Small-scale Desalination Plants Research Articles

Evaluation of two-stage humidification-dehumidification desalination systems operated by a modified heat pump

The humidification-dehumidification desalination system operated by a heat pump is ideal for the decentralized small-scale desalination plant, due to its advantages of low investment and stable freshwater provision. To overcome the heat source limitation of multi-stage humidification-dehumidification system, a modified heat pump with a subcooler is used to operate the two-stage humidification-dehumidification system. With the difference of heated object, two layouts of the heat pump operated two-stage humidification-dehumidification systems are proposed, which are twice water-heated system and twice air-heated system. A parametric study is conducted to analyze the effect of feed seawater temperature and water/air mass flow ratio on the thermodynamic and economic performances of the proposed systems. A performance comparison is also carried out to analyze the difference between water heating and air heating, together with advantages over the reported systems. According to the results, it can be concluded that optimal feed seawater temperature and water/air mass flow ratio exist for the proposed systems. The twice water-heated system outperforms the twice air-heated system with the maximum freshwater productivity and gain output ratio of 34.69 kg/h and 7.69, while the lowest specific electricity consumption and freshwater production cost of 89.18 kWh/m3 and 14.52 $/m3. These results are also superior to those of previously reported HP-HDH systems, fully demonstrating the value of research and development for this novel system and its promising market application prospects.

Small Scale Plant of Desalination Using Multiple Tray Aerator and Two Different Membranes of Reverse Osmosis Using Low-Pressure Pump

The seawater is an abundant source that still not be utilized as potential raw water source to overcome the deficit of drinking water. This paper aims to design the small-scale desalination plant with the capacity of 2000 gpd for treating the brackish and seawater. There are two split processes, i.e., multi-tray aerator and filtration for reducing the Fe and Mn, while the two different type reverse osmosis membranes were used for desalinating process. Parameters used to verify the performance of small-scale plant are salinity and total dissolved solid for membranes, while the parameters for examining the pre-treatment results are TSS, BOD, pH, Fe, and Mn. The test results will be evaluated under the Regulation of The Minister of Health, Number 32/2017. The influence of pump pressure on flow will also be analysed. The results show that multi-tray aerator needs some improvement to reduce the Mn, and Fe. The two types of membranes could significantly reduce the salinity level up to 91.7%, from 22,900 ppm to 1200 ppm. The pump pressure needs to be replaced into the high-pressure pump to reduce the salinity level significantly.

PERFORMANCE ANALYSIS OF SMALL SCALE DESALINATION PLANT BASED ON MULTI TRAY AERATOR, MEDIA FILTER, AND SEAWATER REVERSE OSMOSIS

Seawater as abundant source for clean water is deemed as impossible task, particularly in developing country. Therefore, the feasibility of applying the reverse osmosis technology, particularly in the coastal area for drinking water is need further investigation. This paper aims to design and analyze the performance of small-scale desalination plant using combination of multi tray aerator, media filter, and multiple membranes consisting of ultrafiltration, brackish, and seawater membranes.Parameters used to verify the performance of small plant are salinity and total dissolved solid for membranes, while the parameters for examining the pre-treatment are Fe and Mn. The test results will be evaluated under the regulation of minister of health, Permenkes No. 32/2017. The influence of the pump pressure on the flow will also be analyzed.The result shows that the desalination plant can reduce the salinity concentration significantly from 10,200 ppm to 16 ppm, or 99.84%. The ratio of clean water to rejected water is 36%. However, bacteria of E. Coli are still found in clean water, which is probably caused by biofouling.

