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Desalination (v.196, #1-3)
Desalination status in the Gaza Strip and its environmental impact by Husam Baalousha (pp. 1-12).
Due to the sharp shortage of water and the bad quality of groundwater, desalination plants were set up in the Gaza Strip area in Palestine. Currently, there are six reverse osmosis desalination plants in the Gaza Strip owned and operated by the Palestinian Water Authority (PWA) and different municipalities. In addition, there are many small desalination units owned and operated by private investors for commercial purposes. Currently there is a plan for a regional seawater desalination plant with a capacity up to 150,000 m3/y. According to the PWA plan, desalination seems to be the only viable alternative for water resources. However, large-scale desalination plants seem to be several years in the future. Meanwhile, studies on the environmental impact of desalination should be made in order to take the proper measures to protect the environment. So far, the currently operated plants have unfortunately not taken these measures. The effluent brines from these plants are not properly disposed of and the quality of desalinated water is not monitored. The impact of desalination on the environment was investigated, and possible measures to reduce this impact were introduced.
Keywords: Desalination; Environment; Water resources; Gaza Strip; Brines
Compatibility research on PVC/PVB blended membranes by Yuelian Peng; Yan Sui (pp. 13-21).
Due to the hydrophobicity of poly(vinyl chloride) (PVC), the application of PVC membranes has been limited. In this paper, poly(vinyl butyral) (PVB) was introduced as the second polymer component to hydrophilized PVC ultrafiltration membranes. The miscibility of PVC/PVB blends in N,N-dimethyl acetamide were characterized by the solubility parameter, glass transition temperature of the blended membrane, casting solution viscosity, etc. The results showed that the PVC/PVB blended system was partially miscible at a certain proportion range. Water flux and hydrophilicity of the blended membranes were much better than that of the membranes made from pure PVC or PVB. A cross section of pure PVB and PVC/PVB blended membranes present an asymmetric finger-like structure, and the wall of the finger-like pore had a sponge-like structure. The addition of PVB could improve the hydrophilic property of PVC membranes, and the addition of PVC could increase the pore diameter at the bottom of PVB membranes.
Keywords: Poly(vinyl chloride); Poly(vinyl butyral); Blends; Miscibility
Coagulation/flocculation process in the treatment of abattoir wastewater by O.S. Amuda; A. Alade (pp. 22-31).
The coagulation/flocculation process was used at laboratory bench scale for the removal of chemical oxygen demand (COD), total suspended solids (TSS) and total phosphorus (TP) in abattoir wastewater. The wastewater was allowed to settle for 24 h and TSS and TP removal efficiencies of 65% and 32% were achieved, respectively. Alum, ferric chloride and ferric sulfate were employed during the coagulation/flocculation process. Alum proved more effective in the reduction of TSS and TP present in the wastewater, whereas ferric sulfate was more effective in the reduction of COD. Increasing the dose of alum to 750 mg/l caused the removal efficiency of TP to reach 45%. The rate of removal of TP linearly increased with increasing doses of alum, resulting in a 98% removal efficiency of TP at 1000 mg/l dose of alum. At a 95% confidence interval, alum dose, coagulation velocity gradient/rapid mixing time (coagulation Gt) and flocculation velocity gradient/slow mixing time (flocculation Gt) were not significant for TSS removal efficiency, but alum dose was significant for TP removal. The addition of a polyelectrolyte to an inorganic coagulant proved effective in the reduction of COD, TSS and TP, cut the amount of coagulant used and reduced the cost of the coagulation/flocculation process. A significant degree of particle elimination by size was produced by using alum; this improved further with the addition the polyelectrolyte.
Keywords: Coagulation/flocculation; Abattoir wastewater; Alum dose; Rapid and slow mixing time; Particle size distribution
Feasibility study of treatment of amoxillin wastewater with a combination of extraction, Fenton oxidation and reverse osmosis by Guojun Zhang; Shulan Ji; Beidou Xi (pp. 32-42).
