Bio-P Module Research Articles

Improve the performance of full-scale continuous treatment of municipal wastewater by combining a numerical model and online sensors.

Mathematical models based on instant environmental inputs are increasingly applied to optimize the operation of wastewater treatment plants (WWTPs) for improving treatment efficiency. This study established a numerical model consisting of the activated sludge module ASM3 and EAWAG bio-P module, and calibrated the model using data from a full-scale experiment conducted in a WWTP in Nanjing, China. The calibrated model was combined with online sensors for water temperature, chemical oxygen demand, NH+ 4-N and PO3- 4-P to optimize and dynamically adjust the operation of the WWTP. The results showed that, compared to the original default operation mode, the effluent water quality was significantly improved after optimization even without supplementation of external carbon or alkalinity, and the required aeration rate in spring, summer, autumn, and winter was reduced by 15, 41, 33 and 11%, respectively. The study indicated that there was the potential for application of closed-loop automatic control to regulate operating parameters to improve wastewater treatment processes through the integration of data on influent characteristics and environmental conditions from sensors, and results from simulation models.

Optimization of A2O BNR Processes Using ASM and EAWAG Bio‐P Models: Model Performance

This paper presents the performance of an optimization model for a biological nutrient removal (BNR) system using the anaerobic-anoxic-oxic (A(2)O) process. The formulated model simulates removal of organics, nitrogen, and phosphorus using a reduced International Water Association (IWA) Activated Sludge Model #3 (ASM3) model and a Swiss Federal Institute for Environmental Science and Technology (EAWAG) Bio-P module. Optimal sizing is attained considering capital and operational costs. Process performance is evaluated against the effect of influent conditions, effluent limits, and selected parameters of various optimal solutions with the following results: an increase of influent temperature from 10 degrees C to 25 degrees C decreases the annual cost by about 8.5%, an increase of influent flow from 500 to 2500 m(3)/h triples the annual cost, the A(2)O BNR system is more sensitive to variations in influent ammonia than phosphorus concentration and the maximum growth rate of autotrophic biomass was the most sensitive kinetic parameter in the optimization model.

Comparison of Bio-P module and the Modified Bio-P module in the step-feed biological nutrient removal process

The Modified Bio-P module was evaluated in terms of the kinetic rate expression and engineering parameters, comparing the measured data of full-scale plant with simulated data. To simulate step-feed BNR (Biological Nutrient Removal), the ASM3 (Activated Sludge Model 3) with the EAWAG Bio-P Module (The Swiss Federal Institute for Environmental Science and Technology) and the ASM3+Modified Bio-P module were used. The RMSEs (root mean square error) of the T-N (total nitrogen) concentration of the effluent levels of measured and simulated examples were 2.29 for ASM3+Bio-P and 1.28 for ASM3+Modified Bio-P. In the case of T-P (total phosphorus), the RMSEs were 0.28 for ASM3+Bio-P and 0.25 for ASM3+Modified Bio-P. The annual removal rates for T-N were 0.77 for the measured, 0.69 for the Bio-P, and 0.74 for the Modified Bio-P samples, while the annual removal rates for T-P were 0.64 for the measured, 0.72 for the Bio-P, and 0.60 for the Modified Bio-P cases. With simulated data, the Modified Bio-P model was a better fit for the field data compared to Bio-P. The Modified Bio-P module reproduced the step-feed process more effectively than the Bio-P module.

Optimization of A2O BNR processes using ASM and EAWAG Bio-P models: model formulation

This study is an extended and comprehensive analysis to accomplish optimal sizing for a biological nutrient removal (BNR) system with an A2O BNR activated sludge process using activated sludge models (ASM) kinetic models. A highly nonlinear activated sludge model combined with the EAWAG Bio-P module is formulated and optimized using a generalized reduced gradient solver. Primary and final clarifications are included with the A2O biotreatment scheme along with oxygen-supplying units. This paper includes a detailed description of model formulation, problem definition and discussion of optimal design in terms of capital (CAPEX) and operating (OPEX) cost estimates. The optimization problem is formulated and solved using typical cost factors and operating/design constraints applied to a typical illustrative system treating medium-strength wastewater. Results indicated that maintenance and sludge disposal expenditures represent more than 50% of the total annual cost and 80% of the annual running operating cost. Another major finding was that a primary clarifier is found to be cost ineffective in the A2O BNR process. Sensitivity of the optimal solutions and model performance to varying inflow conditions and to other effluent limits and model parameters will be discussed in another paper.

