Mushtaque Ahmed

Use of evaporation ponds for brine disposal in desalination plants

Abstract Desalination plants are being used increasingly in inland areas of many countries for supplying water for domestic purposes. If these areas are too far away from the sea, the opportunity to dispose the reject brine (also known as concentrate, reject water, or wastewater) in the ocean no longer exists, given that ocean disposal is the common practice for plants located in coastal areas. Evaporation ponds are especially suitable to dispose of reject brine from inland desalination plants in arid and semi-arid areas due to the abundance of solar energy. In irrigation projects facing a soil salinity problem due to a shallow saline groundwater table, evaporation ponds are also in use. Saline water tables are lowered by pumping or tile draining and the drainage water is stored in evaporation ponds. While evaporation ponds have long been used for salt production in many parts of the world, the disposal of concentrate from desalination plants in inland areas using evaporation ponds is of much significance both economically and environmentally. Guidelines are needed for the design, construction, maintenance, and operation of evaporation ponds for reject brine disposal in an economical and environmentally-sensitive manner. This paper provides a critical review of concentrate disposal technology using evaporation ponds. Relevant topics are also covered including chemistry of brine, brine disposal methods, use of evaporation ponds in agriculture, determination of evaporation rate, and evaporation enhancement methods.

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

Abstract Reverse osmosis (RO) desalination plants are used for supplying potable water to small communities in inland areas of Oman as well as small to large communities in the United Arab Emirates (UAE). Most of these desalination plants use brackish groundwater as feedwater. The production of brine (also known as concentrate or wastewater) is an integral part of the operation of desalination plants in the interior parts of Oman and eight RO plants in the coastal areas of the UAE were investigated with regard to their brine disposal methods. The capacity of the Omani plants varied from 50 m 3 /d to a maximum of 1000 m 3 /d. The salinity level of wastewater varied from 9.8 to 61.2 dS/m (1 dS/m = 640 mg/L). Various disposal methods were observed. These included lined evaporation ponds, ocean/beach disposal, and unlined small bores. The depth to the water table in the areas of the investigated desalination plants varies from 40 to 80m, while the average distance between feedwater intake and disposal areas was approximately 200 m. In the UAE, the capacities of the investigated plants varied between 950 to 15,000 m 3 /d. All the UAE plants dispose of their brine in the sea, although some of the plants dispose of their brine in nearby creeks that are linked to the sea. The chemical characteristics of the brine, feedwater, product water, and water from evaporation ponds (or bores) were determined. The presence of other chemicals including iron, copper, zinc, and cleaning agents (such as hydrochloric acid, sodium hexametaphosphate, and anti-scalants) is likely to pollute the groundwater, if the brine were to reach the underlying aquifers. Under certain conditions, brine from the desalination plants can have useful applications. Potentials for such applications are addressed in this paper.

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

Abstract Production and disposal of rej ect brine are an integral part of an overall desalination process. For inland desalination plants, this poses a serious challenge to operators, as the option of ocean disposal of rej ect brine is not available. Various disposal options such as reinjection, lined and unlined evaporation ponds and natural depressions (lake) are currently being used. An alternative approach is to further process the reject brine to extract all the salts. This has the advantages of being environmentally friendly and producing commercial products (i.e., salts and fresh water). A desktop profeasibility study using data from Petroleum Development Oman (PDO), operating plants in Bahja, Rima, Nimr and Marmul, confirmed the technical feasibility of treating reject brines in simple processing routes using SAL-PROC technology. SAL-PROC is an integrated process for sequential extraction of dissolved elements from inorganic saline waters in the form of valuable chemical products in crystalline, slurry and liquid forms. The process involves multiple evaporation and/or cooling, supplemented by mineral and chemical processing. An analysis indicated that various types of salts including gypsum, sodium chloride, magnesium hydroxide, calcium chloride, calcium carbonate, and sodium sulphate can be produced from the reject brine of PDO desalination plants. These products have an approximate market value of US

Integrated power, water and salt generation: a discussion paper

895, 000 annually.

