Raw Seawater Research Articles

Seawater reverse osmosis membrane fouling causes in a full scale desalination plant; through the analysis of environmental issues: raw water quality

Background: Membrane clogging is one of the most important problem for desalination plant operators in Iran, therefore, this study was conducted to investigate the main causes of this problem using field analysis. Methods: In this study, six continuous membranes in a reverse osmosis (RO) pressure vessel under the 33-month service period (April 2017 to November 2019) were selected. The membranes were analyzed through visual evaluation of the outer and inner membrane surface, analyzing the damages and physical harms, oxidative stress tests, iron spot test, fouling chemical analysis using loss on ignition (LOI) tests, X-ray fluorescence (XRF), and Fourier-transform infrared (FTIR) spectroscopy. Results: Particle size distribution in raw seawater (EC = 55 000 µs/cm, turbidity = 11 NTU) was 66.4% smaller than 1 µ and 28.3% between 1 to 1.9 µm. Physical damages were not seen on the membranes but telescopic damages were observed which was due to membrane fouling. Removal efficiencies of turbidity and silt density index (SDI) were 84% and 18%, respectively. Membrane oxidation was also seen. Most of the sediments compositions on the membranes were SiO2 , Al2 O3 , MgO, and Fe2 O3 . Biological fouling was detected on the membranes surface. Conclusion: Inaccurate use of chlorine neutralizer caused the residual chlorine to be present in the membrane entering water, which damaged the membrane. Accumulation of clogging agents on membrane surface showed malfunction of pretreatment function, therefore, revision of design and operation of units is necessary. Biological fouling is due to non-effective pre-chlorination of drinking water. Metallic compounds sedimentation on the membrane is due to improper use of anti-fouling chemicals. High SDI in the influent shows the need to change the cartridge filters.

Heavy Metals Concentration and Possible Health Risks From Shrimp Nurseries at South-West Region, Bangladesh

Water pollution poses a threat of heavy metal accumulation in aquatic animals. This study was designed to determine the heavy metals contamination in shrimp PL (post larvae) nurseries of Khulna region and associated human health risks. Water (raw sea water, treated and outlet water) and PL samples of five shrimp nurseries of Khulna districts were analyzed to measure the concentrations of six heavy metals (Zn, Cr, Mn, Cu, Pb and Ni) by using Atomic Absorption Spectrometer (Model No: AA-7000, Shimadzu). The metal concentrations were higher in almost all PL samples of five nurseries except Mn, which value was below detection level (BDL). Concentrations of Zn and Cu were significantly higher (P<0.05) in PL samples than inlet (raw sea water, treated water) and outlet water samples among five nurseries. The highest value for Cr was found in PL sample (2.95±3.64) ppm but the lowest was in outlet water (0.004±0.004) ppm. The highest value of Pb was found in PL samples (3.48±7.78) ppm and the lowest was in treated water sample (0.54±0.09). The Ni concentration was highest in PL samples (1.71±1.98) ppm while the lowest in both raw seawater (0.01±0.005) ppm and outlet water (0.01±0.004) ppm. In some PL samples, the concentrations of Cr, Cu, Pb and Ni were higher than maximum allowable concentration. The estimated daily intake (EDI) of heavy metals in shrimp PL were followed the order Zn>Cu>Pb>Cr>Ni>Mn. The target hazard quotients (THQ) of PL samples were followed the rank Pb>Cu>Zn>Ni>Cr>Mn. Target cancer risk (TR) of Pb of nursery-2 PL for rural people was 1.1305 × 10-4 while the urban and average TR was 1.4757× 10-4 and 1.2195× 10-4, respectively. The findings of the present study on heavy metal concentrations in PL nurseries indicate the necessities of quality water for prevention of accumulation heavy metals further in shrimp grown-up stages. Proper management strategies should be taken to avoid this risk.
 Bangladesh J. Zool. 48(1): 167-179, 2020

Optimum Dosage of Coagulant and Flocculant on Sea Water Purification Process

This study aims to determine the appropriate dose in the use of coagulant and flocculant, thereby make the use of chemicals This study used a design of experiment methods to determine the effect of treatment variation on water quality, ie coagulant and flocculant dose, raw material flow rate and sea water condition to turbidity and pH. As a reference, pH and turbidity must be below the maximum allowed for process water. The test was done in laboratory by using jar test method. The chemicals used as coagulants and flocculants was PAC polymers (poly amylum chloride). The results showed that coagulant and flocculant dose, flow rate and sea water condition had significant effect on turbidity and pH. The condition of seawater studied here is the tidal and low tide conditions. After variation of dosage and flow rate in sea tide and low tide conditions, the following conclusions were obtained; in tidal conditions, the optimum dose of coagulant and flocculant was 70 ppm at a flow rate of 450 m3 with reference turbidity 0.9 NTU and pH 6.9. While at low tide conditions, the optimum dose of coagulant and flocculant was 70 ppm at a flow rate of 420 m3 with reference turbidity 1.1 NTU and pH 6.9. This result is expected to be applied to factories that use seawater as raw material for process water.

