Water Treatment and Conveyance System Salem Gammoh, Jordan Ministry of Water and Irrigation

Transcription

1 Wadi Ma'in, Zara and Mujib Water Treatment and Conveyance System Salem Gammoh, Jordan Ministry of Water and Irrigation The Ministry of Water and Irrigation in the Hashemite Kingdom of Jordan developed the preliminary design in 2002 of a project to desalinate raw surface water collected from Wadi Ma in, Zara springs, Wadi Mujib and conveying about 47 million cubic meters per Year of potable water to the city of Amman serving more than one million inhabitants. The initial cost of the project was $125 million, predominantly funded by USAID and based on a Design Build Operate (DBO) approach. It was constructed by the consortium Morganti Group Inc. and Infilco Degremont /Suez. The water production started August the 18 th 2006, and the plant was officially inaugurated on the 18 th of November PROJECT DESCRIPTION Raw Water Origin Raw water is a mixture of three main sources: Wadi Mujib, Wadi Ma'in and Zara Hot Springs. These originally flow to the Dead Sea, and are now collected and conveyed to a raw water reservoir of capacity 20,000 m 3 at the treatment plant. Raw Water Analysis Average values of the raw water analysis are given below. The total dissolved solids (TDS) of these combined sources are around 1,485 mg/l. The treatment plant is built to treat this water, meeting WHO and Jordanian standards and pump it to Amman. The TDS of the supplied water is less than 250 mg/l. 12

2 Water Treatment plant Flow Diagram Raw Water Pre-treatment The pre-treatment of the raw water in the plant before desalination provides: 2 log removal of viruses 3 log removal of Guardia cysts and Cryptosporidium Turbidity less than 0.1 NTU Silt Density Index (SDI) less than 3 Water from the raw water reservoir flows to a pumping station, where it is pumped to a static mixer, via (4+1) variable speed submersible pumps, each at a 1570 m 3 /h flow rate. Intermittent shock chlorination of raw water can be done to fight against the development of algae and other microorganisms. In the static mixer chemicals are added to initiate coagulation and flocculation. Ferric Sulfate (a Coagulant) Sulfuric acid (for ph adjustment) Polyelectrolyte (a Coagulant aid) Raw Water Reservoir 10,000 m 3 Chlorination 10,000 m 3 Raw Water Pumping Station Y Ø1200 Ferric Sulfate H 2 SO 4 Polymer 2-8 mg/l Fe mg/l 0.1 mg/l Y Static Mixer Ø700 Pulsatube Clarifiers Raw water from the static mixer is introduced at the bottom of a sludge blanket clarifier called PULSATUBE combining flocculation and clarification in the same area. Vacuum is created within the inlet chamber causing water to rise. Temperature 27 º C Turbidity 12 NTU ph 8.0 Chlorides 575 mg/l as Cl Ca 292 mg/l as CaCO 3 Iron 0.3 mg/l as Fe Sulfates 200 mg/l as SO 4 TH 436 mg/l as CaCO 3 Silica 18.4 mg/l as SiO 2 M-Alkalinity 150 mg/l as CaCO 3 Bicarbonates 190 mg/l as HCO 3 TDS 1,475 mg/l TSS 67 mg/l TCC 3,385 MPN/100 ml TFCC 444 MPN/100 ml 13

3 When the vent opens, water flows down into the bottom and passes upwards through the distribution pipes and the sludge blanket, agglomerating flocks and suspended particles creating larger flocks and so on until it settles. There are 4 PULSATUBE clarifiers each with a flow rate of 1570 m3/h and a surface area of 392 m 2. Clarified water separates from the sludge blanket and collected in the channels near the surface where it passes through the MEDIAZUR dual media filters Mediazur Dual Media Filter Anthracite Sand Gravel Dual Media Filters Large quantities of small sized suspended particles, previously formed and not settled in the clarifier are retained in the dual Media filters. There are 8 filters, each with a surface area of 113 m2 and A flow rate of 785 m 3 /h (Filtration rate ~8 m/h). Cartridge Filtration As a last stage of pre-treatment, filtered water is passed through eight (5µm) cartridge filters as a safety measure to protect the RO membranes in the Desalination process against fouling. Desalination Desalination of the pre-treated water is done by a Reverse Osmosis process. This separation by membrane technique rejects dissolved solids to obtain purer water with very low total dissolved solids (TDS) The RO plant consists of nine skids; each has three stage configurations as shown below and fed by a high pressure pump. A booster pump is used for feeding the third stage. Eight skids are sufficient to produce the required quantity of RO water operating with a conversion rate between 85 and 90%.The brine from the plant discharges to the Dead Sea. 14

4 CO 2 Removal Osmosed Water is conveyed through an aeration Cascade where CO 2 is stripped. Blending Osmosed water is then blended with treated filtered raw water which has been disinfected by the Aquaray H2O UV disinfection system. Re-mineralization Re-mineralization of the blended water is done by Lime injection, which is prepared in the Lime Densadeg to control its ph, TDS, corrosivity or scale-forming tendency (LSI). Disinfection Chlorine is used in the plant to disinfect the product water to provide at least 0.5 log removal of Guardia cysts 2-log removal of viruses Chlorine can be further injected in pumping station No. 5 to increase its residual content before reaching Amman. Conveyance A transmission pipeline approximately 40 km long conveys the potable water to Amman where it is pumped to Dabouq Reservoir, through six pumping stations. The total head is around 1300 meters (see details below). Unexpected Challenges Seasonal feed water quality change required changes to the plant operation including: Improved pre-treatment, Lower flux and/or Recovery, more frequent cartridge filter change out, and more frequent CIP. In particular a flood in the Mujib site caused raw water turbidity to exceed plant design limits. Other notable challenges included supplying quality water while finishing plant construction during final stages of plant installation. Seasonal rain fall and the continued drought effects on raw water sources resulted in inadequate raw water supply from the springs so that production was often at a rate of 100 million m 3 /yr instead of the 130 million m 3 per year plant capacity. Raw water supply to other facilities (factories and agriculture) was also complicated by 15

5 the same volumetric flow limitation of raw water sources and the increased demand placed on them by the desalination plant. Larger challenges involved the interface of the desalination plant with the overall water supply system. The two main ones were problems with the conveyance pumps from the facility to Amman and the organizational challenge of coordinating with 4 separate bodies involved with operating different aspects of the facility: raw water supply, plant O&M, distribution O&M, client owner. Benefits Reliability of water supply to Amman: Before WMZM project Amman suffered from intermittent interruptions in its water supply to residents. Since 2006, After WMZM project had become in operation, water supply in Amman has been uninterrupted and reliable. WMZM also created major benefit for other governorates from which Amman used to draw water by freeing up other fresh water supplies to those governates. WMZM became a prototype model plant for visitors who are interested in brackish water desalination, opened jobs opportunities for qualified personnel, and added experience to employees by providing training programs./ Certification. 16