Design Of Wastewater Treatment Systems Research Articles

MODELLING OF MASS TRANSFER IN WASTEWATER FACILITIES

Problem statement. The design of wastewater treatment systems is a complex process and requires the use of special mathematical models. As a rule, empirical models are used at the stage of designing structures of water drainage systems, which allow obtaining only an “integral” characteristic of the efficiency of wastewater treatment. But in a number of cases, it is important to have information about the spatial distribution of the impurity concentration in the structure. To solve this problem, you need to have three-dimensional mathematical models. In the future, there is a shortage of such models, so the creation of three-dimensional multifactorial models for the analysis of the efficiency of drainage system structures is an urgent task. The purpose of the article. Development of a three-dimensional numerical model for the analysis of the mass transfer process to determine the impurity concentration in the clarifier. Methodology. The analysis of impurity concentration fields in the clarifier is carried out by numerical integration of the three-dimensional equation for the velocity potential and the three-dimensional equation of the convective-diffusion transport of the impurity. For the numerical integration of the Laplace equation for the velocity potential, the variable-triangular method and the Liebmann method are used. Finite-difference splitting schemes are used for numerical integration of the three-dimensional equation of convective-diffusion transport of impurities. Scientific novelty. A dynamic multifactorial numerical model was created for the analysis of the process of mass transfer of impurities in a settling tank by conducting a computational experiment. Practical value. The built multifactorial numerical model makes it possible to analyze the efficiency of wastewater treatment in clarifiers that have a complex geometric shape and cannot be calculated on the basis of existing engineering methods. Conclusions. On the basis of the developed three-dimensional numerical model, a computer code was created, which allows you to quickly obtain information about the distribution of the impurity concentration in the settling tank.

Computer 3D Modeling of the Process of Wastewater Treatment in a Settling Tank

Purpose. Settling tanks are widely used in technological schemes of wastewater treatment. As a rule, horizontal settling tanks are used in practice. However, to increase the efficiency of water treatment in a horizontal settling tank, additional elements can be used, which are placed in different places in the structure. When reconstructing such structures or designing them for new facilities, it is necessary to assess the efficiency of the settling tanks under different operating conditions. To solve this problem, mathematical models play an important role, including conducting physical experiments, which requires considerable time to obtain results. In the case of mathematical modeling of the water treatment process in a sedimentation tank, two problems need to be solved: the hydrodynamic problem and the mass transfer problem. The main purpose of this paper is to develop a 3DCFD model for calculating the impurity concentration field in a sedimentation tank. Methodology. A dynamic multifactorial numerical model was developed for computer calculation of the wastewater treatment process in a settling tank. The hydrodynamics of the wastewater flow in the settling tank was calculated on the basis of a three-dimensional equation for the velocity potential (potential motion model). The calculation of the impurity concentration field in the settling tank was determined by numerical integration of the three-dimensional mass transfer equation. This equation takes into account the non-uniformity of the flow velocity field in the settling tank, the diffusion process, and the gravitational deposition of the impurity in the structure. The numerical integration of the modeled equations was carried out by using finite-difference splitting schemes. Findings. The software implementation of the constructed mathematical model was carried out. The results of a computational experiment to study the process of wastewater treatment in a settling tank with visualization of the calculation results are presented. Originality. A multifactorial three-dimensional CFD model has been developed that allows to quickly assess the efficiency of the settling tank. Practical value. The proposed CFD model can be used in calculations in the design of wastewater treatment systems or to determine the efficiency of wastewater treatment under new operating conditions.

MATTI - a multi-criteria decision analysis framework for assessing wastewater treatment technologies.

The variety of available technologies and the low investment power in sanitation services, especially in regions with low and emerging economies, makes the selection of an optimal wastewater treatment system design an even more complex task for decision-makers. Thus, this study aimed to develop a multi-criteria analysis-based tool to support decision-making on the optimal wastewater treatment technology for the needs and priorities of each region, the Most Appropriate Treatment Technology Index (MATTI). The methodology to apply the MATTI comprises five steps: select suitable technologies; determine the effluent quality parameters; define the most relevant variables for design; normalize and define the weighting criteria; and calculate the level of compliance (0-1, on an increasing scale of suitability). To validate the tool, two different scenarios and seven variables for the Brazilian context were simulated. Different sets of technologies scored above 0.75, and were classified as highly recommended, according to the weight criteria attributed to each scenario. MATTI not only contributed to improving the decision-making process, but also with a more global vision of the parameters to be considered in the selection of technologies to meet the needs and priorities.