Wastewater from the synthesizing of amoxillin is characterized by its very high TOC and low biodegradability and the presence of organic solvents and dissolved salts. These hamper direct biological or membrane-based treatments. A combined process of extraction (EX), Fenton oxidation (FO) and a two-stage reverse osmosis (RO) was proposed to treat such wastewater. EX and FO were performed in a serial approach to function as the pretreatments to remove the solvents and other organics before RO treatment. It was noted the appropriate phase ratio (A/O) was 1:1 and the contact time was 3 h. Appropriate dosages of FeSO4 and H2O2 were 10 g/l and 2 g/l, respectively. Under the appropriate conditions, TOC can be reduced by 50.6% and 37.8% in the EX and FO units, respectively. TOC can be further reduced 10.1% and 1.2% in the first and second RO processes, respectively. There was consequently an overall TOC removal efficiency of 99.7% after the whole process of EX–FO–RO–RO. Dissolved salts were also greatly removed during the two-stage RO process. The observations by using SEM showed that the RO membrane can be protected well by the pretreatments of EX and FO.
Keywords: Amoxillin wastewater; Extraction; Fenton oxidation (FO); Reverse osmosis (RO); TOC removal
Investigations on sorption, diffusion and permeation of chloro-alkanes and -alkenes through fluoroelastomeric membranes by Sangeeta B. Kulkarni; Arjumand A. Kittur; Srikant S. Kulkarni; Mahadevappa Y. Kariduraganavar (pp. 43-54).
Sorption, diffusion and permeation of halogenated liquids such as chloroform, dichloromethane, carbon tetrachloride, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, trichloroethylene and tetrachloroethylene into commercial fluoroelastomer (FC-2177 D) were studied at 30, 40 and 50°C using the sorption gravimetric method. The concentration-independent diffusion coefficients were calculated using Fick's equation from the initial linear portion of the sorption curves. The liquid concentration profiles were also computed using the analytical solution of Fick's equation with the appropriate initial and boundary conditions, and these were presented as a function of penetration depth of molecular migration and time of immersion. These results are discussed in terms of the molecular size of liquid penetrants and temperature. The transport phenomenon was found to follow anomalous behavior. From a temperature dependence of diffusion and permeation coefficients, the Arrhenius activation parameters were estimated. The activation energies for diffusion and permeation did not exhibit any systematic dependence on size of the penetrating molecules, but these were influenced by the nature of the liquids. None of the liquids showed any degradative effects on the membrane.
Keywords: Diffusion; Barrier; Swelling; Activation energy
Performance and cost estimation of nanofiltration for surface water treatment in drinking water production by Ana Rita Costa; Maria Norberta de Pinho (pp. 55-65).
This work addresses the evaluation of nanofiltration (NF) and the minimization of NF membrane fouling in the treatment of surface water for drinking water production. The fouling characteristics of the natural organic matter (NOM) present in the surface water are dependent on the feed water composition and on the NF operating parameters. NF experiments were carried out in a DSS Lab-unit M20 with a membrane surface area of 0.216 m2. Permeation experiments were performed both in total recirculation mode in order to optimize the operating conditions of pressure and recirculation flow rate and in concentration mode for design and optimization purposes. The concentration mode experiments were carried out at 15 bar and at a recirculation flow rate of 554 L/h. The water recovery rates (WRR) ranged up to 75%. A NF model was developed based on solute (NOM) and solvent differential mass balances and incorporating experimental data of the variation of permeation fluxes and total organic carbon (TOC) rejections with WRR. This model was used for the design of a NF plant with a permeate output of 100,000 m3/d. The NF treatment cost was estimated to be €0.214/m3.
Keywords: Nanofiltration; Surface water; Fouling; Cost estimation
Pilot testing of two inside-out UF modules prior to RO for highturbidity seawater desali by Jingjong Zhang; Sunming Gao; Huiming Zeng; Fang Zhang; Changzhen Li; Yanwei Liu; Dongkang Fu; Chunsong Ye (pp. 66-75).
To a seawater reverse osmosis (SWRO) plant, an appropriate pretreatment procedure is one of the most important factors for its steady and safe performance. Many researchers have shown their interest in replacing conventional seawater pretreatment with ultrafiltration (UF) because of the stable product water quality it offers. The purpose of the pilot testing was to evaluate two inside-out UF modules (Module A and Module B) used for pretreatment of highturbidity seawater after coagulation. A pilot-testing UF system was set up at the seashore on the southeast coast of China. Operation parameters such as flux, backwash (BW) time, BW frequency, and frequency of chemically enhanced backwash were varied. Modules A and B were operated at a flux ranging from 69–95 L/m2h and 86–130 L/m2h, respectively; the corresponding transmembrane pressure was 0.18–0.25 bar and 0.30–0.45 bar. The filtrateSDI15 of Module A was maintained below 3 during the test, and the permeateSDI15 of Module B was less than 3.37. These permeates met the requirement of the feed water quality of SWRO. A NaClO concentration of 6 mg/L proved to have little influence on decreasing the filtrateSDI15. Other parameters of water quality such as total Fe, COD, colloidal Si and total bacterial count were also measured. The UF trial was successful in achieving stable membrane permeability.