Attachment of Acidithiobacillus ferrooxidans to pyrite in fresh and saline water and fitting to Langmuir and Freundlich isotherms.

This study aims to investigate the attachment of Acidithiobacillus ferrooxidans to pyrite in two different environments: fresh and saline water (water with 35g/L of NaCl or 0.6M). Adsorption isotherms were analyzed using the Langmuir and Freundlich models. Saline water is water with 35g/L of NaCl (0.6M), which is the concentration of NaCl in seawater. The use of raw seawater in mining is becoming relevant in leaching and flotation process. At the same time the use of microorganisms in both processes is gaining attention. For this reason, it is important to study the behavior of adherence of microorganisms to minerals in saline aqueous environments, similar to seawater. The bacteria showed a higher level of attachment to pyrite in fresh water than in saline water. The Langmuir model fitted better the experimental data obtained in fresh water than in saline water with a coefficient of determination (R2) of 0.85 and 0.61 for fresh and saline water, respectively. This suggests that the bacteria tend to adhere more as a monolayer in fresh than in saline water in the early stage of adhesion.

Struvite crystallization by using raw seawater: Improving economics and environmental footprint while maintaining phosphorus recovery and product quality

Seawater, as an alternative magnesium source, has the potential to improve the overall economics and environmental footprint of struvite production compared to the use of pure magnesium salts. However, the dilution effect and the presence of other ions in seawater can reduce the phosphorus recovery potential and the simultaneous precipitation of other compounds may reduce the quality of the produced struvite. This work presents a comparative study of seawater and MgCl2 by performing a series of thermodynamic equilibrium modeling and crystallization experiments. The results revealed that acceptable phosphorus recovery (80–90%) is achievable by using seawater as the magnesium source for struvite precipitation. Further, the simultaneous precipitation of calcium phosphates was successfully controlled and minimized by optimum selection of reaction pH and seawater volume (i.e. Mg:P and Mg:Ca molar ratios). The increase of temperature from 20 °C to 30 °C reduced the phosphorus recovery by 15–20% while it increased the particle size by 30–35%. The presence of suspended solids in reject water did not have significant effects on phosphorus recovery but it made the struvite separation difficult as the obtained struvite was mixed with suspended solids. The experimental results and economic evaluation showed that the use of seawater can reduce the chemical costs (30–50%) and the CO2-footprint (8–40%) of struvite production. It was concluded that seawater is a potential alternative to pure magnesium sources in struvite production, while studies in larger scale and continuous mode are needed for further verification before full-scale applications.

Fabrication of flat ceramic microfiltration membrane from natural kaolinite for seawater pretreatment for desalination and wastewater clarification

The aim of this work is the manufacturing of flat microfiltration membrane made from Moroccan natural kaolinite clay and corn starch as porosity agent. The membrane was prepared by uniaxial pressing technique and sintering at 1,100 degrees C. The effect of starch on membrane features was investigated from 0 to 15 wt.%. The membrane has a diameter of 37.8 mm and a thickness of 2.3 mm. In order to optimize its properties, prepared membrane was characterized in terms of apparent porosity, water absorption, apparent density, mechanical strength, pore size, microstructure, and water permeability measurements. Experimental results showed that the membrane prepared with 10 wt.% of starch is considered as an optimized membrane which has an average pore size of 2.3 mu m, the mechanical strength of 20.2 MPa, and permeability of 2,129 L h(-1)m(-2) bar(-1). The optimized membrane was applied for pretreatment of raw seawater for desalination and clarification of agro-food effluent using dead-end filtration under pressure of 0.12 bar. Filtration results showed that turbidity rejection achieves 73% and 99%, respectively for raw seawater and agro-food model effluent.

Evaluation of desalinated seawater vs. filtered raw seawater for heap leach copper extraction on mountaintop mines in arid regions

Evaluation of desalinated seawater vs. filtered raw seawater for heap leach copper extraction on mountaintop mines in arid regions

Factors associated with severity of naturally occurring piscirickettsiosis in netpen- and tank-reared juvenile Atlantic salmon at a research aquarium in western Canada.