Design methodology for sewage water treatment system comprised of Imhoff ‘s tank and a subsurface horizontal flow constructed wetland: a case study Dakhla Oasis, Egypt

In this study, in order to reuse the treated wastewater in irrigation in rural areas, a new sewage water treatment system comprised of primary treatment Imhoff’s tank, Hama drying basins, inlet well, a subsurface horizontal flow constructed wetland (HSFW), water control device, and a groundwater tank is proposed and designed in Dakhla Oasis western desert of Egypt. The proposed system serves a population of 5000 capita with a designed discharge of 750 m3 d−1. The kinetic parameters involved macrophyte organisms, media forms, water level, hydraulic retention time (HRT), and hydraulic loading rate (hl) for the system were selected to achieve an efficient wastewater treatment system design. Imhoff’s tank is sized as the primary sedimentation efficiency is 30%, and HSFW is sized based on the first-order kinetics (k-C∗) model, and total hydraulic design theory. The air temperatures were 29.7 °C and 13.8 °C in summer and winter respectively, influent pollutant concentrations after primary sedimentation for BOD, fecal coliforms (FC), total nitrogen (TN), and total phosphorus (TP) were 210 mg L−1, 108 CFU100 mL−1, 30 and 7 mg L−1, respectively. The expected designed effluent BOD and FC were 30 mg L−1 and 1000 CFU100 mL−1 respectively. The results show that FC removal controls the area of the HSFW (2.87 ha), 6 units of reed (Phragmites Australis and Papyrus) plants each one is 66 m with hl of 2.6 cm d−1 and HRT of 6.91 d. The expected overall removal efficiencies for BOD and FC were 85.7%, and 99.9% respectively.

3D MODELING OF BIOLOGICAL WASTEWATER TREATMENT IN AERATION TANK

Purpose. The main purpose of the article is to develop a 3D CFD model for modeling the process of biological wastewater treatment in an aeration tank. Methodology. For mathematical modeling of the process of biological wastewater treatment in the reactor, taking into account the flow hydrodynamics, geometric shape of the aeration tank, convective-diffusion transfer of the substrate and activated sludge, a 3D CFD model was built. The model is based on the three-dimensional equation of motion of an ideal liquid and the equation of mass conservation for the substrate, activated sludge. The field of sewage flow rate in the aeration tank is calculated based on the velocity potential equation. The process of biological transformation of the substrate is calculated on the basis of the Monod model. The splitting scheme was used for numerical integration of the equations of convective-diffusion transfer of activated sludge and substrate. The splitting is carried out in such a way to take into account the transfer of substrate (activated sludge) in only one direction at each step of splitting. The calculation of the unknown value of the substrate (activated sludge) concentration is carried out according to an explicit scheme. The Richardson method is used to numerically integrate the three-dimensional equation for the velocity potential, and the unknown value of the velocity potential is calculated by an explicit formula. Euler's method is used for numerical integration of equations describing the process of substrate transformation and change in activated sludge concentration (Monod model). Findings. The software implementation of the constructed 3D CFD model is carried out. A description of the structure of the developed software package is provided. The results of a computer experiment to study the process of wastewater treatment in an aeration tank with additional elements are presented. Originality. A new multifactor 3D CFD model has been developed, which allows quick assessing the efficiency of biological treatment in an aeration tank. Practical value. The constructed 3D CFD model can be used to analyze the efficiency of the aeration tank under different operating conditions at the stage of sketch design of wastewater treatment systems.

A guarantee rate optimization model for wastewater treatment system design under uncertainty

AbstractWe consider a design problem for wastewater treatment systems that considers uncertainty in pollutant concentration levels at water sources. The goal is to optimize the selection of treatment technologies and pipeline connections, so that treated wastewater can achieve specified effluents discharge limits as well as possible. We propose a new two‐stage model to optimize a set of guarantee levels, that is, the maximum concentration level of source pollutants for which treated wastewater can be compliant with discharge limits. In the first stage, treatment technologies and pipeline connections are selected. In the second stage, when pollutant concentration levels are revealed, wastewater distribution and mixing are determined. A key attractiveness of the proposed guarantee rate optimization model is that it can be simplified into a single‐stage mixed‐integer linear program. In our numerical experiments based on real‐world pollutants data, the guarantee rate model demonstrates its advantages in terms of computational efficiency, scalability and solution quality, compared with the standard probability maximization model. Finally, the methodology proposed in this paper can also be applied to other two‐stage problems under uncertainty with similar uncertainty characteristics.