PERFORMANCE ANALYSIS OF SMALL SCALE DESALINATION PLANT BASED ON MULTI TRAY AERATOR, MEDIA FILTER, AND SEAWATER REVERSE OSMOSIS

Seawater as abundant source for clean water is deemed as impossible task, particularly in developing country. Therefore, the feasibility of applying the reverse osmosis technology, particularly in the coastal area for drinking water is need further investigation. This paper aims to design and analyze the performance of small-scale desalination plant using combination of multi tray aerator, media filter, and multiple membranes consisting of ultrafiltration, brackish, and seawater membranes.Parameters used to verify the performance of small plant are salinity and total dissolved solid for membranes, while the parameters for examining the pre-treatment are Fe and Mn. The test results will be evaluated under the regulation of minister of health, Permenkes No. 32/2017. The influence of the pump pressure on the flow will also be analyzed.The result shows that the desalination plant can reduce the salinity concentration significantly from 10,200 ppm to 16 ppm, or 99.84%. The ratio of clean water to rejected water is 36%. However, bacteria of E. Coli are still found in clean water, which is probably caused by biofouling.

Levelized cost of water assessment for small-scale desalination plant based on forward osmosis process

Availability and supply of fresh water is one of the most relevant challenges to be faced in the upcoming years. Efforts are being made worldwide to develop cost-effective and environmentally friendly technologies for the desalination of water. This work assesses the techno-economic performance of a forward osmosis desalination plant based on thermo-responsible polymers as a draw solute. Analysis of the plant performance for drinkable water production is carried out using a mathematical model for a small-scale application in Lipari (Sicily, Italy). Economic analysis was performed assuming that the thermal energy is provided by either a waste heat source or solar thermal collector, while electrical energy is supplied by either photovoltaic modules or from the grid. It was found that the lowest levelized cost of water of 2.68 €/m3 was reached with a photovoltaic + waste heat configuration and with the highest transmembrane pressure (hence the minimum membrane surface area). This cost is higher than that achieved with a reverse osmosis desalination plant of similar capacity with electricity supplied by photovoltaic modules, equal to 1.65 €/m3. As such forward osmosis technology must undergo significant improvements to become economically competitive.

Assessment of module arrangements of a direct contact membrane distillation process for a small-scale desalination plant

Assessment of module arrangements of a direct contact membrane distillation process for a small-scale desalination plant

Cost analysis and scheduling of the desalination vessel using reverse osmosis technology

Water scarcity issue becomes severe due to climate change and increase of water needs, globally. In order to provide fresh water in islands, small-scale desalination plants (< 100 m3/day) had been installed using reverse osmosis technology. To decrease high desalination cost of small-scale SWRO plants in islands in Republic of Korea, the desalination vessel having RO system (300 m3/day) was recently suggested. The desalination costs of the small-scale SWRO plants in islands and desalination vessel which can provide desalinated water to several islands were analyzed and were compared. The operational schedule of the desalination vessel in Shinan-gun, Republic of Korea was suggested considering the water demands, velocity and water storage of the desalination vessel, and distances between target islands. It was found that the water production cost could be saved when the desalination vessel was applied in Shinan-gun, Republic of Korea.

Improving Prediction Accuracy of Socio-Human Relationships in a Small-Scale Desalination Plant

This study examines who are the social actors in coordinating the environmental hot spots along the process of desalination. The integrated model design of life cycle modeling and Social Network Analysis is evaluated holistically by the inventory of life cycle and actor engagement ratings. Instances of the first small-scale reverse osmosis desalination plant project in Kelantan, Malaysia were used to meet the demands of this study. Environmental performance is measured through the Eco-Indicator 99 method in the Life Cycle Assessment Principles. Meanwhile, the network analysis of the actors’ networks involves stakeholders visualized through the UCINET software. The results show three hotspot points of membrane and brine disposal, the use of electrical energy, and the use of chemicals. The results acknowledged that 87 percent of the actors’ involvement from the dominant stakeholder group has been in control of the management and of the aforementioned hotspot. Undoubtedly, the results of this study can provide a better understanding of the potential market of actors to work with a more accurate and polycentric information flow for the development of more established desalination systems. This intriguing research will require further exploration in future studies.

