Energy consumption and environmental impact assessment of desalination plants and brine disposal strategies

Currently, desalination plants are essential tools for utilizing water from various natural resources like brackish water and seawater. Worldwide, the number of desalination facilities is rising to fulfill the increased requirement for potable water to be utilized for human consumption, public services, and industrial activities. There exist three principle methods of desalination: thermal, electrical, and pressure. Conversely, the brine released will have several negative effects on the surroundings. The current study aimed to give a general awareness into the present progress in the desalination processes through investigating the various available technologies. Different brine disposal approaches are analyzed as well as compared. We have also compared the different technologies based on energy consumption and water production costs. Moreover, we examine the zero liquid discharge (ZLD) technique, its challenges, advantages, operating as well as environmental characteristics, and the up-to-date research progress in this area. In the end, we have briefly analyzed the upcoming research and development approaches for brine management. It was found that this ZLD process is extremely beneficial to the environment with respect to decreasing the pollution caused by the discharged brine and attaining sustainability. Additional pilot or field studies are necessary for validating their commercial-scale performance as well as feasibility in practicing ZLD.KeywordsZero liquid discharge (ZLD) approachBrine disposal strategiesThermal technologiesMembrane technologiesSeawater desalination

Screening and cost assessment strategies for end-of-Pipe Zero Liquid Discharge systems

Energetic, economic and environmental assessment of zero liquid discharge (ZLD) brackish water and seawater desalination systems

Treatment of industrial brine using capacitive deionization (CDI) towards zero liquid discharge – challenges and optimization

Current brine management strategies are based on the disposal of brine in nearby aquifers, representing a loss in potential water and mineral resources. Zero liquid discharge (ZLD) is a possible strategy to reduce brine rejection while increasing the resource recovery from desalination plants. However, ZLD substantially increases the energy consumption and carbon footprint of a desalination plant. The predominant strategy to reduce the energy consumption and carbon footprint of ZLD is through the use of a hybrid desalination technology that integrates renewable energy. Here, we built a computational thermodynamic model of the most mature electrified hybrid technology for ZLD powered by photovoltaic (PV). We examine the potential size and cost of ZLD plants in the US. This work explores the variables (geospatial and design) that most influence the levelized cost of water and the second law efficiency. There is a negative correlation between minimizing the LCOW and maximizing the second-law. And maximizing the second-law, the states that more brine produces, Texas is the location where the studied system achieves the lowest LCOW and high second-law efficiency, while California is the state where the studied system is less favorable. A multiobjective optimization study assesses the impact of considering a carbon tax in the cost of produced water and determines the best potential size for the studied plant.

Energy, exergy, economic and environmental comprehensive analysis and multi-objective optimization of a sustainable zero liquid discharge integrated process for fixed-bed coal gasification wastewater

We are continually inundated with news and views about the demand for water outpacing supply. Our unsustainable development along rivers that do not reach the sea, declining ground water levels, damage to wetlands, high costs associated with acquiring new sources of water, and potential shortages related to global climate change are common news items. In most developed economies, there is little or no unallocated fresh water left to exploit. So, the question becomes: Where do we find “new” water for our burgeoning population? The answer may lie in the treatment of both shallow, brackish ground water and postconsumer water. Recent advances in reverse-osmosis membranes have reduced operational costs and established a linear correlation between total dissolved solids and operational cost of desalination; thus, there is increased interest in brackish water as input source. In the Southwest, the El Paso, Texas, Water Utilities Public Service Board recently dedicated a 100 million L/d desalination plant. Surprisingly, Florida with its high rainfall of more than 100 cm a year and many lakes and rivers is commonly thought of as a water-“rich” state; yet it has more water desalination plants than any other state: the city of Tampa Bay has the largest active desalination plant in the United States and uses brackish water from Tampa Bay. It is estimated that the state of New Mexico contains 16,000 billion m3 (13 billion acre-feet) of shallow brackish ground water (total dissolved solids greater than 500 mg/L and less than sea water, which is 35,000 mg/L). I suspect that development of brackish water aquifers would, in general, have less impact on the ecology than development of fresh water aquifers. That being said, we know little about the extent and chemistry of brackish water aquifers and almost nothing about their boundary conditions. Thus, I propose a federal 10-year sunset assessment of 1‰ per 250 gallons on all the ground water that municipalities extract, or about $1.00 each year for the average household using ground water. It is envisioned that this study would quantify the regional hydrology of these aquifers following the USGS’s Regional Aquifer System-Analysis model for fresh water aquifers. It would also identify any potential deeper formations capable of sequestering desalination concentrate. This small investment coupled with reduced consumption from increased rate changes and conservation measures such as low-flush toilets, low-flow showerheads and watering restrictions will prolong our existing resources and give us time to install the necessary infrastructure. We need to wean ourselves from our “once through, throw it out” philosophy that dominates current water resource management. We also need to reframe the linguistic argument away from “sewerage” or “waste water” toward the more societally acceptable “postconsumer” or “surplus municipal water.” (Remember, it is not a “used” car, it is a “previously owned” car!) Cities will soon no longer have the luxury of passing their used municipal water downstream. “Dilution is the solution to pollution” is a dated and unfair concept of passing water quality problems to the aquatic environment and cleanup expenditures to downstream users. Newly engineered membranes in desalination plants are excellent at removing not only salts but also pharmaceuticals, endocrine disruptors, prions, and other undesirable products left untouched by conventional waste treatment facilities. Combining membrane-treated water with aquifer storage and recovery (ASR) offers some interesting water management possibilities. That is, by recharging refreshed water, which is generally of better quality than native ground water, into aquifers, one can control the blending ratio of refreshed to native ground water in producing well fields. Furthermore, the aquifer provides a unique environment to adjust the temperature and chemistry and continue filtering the recharged water, adding insurance against the transport of many undesirable contaminants. Desalination and ASR are, however, energy-intensive processes; thus, greenhouse gas–free energy is likely to be integrated in any future energy scenario. Currently, approximately 28% of all electrical power generated in the United States is greenhouse gas–free (nuclear 19.3%, hydro 6.5%, biofuels 1.6%, wind less than 1%, and solar less than 1%), so these are likely to be the energy sources for desalination. Because both the membrane and the ASR technologies are mature and well established, development of new water from brackish ground water and postconsumer water could be a rapid and straightforward resolution to many of the domestic and industrial demands of our nation’s water resources well into the future.

