Reverse osmosis desalination plants — marine environmentalist regulator point of view

The environmental characteristics of the brine and its impacts on the marine environment were always the “backyard” and the less concern while planning and operating RO desalination plants. The lack of drinking water in Israel made desalination a national goal. The first huge RO plant was initially operated in Israel on 2005 — 100 Mm³/y and by the end of 2010 305 Mm³/y potable water expected to be produced. Construction and installation of desalination plants requires applying suitable environmental solutions for protecting and preserving the marine and coastal environment from ruin or deterioration.

The Israeli environmental legislation is described including the marine environmental policy and regulations as well as the acquired operational experience during the last two years. Results from the first year of operation and monitoring are shown along with the new appearance of the red phenomenon discharge of VID desalination plant in Ashkelon.

The environmental policy based on the precautionary principle is performed and includes environmental requirements and guidelines for pretreatment, discharge composition, planning marine outfall, background and compliance marine monitoring program and discharge quality standards.     

Desalting seawater and brackish water: a cost update

This report is a second update of costs, originally presented in ORNL/TM-5070, which gave cost estimates for desalting seawater and brackish water based upon first quarter 1975 costs. The first update was based upon 1977 costs. The specific input to the report includes two earlier U.S. Department of Energy reports, recent work sponsored by the U.S. Office of Water Research & Technology, and new equipment and operating cost input from major equipment suppliers and users.

Cost estimates are given for desalting seawater by distillation and reverse osmosis, and for desalting brackish water by reverse osmosis and electrodialysis. The report includes the cost of generating steam and electrical energy on site using coal-fired boilers as well as oil-fired boilers, and dual purpose nuclear/electric seawater distillation plants. The energy costs for both reverse osmosis and electrodialysis are based upon the availability of electricity at a fixed rate. Cost data were computed as a function of plant size, and include both capital costs and construction costs which are considered as typical. These assumptions are used to develop the reference cases of total water cost. The manner of presentation is such, however, that the costs can be easily adjusted to reflect local conditions.     

Catalytic oxidation of phenol in aqueous solutions

The objective of this work is to investigate catalyst systems for the oxidation of phenol in water in a batch autoclave. The main experimental variables are the type and the composition of the catalyst, the catalyst loading, temperature, oxygen partial pressure, initial phenol concentration and the stirrer speed. Commercial catalysts were used. Experimental work was conducted in two different laboratories. In one laboratory, the catalysts tested were 35% CuO+65% ZnO; 5–15% CuO+85–95% Al₂O₃; 26% CuO+74% Cu Chromite. In the other laboratory, the catalysts tested included 35% CuO+65% ZnO; 5–10% Ba₂CO₃+<5% C+30–40% CuO+60–70% ZnO; and 8–15% Al₂O₃+1–5% C+35–45% CuO+40–50% ZnO. With some of these catalysts depending on the operating conditions, complete phenol conversion could be obtained within 90 min. Under certain experimental conditions, the reaction underwent an induction period after which there was a transition to a much higher activity regime. The induction period may be due to an autocatalytic reaction system or to a very slow rate of formation of hydroquinone and catechol which then readily oxidize to o- and p-benzoquinone. An increase in the temperature and the oxygen partial pressure decreased the induction period, which increased as the catalyst to phenol ratio increased. 26% CuO+74% Cu Chromite and 8–15% Al₂O₃+1–5% C+35–45% CuO+40–50% ZnO were found to be the most active catalysts.     

An atomic force microscope study of calcium carbonate adhesion to desalination process equipment: effect of anti-scale agent

Whilst carbon dioxide is water soluble the system is somewhat complex and results in the presence of carbonate anions which interact with cations such as Ca²⁺ and Mg²⁺ present in seawater to form insoluble carbonates, especially at high temperatures. In multistage flash (MSF) desalination plants CO₂ gas becomes less soluble in the brine as a result of the brines high temperature and high salinity which causes the pH to be in the range of 8–9. The presence of these conditions causes the release of CO₂, simultaneous to the formation of scale deposits since its solubility is a function of the solution pH.

