Environmental impacts of reject brine disposal from desalination plants

Use of evaporation ponds for brine disposal in desalination plants

Thermal and membrane based desalination plants are being operated all over the world to address the demand of fresh water required by industries and large cities in water scarce coastal areas. The desalination and energy are very much interlinked, as plants are energy intensive. The energy consumption of desalination plants varies from 5 to 15 kWh m-3 of product water depending on the technology. In addition, the percentage of reject seawater/brine exiting the plants varies from 60% to 80% depending on the desalination technique. The concentrated reject brine is a source of valuable trace elements/metals, which is an untapped source that is wasted. With advances in Desalination technologies, it has been established that recovery of critical metals and elements and their selective recovery from reject brine of desalination plants gives an added advantage of energy credits to desalination plants as well as reduce cost of desalinated water [1, 2]. Research and technological developments are required for brine mining from desalination plants, i.e., by the recovery of nuclear fuel and other valuable materials (e.g. U, Li, Rb), from reject brine streams. This is being achieved by adsorption of these elements/ions onto a selective sorbent that is dipped either in reject brine/inlet seawater or in the open sea [1]. The major factor determining the practical utilization of the technology and lifetime of the adsorbent is fouling of the adsorbent by suspended particles or due to biological growth. The paper presents the status review on a recovery of important trace metals and other alkali metals from seawater and highlights the potential of Indian desalination plants for the recovery of trace metals. The adsorption studies carried out using radiation grafted polymeric adsorbents along with fouling studies are discussed in this paper. The studies involve determination fouling tendency of the adsorbents in a different environment, and recovery of uranium and vanadium from the reject brine. The paper also gives the schematic diagram and major unit operations involved in process flow scheme.

Feasibility of salt production from inland RO desalination plant reject brine: A case study