Wastewater Treatment Plant Synthesis and Design: Combined Biological Nitrogen and Phosphorus Removal

In the present work, a previous superstructure model developed for simultaneous optimization of the process configuration and equipment dimensions, i.e., optimal process synthesis and design and the operation conditions of activated sludge wastewater treatment plants, is extended to account for phosphorus as well as nitrogen removal. Along the activated sludge treatment process, the wastewater stream is exposed to different environmental conditions (anaerobic, anoxic, and aerated zones) in order to facilitate the different microbiological processes such as the release and uptake of phosphorus and the nitrification/denitrification processes. The Activated Sludge Model No. 3 extended with the Bio-P module for computing biological phosphorus removal is used to model the reaction compartments and the Takacs model for representing the secondary settler. The performance criterion selected is the minimization of the net present value that includes investment and operating costs while verifying compliance with th...

An integrated dynamic model for simulating a full-scale municipal wastewater treatment plant under fluctuating conditions

In this study, an integrated dynamic model was developed through combining a mechanistic model, a neural network (NN) model and a genetic algorithm approach, in order to simulate the performance of a full-scale municipal wastewater treatment plant (WWTP) with substantial influent fluctuations. As the base of the integrated model, the mechanistic model was initially established based on the activated sludge model 3 and the EAWAG bio-P module, and was used to generate the residuals for the NN model. The NN model was employed to build the relationship between the input and output variables. The network weights of the NN model were optimized with a genetic algorithm approach. The resulting integrated model was applied to simulate the 5-month performance of a full-scale WWTP with significant influent fluctuations, and the simulation results matched the measured ones of the WWTP well even under influent disturbance conditions. Compared with the individual mechanistic model and NN model, the integrated model was able to capture sufficient residual information to compensate for the inaccuracy of the mechanistic model and improve the extrapolative capability of the NN model. This model established in our work is demonstrated to be an effective and useful tool to simulate the performance of WWTPs.

Inhibition of biological phosphorus removal in a sequencing moving bed biofilm reactor in seawater

A new process was developed to achieve denitrifying biological phosphorus removal in wastewaters containing high levels of nitrate and phosphate with a low level of organic matter. This could particularly be useful in recirculating systems such as aquariums or fish farms to prevent accumulation of nitrate and phosphates and to avoid regular cost extensive and polluting water replacement. Phosphorus (P) was removed from the influent in a sequencing moving bed biofilm reactor, stored in the attached biomass and then cyclically removed from the biomass by filling the reactor with anaerobic water from a stock tank. Phosphate was accumulated in the stock tank which allowed for use as fertilizer. The feasibility of the experimental design was demonstrated by using the activated sludge model No. 3 (ASM3) complemented by the EAWAG Bio-P module implemented in the WEST simulation software. A pilot scale experiment was conducted in two identical reactors in two runs: one to treat water from a marine mesocosm, the other to treat a synthetic freshwater influent. No biological phosphorus removal was achieved during the seawater run. During the freshwater run, average P removal efficiency was 20%, of which 80% was attributed to biological removal and 20% to chemical precipitation. The absence of efficiency in seawater was attributed to the high concentration of calcium.

Use of activate sludge model no. 3 and Bio-P module for simulating five-stage step-feed enhanced biological phosphorous removal process

The ASM3 with EAWAG Bio-P Module (ASM3+P) was used for simulating a five-stage step-feed Enhanced Biological Phosphorous Removal (fsEBPR) process and its applicability was compared with the ASM2d. The fsEBPR process was predicted to achieve effective nitrogen and phosphorus removal from the wastewater even with low C/N and C/P ratios without additional carbon sources. Application of the ASM3+P on this configuration will be an ample chance for expanding the new models in the activated sludge process. Sensitivity analysis and parameter estimation were conducted with the ASM2d and the ASM3+P prior to model application so that calibration of the models could focus only on the sensitive parameters. The ASM2d was less successful for predicting the process behavior. Moreover, the ASM2d required 6 times more computation time than that for the AMS3+P due to its decay-regeneration model structure. To confirm the applicability of parameters determined from the pilot-scale reactor operating results, those were tested on the field data without further correction. Only the ASM3+P successfully predicted nitrogen and phosphate variations in the full-scale plants. Overall examination of simulation results using the pilot and full-scale data has led to the conclusion that the ASM3+P is better than the ASM2d for simulating fsEBPR processes.

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.