Effect of constituent processes and conditions of the hybrid TiO2 photocatalytic system on 1,4-dichlorobenzene degradation

• Improvement of the degradation of 1,4-dichlorobenzene were studied in the new system. • The system was modified in terms of system configurations and operating conditions. • Any unit processes available showed poor photocatalytic degradation performance. • The opposite occurred for the system using multiple processes with proper conditions. • Four intermediate products seemed to be involved in the degradation process. Understanding the performance and mechanism of the degradation of various contaminants is essential for the effective design of wastewater treatment systems. This study examined the degradation of 1,4-dichlorobenzene in a photocatalytic system, which embedded TiO 2 particles (as a thin film) on alumina balls (as a solid support). Decomposition of the parent compound was assessed by introducing a TiO 2 photocatalyst, microwave irradiation, and ultraviolet irradiation jointly or separately (in terms of the system configuration) with and without an adjustment for the microwave intensity, pH, and hydrogen peroxide levels (in terms of the operating conditions) to the photocatalytic system. The results showed that the photocatalytic system adopting multiple processes concomitantly improved the degradation performance of the parent compound that was resistant to the single-unit processes. On the other hand, the decomposition efficiency was increased further with the sophisticated control of the operating conditions, specifically the pH and hydrogen peroxide levels. A dechlorination process as well as substitution and addition reactions involving the hydroxyl radical appeared to occur in the degradation pathway to produce four degradation products from the parent compound. The significance of this study lies in the introduction of a systematic approach to optimizing the operating conditions that facilitate the decomposition efficiency in a given photocatalytic system at no extra cost.

A Review of Pretreatment and Wastewater Treatment System Design in Methanol Production Facilities

A Review of Pretreatment and Wastewater Treatment System Design in Methanol Production Facilities

Design of the wastewater treatment system of an office building

The MIPA Tower office building, an eleven-storey building, which is located in the area of Institut Teknologi Sepuluh Nopember Surabaya, is under construction. The building will be utilized for offices, classrooms, and laboratories. In the operation of the building, domestic and laboratory wastewater will be produced. This wastewater contains compounds that can pollute the environment. A design of domestic and laboratory wastewater treatment system is conducted. The system comprises of a neutralization tank, a grease trap, an equalization tank, an anaerobic filter, and an activated carbon and silica sand filter.
 The steps of the design are (i) collecting primary data and secondary data, (ii) calculating the engineering design, (iii) drawing the Detailed Engineering Design (DED), and (iv) calculating the bill of quantity and budget.
 The conclusion of this design is that the treatment plant will treat a mixture of domestic and laboratory wastewater. The dimension of each unit is as follows: (i) the neutralization tank (Ø = 0.65 m, H = 0.43 m), (ii) the grease trap (4 m x 2 m x 1 m), (iii) the equalization tank (10.5 m x 5.5 m x 2.5 m), (iv) the septic tank (4.5 m x 4 m x 2.5 m), (v) the six-compartment anaerobic filter (2.25 m x 4 m x 2.5 m), and (vi) the filter with activated carbon (H = 50 cm), silica sand (H = 150 cm), and gravel (H = 10 cm), with the diameter of the tank is 1.5 m.

Improvement of Radioactive Wastewater Treatment Technology in Inland AP1000 Nuclear Power Plant

In order to meet the standard of effluent radioactive wastewater from inland nuclear power plant, the improvement of radioactive wastewater treatment technology in inland AP1000 nuclear power plant is determined. Based on the origin radioactive wastewater treatment technology of AP1000 nuclear power plant and the advanced radioactive wastewater treatment technology, an Chemical precipitation + CsTreatRR+ Ion exchange technology is proposed and evaluated. The improved technology can provide reference for inland nuclear power plant radioactive wastewater treatment system design.

