Wastewater Treatment Plant Model Research Articles

MODELLING OF FULL-SCALE WASTEWATER TREATMENT PLANTS: HOW DETAILED SHOULD IT BE?

Dynamic mathematical modelling of full-scale wastewater treatment plants requires an optimal level of detail to be accurate, effective, but still manageable. Single process models tend to oversimplify the complexities of a large-scale plant and result in erroneous calibrated parameter values or limited predictive power for the model – on the other hand, modelling of every process and process unit is usually impractical, since it cannot be supported by reliable plant data, and requires prohibitive sampling costs and effort. Level of aggregation, settler dimensionality and reactivity, and plug-flow hydraulics were investigated with the help of a sophisticated dynamic modelling package. The results show that there is no general rule or global ‘optimal level’ of modelling – the required modelling detail is a function of influent flow and loading levels, and processes to be simulated (BOD removal, nitrification-denitrification, biological phosphorus removal, settling). In the case of real-life plants, supportable modelling level is often constrained by data availability and reliability.

Modeling and Simulation of Municipal Wastewater Treatment Plants by Activated Sludge

A dedicated software has been developped for the dynamic simulation of a municipal wastewater treatment plant by activated sludge. The primary settler, the aeration tank of canal-type with air injection and the secondary settler are modelled. The biological reaction takes into account the solubility and the biodegradability of the pollution and the sensitivity of the biomass to oxygen. The software results are compared to the response of a full-size plant and of a pilot plant to time-dependent perturbations in flowratc and load, related to human activity and weather conditions.

Interpretation of Experimental Data with Regard to the Activated Sludge Model No.1 and Calibration of the Model for Municipal Wastewater Treatment Plants

The wastewater of the municipal treatment plants Zürich-Werdhölzli (350000 population equivalents), Zürich-Glatt (110000), and Wattwil (20000) have been characterized with regard to the activated sludge model Nr.1 of the IAWPRC task group. Zürich-Glatt and Wattwil are partly nitrifying treatment plants and Zürich-Werdhölzli is fully nitrifying. The mixing characteristics of the aeration tanks at Werdhölzli and Glatt were determined with sodium bromide as a tracer. The experimental data were used to calibrate hydrolysis, heterotrophic growth and nitrification. Problems arising by calibrating hydrolysis of the paniculate material and by measuring oxygen consumption of heterotrophic and nitrifying microorganisms are discussed. For hydrolysis the experimental data indicate first-order kinetics. For nitrification a maximum growth rate of 0.40±0.07 d−1, corresponding to an observed growth rate of 0.26±0.04 d−1 was calculated at 10°C. The half velocity constant found for 12 and 20°C was 2 mg NH4-N/l. The calibrated model was verified with experimental dam of me Zürich-Werdhölzli treatment plant during ammonia shock load.

Modelling wastewater treatment plants through time series analysis

AbstractTime series analysis models are very useful in modelling dynamic systems in science and engineering applications. This class of models is in fact able to represent the dynamic features of physical systems that are subject to often uncontrollable inputs with random components. Wastewater treatment plants are examples of dynamic systems, with inputs (flow, organic loads, etc.) that vary stochastically within more or less wide ranges. The use of stochastic models allows a more detailed representation of the dynamic nature of these systems, while retaining the degree of information contained in most deterministic models.In this paper, time series analysis applications to wastewater treatment plant modelling are presented and discussed. Both univariate and multivariate stochastic processes are applied to sewage treatment plant data, and the results thus obtained are further analyzed and compared with those from “conventional” deterministic models.Specifically, the above mentioned models are analyzed with respect to possible application in the daily operation of sewage treatment plants, by virtue of their predictive capacities and relative ease of determination. Furthermore, these models present other attractive features, such as adaptiveness and the possibility of extracting useful information about the system from the analysis of their structure. Adaptiveness refers to the possibility of continuously improving the model's performance as new information about the system is collected by manual or automatic monitoring. Performance of the models herein identified, and possible applications of these models in real systems are discussed.

