MCU16/0012 Attach B Engineering report & SMP

                                            Figure 4. Filter Cartridge



1.2.4   Priming System Function

The treated stormwater collects in the centre tube of the cartridge, which is equipped with a self-priming
siphon system. Figure 1 illustrates this system. The key component of the system is the plastic float. The float
consists of a ball located at the base leading up to a larger portion, which provides increased buoyancy.
Initially the ball rests in a seat effectively closing off the port to the drainage manifold.

As a result, the filter fills the centre drainage tube until the water level has risen high enough to purge the air
from the filter cartridges and displaces the float. At a water depth of 22 inches the float pulls loose and allows
the filtered water to drain out through the manifold. This effectively "primes" a siphon within the drainage
tube and greatly increases the potential across the filter. The priming system increases StormFilter's ability to
be loaded with sediment. A related feature is the cartridge "hood". This hood maintains the siphon effect by
preventing air from being drawn into the cartridge until the external water level drops below the bottom of
the hood.

Cartridges are connected to the manifold with a plastic connector. Since some media used is potentially
buoyant, a threaded connector affixed to the manifold with compression bolts is necessary to ensure the
cartridge isn't lifted out of place. For the heavier leaf media, a slip connector is used.

StormFilter is also equipped with flow spreaders that trap floating debris and surface films, even during
overflow conditions. Depending on individual site characteristics, some systems are equipped with high
and/or low flow bypasses. High flow bypasses are installed when the calculated peak storm event generates a
flow that overcomes the overflow capacity of the system. This is especially important for precast systems.
Low flow bypasses are sometimes installed to bypass continuous inflows caused by ground water seepage,
which usually do not require treatment. All StormFilter units are designed with an overflow. The overflow
operates when the inflow rate is greater than the infiltration capacity of the filter media.

1.2.5   Maintenance Overview




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