Keywords: Inside-out; Ultrafiltration; SWRO; Pretreatment; SDI; Seawater; Desalination
Treatment of oily wastewater by organic–inorganic composite tubular ultrafiltration (UF) membranes by Yu Shui Li; Lu Yan; Chai Bao Xiang; Liu Jiang Hong (pp. 76-83).
A tubular UF module equipped with polyvinylidene fluoride membranes modified by inorganic nano-sized alumina particles was used to purify oily wastewater from an oil field. The membrane water permeations of the UF process were analyzed. Retentions of chemical oxygen demand and total organic carbon were more than 90% and 98%, respectively. The results indicate that after UF treatment, oil content was below 1 mg/L, suspended solids content was below 1 mg/L, and solid particle median diameters were less than 2 μm. The quality of the permeation water met the requirement by oilfield injection or drainage. Fouled membranes and washed membranes were analyzed by scanning electron microscopy, and fouled membranes were backwashed with different solutions. Results show that the addition of nanosized alumina particles improved membrane antifouling performance, and the flux recovery ratio of modified membranes reached 100% washing with 1 wt% of OP-10 surfactant solution (pH 10).
Keywords: Oily wastewater; Ultrafiltration; Tubular membrane; Membrane fouling
Performance analysis of combined humidified gas turbine power generation and multi-effect thermal vapor compression desalination systems — Part 1: The desalination unit and its combination with a steam-injected gas turbine power system by Yongqing Wang; Noam Lior (pp. 84-104).
Humidified gas turbines (HGT) have been identified as a promising way of producing power. The use of the steam-injected gas turbine (STIG) HGT cycle in a combined power and water desalination system was analyzed using energy and exergy performance criteria. A brief description and rationale of the background of HGT cycles and dual-purpose power and water systems is given. A thermal desalination unit was modeled and analyzed, and the results led to the selection of a multi-effect thermal vapor compression (METVC) unit for producing fresh water from seawater for both general use and humidification; then the performance of a STIG-based combined system was investigated. The analysis performed improved the understanding of the combined STIG power and water desalination process and of ways to improve and optimize it. Some specific conclusions are that: (1) a METVC desalination system is preferred to a multieffect evaporation one when the pressure of the motive steam is high enough, >∼3 bar, to run a steam jet ejector; (2) the steam injection rate in the STIG cycle has a strong effect on water and power production, offering good flexibility for design and operation; (3) higher pressure ratios and higher steam injection rates in the STIG cycle increase power generation, but decrease water production rates, and higher turbine inlet temperatures increased both power and water production; (4) a distinct water production gain can be obtained by recovering the stack gas energy. The results indicate that such dual-purpose systems have good synergy, not only in fuel utilization, but also in operation and design flexibility.
Keywords: Integrated power and water system; Humidified gas turbine; Multi-effect thermal vapor compression desalination; Energy and exergy analyses
Pilot plant testing of a new solar desalination process by a multiple-effect-humidification technique by Imed Houcine; Mahmoud BenAmara; Amanallah Guizani; Mohammed Maâlej (pp. 105-124).
After concluding a detailed research on separate pieces of equipment needed for the new desalination process, Phase 1 pilot plant installation for testing and optimizing the whole process was constructed and installed in INRST-Tunisia. The aim of this investigation is to experimentally test the new solar desalination process working with an air multiple-effect humidification–dehumidification technique. A pilot plant unit was designed and constructed to carry out this test investigation. The main parts of the process consist of an air collector field, spray humidifiers and a dehumidifier and heat recovery system. The process flow sheet has undergone several changes: the number of heating–humidifying stages has been lowered from 18 to 15 stages, then to 9 stages, then to 4 stages. The present study concerns Phase 1 installation setup involving two heating–humidifying stages, heat recovery and condensation system and auxiliary equipment (blower, pumps, reservoirs, etc.). Phase 2 installation setup will include the remaining equipment to complete a 4-stage plant. Phase 1 SOLDES pilot plant had been tested during a six-month period (from March to August 2003). The distilled water production had been optimized. Data relative to the operating parameters of each single component of the process (collectors' outlet temperatures, humidifier parameters, recuperated water temperature) are presented. Also, the daily and monthly fresh water production of the pilot plant is obtained. The fresh water production had reached an average value of 355 kg/d during the month of August 2003.
