M. Abdel-Jawad

Fifteen years of R&D program in seawater desalination at KISR. Part I. Pretreatment technologies for RO systems

Abstract Reverse osmosis (RO) has been established as a reliable process for seawater desalination. The reliability of the RO technique depends upon the extent of the pretreatment that must be designed to reduce the suspended and colloidal materials in the feedwater. During the last 15 years of research and development work at the Doha Research Plant (DRP), the Kuwait Institute for Scientific Research (KISR) has evaluated various types of pretreatment technologies for RO systems. These included: conventional pretreatment (CP), microfiltration (MF) and the beachwell (BW) intake systems. This paper gives brief description of these pretreatment technologies which were implemented at DRP and discusses their performances

Economics of seawater desalination by reverse osmosis

Abstract The ultimate goal in the scientific study of desalting and water purification is to design a process that produces potable water at the lowest possible cost. Presently two major techniques are commercially used in different parts of the world: distillation and membrane processes. The dominant distillation process is multi-stage flash (MSF), and the main membrane process is reverse osmosis (RO). Although cost factors vary by site, the total cost of producing potable water from seawater with the RO process is usually less than thermal desalting processes. In this paper results of a study carried out in Kuwait to compare the unit cost of water produced from one-stage and two-stage hollow fiber (HF) and spiral wound (SW) seawater RO systems are presented. Results indicate that an average reduction in product water cost of about 22% could be achieved when one-stage RO is used instead of two-stage RO to produce drinking water from seawater in Kuwait. Moreover, an average of 11.84% of the capital investment cost can be saved by using a one-stage instead of a two-stage RO system. A greater reduction in product water cost is expected in the future as there is more room for improvement in the design, operation and maintenance of seawater desalination by RO technology.

Advanced technologies for municipal wastewater purification: technical and economic assessment☆

Abstract The water resources of Kuwait are limited to desalinated water to meet the requirements for all freshwater needs, unreplenishable brackish water as a supplementary source for blending and agriculture, and municipal wastewater which is treated and mainly discarded to the sea. Limited quantities of the treated effluents are utilized for agriculture and greenery purposes. The large quantities of treated effluents have a great potential to replace the brackish water supplies and to redress the balance of demand for irrigation water. Research work was carried out at the Kuwait Institute for Scientific Research (KISR) to assess the technical viability and economic feasibility of implementing reverse osmosis (RO) technology to renovate Kuwaits treated wastewater effluent. This paper describes the adopted treatment, alternative pretreatment, characteristics of the permeate and cost of the renovation treatment. The results indicate that municipal wastewater can be treated by advanced technologies to produce an excellent water which is almost devoid of salts, pollutants and microorganisms. The total cost of such treatment is estimated to be almost half of the distillate cost produced by multistage flash (MSF) plants, whereas the cost of treating the tertiary treated wastewater alone by additional advanced treatment constitutes only 25% of the MSF distillate costs. The Government of the State of Kuwait has decided to implement this technology in constructing a wastewater treatment and reclamation plant at Sulaibiya in the context of privitization to produce an effluent of a quality that can be considered an additional water resource for non-potable uses.

Performance evaluation of two RO membrane configurations in a MSF/RO hybrid system

