Variations in isotopic composition of desalinated water

Variations in isotopic ratios of water samples collected from three plants functioning on two different desalination processes were evaluated by comparing their measured δ¹⁸O, δ¹⁷O and the δ²H isotopic ratios before and after desalination using a system based on tunable off‐axis integrated‐cavity‐output diode laser spectroscopy (OA‐ICOS). The δ¹⁸O, δ¹⁷O and the δ²H isotopic ratio measurements for water samples collected before desalination are compared against their peers of desalinated water from two desalination plants on the Arabian Gulf that are operating under the Multistage Flash (MSF) process. Also, variations in the δ¹⁸O, δ¹⁷O and the δ²H isotopic ratio measurements due to desalination from a Reversal Osmosis (RO) facility in Dhahran, Saudi Arabia were also reported and compared against variations in isotopic composition of water desalinated in two MSF plants.     

Feasibility analysis of distributed solar electricity penetration in cement manufacturing plants

Industrial manufacturing units like cement and steel are benefited little by solar electricity. This paper presents feasibility of application of solar electricity in cement manufacturing plants in a distributed manner. Distributed solar PV systems without battery have been simulated using HOMER Pro micro grid design software to see the effects on net present cost (NPC), levelised cost of energy (COE), pollutant emissions, coal consumption and cost of cement production. The daily solar radiation ranges from 3.79 to 6.71?kWh/m²/day and the total distributed load supplied by solar electricity is 8876.4?kWh/day which is 0.82% of overall plant load. The results show that proposed system reduces pollutant emissions by almost 23% with an increase of NPC by 3.075% and COE by 0.6436% only. It saves 709,139?kg coal per year with 0.6437% increase in cement production cost. Proposed system will be beneficial economically too when PV prices come down in future.     

Investigation on two integrated membrane systems for the reuse of electroplating wastewater

A pilot study was done on a nanofiltration (NF)‐reverse osmosis (RO) and RO‐NF integrated membrane system about the feasibility of membrane for electroplating rinse wastewater treatment in concentrate stage configuration. Nickel sulphate solution was used as a synthetic wastewater. Water recovery, metal rejection and specific entropy production (SEP) were investigated under different operation pressure, feed temperature and feed concentration. The results showed water recovery of RO‐NF system was more than 10% higher than NF‐RO system but the SEP was 14.47% lower than NF‐RO system. The detailed analysis on economic cost and environmental impact of two systems was conducted based on a certain operation condition. Results indicated that the cost of RO‐NF system was 0.46 $/m³, which was lower than NF‐RO system, and the prevention cost of RO‐NF system was 11.46% lower than NF‐RO system. Generally, RO‐NF system was better than NF‐RO system.     

A case study of ground source direct cooling system integrated with water storage tank system

Energy consumption for the commercial buildings has increasingly gained attentions, due to the significant electricity consumption and peak power demand. To solve this problem, this paper focuses on performance on the Ground Source Direct Cooling (GSDC) system integrated with a Water Storage Tank System (WSTS) in the summer, which directly utilizes the low-grade energy to supply high temperature water for the radiant floor cooling system and make full use of the electric rate difference between on-peak and off-peak periods. In summer, the indoor air temperature is controlled between 23 and 26 °C, resulting in a comfortable thermal environment. The total cooling capacities in 2014 and 2015 were 32.6 kWh/m² and 30.7 kWh/m², respectively. The annual energy consumptions for Electricity Unit Intensity (EUI) in 2014 and 2015 were 33.0 kWh/(m²·yr) and 32.1 kWh/(m²·yr), and the cooling energy consumptions only consumed 4.19 kWh/(m²·yr) and 4.55 kWh /(m²·yr), respectively. The annual operating cost of this cooling system only reaches 9 yuan/(m²·yr) through the analysis of 5 years’ operation. Compared to a conventional air cooled heat pump system, this cooling system has a larger initial cost, but its recovery period is less than 4.3 years, due to the extremely low operating cost. Overall, this GSDC system integrated with WSTS in the summer has remarkable advantages in thermal comfort and energy efficiency.     