Small-Scale Desalination Plant Driven by Solar Energy for Isolated Communities

In the last years, an increasing number of countries has been affected by water shortage. Seawater desalination driven by solar energy, which is usually available in arid regions, might be a solution to satisfy the freshwater demand. In this study, the feasibility of a stand-alone multi-effect desalination (MED) plant driven by solar energy for an isolated community was studied. The system was made up of a solar field, a MED unit, and a thermal storage that mitigated solar energy fluctuations. Simulations with different top brine temperature and inclination and number of the solar panels were carried out in Matlab and Aspen Plus on an hourly basis by considering one typical meteorological year for ambient temperature and solar radiation. Two different sources of electrical energy were considered: A photovoltaic (PV) field and a diesel generator. The results were compared from an energetic and economic point of view, by considering the adoption of plastic as a material for MED heat exchangers. The maximum water production was obtained with December as the design month. Polytetrafluoroethylene heat exchangers allowed the cost of water to be reduced up to 9.5% compared to conventional exchangers. The lowest cost of water (7.09 $/m3) was obtained with September as the design month and a tilt angle of 45° with the PV field as the electrical power source.

Water quality of small-scale desalination plants in southwest coastal Bangladesh

AbstractSouthwest coastal Bangladesh has an acute scarcity of safe drinking water. Both the government and non-government organizations are now promoting reverse osmosis based small scale desalination plants (SSDPs) to ensure safe drinking water. The aim of this study was to assess the physico-chemical and bacteriological quality of the desalination plants (DPs) installed in southwest coastal Bangladesh. Water samples were collected from the inlet and outlet of 10 DPs. The product water mostly complied with water quality standards. High levels of total dissolved solids (TDS) and electrical conductivity (EC) in feed water were reduced significantly after the treatment, although 10% and 20% of the product water samples respectively did not comply with the WHO drinking water standards for those parameters. Compliance of product water with the WHO and Bangladesh drinking water standards for chloride, bicarbonate and sodium were found in respectively 80%, 90% and 70% of the samples, although their concentrations in all the feed water samples were higher than both of the standards. About one-third of the DPs did not meet the drinking water standard for sodium, which may be an important health concern for the people consuming this water. Apart from one of the DPs, all of them complied with the standard for faecal coliform and Escherichia coli. Results suggest that proper maintenance of the SSDPs is necessary to ensure safe drinking water for the coastal population of southwest Bangladesh.

Mass balance for a novel RO/FO hybrid system in seawater desalination

Seawater Reverse Osmosis (SWRO) desalination is being used by several countries to aid the current demand for fresh water, hence numerous large scale and small scale desalination plants have been built during last decade. Despite major advancements in SWRO technology, the desalination industry is still facing significant practical issues. Two of the major issues are (1) generation of higher volumes of pre-treatment sludge, and (2) overall water recovery. This paper proposes a novel hybrid reverse osmosis (RO) – forward osmosis (FO) system to overcome the above two drawbacks. Mass balance calculations based on laboratory experiments have been used to predict increased water recovery and reduced pre-treatment sludge volume arising from large scale (340,000m3/day of intake) and small scale (15,000m3/day of intake) hybrid SWRO desalination plants. The percentage reduction of pre-treatment sludge volume, increase in overall RO water recovery, FO membrane area required and dilution in RO reject have been estimated.

Evaluation of transparent exopolymer particles and microbial communities found post-UV light, multimedia and cartridge filtration pre-treatment in a SWRO plant

