Fabricio Nápoles-Rivera

A systems-integration approach to the optimization of macroscopic water desalination and distribution networks: a general framework applied to Qatar’s water resources

The objective of this article is to introduce an optimization-based approach for the integrated design and operation of macroscopic water networks. A structural representation approach is developed to embed all potential configurations of interest. This representation accounts for water resources, desalination plants, water users, wastewater treatment facilities, and storage. Water recycle/reuse is enhanced via the use of treated water. Water utilization is improved by minimizing the losses of discharged water resulting from the linkage of power plants and thermal desalination plants and the lack of integration between water production and consumption. Excess water is saved in storage systems or injected in aquifers for strategic (long-term) storage. The developed approach also accounts for the economic values of water uses and storage and for the cost of water production and allocation. An optimization formulation is developed and solved to determine the optimal operation of the infrastructure. The solution also determines the optimal monthly allocation and storage of water resources. A case study is solved for managing the water resources in the State of Qatar while accounting for desalination, distribution, and storage. The solution indicates that storage in tanks reaches its maximum capacity in less than a month while storage in aquifers continues throughout the year as a strategic step towards water security. The solution also illustrates the need to treat wastewater in addition to using desalination of seawater. The output water streams with different qualities are assigned to proper destinations.

An optimization approach for the synthesis of recycle and reuse water integration networks

This paper presents a convex mathematical programming model for the global optimization of recycle/reuse water networks. The model is based on a general superstructure that includes the major configurations of interest such as segregation, mixing, recycle, bypass, and treatment of streams needed to satisfy the process and environmental constraints. The basic idea of the model formulation is to consider component balances, treating as optimization variables the individual flowrates. This formulation avoids the bilinear terms that appear when the compositions and total flowrates are considered as optimization variables. The objective function consists in the minimization of the total annual cost including the fresh sources costs, the treatment units costs (which are reformulated as convex functions) and the piping costs. Four examples problems are solved to show the applicability of the proposed model.

Optimal reconfiguration of a sugar cane industry to yield an integrated biorefinery

The sugar cane production is one of the main economic activities of the agriculture sector in several places around the world. Nowadays, the sugarcane production zones face different technologic, economic, and social problems that impact negatively their profitability. The low price of sugar in the market demands the search of alternatives; being the bioethanol production from resides of the sugar cane industry an attractive option. This way, this paper presents a new approach for using the residues from the sugar cane industry to yield a sustainable biorefinery. In this approach, process integration techniques have been implemented to optimize the overall process. A case study from the State of Michoacán in Mexico is presented, where the proposed approach shows significant economic, environmental, and social benefits.

Simultaneous design of water reusing and rainwater harvesting systems in a residential complex

Abstract This paper introduces an optimization formulation to design residential water systems that satisfy the water demands in a housing complex involving rainwater harvesting, storage and distribution as well as the simultaneous design of water networks for recycling, reusing, regenerating and storing reclaimed water. The design task is considered as a multi-objective optimization problem where one objective is the minimization of the fresh water consumption and the other objective is the minimization of the total annual cost. The proposed model accounts for the variability in the water demands through the different hours of the day and for the different seasons of the year. The seasonal dependence of the rainwater has also been considered in the optimization model. A case study for the city of Morelia in Mexico is presented. The results show that significant reductions can be obtained in the total fresh water consumption and in the total cost.

Optimal design of sustainable water systems for cities involving future projections

Abstract Water scarcity is one of the main concerns of several countries around the world. In this context, several approaches have been proposed for resource conservation and available water augmentation through specific actions such as process intensification and the use, reclamation, reuse, and recycle of alternative water sources. Nonetheless, there are no reported methodologies optimizing the multiannual planning of water usage, discharge, reclamation, storage and distribution in a macroscopic system considering natural and alternative water sources. In this paper, a multi-period mathematical programming model for the optimal planning of water storage and distribution in a macroscopic system is presented. The model addresses important factors such as population growth, change in the time value of money and change in the precipitation patterns. The proposed model is applied to the case of a Mexican city. The results show important advantages from the economic and sustainability points of view.

Optimal design of domestic water-heating solar systems

This paper presents a multi-criteria optimization formulation for the optimal design of a water-heating system for homes. The proposed model accounts for the available solar radiation in the specific place where the solar collector is installed and the hot water demands. The goal is to target economic and environmental objectives by optimizing the design and operating conditions including the optimal hot water storage and distribution. The proposed model is applied to several scenarios for homes with different inhabitants and in various cities in Mexico. The results show that the location has significant effects on the optimal design and operation of the water-heating solar system.