Effect of mass recovery evaporator temperature and condenser temperature on the performance of a solar adsorption-based desalination plant

Water scarcity increases alarmingly as the population increases. Over the years, a number of salt water desalination techniques have been proposed and reached limitations. The requirement of minimum energy is very well satisfied by an adsorption system, since it can operate with low-grade energy and waste heat exhaust from most industries. The first part of this work discusses the effect of condenser and evaporator temperatures on the performance of silica-gel adsorption cycle mathematically. The second part discusses the performance variations due to mass recovery in the two-bed adsorption system mathematically. It was found that the reduction in condenser temperature and increase in the evaporator temperature both increase the fresh water productivity and cooling capacity of a plant. A desalination plant with mass recovery assistance is superior in performance than the conventional plant. Portable water productivity of 8?m³/day/ton is achieved with the condenser temperature of 15°C and the evaporator temperature of 30°C.     

天津反渗透海水淡化示范工程(1000m~3/d)

介绍了天津反渗透海水淡化示范工程(1 000 m3/d)的项目概况、工艺设计、设备配置、运行状况及造水成本分析.结果表明,针对天津海域海水浊度高、污染重的特点,采用初步预处理/双膜法淡化工艺完全能达到设计产水量和产水水质指标,并实现系统的稳定运行.     

Reverse osmosis desalination: Water sources, technology, and today's challenges

Reverse osmosis membrane technology has developed over the past 40 years to a 44% share in world desalting production capacity, and an 80% share in the total number of desalination plants installed worldwide. The use of membrane desalination has increased as materials have improved and costs have decreased. Today, reverse osmosis membranes are the leading technology for new desalination installations, and they are applied to a variety of salt water resources using tailored pretreatment and membrane system design. Two distinct branches of reverse osmosis desalination have emerged: seawater reverse osmosis and brackish water reverse osmosis. Differences between the two water sources, including foulants, salinity, waste brine (concentrate) disposal options, and plant location, have created significant differences in process development, implementation, and key technical problems. Pretreatment options are similar for both types of reverse osmosis and depend on the specific components of the water source. Both brackish water and seawater reverse osmosis (RO) will continue to be used worldwide; new technology in energy recovery and renewable energy, as well as innovative plant design, will allow greater use of desalination for inland and rural communities, while providing more affordable water for large coastal cities. A wide variety of research and general information on RO desalination is available; however, a direct comparison of seawater and brackish water RO systems is necessary to highlight similarities and differences in process development. This article brings to light key parameters of an RO process and process modifications due to feed water characteristics.     

Water recovery from treated urban wastewater by ultrafiltration and reverse osmosis for landscape irrigation

Techno-economic feasibility of water recovery from secondary effluents of an urban wastewater treatment plant (WWTP) for landscape irrigation was investigated considering two distinctive strategies: ultrafiltration (UF)/chlorination and UF/reverse osmosis (RO). Experimental performance evaluations were conducted separately for UF membranes and for different RO trans-membrane pressures. The quality of the effluent recovered by the UF/RO system was in accordance with the national and international guidelines. The produced reuse water was first class quality according to the national guideline for all parameters except sodium adsorption ratio (SAR), which can be eliminated readily by direct addition of KCl into the recovered water. Estimated field-scale costs indicated that UF/RO yielded a total cost of US$12,500,000–13,600,000 with annual operating cost being US$482,000–533,000 at 5–20 bar. The economic estimations guaranteed reimbursement with US$7,600,000–7,400,000 net present value, 0.22–0.39 year payback time, US$0.44–0.49/m³ treatment cost, and a benefit/cost ratio of 0.57.     