In today’s present world, billions of people live without reliable access to clean drinking water, and as populations continue to grow, freshwater sources begin to disappear at an equally rapid pace. In an effort to combat these issues, desalination has been introduced as a solution to abstract water from untouched resources. However, while desalination can produce additional potable water, it is also heavily criticised for its flaws; namely cost, energy consumption, and environmental pollution. Thus, in order to promote desalination as a sustainable solution for both the present day and future, improvements need to be implemented to produce less costly, more energy efficient, and environmentally friendly desalination plants. This paper reviews all of the current desalination methods in today’s global market, evaluating which methods are most sustainable for the future of desalination. Options for renewable energies to replace fossil fuels are also studied, as well as various brine disposal methods which can produce more environmentally safe and sustainable desalination facilities. Among the literature reviewed, reverse osmosis was found to be the world’s most sustainable method of desalination due to its energy efficiency and production capacity, while solar photovoltaics were found to be the popular choice among renewable energies. Zero liquid discharge was also found to be the most environmentally friendly method of brine waste disposal, although research in the field was very limited. Each method was closely evaluated and compared among its competitors, offering a detailed perspective on the sustainable state of desalination.

Desalination of brackish water by nanofiltration and reverse osmosis

Techno-economic analysis of a membrane-hybrid process as a novel low-energy alternative for zero liquid discharge systems

Pilot-scale treatment of hypersaline coal chemical wastewater with zero liquid discharge

Water, otherwise known as the pool of life, is the very essence of all living things and as such is vital for survival, whether for living beings, social, economic development or for environmental sustainability. However, its continuing existence is severely threatened for future as a result of climate change, carbon footprint, population growth, environmental damage, combined with natural disasters like droughts and floods. The prospect of an alternative solution such as desalination of sea or brackish water to counter the limit on conventional water resources such as groundwater, which cannot meet demand, is therefore very promising, particularly in arid and semi-arid regions where water scarcity and impaired quality prevails. Consequently, desalination technology has now become a burgeoning industry in North Africa or southern Mediterranean countries, such as in Libya. However, evidence suggests that as a result of by-products being discharged directly into the sea, particularly from coastal desalination plants, the physico-chemical parameters of the receiving water are changing and posing a threat to marine ecosystems. As a result of studies conducted on these parameters to analyse the brine emitted from the Zwuarah and the West Tripoli distillation plants (ZWDP & WTRIS) on the Libyan coastline, evidence shows there is a significant positive correlation at both sites between the biological data and physico-chemical parameters (rs=0.673; p=0.002) and (rs=0.637; p=0.003), which is a clear indication of the impact of brine disposal from both plants on the marine environment. For most of coastal desalination plants on the Libyan coastline, the most practical and least expensive brine disposal option is to discharge it into the sea. It is necessary therefore, to effectively manage desalination reject brine in order to ensure more efficient disposal and reuse. Therefore, it is suggested that experimental studies are aimed for dual benefit of on-site generation of sodium hypochlorite through brine electrolysis and to recover minerals and NaCl from the brine using evaporation ponds, while protecting the environment. Following the first experiment, the outcome of brine utilisation showed a significant production of NaOCl using graphite electrodes (MCCA 1.82 gr/m3). At interelectrode spacing 2 cm and 4 cm, the power consumption was higher, with a greater concentration of sodium hypochlorite generation varying between 10-25 kw/m3 (573-2140ppm) and 29-24 kwm-3 (572-2600ppm) than at interelectrode spacing 6cm 17-13 kwm-3 (350-1790ppm). Consequently, the selection of an optimum electrical consumption level is key in establishing the best scenario in terms of economy and efficiency. Subsequent to the second experiment of brine evaporation in the ponds, results showed that the evaporation rate in August was lower than in September (9.06 mmday-1, 14.63 mmday-1) respectively. The results of the SEM/EDS test showed that due to elevated surges of Na+ and Cl-, halite (NaCl) was the main mineral evident during crystallisation of the salt samples. Hence, the two experiments reveal that brine can be recycled productively, while protecting the environment.

Heat transfer evaluation and economic characteristics of falling film brine concentrator in zero liquid discharge processes

In order to reduce fossil energy consumption at desalination plants, it has become necessary to replace fossil energy with clean energy. Currently, the reverse osmosis systems connected to solar energy is a promising technology for desalination of seawater / brackish water, especially in arid and semi-arid areas that have a large solar deposit and are remote from the public grid. The objective of this work is to show the efficiency of introducing renewable energy in brackish water desalination plants by the effect of comparing the energy consumption for a system without renewable energy source and system powered by the photovoltaic system (solar energy). As well as a program developed on Matlab software environment in order to, optimize the energy consumption of a desalination plant for the proposed plant is about 0.1269 kWh/m3.

Thermodynamic and kinetic analyses of Janus membrane scaling in membrane distillation for zero liquid discharge engineering