The formation of scale deposits, such as CaCO₃ causes fouling in the MSF distillers which has previously been studied by many researchers. A great amount of work has been carried out and more is yet to come in order to fully understand the role of various components and their interaction including the effectiveness of scale control techniques. The deposits may serve as an adsorbing film raising the speed of the loss of crystals or promoting the formation of scale deposits and therefore further adhesion on the wall surfaces of the MSF distillers and other process plant equipment leading to deterioration in the performance and efficiency of the whole desalination plant.

This paper shows direct quantification of the adhesion forces between CaCO₃ crystals and different process equipment surfaces under different conditions. This was carried out using an atomic force microscope (AFM) with an attached CaCO₃ crystal as a colloid probe to bring the CaCO₃ directly into and out of contact with the surfaces and measuring the resultant adhesion. This involved using surfaces different grades of roughness and carrying out measurements in synthetic sea water solutions of differing ionic strengths as well as with real seawater samples. Furthermore, the effect on measured adhesion of adding anti-scalant to the solutions was examined.     

The Influence of the Spray Drying Process on Product Properties

Uniform and repeatable product characteristics are critical in the performance and acceptance of consumer products, and the spray drying process can have a major influence on achieving these characteristics. This article shares experiences in the Spray Drying of powdered detergent granules in Procter & Gamble. It looks at the influence of both process operation and process equipment design on product characteristics. Procter & Gamble (P&G) is a major global producer of consumer products in the areas of fabric and home care; personal and beauty care; health care; and snacks and beverages. Whilst different drying operations, and product quality measuring tools are mentioned by Genskow (Genskow, L.R.¹ Considerations in Drying Consumer Products, Proceedings of 6th International Drying Symposium, Versailles, September, 1988; Keynote lecture, 39-46.) as being involved in all of the categories of Company production, I will concentrate on the counter-current Spray Drying process and controls, used in the manufacture of most of the detergent granules business of P&G. This area is the oldest and largest of the Company's core business activities. Innovative technology development is critical in continuing to satisfy the consumer need for performance and value. Use of modeling in the spray drying process is helping the Company to move faster in delivering these advanced technologies. And, through better understanding of the process, it is possible to minimize capital expenditure, and improve trouble-shooting ability across the global production facilities.     

Synthesis, structure and thermal properties of a novel 3D aluminophosphate UiO-26

The synthesis of a novel 3D aluminophosphate is described. The thermal properties of the material were investigated, and the existence of three high-temperature variants was revealed. The crystal structures of the as-synthesized material (UiO-26-as) and the material existing around 250°C (UiO-26-250) were solved from powder X-ray diffraction data. UiO-26-as with the composition [Al₄O(PO₄)₄(H₂O)]²⁻[NH₃(CH₂)₃NH₃]²⁺ crystallizes in the monoclinic space group P2₁/c (no. 14) with a=19.1912(5), b=9.3470(2), c=9.6375(2) Å and β=92.709(2)°. It exhibits a 3D open framework consisting of connections by PO₄ tetrahedra with AlO₄ tetrahedra, AlO₅ trigonal bipyramids and AlO₅(H₂O) octahedra forming two types of layers stacked along [1 0 0] and connected by Al–O–P bondings. The structure possesses a 1D 10-ring channel system running along [0 0 1], in which doubly protonated 1,3-diaminopropane molecules are located. UiO-26-250 with the composition [Al₄O(PO₄)₄]²⁻[NH₃(CH₂)₃NH₃]²⁺ crystallizes in the monoclinic space group P2₁/c with a=19.2491(4), b=9.27497(20), c=9.70189(20) Å and β=93.7929(17)°. The transformation to UiO-26-250 involves removal of the water molecule which originally is coordinated to aluminum. The rest of the structure remains virtually unchanged. The crystal structures of the two other variants existing around 400 (UiO-26-400) and 600°C (UiO-26-600) remain unknown.     

