Small-scale Reverse Osmosis System Research Articles

A feasibility study of solar-powered reverse osmosis processes

The use of solar-powered reverse osmosis desalination systems is a sustainable and environmentally friendly solution in the desalination industry. However, there are some substantial technical and economic challenges due to the intermittency and fluctuation of solar energy. Recent technological improvement and feed-in tariff policies enable these systems to be competitive with conventional grid-connected reverse osmosis systems. In this paper, a feasibility study of the integration of solar panels with the grid to power small-scale reverse osmosis systems (namely up to 2000 m3/day) is conducted in Iran, as a country with a low price of electricity. For this purpose, a city located on the northern coast of the Persian Gulf, which deals with water shortage but has high solar radiation, is selected as a case study. Five different scenarios are considered, and the impacts of the use of energy recovery devices, energy storage systems and membrane characteristics have been studied. Finally, a detailed cash flow analysis is provided for each scenario. In the end, we show the economic viability of solar-powered reverse osmosis plants when their unused or surplus solar electricity is exported to the grid.

Time-Dependent Desalination Tests for Small-Scale SWRO Pilot Plant Installed at Urla Bay, Turkey

In this work, performance data from a small-scale reverse osmosis (RO) plant based on seawater FilmTec spiral wound RO membranes for different periods of operation are presented and analyzed. A prototype RO set-up with a 2,200 L/d capacity was installed and operated at Urla Bay which was located in Izmir, Turkey. This study typically investigates RO performance in terms of permeate flux, salt and boron rejections. Thin-flm composite membrane-based RO technology was successfully used with this RO set-up, which gave an average salt rejection of more than 95%. It was found that over a period of 36 hours of continuous operation, the permeate flux decreased by approximately 4% of its initial value but salt rejection stayed nearly constant. In this study, long-term data were also compared with a full-capacity operation using two paralleled membranes and a lowered-capacity operation with a single membrane. The results show that the small-scale RO system was successfully operated to mimic typical large-scale RO plants installed for production of potable water.

Case Study of a Small Scale Reverse Osmosis System for Treatment of Mixed Brackish Water and STP Effluent

A case study on utilizing reverse osmosis (RO) technology to fulfill fresh water needs at a mall and a hotel has been done on Bali Island, Indonesia. A mix of brackish water and sewage treatment plant (STP) effluent was used as feed water in the RO system. The system used 36 membrane elements (CSM RE 8040 BLN) arranged into two stages: 8 pressure vessels (PVs) in the first stage and 4 PVs in the second stage, each loaded with 3 membranes. The objectives of this research were to assess the cleaning effectivity in the plant, to evaluate the cleaning of 1 membrane element using a CIP system, and to assess the use of the membrane for filtration in the pre-treatment system. SEM and FTIR analysis indicated that the foulants on the membrane surface were dominated by organic foulants and inorganic deposits. To clean the discarded membrane the proposed method used NaOH solution (pH 12 and pH 13) and citric acid (pH 2 and pH 3). All membranes displayed a dramatic decline in rejection of about 80%. Based on the rejection tests of SO 4 2- , Cl - , turbidity reduction approached 100%. It can be concluded that an RO membrane that has undergone selectivity decline can be re-used as a filtration membrane in the pre-treatment system.

Integration of hybrid power (wind-photovoltaic-diesel-battery) and seawater reverse osmosis systems for small-scale desalination applications

Desalination is a method used to produce water for human consumption and/or industrial use. Seawater treatment systems powered by renewable sources are regarded as sustainable methods for providing drinking water for coastal zones and islands where there is no electrical grid. This study evaluated the operations of seven different (off-grid) power systems (wind-photovoltaic-diesel-battery) used to satisfy the electrical energy demand of a small-scale reverse osmosis system with a capacity of 1m3/h used on Bozcaada Island, Turkey. The hybrid optimisation model for electric renewable (HOMER) software was selected to perform techno-economic analyses of the systems. On the other hand, the reverse osmosis system analysis model (ROSA) was used to determine the energy requirement of the reverse osmosis system examined in this study. The results of this study showed that the electricity cost was $0.308/kWh for the optimal system consisting of wind turbines with a rated power of 10kW, a 20kW PV panel, and a diesel generator with a rated power of 8.90kW, while the water cost was $2.20/m3. Additionally, the results showed that combining the hybrid power system and reverse osmosis system could be a cost-effective method for remote areas with good wind and solar power potential.

