Samir Al-Mashharawi

Estimation of soil salinity in a drip irrigation system by using joint inversion of multicoil electromagnetic induction measurements

Low frequency electromagnetic induction (EMI) is becoming a useful tool for soil characterization due to its fast measurement capability and sensitivity to soil moisture and salinity. In this research, a new EMI system (the CMD mini-Explorer) is used for subsurface characterization of soil salinity in a drip irrigation system via a joint inversion approach of multiconfiguration EMI measurements. EMI measurements were conducted across a farm where Acacia trees are irrigated with brackish water. In situ measurements of vertical bulk electrical conductivity (σb) were recorded in different pits along one of the transects to calibrate the EMI measurements and to compare with the modeled electrical conductivity (σ) obtained by the joint inversion of multiconfiguration EMI measurements. Estimates of σ were then converted into the universal standard of soil salinity measurement (i.e., electrical conductivity of a saturated soil paste extract – ECe). Soil apparent electrical conductivity (ECa) was repeatedly measured with the CMD mini-Explorer to investigate the temperature stability of the new system at a fixed location, where the ambient air temperature increased from 26°C to 46°C. Results indicate that the new EMI system is very stable in high temperature environments, especially above 40°C, where most other approaches give unstable measurements. In addition, the distribution pattern of soil salinity is well estimated quantitatively by the joint inversion of multicomponent EMI measurements. The approach of joint inversion of EMI measurements allows for the quantitative mapping of the soil salinity distribution pattern and can be utilized for the management of soil salinity.

Impact of well intake systems on bacterial, algae, and organic carbon reduction in SWRO desalination systems, SAWACO, Jeddah, Saudi Arabia

AbstractThe intake system can play a significant role in improving the feed water quality and ultimately influence the performance of downstream components of the seawater reverse osmosis desalination processes. In most cases, open-ocean intakes produce poor feed water quality in terms of the abundance of naturally occurring organic matter, which increases the risk of membrane fouling. An alternative intake is the subsurface system, which is based on the riverbank filtration concept that provides natural filtration and biological treatment of the feed water prior to the entry of the water into the desalination plant. The use of subsurface intakes normally improves the raw water quality by reducing suspended solids, algae, bacterial, and dissolved organic carbon concentrations. Therefore, the risk of biofouling caused by these substances can be reduced by implementing the appropriate type of intake system. The use of well intake systems was investigated along the Red Sea shoreline of Saudi Arabia in the Je...

Hydrogeology, water quality, and microbial assessment of a coastal alluvial aquifer in western Saudi Arabia: potential use of coastal wadi aquifers for desalination water supplies

Wadi alluvial aquifers located along coastal areas of the Middle East have been assumed to be suitable sources of feed water for seawater reverse osmosis facilities based on high productivity, connectedness to the sea for recharge, and the occurrence of seawater with chemistry similar to that in the adjacent Red Sea. An investigation of the intersection of Wadi Wasimi with the Red Sea in western Saudi Arabia has revealed that the associated predominantly unconfined alluvial aquifer divides into two sand-and-gravel aquifers at the coast, each with high productivity (transmissivity = 42,000 m2/day). This aquifer system becomes confined near the coast and contains hypersaline water. The hydrogeology of Wadi Wasimi shows that two of the assumptions are incorrect in that the aquifer is not well connected to the sea because of confinement by very low hydraulic conductivity terrigenous and marine muds and the aquifer contains hypersaline water as a result of a hydraulic connection to a coastal sabkha. A supplemental study shows that the aquifer system contains a diverse microbial community composed of predominantly of Proteobacteria with accompanying high percentages of Gammaproteobacteria, Alphaproteobacteria and Deltaproteobacteria.

Feasibility of using a subsurface intake for SWRO facility, south of Jeddah, Saudi Arabia

The Kingdom of Saudi Arabia is the largest producer of desalinated water with about 13% of the global desalination capacity. Most of these desalination plants use the open-ocean intakes to deliver ...

Evaluating the efficiency of different microfiltration and ultrafiltration membranes used as pretreatment for Red Sea water reverse osmosis desalination

Abstract Conventional processes are widely used as pretreatment for reverse osmosis (RO) desalination technology since its development. However, these processes require a large footprint and have some limitation issues such as difficulty to maintain a consistent silt density index, coagulation control at low total suspended solids, and management of higher waste sludge. Recently, there has been a rapid growth in the use of low-pressure membranes as pretreatment for RO systems replacing the conventional processes. However, despite the numerous advantages of using this integrated membrane system mainly providing good and stable water quality to RO membranes, many issues have to be addressed. The primary limitation is membrane fouling which reduces the permeate flux; therefore, higher pumping intensity is required to maintain a consistent volume of product. This paper aims to optimize the permeation flux and cleaning frequency by providing high permeate quality. Different low-pressure polyethersulfone membra...

Aquifer Treatment of Sea Water to Remove Natural Organic Matter Before Desalination

An investigation of a sea water reverse osmosis desalination facility located in western Saudi Arabia has shown that aquifer treatment of the raw sea water provides a high degree of removal of natural organic matter (NOM) that causes membrane biofouling. The aquifer is a carbonate system that has a good hydraulic connection to the sea and 14 wells are used to induce sea water movement 400 to 450 m from the sea to the wells. During aquifer transport virtually all of the algae, over 90% of the bacteria, over 90% of the biopolymer fraction of NOM, and high percentages of the humic substance, building blocks, and some of the low molecular weight fractions of NOM are removed. Between 44 and over 90% of the transparent exopolymer particles (TEP) are removed with a corresponding significant reduction in concentration of the colloidal fraction of TEP. The removal rate for TEP appears to be greater in carbonate aquifers compared to siliciclastic systems. Although the production wells range in age from 4 months to 14 years, no significant difference in the degree of water treatment provided by the aquifer was found.