Pilot filtration study to reduce fouling on Marbella seawater RO plant

The seawater RO plant at Marbella had operated intermittently, and at low flowrates, since its construction 10 years ago. This was because the plant had been designed to operate at times of water shortage, to provide water when the conventional supplies were not available.

During the early part of the 21st century, the mode of the plant changed, and it was expected to operate at design capacity for most of the time. This brought two facts to light — that during high abstraction rates the intake water quality deteriorated significantly, and that the filtration system that had been installed was not capable of adequately filtering the feed water to make it suitable for feeding to a reverse osmosis plant.

The plant was originally built using DuPont B10 permeators. Due to the unavailabilty of these permeators, the plant is currently being converted, stream by stream, to spiral wound membranes supplied by Hydranautics.

At design flowrates, the DuPont system fouled rapidly, and required cleaning every two weeks. The spiral trains fouled more slowly, but still required cleaning at a higher frequency than would be considered normal for this type of plant.

A pilot filtration plant was installed on site to attempt to find the following;

• An optimum coagulant for the water.

• An approximate dose rate for that coagulant.

• The effect of different media on the quality of filtered water.

• The length of run between backwashes using different media.

• The quality of water that can be achieved using this coagulant and media.

By installing pressure tapping points along the length of the filter, the area of differential pressure could be measured. This was used to ensure depth filtration was taking place, and the foulants were being removed through the length of the bed rather than surface filtration.

The trials lasted a total of three months and achieved all of the targets set. The SDI typically achieved by the main plant was approximately 5. The pilot filter showed that the SDI could be reduced to below 2 by modifying the filters and applying a coagulant. Filter runs achieved by the pilot filters were in excess of 48 h.

Following the trials, the plant commenced replacing the media in the filtration system, and is expected to install a coagulant dosing system once this was complete.

This paper describes the pilot plant built, the selection of the media, and the coagulants used, and presents the operating data produced from the trials.     

Desalination costs in Australia: A survey of operating plants

A survey of desalination costs in Australia was conducted using data obtained from plant operators, and is reported in second quarter 1986 A$. Unit water costs range from $0.76/kL (for a precursor to deionisation for boiler feed) to $14/kL (for emergency supplies for an island resort).

However, an average figure for desalination of brackish water is $3–$4/kL, and for seawater, $5–10/kL in medium-sized installations.

Capital costs for brackish water plants have been correlated with plant design capacity ranging from 10 to 3400 kL/d.

There is insufficient information to allow a proper comparison between reverse osmosis and electrodialysis for brackish water desalination.     

The Yuma Desalting Plant

The 96 million gallon per day Yuma desalting plant is part of a complex project intended to solve a long standing water quality problem between the United States and Mexico. Designed to treat up to 129,000 acre-feet of 3200 mg/l irrigation return flows, the plant will deliver 283 mg/l product water to maintain a 115 mg/l differential between water delivered to U.S. users and to Mexico .

Design of the plant was preceded by an extensive research program to determine pretreatment requirements, membrane performance, plant capacity and equipment and instrumentation performance. Two pretreatment systems were tested. Partial lime softening followed by multi-media filtration was chosen for the final design. Nine membrane systems (both reverse osmosis and electrodialysis) were tested. Two spiral wound reverse osmosis systems were chosen as most efficient from physical and economic viewpoint, and contracts for site preparation and construction of the intakes and sedimentation basin is scheduled for award summer 1979 with construction of the main plant and installation of desalting equipment scheduled for award summer of 1980.

Based on January 1979 prices, total cost of the desalting complex is approximately $190 million (including interest during construction). The investment cost per daily gallon of installed capacity is approximately $2. per 1000 gallons of desalted water (capital amortization plus operation and maintenance) is $0.77.     