Treatment using reverse osmosis of an effluent from stainless steel manufacture

Reverse osmosis (RO) and physical/chemical technology were evaluated for treatment of neutralized spent acid effluent (seepage) containing high concentration levels of TDS (7500 mg/l), Ca (400 mg/l), Cr^VI (42 mg/l), nitrate-nitrogen (827 mg/l), ammonia-nitrogen (33 mg/l), fluoride (13 mg/l), phenolics (45 mg/l) and COD (620 mg/l). The calcium concentration level in the seepage could be reduced from approximately 400 to 5 mg/l with soda ash softening. Initial permeate flux (feed and bleed system, 85% water recovery) was 278 l/m²·d. Permeate flux, however, dropped rapidly in the beginning of the run and then remained approximately constant to the end of the run. However, chemical cleaning of the membranes was necessary to maintain flux. The TDS of the RO feed could be reduced in one case from 34,253 to 1560 mg/l (95.5% removal) at 85% water recovery. Nitrate and ammonia nitrogen were reduced from 2691 and 103 mg/l to 414 (84.6% removal) and 15 mg/l (85.3% removal), respectively. Chromium^VI and fluoride were reduced from 183 and 90 mg/l to 0.38 (99.8% removal) and 2.8 mg/l (96.9% removal), respectively. COD removals varied between 60 and 80%. No phenolics, however, could be removed from the feed (approximately 32 mg/l) with the cellulose acetate RO membranes. Phenolics, however, could be effectively removed (<0.2 mg/l) from the RO permeate with hydrogen peroxide oxidation or ion-exchange treatment. Preliminary test work has shown that it should be possible to treat the seepage effectively with RO for pollution control, effluent volume reduction and water recovery. Capital costs for a 600 kl/d plant for lime softening, RO and oxidation equipment are estimated at U.S. $58,000, U.S. $350,000 and U.S. $87,500, respectively.     

Long-term impact of water desalination plants on the energy and carbon dioxide balance of Victoria,Australia: a case study from Wonthaggi

In 2007, the state government of Victoria, Australia, announced plans to build a large desalination plant with a capacity of 150 million m³ per year of desalinated water. Currently, the only feasible source for significant expansion of the greenhouse-gas neutral (GGN) energy generation in the state is wind power. A criterion for GGN of a desalination plant has been formulated. In a case of no greenhouse gas contribution from the desalination plant, the criterion is satisfied if the annual growth of the electrical energy generated by GGN sources is around 6–9% for the period 2010–2070. Higher annual growth of 18% for the period 2008–2015, 8% annually for the period 2015–2035 and 6% annual growth thereafter are required if the desalination plant is contributing to the greenhouse-gas balance of the state.     

Impact of operating rules on planning capacity expansion of urban water supply systems

ABSTRACT

Water utilities often rely on industrial water supply (e.g. desalination) to complement natural resources. These climate-independent sources of supply allow operators to respond quickly to varying operating conditions, but require them to choose operating strategies, or rules. How does such operational flexibility impact the performance of water supply systems? How might it affect long-term plans for capacity expansion? Possibly significantly, as demonstrated by the analysis of a water supply system based on Singapore. First, we simulate the dynamics of the system under multiple rainfall and operating scenarios to understand the extent to which the operators’ behavior affect system performance. Results show that different operating rules can have comparable impact on the variability in system performance as hydrological conditions. Then, we show that small changes in the operating rules can lead to substantial changes in the capacity expansions, such as the size of a new desalination plant.     

Formation and fate of chlorination by-products in reverse osmosis desalination systems