Sorption of Emerging Organic Wastewater Contaminants to Four Soils

Conventional onsite wastewater treatment system design relies on a septic tank and soil treatment unit (STU) for treatment of wastewater and integration of the final effluent into the environment. Organic water contaminants (OWCs), chemicals found in pharmaceutical drugs, detergents, surfactants, and other personal care and cleaning products, have been observed in septic tank effluent and the environment. Sorption of OWC mass to soil is a key mechanism in the removal and retardation of many of these chemicals in effluent as it travels through an STU. The primary purpose of this study was to investigate the relationship between the fraction of organic carbon of soil and the equilibrium sorption partitioning coefficient of a selected group of relevant and diverse OWCs. A secondary goal is to evaluate current methods of modeling the sorption of selected OWCs in soil. Five point Freundlich isotherms were constructed from equilibrium sorption batch tests for target OWCs with four different soils. For soils with organic carbon fraction between 0.021 and 0.054, Kd values were calculated between 60 and 185 for 4-nonylphenol, 75 to 260 for triclosan, 115 to 270 for bisphenol-A, 3 to 255 for 17β-estradiol, 40 to 55 for 17α-ethynylestradiol, and 28 to 70 for estrone. An empirically derived, direct relationship between foc and Kd may be a useful approach to estimating sorption for a soil based on organic carbon content.

Photovoltaic solar cells industry wastewater treatment

Nowadays, in the photovoltaic (PV) industry there still remains a huge potential to be exploited, where markets are dominated by crystalline silicon PV-based cells. However, in the future it is expected that thin films PV will have a larger market share. Until recently, the prevailing technology based on mono-crystalline silicon has been gradually exceeded by poly-silicon technology due to its lower production cost. In PV industry, solar-graded silicon is the main material used in manufacturing process. In this industry, manufacturing and production processes require large amounts of water that result in important discharged industrial effluents containing different pollutants such as hydrogen fluorides, suspended solids, mixed acids, SiO2, and high oxide particles. Among discharged pollutants, the hydrofluoric acid is significantly used in photovoltaic’s (PV) manufacturing for both quartz cleaning and wafer etching. In fact, wastewaters from PV industries have high concentrations of fluoride, typically in a range of 500–2,000 mg/L. They are considered highly toxic and need to be strictly monitored and regulated. Three production phases that generate the highest flow of wastewaters are texturing (multi-crystalline silicon wafers need a mixture of HF/HNO3 dilution and also a hot caustic solution with IPA used for the multi-crystalline wafers mixture), etching, and formation of PV cells. Phosphorus diffusion leads to formation of phosphorus silicate layer that needs to be eliminated by means of hydrofluoric acid (HF) application. Classification of effluents from a point of source, concentration, chemical, or composition feature is compared. Wastewater treatment optimization is often conducted and we discussed major treatment methods in solar cells manufacturing: treatment of HF discharges, neutralization, and collection of isopropanol discharges. The article discusses design of wastewater treatment system that is operational in practice.

A practical encounter with model-based optimum design of wastewater treatment systems – applied to High Purity Oxygen aeration

A practical encounter with model-based optimum design of wastewater treatment systems – applied to High Purity Oxygen aeration

Evaluation of case-based design principles in the design of Soche wastewater treatment plant, Blantyre, Malawi

This paper evaluates case-based design principles in the design of Soche wastewater treatment works (WWTW) in the city of Blantyre, Malawi. According to the Case Study Manager in the ED-WAVE tool, a similar case to both dry season and wet season conditions of Soche plant is Municipal Case 6 in Greece. The raw material at Municipal Case 6 in Greece is raw municipal sewage where the typical wastewater parameters are BOD5, and TSS. The treatment target is BOD5, and TSS reduction. The study confirmed the practical use of case-based design principles in the design of wastewater treatment systems, where after encountering a new situation; already collected decision scenarios (cases) are invoked and modified in order to arrive at a particular design alternative. What is necessary, however, is to appropriately modify the case arrived at through the Case Study Manager in order to come up with a design appropriate to the local situation taking into account technical, socio-economic and environmental aspects.

ED-WAVE tool design approach: Case of a textile wastewater treatment plant in Blantyre, Malawi

The ED-WAVE tool is a PC based package for imparting training on wastewater treatment technologies. The system consists of four modules viz. Reference Library, Process Builder, Case Study Manager, and Treatment Adviser. The principles of case-based design and case-based reasoning as applied in the ED-WAVE tool are utilised in this paper to evaluate the design approach of the wastewater treatment plant at Mapeto David Whitehead & Sons (MDW&S) textile and garments factory, Blantyre, Malawi. The case being compared with MDW&S in the ED-WAVE tool is Textile Case 4 in Sri Lanka (2003). Equalisation, coagulation and rotating biological contactors is the sequencing of treatment units at Textile Case 4 in Sri Lanka. Screening, oxidation ditches and sedimentation is the sequencing of treatment units at MDW&S textile and garments factory. The study suggests that aerobic biological treatment is necessary in the treatment of wastewater from a textile and garments factory. MDW&S incorporates a sedimentation process which is necessary for the removal of settleable matter before the effluent is discharged to the municipal wastewater treatment plant. The study confirmed the practical use of the ED-WAVE tool in the design of wastewater treatment systems, where after encountering a new situation; already collected decision scenarios (cases) are invoked and modified in order to arrive at a particular design alternative. What is necessary, however, is to appropriately modify the case arrived at through the Case Study Manager in order to come up with a design appropriate to the local situation taking into account technical, socio-economic and environmental aspects.

