Implications of desalination for water resources in China — an economic perspective

China is a country with severe water shortages. Water is becoming scarcer due to population growth, industrialization and urbanization. Recent studies show that by the next 50 years water resources per capita will go down to around 1700 m³, which is the threshold of severe water scarcity. Especially in North China, water shortage has become a critical constraint factor for socioeconomic development in the long run. To solve or eliminate water shortage problems, seawater desalination draws more and more attention as an alternative water supply source. The objective of the study is to assess the potential of desalination as a viable alternate water source for China through analysis of the costs of desalination, the water demand and supply situation as well as water pricing practices in China. Based on the investment costs and estimated operation and maintenance costs, an economic appraisal for the costs of desalination for two main processes, MSF and RO, has been conducted. The study shows that there is a decline of unit cost of desalination over time and the average unit cost of the RO process was lower than that of the MSF process. A unit cost of 0.6 $/m³ for desalting brackish water and 1.0 $/m³ for seawater are suggested to be appropriate for the potential application of desalination in China. Future trends and challenges associated with water shortages and water prices are discussed, leading to conclusions and recommendations regarding the role of desalination as a feasible source of water for the future.     

Forecasting the economic costs of desalination technology

Government policy, in the form of grants and contracts for desalination technology, has had a major impact on steadily declining costs of desalination. The process, reverse osmosis (RO), exhibits economies of scale, which increases its feasibility as a water treatment technology for large populations. Ultrafiltration, an RO pre-treatment, also shows economies of scale. The real economic costs of desalination technology can be forecast using an ARIMA model. If these costs fall below those of conventional water treatment processes, RO and ultrafiltration become competitive with conventional water treatment technology. Our ARIMA forecasts are validated by using independent plant level cost data.     

Designing of an electrodialysis desalination plant

The design and operation of an electrodialysis desalination process are based on a set of fixed and variable parameters such as stack construction, feed and product concentration, membrane properties, flow velocities, current density, recovery rates, etc. These parameters are interrelated and may be rather different for different applications. For an efficient operation of an electrodialysis desalination plant, the process has to be optimized in terms of overall costs considering component properties and operating parameters. In this study the design and optimization of an electrodialysis plant to be used for brackish water desalination has been treated. The required equations were derived or, as in the case of the limiting current density, were experimentally determined. As an example, an electrodialysis plant with a sheet-flow stack construction and given feed solution composition was designed and optimized in terms of overall costs and the sensitivities of the different parameters are analyzed.     

Comparative cost analysis of nuclear versus oil-fired dual-purpose desalination plants

Prospects for the application of nuclear energy to sea water desalination for the Kingdom of Saudi Arabia have been evaluated here based only on economic considerations. Updated capital costs of power plants and current prices of oil and nuclear fuel are used. Information on the Kingdom's water demand and current status of water desalination is provided. A comparison is also made of costs of water production from power-cum-desalination nuclear plants versus oil-fired plants. Only dual-purpose nuclear plants are considered because of their overall economic advantages over single purpose (water only) plants. The scope of available data and information can not be provided in such detail as to allow for system planning or for a site-specific feasibility study. However, the results provide guidelines for more in-depth analysis. The results show that, compared to oil-fired plants, there is a net saving of costs in using nuclear plants for desalination. If interest on capital is disregarded in calculation of total capital costs and also in calculation of annual capital charges, the economic advantages of nuclear power plants improved significantly over the oil-fired power plants.     

Section seven - new energy sources : An introduction to new energy sources for desalination

The papers presented in the section “New Energy Sources for Desalination” illustrate that a variety of new energy sources are being utilized to provide power for desalination. However, aside from solar stills there is only limited experience with pilot scale facilities using these new sources. The future of desalination with new energy sources depends on reducing the costs of producing reliable energy conversion devices and increasing the efficiency of the desalination units.     

Current challenges in hydrate-based desalination: Kinetic and thermodynamic perspective

