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Coagulation                                                                                      225


                    Mass flux of polymer as neat emulsion             mass amount required for 6 month’s polymer
                                                                      storage is
                      ¼ 400 mg polymer=s
                      ¼ Q(neat)   C(neat)                         Mass polymer (6 months storage)
                      ¼ Q(neat)   1,064,000 mg polymer=L             ¼ 1000 L=s   0:4mg=L   3600 s=h   24 h=day   180 day
                           Q(neat) ¼ 0:000376 L=s                    ¼ 6221 kg polymer
                                 ¼ 0:376 mL=s                               V(barrel) ¼ 55:0 gal ¼ 208:2L

                                 ¼ 22:5mL= min                      Mass(barrel) ¼ 208:2L   1:064 kg=L ¼ 222 kg=barrel
                                                                  N(barrels) ¼ Mass polymer(6 month storage)=Mass(barrel)
              Discussion
              The example is given to illustrate how the polymer con-     ¼ 6221 kg polymer=222 kg polymer=barrel
              centration is calculated on the ‘‘as supplied’’ mass of     ¼ 28 barrels
              polymer as it comes from the barrel. A second point is
              that the flow of polymer from the barrel, Q(neat), is very  For delivery in 275 gal ‘‘tote’’ tanks with V ¼ 275
              low, for example, 0.000376 L=s, which must be mixed  gal ¼ 1041 L,
                                                     6
              with a flow of 1000 L=s, that is, a factor of 10 . The
              problem is to adequately mix the polymer with the raw
              water flow so that particle-polymer contacts are made       Mass(tote tank) ¼ 1041 L   1:064 kg=L
              (mixing is the topic of Chapter 10).                                   ¼ 1108 kg=tote tank
                                                                  N(tote tank) ¼ Mass polymer
              Example 9.9 Design for Emulsion Polymer Storage,                 (6month storage)=Mass(tote tank)
              Dilution=Mixing
                                                                           ¼ 6221 kg polymer=1108 kg polymer=barrel
                                                                           ¼ 5:6 tote tanks per 6 month period
              Given
              The polymer Clarifloc A-210P, an emulsion polymer (see
                                                                    3. Initial dilution=mixing. Dilute to the recommended
              Example 9.8), has been selected for water treatment with a
                                                                      concentration, that is, 0.5% by weight. The initial
              flow, Q ¼ 1000 L=s.
                                                                      high-energy mixing tank should have a detention time
              Required                                                of 30 s. Since Q (neat) ¼ 0.376 mL=s (Example 9.8),
              Apply the manufacturer’s recommendation for feeding the
              polymer into the raw water flow and translate this into a  M(mass flux neat) ¼ 0:376 mL=s   L=1000 mL   1:064 kg=L
              design.
                                                                                ¼ 0:00040 kg=s
              Solution
                                                                           Concentration(diluted polymer)
                 1. Excerpts from Clarifloc A-210P Data Sheet
                   .  Polymer density (as supplied) ¼ 1.064 kg=L.            ¼ 0:005 kg polymer=kg water
                   .  Suggested in-plant storage life is 6 months in
                     unopened drums.                                          ¼ 5000 mg polymer=L water
                   .  Bulk tanks should be mixed by periodically recir-  Since mass flux polymer ¼ 400 mg=s
                     culating the contents bottom to top. Bulk tanks
                     can also be fitted with an agitator type mixer that  and
                     reaches the bottom 2 ft of the tank. Drums should
                     be mixed very well before first use.
                   .  In most cases, the product should not be applied  Mass flux polymer ¼ Q(first dilution)
                     neat.                                                               C(diluted polymer)
                   .  One method for dilution is adding the neat poly-
                                                                      400 mg polymer=s ¼ Q(first dilution)
                     mer into the vortex of a mixing tank at a concen-
                                                                                        5000 mg polymer=L water
                     tration between 0.25% and 1.0% polymer (0.5%
                     is recommended) by weight.                         Q(first dilution) ¼ 0:08 L=s ¼ 80 mL=s
                   .  The best-feed systems use initial high energy
                     mixing (>1000 rpm) for <30 s to achieve        V(tank, first dilution) ¼ Q(first dilution)   t(tank)
                     good dispersion followed by low energy                         ¼ 0:080 L=s   30 s
                     mixing (<400 rpm) for a longer time, that is,
                     10 < t < 30 min.                                               ¼ 2:4L
                   .  Polymer solution should be aged for 15–60 min.
                     Solution shelf life is 8–16 h.                   The tank requires mixing at about 1000 rpm, which
                 2. Storage. Based on a uniform raw water flow of      can be done using a small mixer set-up; probably a
                   1000 L=s and polymer concentration 0.4 mg=L, the   100 W motor would work.
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