Abstract
Brine disposal is a major challenge facing the desalination industry. Discharged brines pollute the oceans and aquifers. Here is it proposed to reduce the volume of brines by means of evaporative coolers in seawater greenhouses, thus enabling the cultivation of high-value crops and production of sea salt. Unlike in typical greenhouses, only natural wind is used for ventilation, without electric fans. We present a model to predict the water evaporation, salt production, internal temperature and humidity according to ambient conditions. Predictions are presented for three case studies: (a) the Horn of Africa (Berbera) where a seawater desalination plant will be coupled to salt production; (b) Iran (Ahwaz) for management of hypersaline water from the Gotvand dam; (c) Gujarat (Ahmedabad) where natural seawater is fed to the cooling process, enhancing salt production in solar salt works. Water evaporation per face area of evaporator pad is predicted in the range 33 to 83m3/m2·yr, and salt production up to 5.8tonnes/m2·yr. Temperature is lowest close to the evaporator pad, increasing downwind, such that the cooling effect mostly dissipates within 15m of the cooling pad. Depending on location, peak temperatures reduce by 8–16°C at the hottest time of year.
Highlights
Disposal of brines from desalination plants is considered one of the major challenges associated with the desalination industry today
Predictions are presented for three case studies: (a) the Horn of Africa (Berbera) where a seawater desalination plant will be coupled to salt production; (b) Iran (Ahwaz) for management of hypersaline water from the Gotvand dam; (c) Gujarat (Ahmedabad) where natural seawater is fed to the cooling process, enhancing salt production in solar salt works
Motivated by the environmental impact of desalination brines, the limited instances of recovery of salt and minerals from it, and by the opportunities to add value and benefits to such products, this paper investigates a new option for management of desalination brines by seawater greenhouses
Summary
Disposal of brines from desalination plants is considered one of the major challenges associated with the desalination industry today. Improved brine disposal is still quite rare in practice. Almost all brine from seawater desalination plants is disposed of directly to the oceans. The quantity of brine is comparable to that of freshwater produced by desalination – about 80 million m3/day worldwide [4], containing about 5.6 million tonnes of salt per day (2000 million tonnes/yr). This amount is some 8 times the current annual world salt production of 250 million tonnes/yr [5]
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