Water scarcity is becoming a severe problem worldwide due to inadequate freshwater resources and swift population growth. Seawater desalination is one of the vital approaches to meet the demand for freshwater. However, energy and associated costs with conventional seawater desalination techniques are incentivizing non-conventional water desalination processes. Water desalination using gas hydrates formation is one of the emerging non-conventional processes. In this perspective article, recent advances in hydrate-based seawater desalination (HBSD) have been critically analyzed to outline a future path towards a clean and efficient hydrate-based desalination process. It provides a detailed comparison of various processes developed over decades, and measured desalination efficiencies with their process details. Moreover, the current challenges, limitations, and future perspectives of hydrate-based desalination are also discussed. The study also recapitulates the thermodynamics and kinetics aspects of the hydrate-based desalination process. In addition, various factors controlling the desalination efficiencies, such as control of the separation of hydrate crystals, salt deposition on hydrate particles, and hydrate morphology, were thoroughly investigated with their proposed process designs. The kinetics of hydrate formation is also assessed, with the possibility of a zero-induction regime and its consequent impact on hydrate morphology. The current capabilities of the thermodynamics models (Gibbs energy minimization + electrolyte equation of state) were discussed using various commercially available software. Additionally, the role of hydrate promotors is also discussed, which can reduce the higher cost associated with the hydrate-based desalination process.     

Desalination costs in Australia: A survey of operating plants

A survey of desalination costs in Australia was conducted using data obtained from plant operators, and is reported in second quarter 1986 A$. Unit water costs range from $0.76/kL (for a precursor to deionisation for boiler feed) to $14/kL (for emergency supplies for an island resort).

However, an average figure for desalination of brackish water is $3–$4/kL, and for seawater, $5–10/kL in medium-sized installations.

Capital costs for brackish water plants have been correlated with plant design capacity ranging from 10 to 3400 kL/d.

There is insufficient information to allow a proper comparison between reverse osmosis and electrodialysis for brackish water desalination.     

Cost analysis of seawater desalination with reverse osmosis in Turkey

Economically usable water resources per capita are decreasing due to excessive population increase each year in Turkey. For this reason, new water resources should be found in the near future. The potential water resources are seawater or well water both of which need removal of salinity. The most promising treatment method for salinity is reverse osmosis. While reverse osmosis becomes widespread, the cost of the process will decrease. There is no detailed information about cost of seawater desalination in Turkey. In this study, a cost analysis of seawater desalination in Turkey was performed for reverse osmosis systems. The basic parameters of cost analysis such as capacity, recovery, membrane life, energy, chemical costs and flux were evaluated based on the effects on capital, operating and total production costs.     

Recent advances in polymer and polymer composite membranes for reverse and forward osmosis processes

Semipermeable membranes are the core elements for membrane water desalination technologies such as commercial reverse osmosis (RO) process and emerging forward osmosis (FO) process. Structural and chemical properties of the semipermeable membranes determine water flux, salt rejection, fouling resistance, and chemical stability, which greatly impact energy consumption and costs in osmosis separation processes. In recent years, significant progress has been made in the development of high-performance polymer and polymer composite membranes for desalination applications. This paper reviews recent advances in different polymer-based RO and FO desalination membranes in terms of materials and strategies developed for improving properties and performances.     

An approach to improve the economy of desalination plants with a nuclear heating reactor by coupling with hybrid technologies

In order to investigate the possible approach to increase thermal efficiency of desalination plants, decrease water production costs and further optimize the coupling design of a nuclear heating reactor (NHR) with the desalination process, the coupling schemes of NHR reactors with hybrid desalination technologies were investigated. The cogeneration operation mode was adopted in this investigation. Two coupling schemes were selected for the cogeneration mode: NHR + low-temperature MED+RO and NHR + low-temperature MED+MED/VC. Technical specifications and economic aspects of the investigation are briefly presented in this paper.     

海水淡化技术现状及各种淡化方法评述

介绍了海水淡化的各种方法及其原理，对海水淡化技术的研究现状进行了总结，对海水淡化各种方法的能耗、优缺点、适用范围及其发展方向进行了分析讨论，并对海水淡化技术的应用状况进行了分析对比。     

Ashkelon seawater desalination project — off-taker’s self costs, supplied water costs, total costs and benefits

Total desalinated water costs to the Israeli Government, the “off-taker”, from the Ashkelon seawater desalination plant consist of the contracted water costs at the plant’s battery limits plus the government’s own expenditures: a) its initial investments (tender administration, out-of-plant infrastructure required to integrate the product within the national and regional water supply systems, etc.), b) its annual infrastructure O&M, supervisory and administrative costs, and c) the projected additional costs associated with certain project risks assumed by it throughout the life of the project. The paper presents and reviews these risks and quantifies the Government’s anticipated direct and indirect, fixed and variable costs, including several cost escalation scenarios anticipated due to the linkage of the contracted water price to various indices (using an item by item and index by index cost sensitivity analysis). The escalated desalinated water costs are then compared to the similarly anticipated but differently escalating costs of other water sources in Israel, to project, long-term, the resultant gap. The benefits foreseen from the project, and particularly those related to its specific site location, and its mandated daily, monthly and annual water supply schedules and product quality, are presented against: a) the background of Israel’s current water supply system’s water sources’ sustainable capacity, reliability, quality and costs, b) the anticipated growth in demand by various consumer sectors and c) the continuous deterioration of groundwater quality. The resulting risk and cost-benefit analyses are relevant not only to the Ashkelon project, which, as the first large scale government sponsored seawater desalination project in Israel, is a pioneering case study, but also to all pending and future seawater desalination projects in Israel. Some of these are not and will not be BOT, as the Ashkelon project was, but BOO and turnkey contracts, but, though government’s participation and the division of project risks may vary, the key cost-benefit issues, from the government’s point of view, will remain the same. In this context, Israel’s overall seawater desalination program, which is currently fixed at 315 million m³/y by 2010, and its role within the Israeli Water Commission’s long-range planning are briefly reviewed.     

