF. Therefore, when QIn and QCC varied in the OD system, using HRT and IRF to evaluate the variation of QIn and QCC, respectively, was better than using IRR to evaluate their synthetical variation. IRF and T were useful for directly and precisely characterizing the circulation speed and circulation flow rate in the circular corridor, while IRR was more useful for evaluating the dilution effect of reflux on influent.

Evaluation and start-up of an electro-Fenton-sequencing batch reactor for dairy wastewater treatment

This study examined the performance of an integrated wastewater (WW) treatment system, namely an electro-Fenton (EF)-sequencing batch reactor (SBR), for dairy industry WW. The EF process was used as the first stage of the SBR. It degrades bio-refractory compounds via advanced oxidation processes, thereby resulting in the formation of simple biodegradable intermediates. Several factors, including the hydraulic retention time (HRT), sludge volume index (SVI), and sludge retention time (SRT) of the EFSBR, were optimized. The effectiveness was studied for 1 y laboratory-scale experiments under stable conditions (HRT of 10 h, SRT of 15 d, mixed liquor suspended solids concentration of 3500 mg/L, and SVI of 89), which revealed 99% chemical oxygen demand, 97% total nitrogen, and 95% total phosphorus removal. Thus, the developed system is economically feasible and superior to other conventional biological treatment systems.

Process Optimization of Waste Activated Sludge in Anaerobic Digestion and Biogas Production by Electrochemical Pre-Treatment Using Ruthenium Oxide Coated Titanium Electrodes

Anaerobic digestion (AD) appears to be a popular unit operation in wastewater treatment plant to treat waste activated sludge (WAS) and the produced methane gas can be harvested as renewable energy. However, WAS could inhibit hydrolysis stage during AD and hence pre-treatment is required to overcome the issue. This paper aimed to study the effect of electrochemical pre-treatment (EP) towards efficiency of AD using titanium coated with ruthenium oxide (Ti/RuO2) electrodes. The investigation has been carried out using in-house laboratory batch-scale mesophilic anaerobic digester, mixed under manipulation of important operating parameters. Optimization was performed on EP using response surface methodology and central composite design to maximize sludge disintegration and dewaterability. By operating at optimal conditions (pH 11.65, total solids 22,000 mg/L, electrolysis time 35 min, current density 6 mA/cm2, and 1000 mg/L of sodium chloride), the pre-treated WAS in terms of mixed liquor volatile suspended solids (MLVSS) removal, soluble chemical oxygen demand (sCOD), capillary suction time (CST) reduction, and extracellular polymeric substance (EPS) were 38%, 4800 mg/L (increased from 935 mg/L), 33%, and 218 mg/L, respectively. Following AD, the volatile solids (VS) removal and chemical oxygen demand (COD) removal by EP were enhanced from 40.7% and 54.7% to 47.2% and 61.5%, respectively, at steady-state. The biogas produced from control and electrochemical pre-treated WAS were in the ranges of 0.12 to 0.17 and 0.2 to 0.24 m3/kg VSfed, respectively, and the volume of biogas produced was 44–67% over the control. Based on the results obtained, suitability of EP for WAS prior to AD was confirmed.

Effect of Aerobic Granular Sludge Concentrations on Adsorption and Biodegradation to Oxytetracycline

The aerobic granular sludge (AGS) technology has shown a great potential for effectively removing oxytetracycline (OTC) from wastewater in an environmentally friendly way. In this study, the removal mechanism of OTC by the AGS process was investigated. The results showed that AGS has adsorption behavior to OTC and biodegradation at the same time. The adsorption process of OTC by AGS that before acclimation fits the pseudo-second-order kinetic model and the adsorption process by AGS that after acclimation complied well with the pseudo-first-order kinetic model. The adsorption included the boundary layer diffusion, the diffusion of OTC in AGS pores, and the adsorption of OTC on the inner surface of AGS. The adsorption capacity of AGS to OTC was affected by the mixed liquor suspended solids (MLSS) concentration of AGS. When the AGS concentration was 10 g/L MLSS, the adsorption effects of AGS on OTC were better. AGS showed outstanding biodegradation abilities after its adaptation to OTC, and the biodegradation ratio of AGS to OTC was 77%. Thirteen kinds of intermediate products formed during OTC degradation were detected, and accordingly, the biodegradation pathway of OTC was constructed. The results will promote the wide application of AGS biological treatment technology.