Practical approach to parameter estimation for ASM3+bio-P module applied to five-stage step-feed EBPR process

Various parameter optimization approaches to a five-stage step-feed EBPR process modeled using the ASM3+bio-P module were examined. Five stoichiometric (Y(STO,NO), Y(H,O2, Y(H,NO,) Y(PAO,O2), Y(PO4)) and seven kinetic parameters (k(STO), eta(NO), b(H), mu(max),PAO, q(PHA), q(PP), mu(max),A) were estimated. The optimization approaches could be classified based on the data sources (batch experiments or CSTR operation data) and the number of target variables used in calculating the objective function. Optimized parameter values obtained by each approach were validated with CSTR operation data that were not used for parameter optimization. The results showed that the parameter optimization only with batch experimental results could not be directly applied to CSTR operation data. ASM3 + bio-P module parameters could be finely optimized only with CSTR operation data when sufficient target variables for objective function calculation were applied. When the number of target variables was increased, prediction performance was significantly improved. Once optimized, the model was able to predict the characteristic features of the five-stage step-feed process; namely, a high PAO yield, fast PAO growth, fast X(pp) storage, slow X(STO) and X(PHA) storage.

Long-term simulation of the activated sludge process at the Hanover-Gümmerwald pilot WWTP

The aim of this study was to obtain a validated model, consisting of the Activated Sludge Model No. 3 (ASM3) and the EAWAG bio-P module, which could be used as a decision tool for estimating the maximum allowable peak flow to wastewater treatment plants during stormwater conditions. The databases used for simulations originated from the Hanover-Gümmerwald pilot plant subjected to a series of controlled, short-term hydraulic shock loading experiments. The continuous influent wastewater composition was generated using on-line measurements of only three parameters (COD, N-NH 4 +, P-PO 4 3−). Model predictions were compared with on-line data from different locations in the activated sludge system including the aerobic zone (concentrations of N-NH 4 +, N-NO 3 −) and secondary effluent (concentrations of P-PO 4 3−). The simulations confirmed experimental results concerning the capabilities of the system for handling increased flows during stormwater events. No (or minor) peaks of N-NH 4 + were predicted for the line with the double dry weather flowrate, whereas peaks of N-NH 4 + at the line with the quadruple dry weather flowrate were normally exceeding 8 g N m −3 (similar to the observations).

The EAWAG Bio-P module for activated sludge model No. 3

An additional module for the prediction of enhanced biological phosphorus removal is presented on the basis of a calibrated version of ASM3. The module uses modified processes from ASM2d but neglects the fermentation of readily degradable substrate. Biomass decay is modeled in the form of endogenous respiration as in ASM3. The glycogen pool and biologically induced P-precipitation is not taken into account. The module was systematically calibrated with experimental data from various batch experiments, a full-scale WWTP and a pilot plant treating Swiss municipal wastewater. A standard parameter set allowed all data to be simulated.

The eawag bio-p module for activated sludge model no. 3

An additional module for the prediction of enhanced biological phosphorus removal is presented on the basis of a calibrated version of ASM3. The module uses modified processes from ASM2d but neglects the fermentation of readily degradable substrate. Biomass decay is modeled in the form of endogenous respiration as in ASM3. Moreover, an additional glycogen pool and biologically induced P-precipitation were not taken into account. The module was systematically calibrated with experimental data from various batch experiments, a full-scale WWTP and a pilot plant treating Swiss municipal waste water. A standard parameter set allowed all data to be simulated.

Modelling of full-scale wastewater treatment plants with different treatment processes using the Activated Sludge Model no. 3

In 1999 the Activated Sludge Model no. 3 (ASM 3) by the IWA task Group on Mathematical Modeling for Design and Operation of Biological Wastewater Treatment was presented. The model is used for simulation of nitrogen removal. On the basis of a new calibration of the ASM 3 with the easy degradable COD measured by respiration simulation runs of this paper have been done. In 2000 a biological phosphorus removal module by the EAWAG was added to the calibrated version of ASM 3 and is now serving the current requirements for modelling the enhanced biological P-removal. Only little experiences with different load situations of large-scale wastewater treatment plants were made with both new models so far. This article reports the experiences with the simulation and calibration of the biological parameters using ASM 3 and the EAWAG BioP Module. Three different large-scale wastewater treatment plants in Germany with different treatment systems will be discussed (Koblenz: pre-denitrification; Hildesheim: simultaneous denitrification with EBPR; Duderstadt: intermediate denitrification with EBPR). Informations regarding the choice of kinetic and stoichiometric parameters will be given.