Recent advances in reverse osmosis and electrodialysis membrane desalting technology

The potential impact of recent developments in both reverse osmosis and electrodialysis membrane desalting technology are summarized.Particular emphasis is given to the status of advanced technology reverse osmosis membranes with chlorine resistance having single pass seawater desalination capability. Membranes capable of using low operating pressures for brackish water desalting are also reviewed.Results obtained with large prototype reverse osmosis modules and their potential effect on lowering plant capital costs are presented.Possible elimination of acid and use of ultrafiltration as the predominant pretreatment step in seawater desalination plants are also described.Recent developments in the high temperature electrodialysis program for seawater desalting and in the use of newly developed anion membranes for brackish water desalination are reviewed.Finally, the effect of recent budget cut-backs imposed on the office of Water Research and Technology (OWRT) and potential impacts on future membrane desalination R&D activity are discussed.     

The role of desalination in water reuse

If reuse of water is being considered in an area where seawater desalination will be used to produce the basic water source, overall water resource development costs should be considered before selection of the basic desalination process. In cases where the system's wastewater is treated and used for artificial ground-water recharge and recovery, there are inherent benefits in utilizing a thermal rather than a membrane process to produce the basic water source from seawater.     

Optimization of seawater RO systems design

The paper describes the configuration and operating parameters of current large seawater desalination systems.Major advances of RO seawater desalination technology that lead to a remarkable decrease of desalted water costs are evaluated. Process improvements that enable compliance with more stringent requirements of permeate water quality are discussed. Results of field tests conducted to demonstrate a new process approach are described. Some examples of process optimization resulting in lower power consumption and more efficient system operation are presented.     

增湿一去湿海水淡化技术研究进展

增湿-去湿淡化工艺是一种不同于常规蒸馏法和膜法的新型海水淡化技术，具有规模灵活、设备投资和操作成本适中、结构筒单、可利用低位热能等优点。本文介绍了增湿．去湿淡化技术的原理，比较了不同形式的增湿-去湿淡化过程，总结了该工艺的技术特点，并指出了其现阶段的应用现状和发展前景。     

增湿-去湿海水淡化技术研究进展

增湿-去湿淡化工艺是一种不同于常规蒸馏法和膜法的新型海水淡化技术,具有规模灵活、设备投资和操作成本适中,结构简单、可利用低位热能等优点.本文介绍了增湿-去湿淡化技术的原理,比较了不同形式的增湿-去湿淡化过程,总结了该工艺的技术特点,并指出了其现阶段的应用现状和发展前景.     

Development of one pass sea water reverse osmosis module “Hollosep”

CTA hollow fiber membranes with high performance, especially high salt rejection, have been developed for one pass sea water desalination by reverse osmosis.Performances of modules have been studied relating to sea water desalination and are discussed in terms of hollow fiber membrane and module configuration.High salt rejection makes it possible to operate under severe operating conditions of high product water recovery and high salinity sea water.Operating costs are discussed with regard to product water recovery.     

Economic aspects of membrane processes

Care must be exercised, in predicting operating costs for membrane desalination systems for electricity, labor, chemicals, etc. The assumptions made in establishing unit costs can greatly affect the predicted operating cost and hence the ultimate investment decision. The use of data estimating the quantities of chemicals, power, etc., expected to be used per unit of production can assist in predicting costs, as then site-specific cost data can be used. The fact that 0.2 pounds of acid per kgal of permeate is required in a Florida RO plant is more useful for predicting operating costs of an RO plant on the Island of Anegata than is the fact that acid costs at the Florida plant are $0.03/kgal of water produced. Data based on units rather than costs are presented for seven RO facilities and one ED facility in this paper for use in this type of analysis.