By the end of 2005 the global installed capacity for desalination of seawater was about 24.5·106 m3/day. The geographical distribution of the desalination plants was as follows: 77 % in the Middle East and North Africa, 10 % in Europe, 7 % in the Americas and 6 % in the Asia-Pacific region. The volume of brine discharged in the Red Sea increased from 6.4 million m3/day (in 1996) to 6.8 million m3/day (in 2008) and is still increasing due to the observed tendency to improve the average recovery ratio from 30 to 50 %. This will make the environmental concerns much more important in the future. There are two main sources of problems, i.e. the concentrate and chemical discharges and the cooling water effluent discharges. The salinity is expected to increase in the long term if larger and larger amounts of desalinated water are removed from the water bodies. A proper solution for the desalination waste brine disposal process requires a good balance between technical constraints (i.e. placing a pipe on the sea-bottom), environmental conditions (i.e., finding an optimum distance from the seashore where high salinity brine should be discharged without significant environmental impact; also, the availability for long run of brine disposal placement should be considered) and as low as possible overall economic costs.Since the potential cumulative impacts of desalination activity on the marine environment is expected to be more significant in case of regional seas, in this chapter we focus on the desalination plants in Red Sea. The objective is to discuss a modeling framework for the environmental-hydraulic design of the outfall system for desalination plants. The chapter presents an interdisciplinary combination of environmental issues with physical processes and discharge modeling. We assess the technical viability of disposal the brine effluent produced by desalination plants into Red Sea coastal regions via submarine pipes.There are several approaches to mitigate the environmental effects of the brine discharges. By tradition, the brine is discharged back to the sea in open channels. Impacts from high salinity may be avoided by pre-dilution of the desalination plant rejected stream with other waste streams, such as power plant cooling water. Impacts from high temperature may be avoided by ensuring heat dissipation from the waste stream to the atmosphere before entering the water body. However, simulations models for the brine plume dispersion from desalination power plants reveal the inadequacy of using surface discharging outfalls in order to brine discharging. Large capacity plants require submerged discharges which ensure a high dilution, reducing the harmful impacts on the marine environment. Mixing and dispersal of the discharge plume can be enhanced by installing a diffuser system, and by locating the discharge in a favorable oceanographic site which dissipates the heat and salinity load quickly.The central concept of the brine disposal by submerged pipes is the available head at the discharge point. Higher values of the available head ensure larger jet dispersion lengths and better conditions for ejected brine dilution. We have shown that the quality of the dilution process is well quantified by the Froude number of the brine discharge jet, whose optimum values range between 20 and 25. Using the Froude number allowed us to find the optimum pipe length and the optimum depth of the discharge point.About half of the Red Sea desalination plants are based on reverse osmosis. The percentage of RO plants is expected to increase, taking into account the lower production costs and the favorable technological evolution. The most representative RO desalination plants around the Red Sea coast are considered both by country and by capacity points of view. In order to provide relevant conclusions for the study reduced capacity desalination plants were selected due to their large number. For not available/existing desalination plants some hypothetic “case studies” were considered.Optimum brine dispersion may be obtained by using underwater pipes for any sort of high capacity and low capacity RO desalination plants operating on the Red Sea coasts. In case of large capacities, a pipe length around lX = 1,000 m allows optimum operation. A pipe length about lX = 500 m is needed for low capacity RO desalination plants.KeywordsFroude NumberReverse OsmosisDischarge PointDesalination PlantPipe LengthThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Desalination has been growing rapidly as an industry and as a field of research that combines engineering and science to develop innovative and economical means for water desalting. Many countries in the world, especially in the Middle East, depend heavily on seawater desalination as a major source of drinking water and have invested considerable efforts and financial resources in desalination research and training. Desalination plants have seen considerable expansion during the past decade as the need for potable water increases with population growth. It is estimated that the world production of desalination water exceeds 30 million cubic meters per day and the desalination market worldwide is expected to reach $ 30 billion by 2015. One of the major economical and environmental challenges to the desalination industry, especially in those countries that depend on desalination for potable water, is the handling of reject brine, which is the highly concentrated waste by-product of the desalination process. It is estimated that for every 1 m3 of desalinated water, an equivalent amount is generated as reject brine. The common practice in dealing with these huge amounts of brine is to discharge it back into the sea, where it could result, in the long run, in detrimental effects on the aquatic life as well as the quality of the seawater available for desalination in the area. Although technological advances have resulted in the development of new and highly efficient desalination processes, little improvements have been reported in the management and handling of the major by-product waste of most desalination plants, namely reject brine. The disposal or management of desalination brine (concentrate) represents major environmental challenges to most plants, and it is becoming more costly. In spite of the scale of this economical and environmental problem, the options for brine management for inland plants have been rather limited. These options include: discharge to surface water or wastewater treatment plants; deep well injection; land disposal; evaporation ponds; and mechanical/thermal evaporation. Reject brine contains variable concentrations of different chemicals such as anti-scale additives and inorganic salts that could have negative impacts on soil and groundwater. This chapter highlights the main concerns as well as the environmental and economical challenges associated with the generation of large amounts of reject brine as a by-product of the desalination process. The chapter also outlines and compares the most common options for the treatment or disposal of reject brine. The chapter focuses on a novel approach to the management of reject brine that involves chemical reactions with carbon dioxide in the

The relevance of the study is due to the fact that the presented object, namely mineral waters in the modern world have a huge potential and play an important role in farming, the coal industry, and in many other fields of life. Mineral water desalination technologies also affect the environment, so there are requirements for improving the methods of recycling brines and regenerative solutions in the desalination of water, due to which it is possible to make a substantial contribution to meeting the requirements of a number of consumers. The purpose of the study is to conduct an experiment, as a result of which recommendations will be made to eliminate errors and improve the quality of various methods of desalination of mineral waters and prevent the problem of disposal of brine, which, when discharged into reservoirs or evaporative sites, substantially worsen the ecological situation. Among the methods used are analytical, experimental, functional, statistical, classification, synthesis. In the course of the study, the features of mineral waters were noted, errors that were made during treatment, and the causes of their occurrence were analysed, and difficulties in the field of coal industry enterprises were analysed: the formation of water, its composition, properties, and degree of impact on the environment. It is important to understand the possibilities of various methods that allow choosing the best technological modes of operation of water treatment processes and successfully solving environmental problems with minimal consumption of reagents, water, and its discharge to the external environment. The practical value lies in the fact that the results obtained can be useful for the industry where mineral resources are extracted and processed, for researchers engaged in the development of new desalination methods, and can substantially reduce production costs and ensure the ecology of the process.