Seawater reverse osmosis desalination is affected greatly by membrane biofouling which reduces membrane lifetimes and increases cost of permeate production. This work reports on the analysis of pre-treated seawater from a small-scale desalination plant operating with a three-stage pre-treatment system namely, (1) medium-pressure ultraviolet (MP-UV) disinfection, (2) multimedia filtration (MMF), and then finally, (3) cartridge filtration. Transparent exopolymeric particles (TEPs), chlorophyll a, phytoplankton, bacteria and viruses were evaluated in the pre-treated seawater after each pre-treatment stage over a one-year period (July 2012–July 2013). The concentration of TEPs was found to occasionally increase after MP-UV disinfection. MP-UV disinfection had no effect on the phytoplankton, bacterial or viral cell counts. In contrast, MMF was shown to be the most efficient step in removing TEPs and micro-organisms from seawater, while this removal was less significant for viruses. Cartridge filters had limited efficiency. Phytoplankton was observed to be more efficiently removed compared to bacteria. Although phytoplankton removal rates varied over time and were dependent upon cell size and shape, most of the micro-organisms were removed from seawater throughout the period of study. Investigating the seawater pre-treatment system during different season provided, thus, useful insights on its efficiency.

Economic analysis of a small-scale hybrid air HDH–SSF (humidification and dehumidification–water flashing evaporation) desalination plant

The economic factor plays an important role in determining the desalination decision. The current work introduces the economic analysis of a small-scale desalination plant. The desalination plant under investigation was based on two different technologies; the first technology is air humidification–dehumidification process while the second one is the water flashing evaporation process. The economic analysis was performed and compared for two different operating modes, the hybrid mode and the separated mode to show both the economic benefits and the feasibility measurement for each mode. The TCO (total cost of ownership) concept was adopted in the analysis. The TCO concept includes different types costs like; the fixed investment costs, the production costs, the internal rate of return on investment, the operating costs, the energy costs and some other economic parameters. The two modes of desalinations; hybrid mode and separated mode, are modeled, simulated and compared against each other. This comparison is held by using the developed design simulation program. Based on the cost of energy in Egypt, the estimated cost of the generated potable water by the hybrid system was 8.6 US$/m3, while that value was reached 9.74 $/m3 for the separated system. The current study showed that, the solar water heater collecting area and the plant lifetime are considered significant factors for reducing the water production cost. Also; the produced water costs decrease with increasing both the collecting area of the solar water heater and the plant lifetime.

Water quality evaluation of small scale desalination plants in the Gaza Strip, Palestine

The Gaza Strip is a highly populated, small area in which the groundwater is the main water source. During the last few decades, groundwater quality has deteriorated to a limit that the municipal tap water became brackish and unsuitable for human consumption in most parts of the Strip. To overcome this serious situation, the reverse osmosis (RO) technology is used to replace the tap water or to improve its quality. Several private Palestinian water investing companies established a small-scale reverse osmosis (RO) desalination plants to cover the shortage of good quality of drinking water in the whole Gaza Strip. The purpose of this paper is to investigate the chemical and bacteriological water qualities of different small scale of (RO) desalination companies in the Gaza Strip. The results of the chemical and bacteriological parameters were compared with the World Health Organization (WHO) standards. It was concluded that all chemical analyses of RO produced water are within the allowable WHO limits. Bacteriological analyses indicate that 25% of the produced water samples exceeded the maximum allowable value of the total coliform bacteria.

Small-scale desalination plants in Korea: Technical challenges

Desalination is now being proposed for many countries facing water scarcity as a supplement to existing water supplies. In Korea, however, desalination for domestic water usage was restricted to small isolated communities with access to no other water supply. To date, small-scale RO (reverse osmosis) desalination systems, which size ranges from 10 m 3/day to 1000 m 3/day, have been constructed to produce potable water from brackish or seawater. The major issue of these systems is the optimization of system design to minimize capital cost and energy consumption, which is likely to be difficult for small-scale systems. This paper reviews the current status and future challenges of small-scale desalination plants in Korea. The design and operation of existing desalination systems were compared in terms of treatment efficiency and energy usage.

