Abstract
Desalination is a method for producing water for human consumption, irrigation or industrial utilisation. In this study, a reverse osmosis (RO) system for brackish water desalination was theoretically investigated to produce both potable drinking and agricultural water with a lower overall and specific energy consumption. As a case study, the Main Outfall Drain in Iraq is used as the brackish water source. A numerical model based on solution-diffusion theory was developed in Matlab Simulink and used to analyse the design and performance of an RO system. The effect of feed water temperature, pressure, salinity and recovery ratio on the efficiency of the whole RO system was investigated for a wide range of design considerations. The design of an RO system for this application was optimised and economic assessment carried out. Results show that with boosting recovery ratio from 30% to 60%, the specific energy of desalinated water production below 400ppm was reduced from 2.8kWh/m3 to a more economically favourable value of 0.8kWh/m3, when utilizing a pressure exchanger as a recovery device. Salt rejection was reduced from 97% to 88% to obtain large quantities of water for irrigation with an acceptable salinity (<1600ppm), for agricultural use. The reduction in salt rejection is influenced by the feed water temperature and pressure; also the average pore diameter of the RO membrane and in turn determines the reduction in system energy consumption. It was found that the total cost to produce 24,000m3/d of water from a feed salinity of 15,000ppm and a water quality of <400ppm would be 0.11£/m3 with a corresponding investment cost of £14.4million for the drinking water, and for irrigation) obtained product <1600ppm) are £0.9/m3 and £11.3million.
Highlights
In recent years there has been considerable growth in the utilisation of reverse osmosis (RO) processes in major desalination plants [1,2]
Numerical analysis has been conducted to study the performance of reverse osmosis membrane for a brackish water desalination process
As a result of the analysis using the model, it can be seen that, salt rejection can be reduced from 97% to 88% to obtain high quantities of fresh water with an agriculturally acceptable
Summary
In recent years there has been considerable growth in the utilisation of reverse osmosis (RO) processes in major desalination plants [1,2]. Among the benefits of Abbreviations: BWIP, brackish intake and pre-treatment section; ERD, energy recovery device; HPP, high pressure pump; O&M, operating and maintenance; PEC, purchased equipment cost; RO, reverse osmosis; TCI, total capital investment. RO has been used widely for various water and wastewater treatment processes [5,6], in areas with scarce water supplies (as a means of seawater desalination) and importantly for this study the treatment of brackish water. RO desalination suffers from a high energy input demand, fouling of the membranes, and low-quality of the water compared to thermal technologies which produce very high quality [2,3]. Over the past 40 years, as a result of on-going technological advances [6] there has been a significant reduction in the energy required
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