Chlorination by-products may be formed during pretreatment or posttreatment disinfection in reverse osmosis (RO) desalination systems, potentially posing health, aesthetic and ecological risks. To assess the formation and fate of by-products under different conditions likely to be encountered in desalination systems, trihalomethanes, dihaloacetonitriles, haloacetic acids, and bromophenols were analyzed in water samples from a pilot-scale seawater desalination plant with a chlorine pretreatment system and in benchscale experiments designed to simulate other feed water conditions. In the pilot plant, RO rejection performance as low as 55% was observed for neutral, low-molecular-weight by-products such as chloroform or bromochloroacetonitrile. Benchscale chlorination experiments, conducted on seawater from various locations indicated significant temporal and spatial variability for all by-products, which could not be explained by measured concentrations of organic carbon or bulk parameters such as SUVA₂₅₄. When desalinated water was blended with freshwater, elevated concentrations of bromide in the blended water resulted in dihaloacetonitrile concentrations that were higher than those expected from dilution. In most situations, the concentration of chlorination by-products formed from continuous chlorination of seawater or blending of desalinated water and freshwater will not compromise water quality or pose significant risks to aquatic ecosystems.     

双膜法在市政污水处理厂的应用

天津市某污水处理厂再生水回用工程采用双膜法工艺,近期设计规模为2.0×10^4m^3/d,本文介绍了其工艺流程、设备配置情况、工程设计参数等.运行结果表明,采用双膜法对废水进行处理后出水水质良好,可以达到回用标准,其中超滤出水浊度为0.01～0.04 NTU,反渗透产水电导率＜ 15 μs/cm,脱盐率大于99％.经济性分析结果显示,该双膜法再生水回用工程的吨水运行成本为1.584元,具有良好的经济及环境效益.     

Life cycle cost analysis of a double-effect solar still

In this present paper, the study focuses on the development of a double-effect solar still with evacuated tubes for water desalination considered for small-scale applications at remote locations where only saline water or brackish water is available. In this present paper, the potable water cost per litre has been evaluated. The payback periods for different conditions of the distribution of distilled water, namely at the cost it is produced and at the selling price on market rate, have been evaluated. The cost of water per litre was a minimum of Rs. 0.19 with the average distillate output being about 20?l/day, when the interest rate and the lifetime of the solar still are taken as 4% and 50 years, respectively. The lowest payback time of 45 days was obtained when the selling price of water was Rs. 20?per litre.     

Economical viability analysis of an innovative gravity-driven rainwater harvesting system for a commercial office building

Gravity-driven rainwater harvesting (RWH) system showcases a promising alternative solution to reduce energy consumption in rainwater recycling. However, the economic efficiency is one of the most concerns with regard to the adoption of this green infrastructure. In this study, a commercial official building has a rooftop area of 1600 m² and with 560 inhabitants was assumed to apply two configurations of RWH system (i.e., gravity system and pressure system), and comparative study was conducted to evaluate the economic performance of two RWH systems. The potential water saving quantity of the RWH system was simulated based on a daily water balance model and their expected economic efficiency were discussed in terms of benefit cost ratio and net present value. Results shown that only when the building height is higher than 102 m or the property rent is less than 0.4 CNY (China Yuan) per square metre per day, can make the gravity system economically attractive. This study provides an innovative approach to utilize roof rainwater in a more low-energy mode; it is of great significance to promote building energy-saving and carbon reduction.     

Construction and utilization of rock caverns in Singapore Part D: Two proposed cavern schemes

This paper considers cavern schemes for crude oil storage and warehouse-shelter facilities. The crude oil storage scheme, which consists of five caverns, provides a net storage capacity for crude oil of 800,000 m³; the total cost for the facility, including civil construction, mechanical and electrical instrumentation, is in the order of S$80–100 million. The warehouse-shelter scheme consists of five storage caverns with combined storage capacity of 210,000 m³, and a defence shelter with capacity of 2000 persons. The cost for the warehouse-shelter scheme is S$66 million, including all mechanical and electrical utilities, systems for ventilation, fire prevention and smoke extraction, and pump installations for discharging leakage water.     