Keywords: Pilot plant testing and optimizing; Solar desalination; MEH process
Desalination of a thermal power plant wastewater by membrane capacitive deionization by Jae-Bong Lee; Kwang-Kyu Park; Hee-Moon Eum; Chi-Woo Lee (pp. 125-134).
A membrane capacitive deionization (MCDI) system, the one that ion-exchange membranes were added onto a capacitive deionization (CDI) system, has been developed to test desalination performance for power plant wastewater. Several experiments were conducted to compare the MCDI with the CDI in desalination capacity and to determine optimal operation conditions using 1,000 ppm NaCl solution. Salt removal rate of the MCDI system was 19% higher than that of the CDI system. The flow rate and the direct current voltage at which the salt removal rate was the highest were 40 ml/min and 1.2 V, respectively. Desalination performance for the power plant wastewater was investigated at the given operation conditions. The maximum salt removal rate and electric energy consumption were about 92% and 1.96 Wh/L, respectively. It was concluded from this study that the MCDI system could successfully be applied for the reuse of power plant wastewater.
Keywords: Capacitive deionization; Desalination
A review of membrane bioreactor potential for nitrate removal from drinking water by E.J. McAdam; S.J. Judd (pp. 135-148).
Continually elevated drinking water nitrate concentrations worldwide have increased focus on alternative nitrate removal processes accentuated by the limitations of current solutions, namely cost and complex waste generation. Biological denitrification is a comparatively low cost option, though its poor retention of bacteria and requirement for external carbon necessitates further downstream processing. To eradicate the associated disadvantages, the biological process can be integrated with membrane technology. Subsequently several membrane bioreactor (MBR) configurations have been trialled for this duty. Although the science behind each configuration has been justified, issues related to secondary contamination of the product water remain and require further investigation. This paper reviews the research to date appraising advantages and disadvantages associated with each configuration whilst also identifying areas that require further research and consequently assessing which nitrate removal MBR technologies will prevail for the future.
Keywords: Membrane bioreactor; Drinking water; Nitrate removal
Corrosion behavior of materials in RO water containing 250–350 ppm chloride by A.U. Malik; I.N. Andijani; M. Mobin; S. Ahmad (pp. 149-159).
Reverse osmosis (RO) water constitutes about 22% of total desalinated water produced in the world. The rest of the desalinated water is almost entirely from thermal distillation, such as multistage flash (MSF) evaporation and multi-effect desalination (MED) techniques. The RO permeate is more corrosive than water produced by thermal distillation due to its high dissolved salts (TDS) level, particularly chlorides. As the RO water is transported through cementitious or polymer lined pipelines, steel components like pumps, valves and pipes are likely to corrode, if proper material selection is not made. Not much information is available regarding the corrosion behavior of RO water towards the metallic materials particularly steels which forms the bulk of constructional materials. A study has been conducted to investigate the corrosion behavior of some structural materials which include carbon steel 1018, electroless nickel plated carbon steel 1018 ENP, austenitic stainless steel AISI 304, and martensitic stainless steels AISI 410, AISI 420 and AISI 431 in RO water. These materials have been the main constructional materials used in metallic components of pipelines in Saudi Arabia. Studies have been carried out under dynamic conditions (impingement under flow), static conditions (crevice formers) and in presence of an inhibitor (phosphate) using a dynamic test loop. High chromium steels (>15% Cr) appear to provide good resistance where as low chromium steels (<15% Cr) exhibit generally poor resistance under the above mentioned test conditions.
Keywords: Reverse osmosis; Multistage flash evaporation; Stainless steels; Corrosion; Internally lined steel pipe; Impingement; Crevice former; Phosphate dosing
Water usage in variable volume diafiltration: comparison with ultrafiltration and constant volume diafiltration by Greg Foley (pp. 160-163).
Variable volume diafiltration (VVD), also known as volume-decreasing diafiltration, is a process in which fresh water is added continuously to the retentate in a batch ultrafiltration process at a rate that is less than the permeate flowrate, thus providing for simultaneous ultrafiltration (UF) and diafiltration. This process has been analysed recently and it is claimed that VVD uses less water than constant volume diafiltration (CVD) . In this paper, we examine both VVD and UF–CVD and compare the water usage in each process. For a solution containing two solutes, A and B, with rejection coefficients σA = 1 and σB = 0, we show that VVD uses more water than CVD when CVD is performed at the final volume of a UF–CVD process. VVD uses less water than CVD only if the latter is performed at the initial volume of a UF–CVD process. When CVD is performed at the intermediate macrosolute concentration that minimises the process time, namely Cg/ e where Cg is the gel concentration and e is the base of the natural logarithm, it will generally use less water than VVD.
