Tag Archives: desalination

Integrated Nanofiltration and Reverse Osmosis for Desalination

Talaeipour M, Nouri J, Hassani AH, Mahvi AH, An investigation of desalination by nanofiltration, reverse osmosis and integrated (hybrid NF/RO) membranes employed in brackish water treatment. Journal of environmental health science 2017 Jul 21;15:18. doi: 10.1186/s40201-017-0279-x.

BACKGROUND: As an appropriate tool, membrane process is used for desalination of brackish water, in the production of drinking water. The present study aims to investigate desalination processes of brackish water of Qom Province in Iran.

METHODS: This study was carried out at the central laboratory of Water and Wastewater Company of the studied area. To this aim, membrane processes, including nanofiltration (NF) and reverse osmosis (RO), separately and also their hybrid process were applied. Moreover, water physical and chemical parameters, including salinity, total dissolved solids (TDS), electric conductivity (EC), Na+1 and Cl-1 were also measured. Afterward, the rejection percent of each parameter was investigated and compared using nanofiltration and reverse osmosis separately and also by their hybrid process. The treatment process was performed by Luna domestic desalination device, which its membrane was replaced by two NF90 and TW30 membranes for nanofiltration and reverse osmosis processes, respectively. All collected brackish water samples were fed through membranes NF90-2540, TW30-1821-100(RO) and Hybrid (NF/RO) which were installed on desalination household scale pilot (Luna water 100GPD). Then, to study the effects of pressure on permeable quality of membranes, the simulation software model ROSA was applied.

RESULTS: Results showed that percent of the salinity rejection was recorded as 50.21%; 72.82 and 78.56% in NF, RO and hybrid processes, respectively. During the study, in order to simulate the performance of nanofiltartion, reverse osmosis and hybrid by pressure drive, reverse osmosis system analysis (ROSA) model was applied. The experiments were conducted at performance three methods of desalination to remove physic-chemical parameters as percentage of rejections in the pilot plant are: in the NF system the salinity 50.21, TDS 43.41, EC 43.62, Cl 21.1, Na 36.15, and in the RO membrane the salinity 72.02, TDS 60.26, EC 60.33, Cl 43.08, Na 54.41. Also in case of the rejection in hybrid system of those parameters and ions included salinity 78.65, TDS 76.52, EC 76.42, Cl 63.95, and Na 70.91.

CONCLUSIONS: Comparing rejection percent in three above-mentioned methods, it could be concluded that, in reverse osmosis process, ions and non-ion parameters rejection ability were rather better than nanofiltration process, and also better in hybrid compared to reverse osmosis process. The results reported in this paper indicate that the integration of membrane nanofiltration with reverse osmosis (hybrid NF/RO) can be completed by each other probably to remove salinity, TDS, EC, Cl, and Na.

Brackish Groundwater in the United States a Viable Water Supply

Stanton, J.S., Anning, D.W., Brown, C.J., Moore, R.B., McGuire, V.L., Qi, S.L., Harris, A.C., Dennehy, K.F., McMahon, P.B., Degnan, J.R., and Böhlke, J.K., 2017, Brackish groundwater in the United States: U.S. Geological Survey Professional Paper 1833, 185 p., https://doi.org/10.3133/pp1833.

For some parts of the Nation, large-scale development of groundwater has caused decreases in the amount of groundwater that is present in aquifer storage and that discharges to surface-water bodies. Water supply in some areas, particularly in arid and semiarid regions, is not adequate to meet demand, and severe drought is affecting large parts of the United States. Future water demand is projected to heighten the current stress on groundwater resources. This combination of factors has led to concerns about the availability of freshwater to meet domestic, agricultural, industrial, mining, and environmental needs. To ensure the water security of the Nation, currently [2016] untapped water sources may need to be developed.

Brackish groundwater is an unconventional water source that may offer a partial solution to current and future water demands. In support of the national census of water resources, the U.S. Geological Survey completed the national brackish groundwater assessment to better understand the occurrence and characteristics of brackish groundwater in the United States as a potential water resource. Analyses completed as part of this assessment relied on previously collected data from multiple sources; no new data were collected. Compiled data included readily available information about groundwater chemistry, horizontal and vertical extents and hydrogeologic characteristics of principal aquifers (regionally extensive aquifers or aquifer systems that have the potential to be used as a source of potable water), and groundwater use. Although these data were obtained from a wide variety of sources, the compiled data are biased toward shallow and fresh groundwater resources; data representing groundwater that is at great depths and is saline were not as readily available.