The opportunistic examination of factors associated with an outbreak of piscirickettsiosis (SRS) is described in Atlantic salmon Salmo salar post‐smolts held in an open netpen or in tanks supplied with raw sea water at a research aquarium in western Canada. During the outbreak, seawater temperature was significantly higher and salinity significantly lower in the netpen compared with the tanks. Mortality in the netpen began approximately 3 weeks prior to that in the tanks, and cumulative mortality in the netpen (34%) was significantly higher than in the tanks (12%). Piscirickettsia salmonis was confirmed by qPCR in tissues from moribund and dead fish and from colonies grown on enriched blood agar medium. Neither P. salmonis nor SRS were observed in salmon held concurrently in UV‐irradiated sea water. The elevated mortality was curtailed by treatment with oxytetracycline. These observations further indicate warmer, less saline and periodically hypoxic seawater are risk factors for SRS. UV irradiation of sea water is shown to be a tool for SRS management in fish‐holding facilities.

Study on combined freezing-based desalination processes with microwave treatment

Microwave technology was applied in two combined freezing-based processes to desalinate raw seawater. The two processes employed freezing, microwaving and centrifugal desalination (FMCD) process and freezing, microwaving, gravity-induced and centrifugal desalination (FMGCD) process respectively. The removal efficiencies of salt, TDS (total dissolved solids), Cl−, Ca2+ and Mg2+, the ice yield rate as well as the duration time of the two desalination processes were studied. The results were compared with that of our previous study using combined freezing, gravity-induced and centrifugal desalination (FGCD) process. The study showed that microwave treatment can greatly accelerate the desalination in the two combined processes. By applying a two-minute microwave treatment, the desalination effect of FMGCD process is similar to or better than that of FGCD process. Taking TDS and Cl− concentration as reference indicators, the ice product quality of FMGCD process can meet the drinking water standard requirement when the brine reject proportion is >54%.

Usefulness of the Cl/Br ratio to identify the effect of reverse osmosis treated waters on groundwater systems

The chloride-to-bromide molar ratio (R ≡ Cl/Br) is widely used in tracing groundwater salinity. Less experience exists on how some industrial processes such as the reverse osmosis (RO) water treatment modify the R value of desalinated water (P) and reject brine (T), and even less on how distinctive for hydrogeological applications the R changes are. This paper assesses the Cl/Br ratio usefulness to identify the effect of P and T on groundwater systems. First, the experimental R changes produced in P and T during standard RO operations and treatments of raw (I) seawater, brackish groundwater, and tertiary-treated domestic wastewater in nine RO plants (three in Gran Canaria Island and six in south-eastern continental Spain) were determined by means of the XP = RP/RI (R change in P) and XT = RT/RI (R change in T) ratios. XP and XT were respectively 0.90 and 1.07 for treatment 1 (weak pre-acidification) in one RO plant, 0.82 ± 0.09 and 0.94 ± 0.05 for treatment 2 (weak pre-acidification and weak pre-chlorination) in five RO plants, 0.63 and 0.97 for treatment 3 (moderate pre-acidification and strong pre-chlorination) in one RO plant, and 3.21 ± 2.02 and 1.00 ± 0.00 for treatment 4 (post-chlorination) in two RO plants. P was for irrigation (treatments 1 to 3) and for domestic use (treatment 4). Latter, the experimental XP and XT ratios were input data for six theoretical mixing scenarios aimed at showing how groundwater R changes in response to progressive contributions of P and T produced from different I water. The Cl/Br ratio enables to identify the effect of P from treatments 3 and 4, is scarcely effective for treatments 1 and 2, and is especially useful when P produced from seawater is used in other aquifer having different R. The Cl/Br ratio did not clearly identify T from any treatment.