Keywords: Ultrafiltration; Constant volume diafiltration; Variable volume diafiltration; Water usage; Optimisation
Biosorption of heavy metal ions from aqueous solutions by activated sludge by Z. Al-Qodah (pp. 164-176).
Biosorption experiments were performed using different pretreated activated sludge as bioadsorbent for Cu2+, Cd2+ and Ni2+. Pretreatment with NaOH was found to improve the adsorption capacity of the sludge where as treatment with HCl reduces it. The treated and untreated sludge show great affinity towards Cu2+, Cd2+ and low affinity towards Ni2+. The maximum loading capacity of the NaOH treated sludge was 131.6 and 93.4 mg/g for Cu2+ and Cd2+, respectively. It was found that both Langmuir and Freundlich isotherm models fit the adsorption data with the different types of sludge and ions. The value of R2 exceeds 0.95 in most cases. It was found that the maximum adsorption capacity drops 18.3% as the temperature increases from 25 to 45°C. The adsorption capacity was found to increase as the adsorbent mass and mixing speed increase. The optimum pH corresponding corresponds to maximum adsorption efficiency was found to be about 5. Desorption experiments indicate that the desorption efficiency with 0.1 M H2SO4 solution reaches 94% in the first cycle and decreases to 8% in the 4th cycle after collecting 20,700 mg Cd2+/l H2SO4.
Keywords: Biosorption; Adsorption isotherms; Activated sludge; Heavy metal; Industrial wastewater; Langmuir model; Freundlich model
A mathematical model for a thermally coupled humidification–dehumidification desalination process by Rihua Xiong; Shichang Wang; Zhi Wang (pp. 177-187).
The humidification–dehumidification process is an interesting technique that has been adapted for water desalination. Previous works experimentally investigated desalination processes in the shell and tube columns, where the humidification and dehumidification were thermally coupled and simultaneously performed at the tube and shell sides, respectively. In this work, a comprehensive steady-state mathematical model was developed for such a humidification–dehumidification desalination process by taking into account the heat and mass balances on both sides of the desalting column, the mass transfer rate at the humidification side, and the heat transfer rate between the dehumidification side and humidification side. Meanwhile, the mass transfer coefficient at the humidification side and the total heat transfer coefficient between the dehumidification side and humidification side were discussed and correlated. The correlations could represent the experimental data very well.
Keywords: Desalination; Humidification; Dehumidification; Mathematical model; Mass transfer coefficient; Heat transfer coefficient
Performance characteristics of the diffusion driven desalination process by Yi Li; James F. Klausner; Renwei Mei (pp. 188-209).
A diffusion driven desalination (DDD) process has recently been reported where warm water is evaporated into a low humidity air stream, and the vapor is condensed out to produce distilled water. Although the process has a low fresh water to feed water conversion efficiency, it has been demonstrated that this process can potentially produce low cost distilled water when driven by low grade waste heat. A detailed heat and mass transfer analysis has been developed to model the dynamic performance of the DDD process. This analysis is used to parametrically explore the performance of the DDD process over a wide range of operating conditions. The optimum operating condition for the DDD process with a high temperature of 50°C and sink temperature of 25°C has an air mass flux of 1.5 kg/m2-s, air to feed water mass flow ratio of 1 in the diffusion tower, and a fresh water to air mass flow ratio of 2 in the condenser. Operating at these conditions yields a fresh water production efficiency (m fw/m L) of 0.035 and electric energy consumption rate of 0.0022 kW-h/kg fw. A brief economic analysis is presented to demonstrate the added value provided by using a DDD facility to produce fresh water using waste heat from a thermoelectric power plant.
Keywords: Desalination; Diffusion driven; Numerical optimization
An innovative reverse osmosis desalination system using hydrostatic pressure by S. Al-Kharabsheh (pp. 210-214).