Assessment of electricity generation by wind power in nine costal sites in Malaysia

In this article, the wind power potential in Malaysia is examined. Hourly wind speed data for nine sites in Malaysia are used to optimally design wind power systems for remote housing electrification. These nine sites are Bintulu, Kota Kinabalu, Kuala Terengganu, Kuching, Kudat, Mersing, Sandakan, Tawau and Pulau Langkawi. The designed wind power systems are supposed to supply hourly load demand 6.13?kWh/day, 0.52?kW peak with 1% loss of load probability. The unit cost of the energy produced by each system is calculated and compared to the unit cost of the energy produced by a standalone photovoltaic (PV) power systems and a diesel generator power systems. The results show that the average unit cost of the energy produced by a wind power system in Malaysia is 1.6–7.29?USD/kWh while it is 0.35–0.5?USD/kWh and 0.27–0.30?USD/kWh for PV power system and diesel generator power system, respectively. Based on this, the use of wind power systems as standalone systems is not recommended for the selected sites.     

Vacuum membrane distillation of seawater reverse osmosis brines

Seawater desalination by Reverse Osmosis (RO) is an interesting solution for drinking water production. However, because of limitation by the osmotic pressure, a high recovery factor is not attainable. Consequently, large volumes of brines are discharged into the sea and the flow rate produced (permeate) is limited. In this paper, Vacuum Membrane Distillation (VMD) is considered as a complementary process to RO to further concentrate RO brines and increase the global recovery of the process. VMD is an evaporative technology that uses a membrane to support the liquid-vapour interface and enhance the contact area between liquid and vapour in comparison with conventional distillation. This study focuses on VMD for the treatment of RO brines. Simulations were performed to optimise the operating conditions and were completed by bench-scale experiments using actual RO brines and synthetic solutions up to a salt concentration of 300 g L⁻¹. Operating conditions such as a highly permeable membrane, high feed temperature, low permeate pressure and a turbulent fluid regime allowed high permeate fluxes to be obtained even for a very high salt concentration (300 g L⁻¹). For the membrane studied, temperature and concentration polarisation were shown to have little effect on permeate flux. After 6 to 8 h, no organic fouling or biofouling was observed for RO brines. At high salt concentrations, scaling occurred (mainly due to calcium precipitation) but had only a limited impact on the permeate flux (24% decrease for a permeate specific volume of 43L m⁻² for the highest concentration of salt). Calcium carbonate and calcium sulphate precipitated first due to their low solubility and formed mixed crystal deposits on the membrane surface. These phenomena only occurred on the membrane surface and did not totally cover the pores. The crystals were easily removed simply by washing the membrane with water. A global recovery factor of 89% can be obtained by coupling RO and VMD.     

Development of a thermally activated ceiling panel with PCM for application in lightweight and retrofitted buildings

This paper describes the development of a thermally activated ceiling panel for incorporation in lightweight and retrofitted buildings. The system allows use of renewable energy sources for the heating and cooling of office and industrial buildings. The design for the new ceiling panel exploits the properties of the phase change material (PCM) paraffin. Its high thermal storage capacity during phase change—up to 300 Wh/(m² day)—enables the overall panel thickness to be limited to a mere 5 cm. Active control of the thermal storage is achieved by means of an integrated water capillary tube system. The research project also included the development of a numerical model for computation of the thermal behavior of wall and ceiling systems incorporating PCMs. Simulation calculations were performed to determine the necessary thermal properties of the ceiling panels and specify requirements for the materials to be used. Laboratory tests were performed to verify the system’s performance and a pilot application is soon to be tried out in practice.     

Design and analysis of reflectivity for Mylar-coated solar dish

Energy is the key driver of the economy but energy crisis is a problem for the present-day source of energy. The concentrated solar power systems make use of different reflector configurations to convert the solar energy into high-temperature heat energy. Parabolic dish system is considered as the best suitable system for achieving high temperature and so it is opted for the study. Here, a solar dish is designed with an open diameter of 1.8?m (which is 2.5?m² in area), and reflective film is being used to reflect the solar irradiance and concentrated it in the focal point. A receiver of 1?mm thickness and 10?cm diameter is used at the receiver end to measure the temperature of the focal point. The setup has made to attain a maximum temperature of 940°C and average temperature of 850°C in the focal point at clear sky in a sunny day.