Phosphonate-Based Inhibitor Reduces Scaling Potential of Seawater

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of “Mitigation of Scaling Potential of Seawater in High-Temperature Environment Using Phosphonate Scale Inhibitor,” by Raafat M. Yamak and Hisham Nasr-El-Din, SPE, Texas A&M University; Sabiq Rahim, SPE, Halliburton; and Moussa Taleb, University of Calgary, prepared for the 2019 SPE Kingdom of Saudi Arabia Annual Technical Symposium and Exhibition, Dammam, Saudi Arabia, 16–18 April. The paper has not been peer reviewed. In this study, a laboratory analysis was conducted to study the effect of a phosphonate-based scale inhibitor on a mixture of hypersaline Arabian Gulf seawater and formation water under high-temperature/high-pressure conditions. The objective was to identify the minimum scale-inhibitor concentration required at various temperatures to achieve a cost-effective solution in minimizing the formation of common oilfield scales. This research pushes the thermal constraints of a phosphonate-based scale inhibitor to 330°F to test its efficiency and treatment integrity. Introduction Produced water, seawater, and nanofiltered seawater have been explored as environmentally friendly and cost-effective alternatives to fresh water in fracturing fluids at different ratios. Consequently, total-dissolved-solids (TDS) levels, salinity, and bottomhole temperatures have increased, making scale inhibitors more important than ever. In this study, raw Arabian Gulf seawater and a water mixture from the Jafurah formation was used at various ratios and at different temperatures to determine the efficiency of a phosphonate-based scale inhibitor in the presence of ion complexes. High scale formation was associated with the ionic effect on the fluid, especially because of the high content of sulfate in seawater and high barium and calcium concentrations in connate water. Scale-advisory-software results indicated that barium sulfate was the major scale. Additionally, specific ions can affect the pH of the fluid severely, thereby inhibiting the operational function of the buffer systems. Scaling is a natural byproduct of seawater-based fracturing. As a result, various water treatments have been implemented to decrease scale formation. One such method involves nanofiltration. Experimental results have shown that nanofiltration caused sulfate reduction in seawater sources down to 300 ppm. This lowers the scaling tendency to a point at which it is controllable by conventional chemical treatments. To address the issue of freshwater scarcity and associated treatment costs of alternatives such as waste water, the use of raw seawater has received attention. The TDS content of the source water used in this paper is one of the highest in the world, given that the Arabian Gulf is known for its hyper-saline conditions. Furthermore, the cations present in the water, namely calcium and magnesium, are known to cause problems in the formulation process of hydraulic-fracturing fluid. As a result, it is expected that certain fracturing-fluid additives must be increased to meet these challenges and ultimately create a stable seawater-based fracturing-fluid system with appropriate gelation timing that meets industry standards. This study aims to find an alternative source to freshwater-based fracturing fluid and contribute to the study of scale inhibition as dirtier water sources are considered.

Slow sand filtration for biofouling reduction in seawater desalination by reverse osmosis

Control of the organic substrate pool that determines the microbial growth potential (MGP) of feedwater in seawater reverse osmosis (SWRO) is a challenge unresolved in conventional or advanced membrane pretreatment. Slow sand filtration (SSF) combines filtration with biodegradation, but its capability of reducing MGP, proteins and carbohydrates on seawater feeds is not known. Two SSF, one constructed with new media (newSSF) and one from a previous filtration run (oldSSF), reduced MGP as measured in a growth assay with the marine organism Pseudoalteromonas songiae by one order of magnitude after maturation periods of 76 and 61 days, respectively. The reduction of the amount of biopolymers deposited on the surfaces of SWRO membranes in laminar fluid flow cells was significant with filtrates from biologically non-acclimated SSF (proteins: 60% (oldSSF) and −66% (new SSF), carbohydrates: 75% (oldSSF) and −70% (newSSF)) and an even greater reduction was observed after filter maturation (proteins: 81% (oldSSF) and −76% (new SSF), carbohydrates: 88% (oldSSF) and −88% (newSSF). Turbidity was less than 0.3 nephelometric turbidity units (NTU) and silt density index (SDI) < 4 immediately after startup and during the 181 days operating period regardless of the oscillations of the raw sea water quality. Filtration and biological activity were restricted to the top 30 cm of the media column, with no significant further contribution of the deeper media layers to filtrate quality.

ATP measurement in seawater reverse osmosis systems: Eliminating seawater matrix effects using a filtration-based method

A direct method for measuring adenosine-triphosphate (ATP) in seawater was developed recently, in which commercial reagents are added directly to seawater. However, calibration is required if seawater quality changes (such as changes in salinity, pH, Mg2+, Fe3+) as the seawater matrix interferes with ATP measurement. In this research, a 0.1 μm filtration process is introduced to eliminate such interferences. In addition, a filter rinsing step with sterilized artificial seawater is proposed to eliminate interference of free ATP.The ATP-filtration method is fast (<5 min), reproducible (VC = 7%), six times more sensitive than the direct ATP-method and correlates (R2 = 0.72, n = 100) with intact cell concentration. Microbial ATP concentration measured using the ATP-filtration method and the ATP-direct method were comparable. Microbial ATP measured along the treatment train of a full-scale seawater reverse osmosis (SWRO) plant decreased from 530 in the raw seawater to 10 ng-ATP/L after pre-treatment and to 0.5 ng-ATP/L in the SWRO permeate. The method was also applied to monitor bacterial growth potential (BGP) across the pre-treatment train of a (pilot) seawater desalination plant, where the removal of BGP through the media filtration and ultrafiltration was 44% and 7%, respectively.