Size of biological flocs in activated sludge systems: Influence of hydrodynamic parameters at different scales

In conventional activated sludge (CAS) systems and membrane bioreactors (MBR), aeration, mixing and filtration are affected by various properties of activated sludge (AS) and especially viscosity and morphological properties of flocs. The aim of the present study was to understand the relationship between hydrodynamic conditions and AS floc size properties. Floc size distribution (FSD) measurements were performed in four systems showing different hydrodynamics: (i) a standard stirred reactor (SR), (ii) a pilot bubble column (BC), (iii) a full-scale aeration zone equipped with fine bubble diffusers, (iv) a full-scale filtration zone equipped with coarse bubble diffusers. The measurements were carried out on-site, using the mixed liquor from a full-scale MBR. The FSD of the given activated sludge mainly depends on the average shear rate (γ̇) and on the circulation time in the SR. To a lesser extent, local properties, such as maximal shear rate, also influence the FSD. In the same way, the main operating parameter governing the FSD in the BC was γ̇. For a similar γ̇, the flocs were slightly larger in the BC than in the SR. In addition, in the full-scale systems, for a similar γ̇ estimated, the FSD characteristic diameters were lower in the filtration zone (with coarse bubbles) than in the aeration zone (with fine bubbles). The FSD in the aeration zone was well correlated with the FSD in the BC whereas the flocs were slightly smaller in the filtration zone than in the BC.

Log removal values in membrane bioreactors: Correlation of surrogate monitoring and operational parameters

Log removal values (LRV) for a range of pathogens in membrane bioreactors (MBRs) were aggregated for 180 sampling events across 11 municipal scale installations. Important correlations were established between LRV for biological (LRVBio) and physical (LRVMem) inactivation with reactor conditions (pH, temperature, solid and hydraulic retention times (SRT, HRT), and mixed liquor suspended solids (MLSS)), membrane properties (pore size and flux), operational variables and filtrate quality. LRVBio correlated positively and significantly between all microorganism indicators and dissolved organic carbon (DOC), becoming a suitable monitoring technique for biological removal. LRVMem correlated positively for protozoa indicators and bacteria consistent with size exclusion as a predominant removal mechanism. Strong correlations between LRV for protozoa, virus and bacteria indicators were established at lower flux, TMP and MLSS, higher pH and temperature and longer solids and hydraulic retention time. The implications of this study provide important guidance for the validation of MBRs producing safe and consistent recycled water.

Determination of Kinetic Constants for Treating Tannery Wastewater Using Activated Sludge Process (ASP)

A study was conducted to evaluate the feasibility of Activated Sludge Process (ASP) for the treatment of tannery wastewater and to develop a simple design criterion under local conditions. A bench scale model comprising of an aeration tank and final clarifier was used for this purpose. The Lab scale reactor was operated continuously and settled tannery wastewater was used as influent to the aeration tank. Five days Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) of the influent and effluent were measured to find process efficiency at various mixed liquor volatile suspended solids (MLVSS) and Hydraulic Detention Time (θ).The results of the study demonstrated that an efficiency of above 90% and 80% for BOD5 and COD, respectively could be obtained if the ASP is operated at an MLVSS concentration of 3500 mg/L keeping an aeration time of 12 hours.ASP is a feasible treatment technology for tannery wastewater treatment, by conducting experiments at the HRTs of 12,10,8,6 and 2 h, it was found that the maximum COD removal efficiency of 84.20% was recorded at 12 h HRT. In this study, the Mathematical Models such as Monod, Grau Second Order, Modified Stover-Kicannon and First Order Kinetic Models were applied for the performance evaluation of the Reactor at any given time and found that the data were in good agreement with the observed ones in the models, such as, Grau second order and Monod. Further, the correlation coefficient value (R2) obtained for the experimental and predicted effluent COD concentration using the above mentioned (Grau second order and Monod) models also confirmed the suitability applying the models to predict the performance of the reactor under lab scale-controlled environmental conditions.