Category Archives: Desalination

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.,

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.

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Brackish Water Treatment System Powered by Photovoltaics

Manoj Chandra, Himanshu Joshi. Optimization and economic analysis of small scale nanofiltration and reverse osmosis brackish water system powered by photovoltaics. Desalination, Volume 353, 17 November 2014, Pages 57–74.

Integration of renewable energy with desalination technologies is a strongly emerging field in many regions of the world having drinking water and energy crisis. This study presents the results of a techno-economical investigation of a small scale, photovoltaic (PV) powered hybrid nanofiltration (NF) and reverse osmosis (RO) membrane system for the brackish water treatment. Optimization experiments of six commercially available small scale RO and NF membranes were carried out using central composite design (CCD) of response surface methodology (RSM). Experiments employing optimized input conditions validate the developed RSM model. Predictive model, using multiple response optimizations, revealed that CSM RO and NF250 membranes showed the optimal efficiency with 20.24% and 18.98% water recovery, 90.22% and 70.64% salt rejection and 17.87 and 9.35 kWh/m3 of SEC respectively. Comparison of membranes was also carried out by membrane characterization duly supported by experimental observations. Membrane surface was characterized by AFM, contact angle measurement and FTIR. Hybrid experiments were performed with NF and RO membranes in concentrate and permeate staging configurations. Results also suggested that techno-economic performance of the hybrid PV–NF/RO system was affected by factors like mode of integration of NF and RO membranes, recovery ratio, daily average operating hours and government subsidy.

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Performance Evaluation of a Parabolic Solar Still

Shiva Gorjian, Barat Ghobadian, Teymour Tavakkoli Hashjin, Ahmad Banakar. Experimental performance evaluation of a stand-alone point-focus parabolic solar still. Desalination Volume 352, 3 November 2014, Pages 1–17

A stand-alone point-focus parabolic solar still (PPSS) was designed and fabricated for desalination of seawater or brackish water and purification of non-potable water. The system consists of a parabolic dish concentrator; a two axis sun tracker based on programmable logic controllers (PLCs) and two plate heat exchangers (PHEs) to preheat the salt water before entering the absorber located at the focal point as well as condense the generating steam. Distillate productivity of the PPSS was measured along with evaluation of the effects of environmental and operational parameters that includes: beam solar insolation, wind speed, air temperature, absorber wall temperature and raw water salinity under the climatic conditions of Tehran during October. The maximum productivity of 5.12 kg within 7 h in a day was measured with the maximum average solar insolation of 626.8 W/m2 and the absorber wall temperature of 150.7 °C. However, no significant effect of air temperature, wind speed, and water salinity on the productivity was observed. The maximum daily efficiency of 36.7% was calculated with a maximum hourly output of 1.5 kg/h. The quality of lab-prepared salt water samples was analyzed before and after desalination and the results comply with the WHO guidelines for drinking water quality.

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Economic feasibility of solar still desalination

George M. Ayoub, Lilian Malaeb. Economic feasibility of a solar still desalination system with enhanced productivity. Desalination, Volume 335, Issue 1, 17 February 2014, Pages 27–32.

Solar still desalination systems offer sustainable tools for fresh water production. However, their widespread application is often hindered by their relatively low production rates compared to other desalination methods. In this study, a simple amendment, in the form of a slowly-rotating hollow cylinder, was introduced within the solar still, significantly increasing the evaporative surface area. This new modified still was analyzed in terms of both operation and economic feasibility. The introduced cylinder resulted in a 200–300% increase in water output relative to a control, which did not include the cylinder. The resulting percent improvement far exceeds that obtained by other modifications. Unit production cost estimates varied between 6 and 60 $/m3 depending on discount rates, productivity, service lifetime and initial capital costs. These projections are well within reported cost ranges for renewable-based technologies. In order to evaluate the system’s feasibility in real market value, different scenarios that introduce carbon-trading schemes and environmental degradation costs for fuel-based desalination, were performed. Reported costs for fuel-based brackish water and seawater desalination were thus adjusted to include unaccounted-for costs related to environmental damage. This analysis yielded results that further justify the economic feasibility of the new modified solar still, particularly for seawater desalination.

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A novel approach to sea water reverse osmosis pretreatment

Edo Bar-Zeeva, Natalia Belkina, Boris Libermanb, Ilana Berman-Franka, Tom Bermanc. Bioflocculation: Chemical free, pre-treatment technology for the desalination industry. Water Research. Volume 47, Issue 9, 1 June 2013, Pages 3093–3102.

Rapid sand filtration (RSF), proceeded by chemical coagulation and flocculation, is a commonly used, effective pretreatment in the desalination industry. We designed and tested a novel, large pilot-scale, two-stage granular Rapid Bioflocculation Filter (RBF) based on a first-stage Bioflocculator (BF) unit followed by a mixed-media bed filter (MBF). The BF filter bed consisted of an extremely porous volcanic Tuff granular medium which provided an enlarged surface area for microbial development and biofilm proliferation. We compared the efficiency of the pilot RBF to that of a full-scale RSF, operating with upstream chemical coagulation, by measuring the removal from the same untreated seawater feed of key factors related to membrane clogging: SDI, turbidity, chlorophyll a (Chl a) and transparent exopolymer particles (TEP). After 2 weeks of operation, the Tuff grains were colonized extensively by coccoid bacteria that formed biofilm along the entire BF. With bacterial colonization and biofilm development, numerous aggregates of bacteria and some algal cells embedded in an amorphous organic matrix were formed on and within the Tuff grains. By 1–3 months, the biotic diversity within the Tuff filter bed had increased to include filamentous bacteria, cyanobacteria, fungi, protista and even crustaceans and marine worms. During and for ∼24 h after each cleaning cycle (carried out every5 to 7 days by upward flushing with air and water), large numbers of floc-like particles, from ∼15 μm to ∼ 2 mm in size were observed in the filtrate of the BF unit. Microscopic examination of these flocs (stained with Alcian Blue and SYTOR 9) showed that they were aggregates of many smaller particles with associated bacteria and algae within a polysaccharide gel-like matrix. These biogenic flocs (bioflocs) were observed to form during normal operation of the RBF, accumulating as aggregates of inorganic and organic material on the Tuff surfaces. With each flush cleaning cycle, these bioflocs were released into the BF effluent but were retained by the second phase MBF unit. No flocs were seen in the MBF filtrate. Over a year-long study, both the pilot RBF and the full-scale RSF showed similar filtration efficiencies, measured as the percentage removal of Chl a, TEP, turbidity and SDI from the same seawater feed. These results indicate the potential of the bioflocculation approach with no chemical additives as an alternative to conventional RSF pretreatment for large SWRO facilities.

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