Small scale desalination pilots powered by renewable energy sources: case studies

In Tunisia, water resources are very limited and have high salinities. Domestic water in rural communities has TDS reaching 2750 ppm. Inhabitants of these areas are scattered and lack proper infrastructure for the implementation of conventional desalination plants. However, these regions have an important potential of renewable energy (RE), especially solar energy where sunshine in southern regions can reach 2500 h per year. RE can be harnessed to power small-scale desalination plants in order to produce the fresh water necessary to cover the basic requirements (drinking and cooking). This paper aims to identify the potential of renewable energies, mainly solar and geothermal. It illustrates the quality of distributed water in rural communities. It presents several studies that were carried out, including solar multiple effects distillation, reverse osmosis driven by photovoltaic panels, and lately membrane distillation using a geothermal resource. The experimental results show technical promise. However, more investigations will need to optimise the operating parameters and improve economic feasibility.

Regulatory challenges of Palestinian strategies on distribution of desalinated water

The Palestinian Water Authority (PWA) as a regulator for the water sector in Gaza and the West Bank had initiated a strategy to build small-scale RO seawater desalination plants (600-1250 m3/d) using the donor community funds as a supporting source of potable water to be operated and managed by the private sector. It had been planned to distribute that water through water shops, tankers or direct connections to bulk users. In parallel a number of small scale private brackish water desalination plants along with a number of desalinated water vendors have been licensed to produce and distribute desalinated water usually by tankers and small reservoirs located at shops or streets. Different power costs, tariff and water quality between RO seawater and RO brackish water desalination plants is resulting in high competition in the local market. The competition is leading the seawater desalination plant operator to reduce operational hours, which in turns result into higher specific operational costs per cubic meter of water produced. The licensing procedures for brackish water RO plants neither clearly take in consideration product details of water quality nor the follow up and monitoring. This paper presents the regulatory actions and a monitoring plan to be taken by the Palestinian Water Authority on the strategy of licensing and operation of small-scale desalination plants for the benefit of consumers and operators.

Regulatory challenges of Palestinian strategies on distribution of desalinated water

The Palestinian Water Authority (PWA) as a regulator for the water sector in Gaza and the West Bank had initiated a strategy to build small-scale RO seawater desalination plants (600-1250 m3/d) using the donor community funds as a supporting source of potable water to be operated and managed by the private sector. It had been planned to distribute that water through water shops, tankers or direct connections to bulk users. In parallel a number of small scale private brackish water desalination plants along with a number of desalinated water vendors have been licensed to produce and distribute desalinated water usually by tankers and small reservoirs located at shops or streets. Different power costs, tariff and water quality between RO seawater and RO brackish water desalination plants is resulting in high competition in the local market. The competition is leading the seawater desalination plant operator to reduce operational hours, which in turns result into higher specific operational costs per cubic meter of water produced. The licensing procedures for brackish water RO plants neither clearly take in consideration product details of water quality nor the follow up and monitoring. This paper presents the regulatory actions and a monitoring plan to be taken by the Palestinian Water Authority on the strategy of licensing and operation of small-scale desalination plants for the benefit of consumers and operators.

Decentralized desalination of brackish water by a directly coupled reverse-osmosis-photovoltaic-system - a pilot plant study in Jordan

Fresh water is scarce in the Kingdom of Jordan. The situation is aggravated by a fast growing population and an increasing per-capita consumption of water. Desalination of brackish water can solve this problem at least partially, since, especially in Jordan, larger sources of brackish water exist. Since Jordan has few fossil fuel sources of its own, it seems to be important combining brackish water desalination with renewable energy sources. Such a concept is especially promising in cases of smaller capacities. However, there is a lack of experience with small-scale, decentralized desalination plants powered by renewable energies. Therefore, an investigation of the technical feasibility and a cost benefit analysis of a brackish water small-scale desalination plant in a rural area has been being carried out. It revealed the best socio-economic performance for a reverse osmosis directly coupled with a photovoltaic-system. In Phase II of this project a pilot plant with a fresh water capacity of 40 m 3/d consisting of a directly coupled reverse-osmosis-photovoltaic-system will be realized in Qatar (Jordan). This pilot plant study is financed by the Ministry of Science and Research of the German State North Rhine Westfalia.