IMPROVED PNEUMATIC SLUDGE HANDLING IN POLYGEYSER FLOATING BEAD FILTERS

Sludge handling has occasionally proven problematic in both commercial RAS production systems and even in ornamental koi pond applications filtered by PolyGeyser filters.  The PolyGeyser filters have the ability to store sludge across several backwash cycles.  Manual sludge removal is required periodically.  Many operations have employed some degree of electronic automation to perform this task.  As an alternative strategies have been developed that utilize the internal PolyGeyser pneumatic backwashing to remove accumulated sludge from the filter hull.  The most direct approach is the "Direct Pneumatic Discharge" (DPD) that results with the immediate removal of sludge during each backwash sequence.   In this approach, the air pressure in the charge chamber is combined with the hydrostatic pressure of the sludge in an internal sludge storage basin to develop a controlled lift (typically about 25 centimeters (ten inches) just before a backwash event.  This strategy produces a small amount of relatively concentrated sludge (4-6%) during each backwash cycle.    DPD units are capable of operating literally for months without manual intervention, as long as air is continually delivered to the charge chamber.   This technique is only applicable to constant head systems where the pressure head on the filter is constant or nearly constant.  A second indirect strategy, "Pneumatic Sludge Exchange" (PSE) employs a concentration tank that is hydraulically attached to the PolyGeyser's internal sludge storage basin to effectuate an exchange between the concentration tank and the PolyGeyser.   At the end of a backwash, a relatively dilute (<1%) sludge is transported into the concentration tank as the water in both units rise.  A movement that is driven by the influent to the PolyGeyser by gravity or pump.    The connection to the concentration tank is near the top, so the dirty water fills the upper portion of the concentration tank as the backwash sequence ends.  During the filtration cycle (typically 3 or more hours) the solids settle out of the upper portion becoming trapped in the sludge storage basin below.   As the charge chamber discharges during the subsequent backwash waters level in the PolyGeyser quickly drop, the exchange pipe drains the now clarified water layer at the top of the concentration tank back into the PolyGeyser completing the cycle.  The PSE approach is extremely robust, allowing for prolonged sludge storage in an attached concentration tank.   Capable of displaying extremely low water losses <3 liters/kg-feed (<0.35 gal/#-feed), the PSE strategy is most suitable for marine applications where water loss minimization is desirable.    Sludge digestion in the concentration chamber contributes to denitrification for RAS applications and mineralization in aquaponics systems.