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The MBR Book: Principles and Applications of Membrane

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218 <strong>The</strong> <strong>MBR</strong> <strong>Book</strong><br />

pressures had initially doubled, the foam gradually subsided over a number <strong>of</strong> days<br />

<strong>and</strong> differential pressure gradually recovered without intervention over a 1–2 week<br />

period.<br />

5.2.1.4 Running Springs<br />

Background <strong>The</strong> Running Springs Water Recycling Plant represents the first installation<br />

<strong>of</strong> the double-deck (EK) membrane module in the United States. <strong>The</strong> plant is<br />

located at Big Bear National Park in California <strong>and</strong> is operated <strong>and</strong> owned by the CA<br />

County Water District. <strong>The</strong> <strong>MBR</strong> installed at Running Springs resulted from a<br />

change in the discharge permit granted to the existing ASP plant, designed for BOD<br />

removal only, in which limits for nitrogen <strong>and</strong> phosphorous were tightened. <strong>The</strong><br />

operators originally attempted to meet the new consents by extending the sludge age<br />

to increase the MLSS concentration in the aeration tanks. However, since the existing<br />

rectangular secondary clarifiers could not h<strong>and</strong>le the increased loading, other<br />

options had to be explored. Between April <strong>and</strong> September 2003, the existing plant<br />

was converted to an <strong>MBR</strong> system by retr<strong>of</strong>itting with Kubota membranes (Fig. 5.7)<br />

coupled with the SymBio ® process, a proprietary technology designed to achieve<br />

simultaneous nitrification/denitrification (SNdN) <strong>and</strong> partial enhanced biological<br />

phosphorus removal in the same zone.<br />

Process design <strong>The</strong> plant has a design flow <strong>of</strong> 2.3 MLD with a peak flow <strong>of</strong> 4.5 MLD.<br />

It is an example <strong>of</strong> a treatment strategy referred to as the UNR (Ultimate Nutrient<br />

Removal) by Enviroquip, the suppliers, essentially referring to the combined SNdN<br />

process <strong>and</strong> the <strong>MBR</strong>. It is thought that such <strong>MBR</strong> systems reject more coagulated<br />

phosphorous than conventional clarification technologies <strong>and</strong> are better suited to<br />

h<strong>and</strong>le seasonal <strong>and</strong> diurnal load variations through MLSS control.<br />

Figure 5.7 Retr<strong>of</strong>itting <strong>of</strong> membranes to the aeration tanks at Running Springs

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