Towards cleaner technologies: emissions reduction, energy and waste minimisation, industrial implementation

This editorial introduces and provides an overview of a Special Issue dedicated to the jubilee 10th Conference of Process Integration, Modelling and Optimization for Energy Saving and Pollution Reduction—PRES’07. It contains thirteen selected papers covering various fields of cleaner technologies and environment policy problems. The technologies address recent developments in CO2 capture in Combined Cycle power plants, CO2 reduction in pulp and paper mills, process efficiency increases combined with energy savings at a mill, distillation separation enhancements and emissions control at gas plants, pre-combustion decarbonisation for polygenertion from fossil fuels, minimisation of CO2 emissions in steam and power plants, a study of co-pyrolysis of biomass and plastic wastes, waste-to-energy system design (with a focus on incineration and gasification technologies), optimal design of wastewater treatment systems, and integrated production of sugar and biofuels from sugar beet. Among these topics, The Special Issue includes demonstration of the technologies in the form of Advanced Case studies.

Linear program-based algorithm for the optimal design of wastewater treatment systems

This paper presents a new approach for the optimal design of distributed wastewater treatment networks with multiple contaminants. It consists of a two-stage solution strategy. In the first stage, a decomposition method is employed that replaces the general non-linear program (NLP) by a succession of linear programs, one for each treatment unit. In the second stage, the resulting network is used as a starting point for the solution of the general NLP by a local optimization solver. The decomposition process considers a specific substructure, where it is assumed that the wastewater streams go through the treatment units in sequence. To consider all combinations, the two-stage solution strategy is applied as many times as the number of possible sequences. This allows considering multiple and structurally different starting points, thus increasing the probability of finding global optimal solutions. The results have shown that the proposed approach can find better solutions than other approach reported in the literature, however with a drawback of being more demanding computationally.

An efficient heuristic procedure for the optimal design of wastewater treatment systems

This paper presents a new approach for the optimal design of wastewater treatment systems. An algorithm that can be divided in two parts is proposed for finding global optimal solutions to the problem. The first part comprises a new linear program formulation that is used to generate good starting points for the solution of the general non-linear program (second part). Since the starting point is dependent on the treatment sequence, all possible treatment sequences are considered and thus multiple starting points are generated. The best solution of the several non-linear problems that are solved is then assumed to be the global optimal solution, although there is no theoretical guarantee that this is so. The proposed algorithm has been compared to a global optimisation solver on a set of example problems taken from the literature and the results show that the same global optimal solutions can be obtained in significantly less time when our approach is used.

A MATLAB toolbox for solving acid-base chemistry problems in environmental engineering applications

A MATLAB toolbox incorporating several computer programs has been developed in an attempt to automate laborious calculations in acid-base chemistry. Such calculations are routinely used in several environmental engineering applications including the design of wastewater treatment systems and for predicting contaminant fate and transport in the subsurface. The computer programs presented in this study do not replace student thinking involved in formulating the problem solving strategy but are merely tools that simplify the actual problem solving process. They encompass a wide variety of acid-base chemistry topics including equilibrium constant calculations, construction of distribution diagrams for mono and multiprotic systems, ionic strength and activity coefficient calculations, and buffer index calculations. All programs are characterized by an intuitive graphical user interface where the user supplies input information. Program outputs are either numerical or graphical depending upon the nature of the problem. The application of this approach to solving actual acid-base chemistry problems is illustrated by computing the pH and equilibrium composition of a 0.1 M Na2CO3 system at 30°C using several programs in the toolbox. As these programs simplify lengthy computations such as ionization fraction and activity coefficient calculations, it is hoped they will help bring more complicated problems to the environmental engineering classroom and enhance student understanding of important concepts that are applicable to real-world systems. The programs are available free of charge for academic use from the authors. © 2005 Wiley Periodicals, Inc. Comput Appl Eng Educ 13: 257–265, 2005; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20051

On-Site Wastewater Treatment System Design for a Marshy Urban Area in Nigeria

On-Site Wastewater Treatment System Design for a Marshy Urban Area in Nigeria