One of the most important contributions of this assessment is the creation of a database containing chemical characteristics and aquifer information for the known areas with brackish groundwater in the United States. Previously published digital data relating to brackish groundwater resources were limited to a small number of State- and regional-level studies. Data sources for this assessment ranged from single publications to large datasets and from local studies to national assessments. Geochemical data included concentrations of dissolved solids, major ions, trace elements, nutrients, and radionuclides as well as physical properties of the water (pH, temperature, and specific conductance). Additionally, the database provides selected well information (location, yield, depth, and contributing aquifer) necessary for evaluating the water resource.

The assessment was divided into national-, regional-, and aquifer-scale analyses. National-scale analyses included evaluation of the three-dimensional distribution of observed dissolved-solids concentrations in groundwater, the three-dimensional probability of brackish groundwater occurrence, and the geochemical characteristics of saline (greater than or equal to 1,000 mg/L of dissolved solids) groundwater resources. Regional-scale analyses included a summary of the percentage of observed grid cell volume in the region that was occupied by brackish groundwater within the mixture of air, water, and rock for multiple depth intervals. Aquifer-scale analyses focused primarily on four regions that contained the largest amounts of observed brackish groundwater and included a generalized description of hydrogeologic characteristics from previously published work; the distribution of dissolved-solids concentrations; considerations for developing brackish groundwater resources, including a summary of other chemical characteristics that may limit the use of brackish groundwater and the ability of sampled wells producing brackish groundwater to yield useful amounts of water; and the amount of saline groundwater being used in 2010.

Lower Magnesium Intake from Desalinated Seawater Associated with Cardiovascular Effects

Shlezinger M, Amitai Y, Goldenberg I, Shechter M. Desalinated seawater supply and all-cause mortality in hospitalized acute myocardial infarction patients from the Acute Coronary Syndrome Israeli Survey 2002-2013. International Journal of Cardiology. 2016 Jun 29;220:544-550. doi: 10.1016/j.ijcard.2016.06.241.

BACKGROUND: Consuming desalinated seawater (DSW) as drinking water (DW) may reduce magnesium in water intake causing hypomagnesemia and adverse cardiovascular effects.

METHODS: We evaluated 30-day and 1-year all-cause mortality of acute myocardial infarction (AMI) patients enrolled in the biannual Acute Coronary Syndrome Israeli Survey (ACSIS) during 2002-2013. Patients (n=4678) were divided into 2 groups: those living in regions supplied by DSW (n=1600, 34.2%) and non-DSW (n=3078, 65.8%). Data were compared between an early period [2002-2006 surveys (n=2531) – before desalination] and a late period [2008-2013 surveys (n=2147) – during desalination].

RESULTS: Thirty-day all-cause-mortality was significantly higher in the late period in patients from the DSW regions compared with those from the non-DSW regions (HR=2.35 CI 95% 1.33-4.15, P<0.001) while in the early period there was no significant difference (HR=1.37 CI 95% 0.9-2, P=0.14). Likewise, there was a significantly higher 1-year all-cause mortality in the late period in patients from DSW regions compared with those from the non-DSW regions (HR=1.87 CI 95% 1.32-2.63, P<0.0001), while in the early period there was no significant difference (HR=1.17 CI 95% 0.9-1.5, P=0.22). Admission serum magnesium level (M±SD) in the DSW regions (n=130) was 1.94±0.24mg/dL compared with 2.08±0.27 mg/dL in 81 patients in the non-DSW (P<0.0001).

CONCLUSIONS: Higher 30-day and 1-year all-cause mortality in AMI patients, found in the DSW regions may be attributed to reduced magnesium intake secondary to DSW consumption.

Is Complete Demineralization of Drinking Water Desirable?

Verma KC, Kushwaha AS. Demineralization of drinking water: Is it prudent? Medical journal, Armed Forces India. 2014 Oct;70(4):377-9. doi: 10.1016/j.mjafi.2013.11.011.

Water is the elixir of life. The requirement of water for very existence of life and preservation of health has driven man to devise methods for maintaining its purity and wholesomeness. The water can get contaminated, polluted and become a potential hazard to human health. Water in its purest form devoid of natural minerals can also be the other end of spectrum where health could be adversely affected. Limited availability of fresh water and increased requirements has led to an increased usage of personal, domestic and commercial methods of purification of water. Desalination of saline water where fresh water is in limited supply has led to development of the latest technology of reverse osmosis but is it going to be safe to use such demineralized water over a long duration needs to be debated and discussed.