Genome-resolved metagenomic analysis reveals roles of microbial community members in full-scale seawater reverse osmosis plant

Biofouling of Reverse Osmosis (RO) membrane is a significant issue for the water treatment industry. In this study, we apply the metagenomic shot-gun sequencing technology to characterise the composition and functional potential of the microbial community in a full-scale RO plant, at different stages of seawater treatment. We find Proteobacteria, Bacteroidetes and Planctomycetes to be the most abundant bacterial phyla. The genetic potential of the RO membrane microbial community shows the enrichment of genes involved in biofilm formation, representing the selective pressure of the biofilm formation process. We recover 31 metagenome-assembled genomes (MAGs) from intake (raw seawater), fouled RO membranes (leading and middle RO module) and brine reject water. A total of 25 MAGs are recovered from the biofilm samples (leading and middle RO modules), with 9 of them (36%) belonging to Planctomycetes. We investigate all 25 MAGs for genes (pili, flagella, quorum sensing, quorum quenching and nitrate reduction) that play an important role in biofilm formation and sustenance of cells. We show that Planctomycetes contain genes for the formation of flagella and pili, and the reduction of nitrate. Although genes for quorum sensing are not detected, quorum quenching genes are identified in the biofilm MAGs. Our results show that Planctomycetes, along with other microbes, play an important role in the formation and sustenance of biofilms on seawater RO membranes.

Pemanfaatan Limbah Ikan Menjadi Tepung Silase dengan Penambahan Tepung Eceng Gondok (Eichhornia crassipes)

The purposes of this research were to utilize fish waste and to study effect of water hyacinth flour nonfermented and fermented as material of silage . Data were analyzed using paired sample t-test trought SPSS 16.0 programme. Treatments included different fish waste raw material (fresh water and sea water) dan the type of water hyacinth (fermented and nonfermented flour) added with 3 repetation. Based on the result of t test indicate that the different type of fish waste is significantly different from the content of ash, fat content and calcium on silage flour. While differences in water hyacinth flour significantly different to the bulk density, moisture content, protein, and crude fiber in the resulting silage flour. Different types of fish waste and water hyacinth flour were not significantly different from the phosphorus content, and NaCl in the resulting silage flour. Product that approach SNI quality of fish flour is using raw material sea water fish waste with the addition of water hyacinth fermented flour which obtained 0.56% bulk density, 11.91% water content, 22.73% ash content, 46.5% protein content, 15.19% fat content, 2.34% crude fiber content, 3.1% calcium, 2.26% phosphorus, and 2.65% NaCl.

Chlorination caused a shift in marine biofilm niches on microfiltration/ultrafiltration and reverse osmosis membranes and UV irradiation effectively inactivated a chlorine-resistant bacterium.

The effect of chlorine disinfection on marine biofilm populations and communities formed on membrane surfaces was investigated under two feedwater conditions: raw seawater and deep bed filtration-treated seawater. As a result of chlorination, the structure of the biofilm community on the microfiltration/ultrafiltration and reverse osmosis membrane coupons shifted significantly at the genus level. However, the total bacterial population was not reduced under the two feedwater conditions. This failure to control the biofilm was attributed to the adaptation and survival of selected bacteria under chlorine stress. Phaeobacter caeruleus, isolated from the biofilm, was examined as a representative chlorine-resistant biofilm-forming bacterium. The number of viable P. caeruleus was significantly reduced (as much as 99.8%) after ultraviolet (UV) disinfection. The results indicated that additional disinfection by UV irradiation can inactivate chlorine-resistant bacteria. Therefore, tandem chlorination-UV disinfection may enhance the efficiency of biofouling control in seawater reverse osmosis processes. The synergistic effects of tandem chlorination-UV irradiation on the marine biofilm community should be investigated in future studies.

