Water. Desalination + reuse
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PROJECTS (189,000 m3 needed to meet the urgent need of more water in San Diego County. Figure 2 shows only one simple drawing of the SWRO design without the details of the two-stage SWRO configuration, equipped with needed energy-recovery devices, which are definitely included in the plant design. Figure 3 shows the alternate design /d) of fresh drinking water reject increased plant water yield, as shown in Table 1, from 16.2 MGD (61,300 m3 up to 25.3 MGD (95,750 m3 plant from the two water sources were reduced, but not significantly, by this operation from a water increase of 79.3 MGD (300,000 m3 approach for the Carlsbad plant by first adding NF pretreatment and integrating it with existing SWRO plant, followed by the addition of a high TBT MED unit. The conversion as shown produces different water quantities from the upgraded plant design, which also can be accomplished, as shown in Table 1 on page 20, by varying the plant operation conditions. The addition of NF pretreatment to the plant firstly cleans fouling matter and bacteria from the feed (Figure 4 on page 20) and reduces feed TDS to the SWRO (Figure 4) from 33,500 ppm down to about 23,450 ppm. Secondly, it reduces scale-forming ion concentration in the SWRO reject (Figure 5 on page 20) to a level where no scale is formed, even at high TBT MED operation. Other benefits can include l Increased water product; l No anticipated additional chemicals or membrane cleaning; l Longer membrane life; l Increased plant affordability and greater environmental compatibility safely operated and equally varied as shown in Table 1. Although, the MED recovery ratio of water product/SWRO reject can be practically varied from 60% down to 50% by varying the MED operating temperature, as was established recently at SWRDI. Here, however, it was fixed at a 60% ratio. As shown in Table 1, the SWRO recovery in Figure 2 was varied from 70% down to 50% to yield an SWRO permeate for a decreasing SWRO water recovery respectively from 63.1 MGD (238,800 m3 (178,500 m3 same ratio used in the Carlsbad plant design. /d) down to 47.17 MGD /d). This last value was the conditions, MED processing of the SWRO Under the last SWRO recovery ratio May-June 2012 | Desalination & Water Reuse | 19 | l Thermal unit safely operated at top brine temperature (TBT) much higher than that normally allowed without scaling, which increases the desalination plant water yield. Both SWRO and MED processes can be SWRO recovery ratio down to 72.5 MGD (274,400 m3 /d) at 70% ratio. This last lowest value is still 44% /d) at a 50% SWRO recovery The total water-recovery ratios of the /d). /d) higher than that of the 50 MGD (189,000 m3 (see Table 1). /d) SWRO design value FACTORS IN WATER PRODUCTION It is obvious that water production of the NF-SWRO upgrading in Table 1 is directly controlled by three effective factors: l Introduction of NF pretreatment GEOSCIENCE Desalination Subsurface Intakes GEOSCIENCE +1 909.451.6650 | www.gssiwater.com GEOSCIENCE Support Services, Inc. LEADERS IN SUBSURFACE INTAKE SYSTEMS