The relevance of the study is due to the fact that the presented object, namely mineral waters in the modern world have a huge potential and play an important role in farming, the coal industry, and in many other fields of life. Mineral water desalination technologies also affect the environment, so there are requirements for improving the methods of recycling brines and regenerative solutions in the desalination of water, due to which it is possible to make a substantial contribution to meeting the requirements of a number of consumers. The purpose of the study is to conduct an experiment, as a result of which recommendations will be made to eliminate errors and improve the quality of various methods of desalination of mineral waters and prevent the problem of disposal of brine, which, when discharged into reservoirs or evaporative sites, substantially worsen the ecological situation. Among the methods used are analytical, experimental, functional, statistical, classification, synthesis. In the course of the study, the features of mineral waters were noted, errors that were made during treatment, and the causes of their occurrence were analysed, and difficulties in the field of coal industry enterprises were analysed: the formation of water, its composition, properties, and degree of impact on the environment. It is important to understand the possibilities of various methods that allow choosing the best technological modes of operation of water treatment processes and successfully solving environmental problems with minimal consumption of reagents, water, and its discharge to the external environment. The practical value lies in the fact that the results obtained can be useful for the industry where mineral resources are extracted and processed, for researchers engaged in the development of new desalination methods, and can substantially reduce production costs and ensure the ecology of the process.

Reverse osmosis is the technology commonly used to produce fresh water from brackish groundwater. Due to the reject brine generated in desalination plants by reverse osmosis, vulnerability assessment to define critical areas to monitor waters from desalination has been an important tool for delineating the monitoring networks required for surveillance of potential salinization sites. The objective of this study was to assess the quality of waters sampled in desalination plants by a quality index, which provides a relative assessment of water vulnerability to potential salinization. The present study proposes an index to assess the quality of waters from desalination plants initially using the chemical parameters electrical conductivity, sodium adsorption ratio, Mg2+/Ca2+ ratio, and the ions sodium, chloride and bicarbonate. The index to assess quality of waters from desalination plants showed good performance and can include additional parameters referring to the soil and crop exploited. High values of the relative index of quality of waters from desalination plants are considered as possible indicators of risk of soil salinization and groundwater contamination. The highest level of land use impact on the quality of waters from desalination plants was found in reject brine samples followed by well water samples.

Impact of land disposal of reject brine from desalination plants on soil and groundwater

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.

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.

Chapter 9 - Desalination Concentrate Management and Valorization Methods

Control and management of brine disposal for inland desalination plants

Chalcocite (Cu2S) has the fastest kinetics of dissolution of Cu in chlorinated media of all copper sulfide minerals. Chalcocite has been identified as having economic interest due to its abundance, although the water necessary for its dissolution is scarce in many regions. In this work, the replacement of fresh water by sea water or by reject brine with high chloride content from desalination plants is analyzed. Additionally, the effect of adding MnO2 from available manganese nodules in vast quantities at the bottom of the sea is studied. Reject brine shows better results than sea water, and the addition of MnO2 to the brine significantly increases the kinetics of chalcocite dissolution in a short time. H2SO4 concentration is found to be irrelevant when working at high concentrations of chloride and MnO2. The best results, 71% Cu extractions in 48 h, are obtained for reject brine, 100 mg of MnO2 per 200 g of mineral and H2SO4 0.5 mol/L. The results are expected to contribute to a sustainable process of dissolution of chalcocite by using the reject brine from desalination plants.

Brine disposal from reverse osmosis desalination plants in Oman and the United Arab Emirates