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The MBR Book: Principles and Applications of Membrane

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

Permeate<br />

Two-phase mix<br />

Mixed liquor<br />

Figure 4.21 <strong>The</strong> MemJet ® module with integral jet aerator<br />

entrained in mixed liquor are introduced into the module using a patented twophase<br />

mixing system (Fig. 4.21). This creates high-shear conditions, thereby minimizing<br />

solids concentration polarisation at the membrane surface near the jet. Higher<br />

membrane packing densities are permitted as a result, along with SAD m values below<br />

0.3 Nm 3 /h m 2 membrane. Mean fluxes between 20 <strong>and</strong> 50 LMH are claimed, implying<br />

specific aeration dem<strong>and</strong> values below 15 m 3 air/m 3 permeate on average. <strong>The</strong><br />

predicted TMP range is 0.05–0.5 bar, though the membranes can apparently tolerate<br />

pressures <strong>of</strong> up to 3 bar.<br />

Modules are provided in two sizes: 10 m 2 (the B10R) <strong>and</strong> 38 m 2 (the B30R). A<br />

rack <strong>of</strong> modules (Fig. 4.22) may contain up to 40 B10R or 16 B30R modules, which<br />

can then be arranged in rows within a cell. This modularisation follows the same<br />

format as that used in potable water Memcor systems. <strong>The</strong> recommended mixed<br />

liquor suspended solids (MLSS) concentration range for the bioreactor is 5–15 g/L at<br />

an associated solids retention time (SRT) <strong>of</strong> 5–50 days <strong>and</strong> loading rates <strong>of</strong><br />

0.3–1.5 kg biochemical oxygen dem<strong>and</strong> (BOD)/(m 3 day), generating sludge at rates<br />

<strong>of</strong> 0.1–0.7 kg SS/kg BOD removed. <strong>The</strong> expected cleaning in place (CIP) interval<br />

under the operating conditions stipulated is �3 months. <strong>The</strong> typical operation protocol<br />

recommended by Memcor is 12 min filtration followed by 1 min relaxation.<br />

Memcor also produce a package plant for flows up to 0.5 MLD. As with the larger<br />

scale systems, the MemJet ® Xpress (Fig. 4.23) has separate biotreatment <strong>and</strong><br />

membrane tanks to assist operation <strong>and</strong> maintenance <strong>of</strong> the membrane <strong>and</strong>, in<br />

particular, membrane CIP.<br />

Air

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