Minimum Water Targets Research Articles

Holistic Approach for Design of Minimum Water Networks Using the Mixed Integer Linear Programming (MILP) Technique

Minimum fresh water consumption and wastewater generation in a facility can be achieved when all options for water minimization including source elimination, reduction, reuse/recycle, outsourcing, and regeneration have been considered. This work presents the development of a new generic mixed integer linear programming (MILP) model to holistically minimize fresh water consumption and wastewater generation for systems involving multiple contaminants where the various options for water minimization are simultaneously considered in order to ultimately generate a minimum water utilization network. The MILP model proposed in this work can be used to simultaneously generate the minimum water targets and design the minimum water network for global water-using operations for buildings and industry. This work also includes cases where fresh water concentrations for all contaminants are assumed to be either zero or non-zero. The approach has been successfully implemented in case studies involving an urban building (Sultan Ismail Mosque, UTM) and a manufacturing plant (a chlor-alkali plant).

Generic Graphical Technique for Simultaneous Targeting and Design of Water Networks

Current graphical techniques for design of water networks based on pinch analysis typically separate targeting from network design stage. In addition, most graphical allocation and network design tools that use the cleanest source to satisfy the cleanest demand fail when the flow rate of a demand is met but the mass load is not. This work presents a versatile and generic approach for simultaneous targeting and design of water networks. It includes new heuristics and significant new insights on source and demand allocation composite curves, and it introduces a new visualization tool known as the network allocation diagram (NAD). This approach can generate targets for cases with both flow-rate and mass-load constraints and simultaneously solve complex design problems involving multiple pinches. NAD also allows designers to graphically visualize, explore, evolve, and systematically choose networks that yield either the minimum water targets or the minimum number of streams.

Targeting Multiple Water Utilities Using Composite Curves

The majority of techniques to determine the minimum water targets based on water pinch analysis (WPA) have assumed freshwater as the sole utility that exists at zero concentration. In practice, regenerated water and externally outsourced water such as rainwater, river water, snow, and imported spent water may exist at varieties of concentrations and can be used to reduce freshwater utility. This paper presents new procedures to establish the minimum flow rate targets for multiple water utilities using the source and sink composite curves. The work offers significant new insights into systematic placement of multiple new utilities through water outsourcing in the context of WPA.

A holistic framework for design of cost-effective minimum water utilization network

Water pinch analysis (WPA) is a well-established tool for the design of a maximum water recovery (MWR) network. MWR, which is primarily concerned with water recovery and regeneration, only partly addresses water minimization problem. Strictly speaking, WPA can only lead to maximum water recovery targets as opposed to the minimum water targets as widely claimed by researchers over the years. The minimum water targets can be achieved when all water minimization options including elimination, reduction, reuse/recycling, outsourcing and regeneration have been holistically applied. Even though WPA has been well established for synthesis of MWR network, research towards holistic water minimization has lagged behind. This paper describes a new holistic framework for designing a cost-effective minimum water network (CEMWN) for industry and urban systems. The framework consists of five key steps, i.e. (1) Specify the limiting water data, (2) Determine MWR targets, (3) Screen process changes using water management hierarchy (WMH), (4) Apply Systematic Hierarchical Approach for Resilient Process Screening (SHARPS) strategy, and (5) Design water network. Three key contributions have emerged from this work. First is a hierarchical approach for systematic screening of process changes guided by the WMH. Second is a set of four new heuristics for implementing process changes that considers the interactions among process changes options as well as among equipment and the implications of applying each process change on utility targets. Third is the SHARPS cost-screening technique to customize process changes and ultimately generate a minimum water utilization network that is cost-effective and affordable. The CEMWN holistic framework has been successfully implemented on semiconductor and mosque case studies and yielded results within the designer payback period criterion.

Application of the water cascade analysis technique for water minimisation in a paper mill plant

The Water Cascade Analysis (WCA) technique was used to identify opportunities for reduction in freshwater usage as well as wastewater generation and to assist in the retrofit of an existing paper mill water distribution network. This procedure involves three key steps; i.e., a global analysis of the present water distribution and consumption, setting the baseline minimum water targets using WCA technique and retrofit of water network to achieve the minimum water targets. Notwithstanding the extensive water recycling currently employed in the paper mill, this study identified a potential scope of reducing 13.3% freshwater and 13.3% wastewater. Water reduction represents a total potential annual savings of RM 595,232, taking into account the raw water and wastewater treatment costs, pumping and chemical costs.

Assessing the sensitivity of water networks to noisy mass loads using Monte Carlo simulation

For many water-intensive processes, water reuse can reduce water consumption as well as effluent generation. Process integration approach based on graphical pinch methodology for targeting and water network synthesis is often employed. The integrity of water network design to achieve the minimum water targets is highly sensitive to the availability of reliable process data. Existing network design process, however, assume that process data are fixed and well-defined, whereas the actual operating conditions such as water flowrate and the corresponding mass loads may fluctuate over time. These fluctuations in processing conditions can lead to process disruptions and product quality problems. This work demonstrates the use of Monte Carlo simulation in assessing the vulnerability of water networks to noisy mass loads. A case study illustrates the procedure of selecting the most robust network configuration from three alternative designs that achieve comparable water savings.

Water pinch analysis for an urban system: a case study on the Sultan Ismail Mosque at the Universiti Teknologi Malaysia (UTM)

This paper describes how the water cascade analysis (WCA) technique, based on the pinch analysis concept, was adapted to establish the minimum water targets for the Sultan Ismail Mosque at the Universiti Teknologi Malaysia. The WCA is a numerical alternative to the graphical water targeting technique known as a water surplus diagram. Two cases were analysed using WCA to predict potential savings with reuse as well as with reuse and regeneration. The results were compared with the savings predicted via a conventional water management solution. The conventional system predicted reductions of 25% fresh water and 19.8% wastewater. The WCA technique predicted savings of 65.1% fresh water and 51.5% wastewater with reuse only, and up to 85.5% fresh water and 67.7% wastewater with reuse and regeneration. The WCA technique based on the pinch analysis concept can rapidly yield accurate minimum water targets, pinch-point locations and water allocation targets for an urban water network.

Targeting the minimum water flow rate using water cascade analysis technique

AbstractThis work presents the water cascade analysis (WCA) as a new technique to establish the minimum water and wastewater targets for continuous water‐using processes. The WCA is a numerical alternative to the graphical water targeting technique known as the water surplus diagram. The WCA is to the water surplus diagram in water pinch analysis (WPA) as problem table analysis (PTA) is to the grand composite curves in heat pinch analysis. By eliminating the tedious iterative steps of the water surplus diagram, the WCA can quickly yield accurate minimum water targets, pinch point locations, and water allocation targets for a maximum water recovery (MWR) network, thereby offering a key complementary role to the water surplus diagram in the synthesis of water network. As in the case of the water surplus diagram, the WCA is not limited to mass‐transfer–based operations and is applicable to a wide range of water‐using operations. © 2004 American Institute of Chemical Engineers AIChE J, 50: 3169–3183, 2004