A description and energy efficiency analysis is presented for an innovative reverse osmosis (RO) desalination system utilizing hydrostatic pressure. Hydrostatic pressure of a water column of sufficient height to create the required pressure to drive the RO desalination system is used. The system consists of a storage tank, connecting pipes, RO module with a moving hollow piston, filter boxes, seawater storage tank, pump, and valves. The storage tank is to be placed at the top of a mountain and is to be connected to the RO module that is placed slightly above sea level. Energy efficiency analysis shows that the system energy requirement is 0.85 kWh/m3 of fresh water produced from seawater, which is much less than that required by conventional RO plants, usually 3–10 kWh/m3 of fresh water produced from seawater.
Keywords: Reverse osmosis; Desalination; Hydrostatic pressure; Seawater desalination
Effluent from an advanced wastewater treatment plant — an alternate source of non-potable water for Kuwait by S.B. Al-Shammari; A.M. Shahalam (pp. 215-220).
During the past few years, Kuwait has been encouraging the development of alternative water resources. This stems from the fact that the available natural water resources are scarce, and water demands are growing due to increasing population growth. A potential alternative water resource which may replace existing water resources for non-potable use is renovated wastewater. Currently, a huge amount of municipal wastewater is conventionally treated in Kuwaiti sewage treatment plants, and a major portion of this treated effluent is discharged to the Gulf. Advanced treatment of treated wastewater would yield a better quality effluent which can be used as an alternative water resource and therefore reduces the demand on fresh and brackish water supplies. The potential for using advanced treated wastewater in meeting the growing water demands in the State of Kuwait was explored.
Keywords: Water demand; Advanced treatment; Wastewater reuse
Separation of inorganic and organic compounds by using a radial flow hollow-fiber reverse osmosis module by S. Senthilmurugan; Sharad K. Gupta (pp. 221-236).
Phenol, 2,4-dinitrophenol (DNP), pentachlorophenol (PCP), NaCl, NaBr and KBr were separated from aqueous solutions under a variety of operating conditions by using a Permasep B9 hollow-fiber reverse osmosis module. The permeate characteristics for all compounds were analyzed by the combined film Spiegler–Kedem (CFSK) model available in the literature. The errors between experimental and theoretical predictions were less than 15% for both permeate flow rates as well as permeate concentrations. The model parameters such as the solute permeability and the reflection coefficient were constant for all phenolic compounds and KBr at constant temperature and pH. However, in the case of NaCl and NaBr, the solute permeability increased as the feed concentration increased to 15,000 ppm, after which the concentration of the solute permeabilities became independent of the feed concentration. On the other hand, the reflection coefficient for both NaCl and NaBr went through a minimum and then increased to a maximum before reaching a constant value as the feed concentration was increased. It is also shown that for both organic as well as inorganic compounds. the CFSK model provides much better theoretical predictions than the combined film solution diffusion model.
Keywords: Reverse osmosis; Spiegler–Kedem model; Concentration polarization; Organic compound; Inorganic salt
Inhibition of calcium and magnesium-containing scale by a new antiscalant polymer in laboratory tests and a field trial by Hai-Yan Li; Wei Ma; Lu Wang; Ru Liu; Lin-Sen Wei; Qiang Wang (pp. 237-247).
Membrane scaling is caused by the deposition of unsoluble salts as feedwater converted to brine, affectting the operation of seawater RO plants. Membrane scaling at the Dalian RO desalination plant was analyzed using Dalian seawater. Based on the characteristics of Dalian seawater, a new environmentally friendly, biodegradable antiscalant PAP-1 was synthesized in the laboratory. The performance of PAP-1 to inhibit calcium and magnesium-containing scale was studied both in the laboratory and at the Dalian seawater RO desalination plant. It was found that PAP-1 is effective in inhibiting scale formation. The experimental results in the laboratory indicate that the proper dose is 3–5 ppm when the concentration of calcium is 1000 mg/L and of magnesium is 2800 mg/L. The pH of the feed water was in the range of 3–9. The efficiency of calcium scale inhibition of PAP-1 is higher than 97.24% and magnesium scale inhibition is higher than 98.63% with 9 ppm PAP-1. The test performed at the Dalian seawater RO plant confirmed the scale inhibition ability of PAP-1 compared with the Nalco PermaTreat 191 scale inhibitor. The results from both antiscalants were similar. The average scale formation rates of calcium and magnesium of 14 samples was 2.822 g/h and 5.562 g/h separately with the addition of PAP-1 in each membrane unit; PAP-1 was more effective than Nalco PermaTreat 191. At the same time, the algae growth inhibition test showed that the addition of PAP-1 does not affect the growth of algae, which is an indication that PAP-1 has no toxicity and is a suitable and environmentally friendly antiscalant.