Solar still an appropriate technology for potable water need of remote villages of desert state of India — Rajasthan

Rajasthan, the largest state of the India faces a grim scenario in relation to water availability resources. Rajasthan has two-third of its area as desert and it faces scanty rainfall, recurring droughts in 3–4 years in a cycle of 5 years. It would be seen from the present status of drinking water detailed out of 237 blocks in Rajasthan that only 49 are safe in terms of ground water while 101 are critical and semi critical and 86 are over exploited. It is a hard reality that state dependence on ground water is 91% for drinking water. About 21,190 villages/habitations suffer from the problem of excessive salinity, 23,297 villages/habitations suffer from excess fluoride problem and 20,659 villages/habitations suffer from excess nitrate problem. Based on the WHO guidelines for drinking-water quality about 56% of the water sources are un-potable.

But on other hand Rajasthan is blessed with ample amount of solar radiation. The arid parts of Rajasthan receive average maximum solar radiation of about 7.5 kW h/m² in the month of May and minimum of about 4.6 kW h/m² in the month of Dec & Jan. Part of this energy may be utilized to meet out drinking water need of remote area dwellers of Rajasthan.

Solar distillation and desalination unit is most appropriate for remote area dwellers because it is economical, easy to construct and maintain. Most parts of Rajasthan have enough solar radiation available which is the prime input for the system.

A low cost high efficiency solar still with porous evaporating surface is fabricated for the purpose and cost analysis is done to calculate the cost of water in this paper [Bassam et al., Experimental study of a solar still with sponge cubes in the basin, Energy Conserv. Manage., 44 (9) (2003) 1411–1418; Bouchekima et al., Performance study of the capillary film solar distiller, Desalination, 116 (1999) 185–192; Bassam et al., Water film cooling over the glass cover of a solar still including evaporation effect, Energy, 22 (1) (1997) 43–48].

Water samples are collected from a remote village of state and analyzed to find the quality of drinking water. The working habits and medical history of the villagers is also investigated to work out cost analysis more realistically.     

An innovative trigeneration system using biogas as renewable energy

One of the ways to decrease the global primary energy consumption and the corresponding greenhouse gas emissions is the application of the combined cooling, heating and power generation technologies, known as trigeneration system. In this research an innovative trigeneration system, composed by an absorption heat pump, a mechanical compression heat pump, a steam plant, and a heat recovery plant is developed. The low temperature heat produced by absorption chiller is sent to a mechanical compression heat pump, that receives process water at low temperature from the heat recovery plant and bring it to higher temperatures. The trigeneration system is fed by biogas, a renewable energy. A design and a simulation of the system are developed by Chem Cad 6.3? software. The plant produces 925 kW of electrical energy, 2523 kW of thermal energy and 473 kW of cooling energy, by the combustion of 3280 kW of biogas. Primary energy rate(P.E.R.) is equal 1.04 and a sensitivity analysis is carried out to evaluate the effect of cooling capacity, produced electrical energy and process water temperature. The first has a negative effect, while other parameters have a positive effect on P.E.R. Compared to a cogeneration system, the trigeneration plant produces the 28% higher of power and the 40%lower of carbon dioxide emissions. An economic analysis shows that the plant is economically feasible only considering economic incentives obtained by the use of heat pumps and steam plant at high efficiency. Saving 6431 t·a~(-1) corresponding to 658000 EUR·a~(-1) of incentives, the plant has a net present value(N.P.V.) and a pay back period(P.B.P.) respectively equal to 371000 EUR and 4 year. Future works should optimize the process considering cost and energetic efficiency as the two objective functions.     

Coupling of standard condensing nuclear power stations to horizontal aluminum tubes multieffect distillation plants

No large nuclear back-pressure turbines are available to day. Standard condensing nuclear turbines could operate continuously with a back-pressure of up to 7″ Hg, exhausting huge amounts of steam at 56°C - 640°c with a loss of electricity production of only 6%–10%. p]The horizontal aluminium tube multieffect distillation process developed by “Israel Desalination Engineering Ltd.” is very suitable for the use of such low-grade heat. A special flash-chamber loop constitutes a positive barrier against any possible contamination being carried over by the steam exhausted from the turbine to the desalination plant. The operation is designed to be flexible so that the power plant can be operated either in conjunction with the desalination plant, or as a single purpose plant. Flow sheets, heat and mass balances have been prepared for eight different combinations of plants. Only standard equipment is being used in the power plant.