Optimal design of reusing water systems in a housing complex

The excessive demand for water worldwide has promoted the development of strategies for its efficient use. The industrial sector has developed several water recycle and conservation strategies that have led to reduction in the fresh water consumption and the wastewater discharged to the environment. Comparable environmental and economic benefits can accrue as a result of adopting similar water strategies in the residential sector. This paper proposes an optimization formulation for the design and operation of networks for the recycle, regeneration, and storage of water in residential complexes. Segregation of wastewater streams is considered to avoid the mixing of streams with different qualities prior to treatment and recycle. The optimization model accounts for the simultaneous minimization of the total annual cost and the fresh water consumption. A case study for a residential complex of the city of Morelia Michoacán in Mexico is used to apply the proposed approach. The results show significant economic and environmental benefits (such as reduction of natural resources consumption and waste generation) for the implementation of the proposed approach. The developed optimization model also enables tradeoff between the considered objectives.

Stochastic Optimal Control for the Treatment of a Pathogenic Disease

Abstract Mathematical modeling as a tool for the treatment of a pathogenic disease has been widely proposed in the literature. Most of the modeling approaches represent the immune system dynamics as deterministic optimal control problems. Deterministic approaches, however, do not consider uncertainties in model parameters and variability among different individuals. To include uncertainties in the formulation, the aim of this paper has been using stochastic optimal control theory to develop protocols for the treatment of human diseases. We model time dependent uncertainties as Ito processes. That results in an optimal control problem where the constraints are stochastic differential equations and the objective function is an integral equation. The optimality conditions of the problem are obtained through the stochastic maximum principle, which results in a boundary value problem. The boundary value problem is solved iteratively by using a combination of the gradient method and a stochastic version of the Runge-Kutta method derived in this work. As an illustration of the proposed approach, we solve a mathematical model to determine the evolution of a generic disease and obtain regimens for applying therapeutic agents in a manner that maximizes efficacy while minimizing side effects. We show that stochastic optimal control theory can indeed help develop clinical insight in treating illness under uncertainties in model parameters.

Optimal reconfiguration of water networks based on properties

This paper presents a mathematical programming model for the reconfiguration of existing water networks based on the stream properties that impact the performance of the process units and the environment. To develop an improved configuration, the model simultaneously evaluates the repiping of the existing network through the placement/reassignment of the existing treatment units, and the addition of new treatment units while addressing environmental constraints. The model also accounts for the options of process modification and increased capacity of the plant. The objective function of the optimization model seeks to minimize the total annualized cost of the system which incorporates the capital investment associated with process retrofitting and the operating cost which includes the cost of fresh resources. The applicability of the proposed model is illustrated through several case studies.

An Optimal Planning for the Reuse of Municipal Solid Waste Considering Economic, Environmental and Safety Objectives

Abstract Nowadays, the waste generation is a serious problem mainly in the countries with inefficient waste management systems. However, some waste can be reused as raw material for several products using a set of available technologies. In this context, several options to attack this problem have been implemented, but just a few alternatives consider the waste management as an integral part in the supply chain. This way, several technical, environmental and economic aspects have been taken into account for the assessment of the entire supply chain; although, the incorporation of safety criteria into the assessment of the supply chain focused in municipal solid waste have not been implemented in previous papers. Therefore, in this paper is proposed a mathematical programming model for the optimal planning of the reuse of municipal waste to maximize the economic benefits considering sustainability and safety criteria simultaneously. This methodology considers several phases: the separation of waste, distribution of waste to processing facilities, processing of waste to obtain useful products and distribution of products to consumers. Additionally, the safety criteria are based on the fatalities associated with the supply chain for the waste management. The problem is formulated as a multi-objective problem that considers three different objectives: the net annual profit, the amount of reused waste and the total fatalities generated with the considered risks. Results show that it is possible to implement a distributed processing system to reuse municipal waste in an economically attractive way. In addition, results can be used for governments to take decisions about the waste disposal and define the amount of waste that must be reused to obtain several products. It should be noted that results include the supply chain configuration. In addition, in future works this methodology can be extended to problems focused in supply chain design and retrofit simultaneously.