Discussion of “ Preliminary Optimal Design Model for Wastewater Treatment Plant ” by Okitsugu Fujiwara (January/February, 1990, Vol. 116, No. 1)

Discussion of “ <i>Preliminary Optimal Design Model for Wastewater Treatment Plant</i> ” by Okitsugu Fujiwara (January/February, 1990, Vol. 116, No. 1)

Closure to “ Preliminary Optimal Design Model for Wastewater Treatment Plant ” by Okitsugu Fujiwara (January/February, 1990, Vol. 116, No. 1)

Closure to “ <i>Preliminary Optimal Design Model for Wastewater Treatment Plant</i> ” by Okitsugu Fujiwara (January/February, 1990, Vol. 116, No. 1)

Temperature profile and heat transfer model for a chemical wastewater treatment plant

AbstractThis paper presents a heat transfer model for equalization, activated sludge, and trickling filter unit processes that can be used to assess the effect of operating temperature on unit process selection, materials of construction selection, and heat retention and cooling requirements. In developing this model, the individual variables that affect the operating temperature of biological systems were first identified. Mathematical relationships were then developed to described system behavior, based on conservation laws and rate equations. The heat transfer models were then used to develop a temperature profile of the two alternative WWTP configurations.

Preliminary Optimal Design Model for Wastewater Treatment Plant

A mathematical programming model for the least-cost design of a wastewater treatment plant is presented for the preliminary screening of projects. This model represents the treatment plant as a network of unit processes and uses a cost function that depends not only on waste removal efficiency, but also on influent flow rate and concentrations of various effluent quality criteria, such as biochemical oxygen demand, phosphorus, and nitrogen. The model also incorporates the concept of generalized bypass piping, allowing a bypass after each unit process, which makes it possible to enhance the flexibility and economy of designs. The proposed approach facilitates a number of important decisions for the optimal design of wastewater treatment plants, especially selection of the combination of unit treatment processes, their sizes and removal efficiency levels, and the flow distribution. Since the cost functions are simplified in this model, more elaborate mathematical programming models should be used to reach a final decision.

Analysis and evaluation of a wastewater treatment plant model by stochastic optimization

A stochastic optimization procedure, Integrated Controlled Random Search, is applied to evaluate the model of a wastewater treatment plant. Equation sequencing and design variable selection algorithms are used to solve the set of equality constraints in a simple manner, offering the right choice of design variables. Subsequently, the sensitivity of the objective function defined in terms of the total construction cost is tested with respect to the design variables selected. The results permit an interpretation of the model structure and allow the shortcomings to be removed before the optimization stage.

An application of adaptive pH-control algorithms based on physico-chemical modelling in a chemical waste-water treatment plant

A pH-process model for a chemical waste-water treatment plant is constructed by applying basic physico-chemical laws. The unknown composition of the wastewater is modelled by a composition of hypothetical chemical species which best describe the titration curves of real liquid samples. The dissociation parameters of the coagulant, aluminium sulphate, is also determined by using appropriate titration curves. The overall pH-model comprises a linear state model of concentrations and an implicit output model describing the physico-chemical equilibrium conditions. The estimation of the hypothetical concentrations is performed by a Kalman-type filtering algorithm obtained with the aid of a certain transformation. Using a non-linear transformation of the estimates, a deviation signal is generated and fed into the PI-controller. A feedforward control loop was connected to the algorithm and results of two simplifications of the algorithm are presented. After tuning by simulation, these algorithm variations we test...

Nonlinear Programming Model of Wastewater Treatment Plant

The optimal design of a wastewater treatment plant involves two complementary aspects—the mathematical model and the optimization technique—both of which have to be equally developed. This was seldom the case in previous literature. A complete mathematical model is described reflecting the operation of a treatment plant including six units (primary settler, aerator, final settler, thickener, anaerobic digester, and vacuum filter). Although many of the basic relationships come from the literature, some new equations and concepts are proposed. Basically, these are based on the disaggregation of the waste load into four components (biodegradable and nonbiodegradable suspended solids, biodegradable dissolved solids, and biomass). The model equations described the evolution of each of these components during biological and physicochemical phenomena occuring in the treatment plant. The development of an efficient optimization method and the results from various runs are reported in a companion paper.

Mathematical modeling and economic optimization of wastewater treatment plants

Mathematical modeling and economic optimization of wastewater treatment plants