Renewable energy powered reverse osmosis system for seawater desalination.
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Date
2022
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Abstract
Desalination is one of the most successful procedures for freshwater supply from seawater in the
world. Reverse osmosis (RO) is a major technology in the business of seawater desalination
because of its ability to produce excellent potable water of highest quality from the seawater source
with low energy consumption compared to other technologies. Freshwater is a prerequisite for life
and procreation. Water as an essential commodity is used in every phase of human life, ranging
from domestic activities such as drinking, cooking, washing, etc., to innumerable industrial and
agricultural purposes such as power generation. Today's increasing demands for freshwater by the
world population cannot be met by the available fresh water in our ecosystem. This is why
numerous technologies for seawater desalination have been established and advanced over the
years to augment/satisfy the ever-increasing global demand for freshwater. One such technological
development is the use of computer-based modeling for the design and system analysis of the RO
treatment process for optimum performance. The hands-on modeling of an efficient full-scale
reverse osmosis (RO) system may be daunting work due to the RO systems’ operating conditions
which continually fluctuate due to cyclical variations in seasons and progressive fouling of the
membrane during long-term filtration. The RO plants design, the cost of capital estimation
(CAPEX), and operation expenses (OPEX) for large projects have become important factors for
potential investors and consulting engineers to bear in mind for pre-construction planning and
proper evaluation.
This study reviews existing seawater reverse osmosis (RO) desalination protocols, covering key
areas such as pretreatment, RO treatment, and post-treatment of seawater desalination for best
performance, with emphasis on solar energy powered RO systems for seawater desalination. This
study also models an RO desalination plant using ultrafiltration and IX polishing for feed water
pretreatment and post-treatment respectively using the W.A.V.E. software program for design
efficiency. The success of seawater desalination using RO technology is predicated upon an
efficient feed water pretreatment and post-treatment regime. The use of an ultrafiltration system
in combination with filtration has been tested and adjudged to generate excellent quality feed water
for the RO system, notwithstanding the quality of the raw seawater. The model framework
depicted in this study can serve as a guide for design engineers in providing effective tools for the
design of an efficient RO system while maintaining an acceptable balanced hydraulic performance with considerable cost savings. For the experimental study, the physical experiment was conducted
at the Victoria and Alfred (V & A) Waterfront Desalination Plant in Cape Town, South Africa.
The experiment was aimed to investigate and quantify the effects of feed water temperature,
pressure, salinity, and pH parameters on RO membrane elements. The raw data collected were
processed and analyzed to establish the working principle of SWRO, and at the same time develop
a relationship model based on the identified system parameters for a better understanding of
SWRO operation. The modeling results are validated against the experimental result to evaluate
RO system performance. This financial analysis covering capital expenditures CAPEX and
operational expenditure (OPEX) of a traditional seawater reverse osmosis (SWRO) desalination
plant was conducted. The key parameters involved in the determination of life cycle costs of
seawater desalination were listed and analyzed. The parameters include water quality characteristics, production or plant capacity, location, energy consumption, materials,
maintenance, operation, RO module costs, chemicals, and award year. For clarity, a 2 MGD
SWRO plant was designed using WAVE software, and the design result was used to calculate the
lifecycle cost of producing a unit (m3/d) of potable water in Lagos, Nigeria, deploying a curve fit
approach and pertinent water economic analysis tools to develop a reliable life cycle cost for RO
systems with acceptable levels of accuracy, based on verifiable and practical parameters
Description
Masters Degree. University of KwaZulu-Natal, Durban.