SOLUTION-DIFFUSION MODEL FOR A SMALL SCALE REVERSE OSMOSIS SYSTEM

Reverse osmosis (RO) often used for desalination, in producing the ultrapure water for electronics, pharmaceuticals and power generation industries and also it was used in small niche process such as food processing and pollution control. Analysis of membrane performance required multiple of experimental run. Experimental work can be time consuming and costly. Hence, this work aims to model a small scale RO system by using a solution-diffusion model to minimize the experimental work. The model was verified by comparing the data obtained from the model and experimental data. Other studies, which include, the influence of solute feed concentration on the RO system was also been investigated. A commercial RO Trisep flat sheet membrane was used. The solute permeate concentrations, solvent permeate flux, final solute feed concentrations and rejection rate of sodium chloride (NaCl) was analyzed to observe the membrane performance. Result shows that some experimental data has almost similar trend with the simulated data. Both solute feed concentration and rejection rate of NaCl over time show almost similar trends with percentage errors are 8.89% and 0.76% respectively. As solute feed concentration increased, the solute permeate concentration increased. In contrast to the solute permeate concentration, when the solute feed increases the solvent permeate flux decreases and rejection rate will also decrease.

Pilot study on arsenic removal from groundwater using a small-scale reverse osmosis system—Towards sustainable drinking water production

Arsenic contamination of groundwater is posing a serious challenge to drinking water supplies on a global scale. In India and Bangladesh, arsenic has caused the most serious public health issue in the world for nearly two decades. The aim of this work was to study an arsenic removal system based on reverse osmosis at pilot scale treating two different water sources from two different locations in the State of Bihar, India. For this purpose two villages, Bind Toli and Ramnagar in the Patna District were selected, both located very close to the river Ganga. The trials were conducted with aerated and non-aerated groundwater. It is the first time that the arsenic removal efficiency for aerated and non-aerated groundwater by reverse osmosis technology in combination with an energy-saving recovery system have been studied. As the principle of reverse osmosis requires a relatively high pressure, its energy demand is naturally high. By using an energy recovery system, this demand can be lowered, leading to an energy demand per liter permeate of 3–4Wh/L only. Due to high iron levels in the groundwater and as a consequence the precipitation of ferric (hydr)oxides, it was necessary to develop a granular media filter for the trials under aeration in order to protect the membrane from clogging. Two different materials, first locally available sand, and second commercially available anthracite were tested in the granular media filter. For the trials with aerated groundwater, total arsenic removal efficiency at both locations was around 99% and the arsenic concentration in permeate was in compliance with the WHO and National Indian Standard of 10μg/L. However, trials under anoxic conditions with non-aerated groundwater could not comply with this standard. Additionally a possible safe discharge of the reverse osmosis concentrate into an abandoned well was studied. It was observed that re-injection of reject water underground may offer a safe disposal option. However, long-term hydrogeological studies need to be conducted for confirmation.

Techno-Economy Analysis A Small Scale Reverse Osmosis System for Brackish Water Desalination

This study aims to get the design process and the economics of small-scale desalination of brackish water in Indonesia which has interest in the range of 12-14%, electricity cost of $0.09-0.13/kWh, and groundwater tax regulation. The use of BWRO desalination system in Indonesia has been generally done at small scale. This study based on Bali island with electricity cost at $0.1/kWh and water tax at $0.37/m 3 . Techo economy evaluation was analysed for plant capacity of 150-1,00 m 3 /day, recovery of 40% with brackish water water salinity of 5,000 ppm. Price of desalted water during first year a case study is $1.31/m 3 . It can be concluded that e conomic evaluation based on NPV and IRR shows that it is worth ed.