The desalination plant consists of 6 to 12 parallel double lines, each of them similar to a large prototype now being designed.

Water production varies between 50 and 123 MGD and water cost between 90 and 137 ¢/1000 gallons.

Costs are based on actual bids.     

Quantitative comparison of dynamic controllability between a reactive distillation column and a conventional multi-unit process

A comparison of the steady-state economic optimum designs of two alternative chemical processes was presented in a previous paper [Kaymak, D. B., & Luyben, W. L. (2004). A quantitative comparison of reactive distillation with conventional multi-unit reactor/column/recycle systems for different chemical equilibrium constants. Industrial & Engineering Chemistry Research, 43, 2493–2507]. A generic exothermic reversible reaction A + B ↔ C + D occurs in both flowsheets, which consist of a conventional multi-unit reactor/separator/recycle structure and a reactive distillation column. Results showed that the reactive distillation process is significantly less expensive than the conventional process for a wide range of the chemical equilibrium constant when there is no mismatch between the temperature favorable for reaction and the temperature favorable for vapor–liquid separation.

A reactive distillation column has fewer control degrees of freedom than a conventional multi-unit system. Therefore a reactive distillation column may have worse dynamic response than a conventional process. The purpose of this paper is to compare the dynamic controllability of these two alternative processes.

Three different chemical equilibrium constants are considered. Several control structures are developed for each flowsheet, and their effectiveness is evaluated. Disturbances in production rate and fresh feed compositions are considered.

The conventional multi-unit process provides significantly better control. The operability region is much larger, there is less variability in product quality and the dynamic responses are faster than those of the reactive column. Thus, these results demonstrate that there is a significant trade-off in this system between optimum economic steady-state design and dynamic controllability.     

通用炼油厂水系统优化模型开发与应用

传统水系统优化往往只考虑了新鲜水用量,而忽视了除盐水、除氧水、各等级蒸汽、蒸汽冷凝水、循环冷却水等类型的水,缺乏对各类型水量关联性的研究。针对这种局限性,提出了包含多种类型水的通用用水过程模型,以及通用炼油厂水系统优化的超结构和相应的数学模型,模型中集成了各装置及各种类型水之间关联的物料衡算方程。利用商业软件GAMS对某炼油厂的水系统进行建模求解,案例分析结果表明,除盐水用量有所下降,回用水用量增加,在优化前后雨水量保持469.36 t·h^-1的情况下,系统的新鲜水用量从489.44 t·h^-1减小到283.94 t·h^-1,以系统新鲜水量和雨水量之和为基准,节水率达到21.4%。加工吨原油取水量从0.649 t减小至0.510 t,接近国内先进水平。案例研究表明,提出的优化模型能够有效地计算整个炼油厂水系统的新鲜水用量,验证了该模型的实用性。     

Sea water desalination by reverse osmosis in chigasaki laboratory

For the purpose of constructing a reverse osmosis [RO) sea water desalination plant of 800 m³/day capacity, a series of tests on the following themes have been carried out in the Chigasaki Laboratory:

1. Performance and durability of 8B modules made in Japan

2. Simplification of pretreatment system

3. Establishment of energy recovery system.

Domestic modules showed good and stable performance during long term operation, and water recovery ratio of these modules have been raised to 40%.

In-line coagulation and filtration system has been established for the pretreatment of feed sea water, instead of coagulation, sedimentation and filtration system.

The energy recovery equipment is consisted of a high-pressure pump, a motor and a hydraulic turbine on a common base. Recovered energy from pressurized brine is used for the auxiliary motive power of the high-pressure pump. The experimental data show that about 20% of required power for the pump was recovered.     