Biodepression of pyrite using Acidithiobacillus ferrooxidans in seawater

In Cu-Mo deposits it is usual to find considerable amounts of pyrite (FeS2). When processing this kind of ore by flotation, pyrite is rejected using lime to increase the pH to alkaline conditions (pH ∼ 10–12). In the case of using seawater without pre-processing (raw seawater), the lime consumption increases dramatically and the recovery of molybdenite drops due to the precipitation of secondary ions (e.g. magnesium, sulfate, calcium and bicarbonate) on its surface. In order to avoid these negative effects, alternative ways of depressing pyrite should be considered.The current work introduces the use of Acidithiobacillus ferrooxidans, bacteria commonly used in bioleaching, as an alternative to depress pyrite in seawater flotation. This work presents the results of biodepression, at microflotation scale, in three systems: fresh water, saline water (35 g/l of NaCl, which corresponds to the salt concentration in seawater) and seawater. It was determined that when pyrite is bio-conditioned with A. ferrooxidans before flotation, recovery of pyrite at pH 8 drops from 99% to 24% and 34% in fresh water and saline water, respectively. A similar behavior is observed when running the experiments in seawater, where recoveries drop from 97% to 36% in the presence of A. ferrooxidans in flotation at natural pH (7.8–8.2). Results show that it is possible to bio-depress pyrite with A. ferrooxidans in seawater flotation at natural pH.

Flat ceramic microfiltration membrane based on natural clay and Moroccan phosphate for desalination and industrial wastewater treatment

A new microfiltration ceramic membrane has been developed by uniaxially compressing natural Moroccan materials: red clay of Safi and natural phosphate of Youssoufia, which is rich in organic matter. The natural phosphate can be beneficial to porosity formation. The effects of natural phosphate on the morphological and flexural strength of the flat disks sintered at 1100°C were studied to identify the optimal mass ratio of clay and phosphate via X-ray diffraction, scanning electron microscopy and flexural strength testing. The optimal composition of the flat ceramic membrane contained 40wt% natural phosphate, which led to a linear thermal expansion coefficient less than 13.42×10−6°C−1, flexural strength of 17.5MPa and Young's modulus of 40.12GPa. The average pore diameter and water permeability of the obtained ceramic membrane were respectively 2.5μm and 928L/(h·m2·bar). The microfiltration membrane efficiency was evaluated by filtering three feed solutions types: a tannery beamhouse effluent, a raw seawater and a synthetic solution of aluminium chloride (at high pH). The obtained ceramic membrane exhibited superior turbidity removal efficiency for all studied feeds: effluent (99.80%), seawater (99.62%) and synthetic solution (99.86%). Moreover, this microfiltration membrane showed good microstructure and mechanical stability after filtration experiments.

Effects of watering parameters in a combined seawater desalination process

Seawater desalination experiments using patented experimental platform that could recycle cold energy released from LNG (liquefied natural gas) re-gasification process were conducted in laboratory. Combined freezing, watering and centrifugal desalination (FWCD) process was employed. The effects of the key watering parameters, including proportion, temperature and pure water or seawater, on removal efficiencies of salt and measured ions and on ice yield rate were investigated. Results showed that watering process benefits the brine-ice separation through centrifugation and therefore the ice purity can be enhanced. To ameliorate ice product purity, increasing the mass proportion of watering raw seawater is a more feasible method than watering pure water. The desalination effect of adding raw seawater would be better in summer than in winter when other parameters constant. Comparing with combined freezing, gravity-induced and centrifugal desalination (FGCD) method, FWCD is a continuous process that can accelerate the desalination duration, and more ice with the same purity can be yielded within the salt removal efficiency range of FWCD method. Whereas more energy has to be consumed using FWCD process because higher centrifugation rotation rate is also necessary to achieve the same salt removal efficiency. Whereas the total energy consumption for unit ice product is acceptable.

PCA as tool for intelligent ultrafiltration for reverse osmosis seawater desalination pretreatment

A novel fouling monitoring methodology based on principal component analysis (PCA) has been validated using transmembrane pressure (TMP) data of a pilot-scale pressurized ultrafiltration (UF) system operated with seawater. The evolution of membrane fouling was investigated to determine its relation to the used cleaning strategy on the one hand and the quality of the raw seawater on the other hand. The developed models showed that in terms of cleaning efficiency there are no significant differences between the standard and optimized backwashing protocols that were employed. This confirms the hypothesis of being able to use the optimized operation in a sustainable manner and benefit from lower cleaning frequencies. In addition, it has been demonstrated that the use of PCA as a monitoring technique to detect abnormal fouling behaviour is a robust tool. By using PCA, decisions on cleaning sequences or frequencies could be taken dynamically instead of running the system with fixed cycles.