Abstract Although integration between multistage flash distillation (MSF) and reverse osmosis (RO) in hybrid desalination systems has been long discussed in the literature, and has been shown to be technically and economically superior to nonintegrated MSF and RO systems, no serious attempts have yet been made to adopt or implement such an approach in the design or construction of new desalination plants. This, perhaps to some extent, may be attributed to the real need first for some tangible experience on an acceptable scale and to the lack of experimental data on the performance of RO membranes in MSF/RO hybrid systems. Hence, this paper attempts to fill in this gap by presenting: operational experience using reasonably-sized RO production plants, a large body of experimental data on RO membrane performance in a simple MSF/RO hybrid model, and an overall evaluation of the performance of the RO membranes operating under the given conditions. The work represents the second phase of an experimental investigation of MSF/RO hybrid systems. In this phase the performances of two types of RO membranes operating in a simple easy-to-implement MSF/RO hybrid model were measured and evaluated. The experiments were carried out at the Doha Desalination Research Plant (DRP) using two RO units linked with the nearby MSF unit A-1 of the Doha East Distillation Plant via one common feed water header and pretreatment unt. The common feed water system, however, does not prevent either of the two RO units from being operated independently from each other. The RO units are of the spiral-wound and the hollow-fiber twin seawater RO membrane configurations, each of 300 m3/d nominal production capacity. Descriptions of the MSF/pretreatment/RO experimental model, measurements of performance data, analytical procedures, and discussions of the results obtained are presented. The results indicate that the two tested types of membranes behave in a very similar fashion, both qualitatively and quantitatively. RO product water recovery under hybrid operation is significantly higher than under isolated surface seawater operation. Up to a 43% increase in the RO product water recovery was realized when data under hybrid operation were compared with those under isolated surface seawater operation and similar feed pressures. The average change in RO product water recovery was almost linearly related to the change in feed water temperature at an average rate of 2.2% 1° C change in feed water temperature.

Pilot study of MSFRO hybrid systems

Abstract Evaluation of the reverse osmosis (RO) process performance in an multistage/reverse osmosis ( MSF RO ) hybrid system is of particular interest due to the obvious advantages of hybrid desalination plants over isolated ones. Meaningful evaluation of the RO process performance in a hybrid model requires continuous monitoring of an RO test unit for an appreciable period of time during the winter season when the ambient seawater temperature is low. The primary objective of this study was to systematically confirm possible gains in the RO product water flow rate and to examine the overall performance of an RO plant operating in a hybrid environment. Experiments were carried out at the Doha Desalination Research Plant (DRP) using a carefully designed and equipped 20 m3/d RO test unit linked with the nearby MSF unit A-1 of the Doha East Distillation Plant. Actual hybrid testing of the RO unit started during the cold season and continued for about 1,800 h. The temperature of the RO seawater feed withdrawn from the MSF reject stream ranged from 24 to 31°C. Operating data collected from the RO test unit included temperature, pressure, flow rate, concentration, silt density index (SDI), and pH according to the function of each stream. A description of the experimental model, including the MSF RO arrangement, performance data, and a discussion of the results obtained are included in the course of this paper. It was shown that an increase of up to 49% in the RO product water recovery was realized when data from before and after hybridization were compared. Also, a 42–48% gain in RO product water recovery was estimated for a seawater feed temperature of 33°C as compared to an isolated RO plant using surface seawater at a temperature of 15°C and at a reference feed pressure of 55 bar. Higher SDI values, increased frequency of backwash and chemical dosing, and loss of the membranes salt rejection were also encountered during the hybrid testing.

Pretreatment of the municipal wastewater feed for reverse osmosis plants

Potable water can be produced at a reasonable cost if reverse osmosis (RO) technology can be applied to renovate secondary/tertiary wastewater effluent. This implementation would yield many advantages to Kuwait, namely satisfying the increasingly agricultural, industrial and domestic demands for good quality water free of viruses and bacteria, preserving the natural strategic water resources, reducing environmental pollution resulting from direct discharge of secondary/tertiary municipal effluents to the sea and meeting unexpected emergency cases of shortages in fresh water production for certain applications. Membrane fouling is the most important obstacle that has to be overcome for successful RO. Membrane fouling usually results in reduction of the permeate production rate, an increase in salt passage with time and/or membrane damage. Causes of fouling include scaling, plugging of membrane pores by suspended matter, biological fouling and degradation of the membrane itself. Membrane fouling is very much aggravated with the use of wastewater effluent as a feed for RO systems. The Kuwait Institute for Scientific Research (KISR) is implementing a research project to desalinate tertiary treated wastewater using RO in Kuwait. This paper describes the process of designing a proper pretreatment process capable of producing a substantial reduction in potential membrane foulants. Results obtained from laboratory and pilot studies revealed that fast mixing, coagulation, flocculation and sedimentation using Fe III, cationic polyelectrolyte and a sanitizing agent can produce an acceptable quality of effluent feed for the RO process. This paper discusses the progress made in establishing proper pretreatment of this feed to meet the requirements of RO membrane manufacturers.