Freezing‐Melting Process and Desalination: I. Review of the State‐of‐the‐Art

Abstract Cogeneration of electricity and desalinised water — for water production — is an accepted principle in many countries. However, there is an opportunity to extend the concept to obtain greater efficiencies by reassessing the desalination paradigm. The new paradigm considers desalination as only part of the saline water processing chain. It looks at value-adding opportunities through further processing of salt by-products, particularly bitterns. It considers aspects such as multiple use of evaporation basins, electricity generation from solar ponds using bitterns as a main constituent, and opportunities for resource recovery from bitterns. Above all, it considers the integration of water, salt and power production, as a mutually supporting system. The overall concept of better integration of water, salt and power production is discussed with a focus on the utilisation of saline effluent from desalination plants.

Freezing-melting process and desalination: Review of present status and future prospects

Abstract A thorough literature survey was conducted on the freezing‐melting (FM) process for desalination. Collected literatures were studied and analyzed to identify the current state‐of‐the‐art of the FM process, and its practical limitations. The main advantages of the FM process are the requirement of low energy and low temperature operation compared to thermal desalination. Other advantages are less scaling or fouling and fewer corrosion problems, ability to use inexpensive plastics or low‐cost material, and absence of pretreatment. The three broad classes of FM process are: direct contact freezing, indirect contact freezing, and vacuum freezing. Different types of processing options in each class are discussed with their operating principles and merits and downsides of each process.

Design, construction and evaluation of an ablution water treatment unit in Oman: a case study

The main factors affecting the use of freezing-melting (FM) process are the capital cost and the process complexity. The FM technology was successful when these two factors were compensated by other advantages. The success in food industry was mainly due to its ability of producing high-quality products compared to the available thermal technology in the market. In chemical industry it is generally adopted when there are no other alternatives. It would be difficult to utilise the above advantages to adopt FM process for desalination. Furthermore, misconceptions and negative attitudes also affected the progress of FM process. In desalination, a number of existing technologies are available. The pilot studies in several countries indicated that the hybrid techniques of combining FM process and other desalination methods have high potential for development. The strategies for the commercial success of the FM process in desalination industry are identified in this paper.

Brine disposal from inland desalination plants research needs assessment

In arid and semi‐arid countries, there is a need to identify alternative sources of water and develop appropriate technology to harness them. Greywater can be a cost‐effective alternative source of water. Collection of greywater from households requires dual plumbing to separate greywater from blackwater. This constraint does not exist at most mosques, where a significant quantity of ablution water is produced in Wudhu (ablution) rooms with plumbing to separate the ablution water from blackwater. Commercial greywater treatment systems are too expensive to treat ablution water produced at most mosques, because the quantity of water produced is usually less than 2 m3 per day. Therefore, a cost‐effective, low maintenance treatment system, WWW – Wudhu Water Works – has been designed to collect, treat and reuse ablution water from small to medium‐sized mosques. The system includes a sand trap, an ablution water collection tank, a filtration unit, chlorination chute, and treated water collection tank. Treatment and reuse is automated using submersible pumps and timers. Details of the design, construction and performance of the WWW are presented in this paper. The treatment unit improves used ablution water quality to acceptable limits for irrigation, and has a favourable internal return rate (IRR) of 14.9%.

Managed aquifer recharge using quaternary-treated wastewater: an economic perspective

Abstract Desalination plants are being widely used in the inland areas of many countries to supply water for domestic purposes. When these areas are far from the shorelines of salt-water bodies, the opportunity to dispose of the reject brine (also known as concentrate, reject water, or wastewater) back into these water bodies no longer exists. In such instances, the use of evaporation ponds is very significant, both economically and environmentally. Other alternatives for brine disposal may also be very effective in some instances. Under certain conditions, brine from desalination plants can have useful applications. Potentials for such applications are addressed in this paper along with a critical review of current innovative concepts for the disposal of reject brine from inland desalination plants. This paper will also assess the present status of disposal mechanisms of brine from desalination plants and outline future research areas that could be pursued for effective, economical, and environmentally sound means for brine disposal from such plants.

Climate change, vulnerability and adaptation experiences of farmers in Al-Suwayq Wilayat, Sultanate of Oman

An excess of 31 million m3/y of tertiary-treated wastewater is expected in Muscat, Oman, by 2015. This paper addresses the technical and cost estimation of managed aquifer recharge after reverse-osmosis treatment. The results indicate that the project is appealing from an economic perspective. The total cost varies between USD 0.353 and USD 0.550 per cubic metre, depending on the cost of electricity, the interest rate and the life span of the project. The project may face rejection from domestic users, who may be unwilling to accept mixing treated wastewater with the current water supply due to health risks. An alternative to indirect potable reuse is the installation of a separate network to service industrial users.