Keywords: Membrane scaling; Antisclant; RO; Desalination
Adsorption of acid dyes in aqueous solutions by shells of bittim ( Pistacia khinjuk Stocks) by Haluk Aydın; Gülay Baysal (pp. 248-259).
The effectiveness of adsorption for dye removal from wastewaters has made it an ideal alternative to other expensive treatment options. The removal of acid red 183 (AR) and acid green 25 (AG) onto shells of bittim ( Pistacia khinjuk Stocks) (BTS) from aqueous solutions was investigated using parameters such as contact time, pH, temperature, adsorbent doses, and initial dye concentration. Adsorption isotherms of dyes onto BTS were determined and correlated with common isotherm equations such as the Langmuir and Freundlich models. Adsorption equilibrium was reached within 30 min. It was found that the Langmuir isotherm appears to fit the isotherm data better than the Freundlich isotherm. Parameters of the Langmuir and Freundlich isotherms were determined using adsorption data. The maximum adsorption capacities for AR and AG onto BTS at 308, 313, and 318 K were found to be 33, 28, and 20; 16, 18, and 7 mg/g, respectively. The adsorption kinetics of AR and AG could be described by the pseudo-second-order reaction model.The data obtained from adsorption isotherms at different temperatures were used to calculate several thermo-dynamic quantities such as the Gibbs energy (Δ G0), enthalpy (Δ H0), and entropy (Δ S0) of adsorption. The adsorption process was found to be spontaneous, endothermic and physical in nature. Locally available adsorbent BTS was found to have a low cost and was promising for the removal of AR and AG from aqueous solutions.
Keywords: Adsorption; Langmuir isotherm; Freundlich isotherm; Acid dyes; Low-cost materials; Adsorption modeling
Fundamental studies on the intermediate layer of a bipolar membrane. Part VI. Effect of the coordinated complex between starburst dendrimer PAMAM and chromium (III) on water dissociation at the interface of a bipolar membrane by Rong-Qiang Fu; Yi-Yun Cheng; Tong-Wen Xu; Wei-Hua Yang (pp. 260-265).
Starburst dendrimer polyamidoamine (PAMAM) is an ellipsoidal tree-like macromolecule with a well defined structure and many more amino groups than conventional macromolecules, which can be used to catalyze water dissociation in a bipolar membrane according previous work. The purpose of this research is to discover the effect of the coordinated complex between PAMAM G4 and Cr(III) on water dissociation in a bipolar membrane. The coordinated reaction between G4 and Cr(III) was investigated by UV–VIS absorption spectroscopy, and finally the molar ratio Cr(III)/G4 was chosen as 20. The I–V curves showed that the coordinated complex could be applied to accelerate water dissociation in a bipolar membrane, and the accelerative or catalytic effect was more prominent than separated G4 or Cr(III). Furthermore, the V–t curves showed that the coordinated complex in the intermediate layer was comparatively chemically stable, namely G4 had the function of fixing Cr(III) ions in the intermediate layer. Thus, it is expected that a bipolar membrane with high efficiency and comparative stability can be prepared by applying the coordinated complex between G4 and Cr(III) as the intermediate layer.
Keywords: Bipolar membrane; Water dissociation; Intermediate layer; Polyamidoamine; Chromium
Seawater bitterns as a source of liquid desiccant for use in solar-cooled greenhouses by P.A. Davies; P.R. Knowles (pp. 266-279).
The processes of desalination and sea-salt production currently produce large quantities of by-product, in the form of brine and bitterns, which is generally regarded as waste. This article explores the scope for exploiting the hygroscopic salts occurring in these by-products — such as magnesium, calcium and sodium chloride — as desiccant solutions in a greenhouse cooling system. These solutions are compared to other liquid desiccants more conventionally used in solar-driven refrigeration: namely solutions of lithium chloride, lithium bromide and zinc chloride. To establish which properties are relevant, we discuss the relation of the properties of the liquid desiccant to the attributes of the greenhouse as a whole. A property of primary importance is hygroscopicity, as quantified by the equilibrium relative humidity (ERH). Further properties reviewed include cost, availability, density, viscosity, specific heat capacity, thermal conductivity, heat of dilution, water absorption capacity, human- and ecotoxicity, and corrosivity. Calculations based on five locations (Tunis, Jiddah, Abu Dhabi, Mumbai and Bangkok) show that the liquid desiccant should have ERH ≤50% to give improved cooling compared to both direct and indirect evaporative systems. Except for sodium chloride, all six salts considered meet this requirement. Magnesium chloride is the most abundant salt in seawater bitterns and both magnesium and calcium chloride stand out as being of low toxicity. Their hygroscopic properties, though inferior to those of the lithium and zinc salts, make them suitable for cooling of greenhouses (even if not of human dwellings). We envisage an integrated desalination and agricultural system, comprising a solar desalination plant supplying freshwater (for irrigation) and bitterns (for cooling) to greenhouses, enabling efficient water use and local crop production in hot climates.