Effects of Well Intake Systems on Removal of Algae, Bacteria, and Natural Organic Matter

Analyses of the changes in concentration of algae, bacteria, transparent exopolymer particles (TEP), and the fractions of natural organic matter (NOM) impacts between surface seawater and the discharges of well intake systems were evaluated at seven different seawater reverse osmosis water (SWRO) treatment plants. In nearly all cases, travel of the raw seawater through the seabed into the aquifer and into the wells removed all of the algae. Bacteria removal was up to 98.5 %, but varied greatly between sites and in different wells at each site. The TEP concentration was significantly lowered compared to the natural seawater. The biopolymer fraction of NOM was significantly lowered at all sites, but the lighter fractions of the NOM were removed at lower percentages. The removal percentage of NOM fractions appears to be based on molecular weight (and size) with the lighter weight fractions removed at lower percentages. A key factor controlling the removal of organic material appears to by the hydraulic retention time which is controlled by the length of the flowpath and the type of aquifer porosity. Specific site geology does not seem to be a significant factor. Vertical well systems showed greater organic materials removal compared to horizontal and tunnel intake systems. Again, this appears to be related to the length of the flowpath and the hydraulic retention time. The horizontal well system at Alicante, Spain showed poor removal of organic matter and breakthrough of algae occurred in the system.

Effects of Intake Depth on Raw Seawater Quality in the Red Sea

It has been suggested that using a deep open-ocean intake would improve feed water quality and would reduce the cost of SWRO water treatment by lessening membrane biofouling potential. The feasibility of developing deep intake systems for large-capacity SWRO plants located on the Red Sea was assessed. A bathymetric survey showed that the continental shelf along the Red Sea nearshore has a nearly vertical drop into deep water beginning at depths between 20 and 40 m. The vertical nature of the bathymetric profile and the issue of active seismicity make the development of a SWRO intake at a depth of greater than 100 m below surface a very risky venture along the Red Sea coast of Saudi Arabia. Detailed assessment of temperature and salinity with depth show a decrease of 5 °C and an increase of 1100 mg/L respectively over 90 m. Concentrations of algae, bacteria, total organic carbon, particulate and colloidal TEP, and the biopolymer fraction of natural organic carbon all showed declines in concentration. However, the general water quality improvements in reduced concentrations of organic matter were insufficient to reduce the intensity of pretreatment for an SWRO system. Overall, the Red Sea does not appear to be a good location for the use of deep SWRO intakes because of the structural risk of installing and maintaining an intake at near or below 100 m of water depth.

Coastal Evaluation and Planning for Development of Subsurface Intake Systems

The feasibility of using a subsurface intake system for a seawater reverse osmosis (SWRO) water treatment plant is based on the site-specific hydrogeologic conditions which control the type of intake design that can be used and the capacity of the intake. Planning for future development of subsurface intake systems requires a careful analysis of the shoreline and shallow offshore area. Example regions, the Red Sea coast of Saudi Arabia and the shoreline of Florida (USA), were investigated to develop general feasibility criteria for possible development of SWRO intake systems. Within the Red Sea, it was found that various well intake systems could be feasible for low-capacity SWRO facilities and high capacity intake systems would be limited to seabed gallery intakes. Coastal Florida had more subsurface intake options available, including wells, beach galleries, and seabed galleries which could be used based on the required capacity and the specific site conditions. The presence of high transmissivity carbonate aquifers containing seawater in Florida would allow medium capacity SWRO systems to use conventional vertical wells. High capacity systems could be developed using beach gallery systems in many locations. The methods developed for shoreline and nearshore evaluation contained herein could be applied to any coastal region of the world for subsurface intake evaluation.

Feasibility and Design of Seabed Gallery Intake Systems Along the Red Sea Coast of Saudi Arabia with Discussion of Design Criteria and Methods

Geological characteristics of the Red Sea coastline of Saudi Arabia were evaluated to assess the technical feasibility of designing and constructing seabed gallery intake systems to provide feed water for seawater reverse osmosis (SWRO) desalination plants. Five sites were investigated in detail at King Abdullah Economic City, Om Al Misk Island, Jeddah, Shoaiba, and Shuqaiq. It was found that a large part of the Red Sea nearshore area contains a low-sloping inner reef area from the beach seaward to the reef tract. Water depth ranges from 0 to 2 m in this shelf area and there is minimal coral growth and a small percentage of seagrass cover. There is a carbonate or siliciclastic sand cover over a moderately hard to soft limestone. It was found that seabed gallery systems could be designed and constructed at each of the sites investigated. The site-specific conditions varied which necessitated different designs of the filter with the upper, reactive layer varying with regard to the mean grain diameter of the media to match the site conditions and the layer thickness to provide adequate water treatment. Preliminary design infiltration rates varied between 5 and 10 m/d with hydraulic retention times ranging from 3.4 to 7 h. Each gallery intake design was divided into a number of cells, each to be equipped with a pump to achieve overall high system reliability. The Saudi Arabia nearshore area of the Red Sea appears to be an ideal location for the development of seabed gallery intake systems based on the shallow water and relative ease of construction.