Fifteen years of R&D program in seawater desalination at KISR part II. RO system performance

Kuwait Institute for Scientific Research (KISR) and the Ministry of Electricity and Water (MEW) collaborated over the past 15 years in developing and adapting the seawater reverse osmosis (RO) technology to the Gulf seawater conditions (one and half time the salinity of open seas and large temperature variations between summer and winter in the range of 35°C and 10°C, respectively). The development process went through several stages involving performance evaluation of three types of membrane configurations under various operating conditions and using different types of feed water pretreatment techniques. It went also through the evaluation of various commercially available energy recovery systems and the development of a new system. During this period, the RO research program evaluated the performance of ten different seawater membranes, cleaning and restoration techniques and procedures, using various potential agents. Furthermore, computer aided design program and process design and optimization procedures were developed specifically for Gulf seawater conditions. The studies also involved two-phase evaluation of multistage flash/reverse osmosis (MSF/RO) hybrid systems. Cost assessment of product water from RO under different operating conditions and various system configurations was always an important integrated part of each research project.

Microfiltration system as a pretreatment for RO units: Technical and economic assessment

Abstract Microfiltration (MF) seems to be a very attractive pretreatment technique that is increasingly being used in drinking water, seawater, and wastewater applications. Recently, it has been used as a pretreatment in reverse osmosis applications. This paper presents the results of a research project on the viability and the economics of MF as a pretreatment technique for a seawater reverse osmosis (SWRO) system. The overall performance of the MF unit indicates that the SDI of the surface seawater feed ranges between 0.26 and 3.10% with an average SDI value of 2.24. SDI of surface seawater feed is above 6.5%. Average filtrate flowrate is 3.20 m3/h. The optimal backwash interval is 10 min at variable feed flowrate. The MF unit is capable of reducing COD and BOD values and producing good quality water suitable as a feed for RO systems. The techno-economic study revealed that the total unit water costs produced by beachwell, MF and conventional surface pretreatment systems are 11.082, 12.264 and 28.153 fils/m3,† respectively. It is clear that the beachwell system is the most cost-effective among the three available techniques for seawater pretreatment. If for some reason the beachwell system is not technically feasible, then the MF system is the next most cost-effective system for seawater pretreatment. It has the added advantage of better water quality.

Technical and Economical Comparison Between Large Capacity Multi Stage Flash and Reverse Osmosis Desalting Plants

Abstract In the course of evaluating the unit cost of desalted water by either the predominant multi stage flash (MSF), and its competitor reverse osmosis (RO) desalting systems, a quantitative comparison of the equipment used was conducted. The chemical and energy consumptions are also compared for both systems. More expensive materials and more energy are consumed in the MSF system than in RO so that the unit cost of seawater desalted by the RO system is lower than that obtained by the MSF system. Moreover, prospects for lower cost by the RO system exist by developing a more efficient energy recovery system and reducing the cost of the membranes. It is believed that the present cost of membranes is much higher than the real manufacturing cost.

Conventional pretreatment system for the Doha Reverse Osmosis Plant: Technical and economic assessment

Abstract The conventional pretreatment method is widely used to treat surface seawater feed for the seawater reverse osmosis (SWRO) process; however, this method is cumbersome and costly and has many drawbacks that lead to higher product water cost by RO desalination technology. This paper outlines the experience gained from 65 months of operation of a surface seawater conventional pretreatment system at the Doha Reverse Osmosis Plant (DROP) in Kuwait. The paper describes the pretreatment system used, problems and drawbacks encountered during the course of operation, namely: instability of Silt Density Index (SDI) value, high rate of chemical consumption, high rate of water consumption for backwashing and high energy consumption, and gives an economic assessment for the pretreatment system. The economic analysis shows that the cost for the conventional pretreatment system acounts for 26.7% of the total capital investment cost for a 4,546 m 3 /d two-stage spiral-wound (SW) RO system, similar to the one used at DROP. A 30% saving in unit product water cost could be achieved if a beachwell intake pretreatment system is used instead of the conventional pretreatment system.