Design of power systems for reverse osmosis desalination in remote communities

AbstractMany remote communities lack access to a reliable water supply. They often have access to brackish groundwater or seawater, making reverse osmosis desalination a possible solution. However, reverse osmosis desalination is an energy-intensive process and many remote communities are off the electrical grid. Determining the most economic reverse osmosis system configuration and electrical power source for a given remote community is a challenge due to their unique resource availabilities. This paper presents an optimization-based approach to compare the economics of different small-scale reverse osmosis systems and power sources for remote communities. In this approach, physical models describe the performance of electrical power systems composed of photovoltaics, wind turbines, diesel generators, batteries, and hybrid systems. These power system models are coupled to a reverse osmosis system model to determine the water production. An optimization is performed to determine the most economic power sy...

Energy recovery through a water-hydraulic motor in a small scale RO desalination system

The use of energy recovery devices (ERDs) is now well known in seawater desalination. These devices are classified into two kinds of ERDs — one is the centrifugal turbine type and the other is the positive displacement type. However, because these ERDs are appropriate for large-scale reverse osmosis (RO) systems, a different type of ERD suitable for small-scale RO systems is required. For energy recovery in small desalination plants, hydraulic pump-hydraulic motor assembly is preferred due to the benefits including high efficiency, low pulsation, and no maintenance. For this reason, we are developing an integrated pump combined with energy recovery function. That is, the pump and motor pistons are contained in one cylinder barrel so that this integration can provide compact design. In this work, we present the experimental results of the small reverse osmosis system equipped with a water-hydraulic motor of axial piston type based on the swashplate principle for feasibility test about the mechanism of ERD-...

NUMERICAL MODELING OF CONCENTRATION POLARIZATION IN REVERSE OSMOSIS DESALINATION SYSTEMS

Fresh water is rapidly becoming a scarce resource in many countries around the world. Modern desalination technologies, applied to seawater and brackish water, offer effective alternatives in a variety of circumstances. Out of the several desalination processes considered, reverse osmosis is one of the major processes used in desalination. Reverse osmosis is in general the most economical process for desalination of brackish water and seawater. As widely accepted technology, reverse osmosis became more and more competitive and is superior to the traditional thermal process when a comparison is made of capital investment and energy consumption. The present study pertains to modeling numerically of a seawater desalination system. The proposed method considers solving the momentum, energy and mass transfer conservation equations for a smallscale reverse osmosis system. The solution of the conservation equations was obtained using the SIMPLE (Semi-Implicit Method for Pressure Linked Equations) pressure-correction scheme and the high order discretization scheme QUICK (Quadratic Upwind Interpolation Convective Kinematics) is employed for the discretization of convection terms in the frame of staggered grid. The model was verified using the experimental data from the literature. Parameter sensitivity was carried out to select the proper time and spatial step sizes. The calculations were run for a very long time enabling a prediction of operational performance at high overall system recoveries. Effects of the feed temperature variations on the operating parameters are also considered in this study.

Mathematical modeling of reverse osmosis systems

The present investigation pertains to modeling of seawater desalination system. A simulation model was developed and verified for a small-scale reverse osmosis system. The proposed model combines material balances on the feed tank, membrane module andproduct tank with membrane mass transfer models. Finally a comprehensive simulation model has been developed incorporating the effect of mass transfer inhibition The model is non-linear differential equation representing the feed concentration as a function of operating time and space. The solution of the simultaneous differential equations was obtained using the fourth order Runge-Kutta method, due to self starting and stability. The model was verified using the experimental data from the literature [17,24]. Parameter sensitivity was carried out to select the proper step size. The simulation was run for over 1000 11 enabling a prediction of operational performance at high overall system recoveries.

Modeling of small scale reverse osmosis systems

A simulation model was developed and verified for a small scale reverse osmosis (RO) system operating in a closed-loop concentrating mode. The model combines material balances on the feed tank, membrane module and product tank with membrane mass-transfer models. The proposed model is a nonlinear differential equation representing the feed concentration as a function of operating time. Correlations of flux, solute concentrations, and rejection with operating time and overall system recovery are functions of the model. Total dissolved solids (TDS) was the parameter representing solute concentration. Data from simple salt and industrial wastewater experiments were used to verify the model. The model suggests a good fit to the data over the range studied.