Photocatalytic degradation of organic compounds diluted in water using visible light-responsive metal ion-implanted TiO2 catalysts: Fe ion-implanted TiO2

The application of metal ion-implantation method has been made to improve the electronic properties of the TiO₂ photocatalyst to realize the utilization of visible light. The photocatalytic properties of these unique TiO₂ photocatalysts for the purification of water have been investigated. By the metal ion-implantation method, metal ions (Fe⁺, Mn⁺, V⁺, etc.) are accelerated enough to have the high kinetic energy (150 keV) and can be implanted into the bulk of TiO₂. TiO₂ photocatalysts which can absorb visible light and work as a photocatalyst efficiently under visible light irradiation were successfully prepared using this advanced technique. The UV-Vis absorption spectra of these metal ion-implanted TiO₂ photocatalysts were found to shift toward visible light regions depending on the amount and the kind of metal ions implanted. They were found to exhibit an effective photocatalytic reactivity for the liquid-phase degradation of 2-propanol diluted in water at 295 K under visible light (λ>450 nm) irradiation. The investigation using XAFS analysis suggested that the substitution of Ti ions in TiO₂ lattice with implanted metal ions is important to modify TiO₂ to be able to adsorb visible light.     

Excimer Laser Induced Removal of Particles from Hydrophilic Silicon Surfaces

A pulsed KrF excimer laser was used to remove several types of submicron-sized particles from silicon surfaces. Polystyrene latex particles, 0.1 μm and larger, were removed from silicon surfaces by dry laser cleaning (no water layer condensed on the surface) but SiO₂ particles could not be so removed. However, during steam laser cleaning, in which a thin film of water is deposited on the surface as both an energy transfer medium and an adhesion force reduction agent, these 0.1-0.2 μm SiO₂ particles were almost entirely removed. Calculations of the various forces contributing to adhesion indicate that hydrogen bonds are the major contributor to the adhesion of inorganic particles to substrate surfaces. Photoacoustic detection, using piezoelectric transducers, monitored the surface vibrations induced by the laser pulses.     

Operating experiences of a 15,000 cubic meter per day municipal desalting plant at Corfu, Greece

The initial eighteen month period of operation of the 15,000 m³/day municipal plant on the Island of Corfu, Greece, is described.

The 15,000 m³/day desalting plant employing the electrodialysis reversal process (EDR) produces potable water (500 ppm) from a blend of brackish sources with salinities up to 2000 ppm TDS. The paper describes the plant and integration of the plant into the municipal system. The unique system employed to segregate the treatment of the different brackish waters employing only the highest salinity water for blowdown water is also described.

The plant was started up in the fall of 1977 and provided water to the municipal system during the 1978 season.

The paper presents operating cost data for this period and compares these costs with projected costs which form part of the contractual agreement, with the Municipality.     

Electrochemical adsorption of organic bases and their conjugate acids—I. Adsorption of neutral bases at mercury

Following previous studies on solid metals, electrocapillary measurements are reported for the adsorption of a series of heterocyclic and aromatic bases (and their ions) at the mercury electrode. The adsorption isotherms are derived for various electrode potentials and standard electrochemical free energies Δ ° of adsorption are deduced and related to molecular and electronic structure of the adsorbates. Specific π-orbital interaction effects are indicated which determine the orientation of the bases at the electrode. It is shown that dipole interaction effects lead to variations of Δ ° (adsorption) with the 3/2 power of surface coverage θ; this prediction is confirmed experimentally. The variation of Δ ° with θ^3/2 has two distinct linear regions, the change of slope (∂Δ °/∂θ )_E being related to molecular orientation at high fields and coverages. The effects are closely related to the shifts of the potential of the electrocapillary maximum (e.c.m.) observed in the solutions of the bases. The observed Δ ° values at the e.c.m. are related to those found for adsorption of two bases at the air/water interface.