Click here for paper (Open Access).

Water quality impacts reverse osmosis biofouling in desalination

Siqian Huanga, Nikolay Voutchkovb, Sunny C. Jianga. Investigation of environmental influences on membrane biofouling in a Southern California desalination pilot plant. Desalination, Volume 319, 14 June 2013, Pages 1–9.
http://dx.doi.org/10.1016/j.desal.2013.03.016

One of the challenges the seawater desalination industry faces today is reverse osmosis (RO) membrane biofouling. Traditional water quality parameters such as SDI and the RO feed water turbidity are inadequate at protecting the membrane from biofouling. This research investigated the environmental and water quality parameters in a Southern California desalination plant in order to develop a set of seawater desalination RO membrane biofouling indicators. Statistical analysis was performed on data collected onsite over two years. The relationships between operation parameters, rain precipitations, TOC, UV254, chlorophyll fluorescence in raw seawater and the performance loss of the RO desalination process are presented. The environmental triggers for accelerated RO membrane biofouling was further investigated by developing membrane fouling simulators at the desalination pilot plant. Biofouling was confirmed by confocal laser scanning microscopy investigation of membrane biofilm and live and dead bacterial cell counts. The results of this study indicated that biofouling was significantly correlated with water quality changes. Thus, chlorophyll fluorescence measurements can be used as a precursor for desalination membrane biofouling.

Click here for full paper (fee).

Dissolved solids in Southwestern US water resources

Anning DW. Modeled Sources, Transport, and Accumulation of Dissolved Solids in Water Resources of the Southwestern United States. J Am Water Resour Assoc. 2011 Oct;47(5):1087-1109.

jawr0047-1087-f1

Information on important source areas for dissolved solids in streams of the southwestern United States, the relative share of deliveries of dissolved solids to streams from natural and human sources, and the potential for salt accumulation in soil or groundwater was developed using a SPAtially Referenced Regressions On Watershed attributes model. Predicted area-normalized reach-catchment delivery rates of dissolved solids to streams ranged from <10 (kg/year)/km(2) for catchments with little or no natural or human-related solute sources in them to 563,000 (kg/year)/km(2) for catchments that were almost entirely cultivated land. For the region as a whole, geologic units contributed 44% of the dissolved-solids deliveries to streams and the remaining 56% of the deliveries came from the release of solutes through irrigation of cultivated and pasture lands, which comprise only 2.5% of the land area. Dissolved-solids accumulation is manifested as precipitated salts in the soil or underlying sediments, and (or) dissolved salts in soil-pore or sediment-pore water, or groundwater, and therefore represents a potential for aquifer contamination. Accumulation rates were <10,000 (kg/year)/km(2) for many hydrologic accounting units (large river basins), but were more than 40,000 (kg/year)/km(2) for the Middle Gila, Lower Gila-Agua Fria, Lower Gila, Lower Bear, Great Salt Lake accounting units, and 247,000 (kg/year)/km(2) for the Salton Sea accounting unit.

Click here for the full paper (Open Source).

Solar and wind aided evaporation of RO reject water

Ligy Philip, K.S. Reddy, Bhuvanesh Kumar, S. Murty Bhallamudi, A. Kannan. Performance evaluation of a solar and wind aided cross-flow evaporator for RO reject management. Desalination 317 (2013) 1–10.

In the present study, an attempt was made to evaluate the performance of a solar and wind aided cross-flow evaporator prototype as an alternative to conventional evaporators for concentrating reverse osmosis (RO) rejects. The performance of the solar andwind aided cross-flowevaporatorwas evaluated for different operating conditions such as (i)wind velocity, (ii) relative humidity in the ambient air, (iii) temperature of inletwater, (iv) trickling rate and (v) different packing geometries. Empirical correlations for evaporation loss were developed, as a function of the above variables. Among the various synthetic and natural media tried, plastic flexi ring was the most effective. Solar and wind aided cross-flow evaporator with random packing performed better than that with structured packing, as long as the air flow is not blocked by the packing. Studies revealed that the exposed surface area and depth of packing in the direction of wind are the important dimensions of the natural evaporator. Itwas also found that solar pre heating significantly increased the evaporation rate. Evaporation rate decreased as the concentration of salt in the water increased.

Click here for full article (Open Source).