Keywords: Bitterns; Solar energy; Greenhouse; Refrigeration; Agriculture; Water-use efficiency; Integrated system
Ranking of antiscalant performance for gypsum scale suppression in the presence of residual aluminum by Wen-Yi Shih; Junbo Gao; Anditya Rahardianto; Julius Glater; Yoram Cohen; Christopher J. Gabelich (pp. 280-292).
An approach to ranking antiscalant effectiveness for gypsum scale suppression using combined bulk crystallization and membrane scaling diagnostic tests was explored with a focus on the adverse impact of residual aluminum in dissolved (Al3+) and as colloidal species on gypsum scale suppression. Five commercial antiscalants were ranked based on the crystallization induction time as determined in a well-mixed crystallization vessel with a back-light scattering turbidity meter to monitor gypsum formation. The presence of aluminum, even at trace levels (up to 100 μg/L), significantly reduced the crystallization induction time, thereby reducing antiscalant effectiveness. For a given antiscalant dose, the crystallization induction time decreased with increasing total aluminum concentration according to a log-linear relationship. Although the above qualitative behavior was similar for the tested commercial anti-scalants, the adverse impact of aluminum on antiscalants effectiveness differed markedly among the different antiscalants. Diagnostic scaling tests in a plate-and-frame RO module demonstrated antiscalant performance ranking of the same order as that obtained based on bulk crystallization induction time measurements.
Keywords: Aluminum; Gypsum; Mineral salt scaling; Antiscalant; Reverse osmosis; Pretreatment
Thermoeconomic analysis of a coupled municipal solid waste thermovalorization–MSF desalination plant: an Italian case study by Fabio Lo Mastro; Marina Mistretta (pp. 293-305).
A thermoeconomic analysis of a cogenerative system with steam bleedings produced starting from the thermal energy recovered in a municipal solid waste thermovalorization plant is presented. The authors assume that the bled steam is used to feed a seawater multi-stage flash (MSF) desalination plant. A case study was carried out for the desalination plant, which operates in Raffineria di Gela (Sicily). In particular, the MSF process is described and the most significant features of the plant are presented. Besides, an economic analysis of a hypothetically coupled MSW thermovalorization–MSF plant was carried out to estimate the capital and operating costs and the gain derived from the sale of distilled water.
Keywords: Cogeneration; Desalination; Energy; Multi-stage flash; Recovery
Usefulness of reverse osmosis in the treatment of condensates arising from the concentration of distillery vinasses by Estelle Morin Couallier; Blanca Salgado Ruiz; Marie-Laure Lameloise; Martine Decloux (pp. 306-317).
This work forms part of a global study on the recycling into alcoholic fermentation of condensates arising from the concentration of vinasses. Its purpose is to demonstrate the usefulness of reverse osmosis (RO) in the treatment and exploitation of these condensates, i.e., elimination of the anti-fermentation molecules they contain (formic, acetic, propionic, butyric, valeric, hexanoic acids, 2,3-butanediol, furfural and phenyl-2-ethyl-alcohol) so that they could be recycled. The experimental system used was a DSS Labstack M20-0.72 filtration system with flat, Filmtec FT30 Sea Water (SW) membranes from Dow. As the inhibitory compounds include organic acids, the effect of pH was studied: trials at pH 3.0, 5.2, 7.5 and 10 were performed at 40 bar and 25–30°C, and monitored by chemical analysis and inhibition tests. Rejection coefficients were found to be higher than 85% for all compounds at pH >5. RO permeates arising from the treatment of condensates with a pH 7.5 and 10 proved not inhibitory. Because of a strong rise between 6 and 12 during the titration, working at pH higher than 6 needs a fine tuning of pH value or the use of membranes resisting high pH values. At pH 6, however, 10% inhibition is still present; in order to eliminate all traces of inhibition, it would then be necessary to envisage double RO or coupling with another process.
Keywords: Wastewater treatment; Vinasses; Water; Recycling; Reverse osmosis; Inhibition