PolyGeyser® Bead Filter Technical Tips
Models DF-3 and DF-6:
1. I Cannot See the Beads in the Window
After installing the filter, it is necessary to set the backwash frequency at the highest rate possible for 24 hours to facilitate the movement of the bead media from the charge chamber to the filtration chamber. During shipping, the beads naturally migrate into the charge chamber. Multiple backwashes are necessary to flush them from the charge chamber once the filter is placed into operation.
2. The Beads Seem to Be Fluidizing / I Can See Under the Bottom of the Bead Bed Through the Window
The PolyGeyser® is designed for a max. flow rate. If you exceed this flow rate, you can cause the beads to fluidize. To correct this problem, simply reduce the flow through the filter.
3. My Flow Rate Is At Or Below recommendation And It Still Appears That The Beads Are Fluidizing
The inlet injection line has three flow interrupters installed in it to equalize the flow of water through the inlet pipe along the length of the inlet pipe. If your injection line is installed so that it enters the inlet line at an upward angle, it is possible to inject the water above the flow interrupters in which case the water jets from the inlet pipe cause fluidization. This is common in installations using flexible PVC pipe to connect to the inlet line.
A. In order for the filter to operate properly, it must be set up on a flat level surface. If the filter is not level, the air charge chamber may “short-circuit”, allowing air to escape from the charge chamber before a complete charge has been established, thus air will continuously burp up through the drop chute. If this occurs, the trigger will not fire and the filter will not backwash. To correct this issue, simply level the filter.
B. If the filter is level and the trigger still does not fire properly, raising the trigger 1/8” to ¼” may be required. Note we test fire each trigger at AST to ensure they are set correctly before and after we add the bead media to the filter. The trigger should be set as low as possible against the uni-seal and the air inlet holes must be below water level. Also ensure that the trigger is level. To re-set the trigger you must drain your filter, remove the beads and unbolt and remove the top half of the filter unit. Once you have done this, refill the filter with water, ensure that the trigger is full of water and turn on your backwash air at a rate high enough to initiate a backwash within several minutes. This will allow you to observe what is actually occurring. If air bubbles come up the drop shoot before the trigger fires, then you do, in fact, have to raise the trigger. To raise the trigger simply grasp it firmly and pull it up 1/8” to ¼”. Note the higher you set the trigger the less volume of air available during a backwash. To ensure a vigorous backwash the trigger should be set as low as possible. Before attempting to raise the trigger, I suggest you contact the dealer from whom you purchased your filter or call Aquaculture Systems Technologies at (800) 939-3659.
5. Elevated Nitrite (NO2) Levels
A. Elevated levels of Nitrite may occur if the dissolved oxygen concentration in the effluent leaving the filter drops below 2 mg/l. Low DO concentrations leaving the filter can often be solved by increasing the dissolved oxygen levels in the tank or pond through increased aeration or by increasing the flow rate through the filter. The model DF6 is rated for 90 gpm (340 Lpm).
B. Elevated Nitrite levels may also occur if your total alkalinity (as CaCO3) drops below 80mg/l. We recommended you maintain your alkalinity at 100-200 mg/l as CaCO3 at all times. If you experience low alkalinity simply add baking soda to the system periodically to maintain proper levels.
C. Elevated Nitrite levels can also occur from over washing the bead bed. If the flow rate, effluent oxygen and alkalinity are satisfactory, the backwash frequency can simply be reduced. This situation typically occurs when you go from periods of high loading and frequent backwashing to periods of reduced loading but still maintain frequent backwashing.
6. Low Effluent Dissolved Oxygen
A. Low Effluent Dissolved Oxygen concentrations are usually the result of too low a flow rate. Effluent D.O. concentrations should be maintained above 2 mg/l at all times. If you are not flowing water through the filter at the filters maximum flow rate (90 gpm) simply increase the flow through the filter.
B. Or you can increase the amount of aeration in the tank or pond to increase influent D.O. concentrations, which will usually result in increased effluent D.O. concentrations.
C. Low DO concentrations may also occur if the backwash frequency is set too low. If the bead bed is allowed to clog, reduced flow and effluent oxygen concentrations will occur, which will affect the nitrification performance. Please refer to “Backwash Frequency” section for recommended backwash frequencies at various feeding rates.
D. Low D.O. concentrations can also result if you do not remove sludge and waste from the filter often enough. The sludge should be drained every 2-3 days to prevent excessive oxygen consumption by the activity of heterotrophic bacteria.
7. Pressure Loss/Reduced Flowrate
A. Pressure loss and subsequently reduced flowrates may occur if the backwash frequency is set too low. The filter is designed to backwash frequently with minimal energy input, so if you do not backwash frequently enough the bed may clog. To overcome this problem, simply increase the air flow to effect a more frequent backwash.
B. If this does not solve the problem, check the outlet screen for clogging and clean if necessary.
8. Sulfide Production
Sulfide production in the PolyGeyser® filter can occur in the offline sludge storage basin. These sulfides are isolated within the sludge. Water slowly returned to the pond from this basin may contain a low level of sulfides, however, it is first diluted by the recirculating flow (at a ratio of over 100 to 1) and then must pass through a two foot aerobic bead bed. The aerobic bed assures any sulfide residuals are converted to the safe sulfur form of sulfate. The processes that produce the sulfides are identical to the natural processes that occur in the bottom of virtually every mud pond and are instrumental in the recycling of trace elements essential for plant and fish nutrition. Sludge storage in the off line basin is a matter of convenience, the filter’s operation does not require it, but, given the fact that there has been no observation of sulfide accumulation in any tank or recirculating pond waters, there seems to be no reason not to take advantage of this time saving feature.
9. Sludge is Slow to Drain from the Filter
A. Sludge normally drains rapidly from the filter, but now drains very slowly. The screen on the sludge discharge line may be clogged. Cleaning it may be as simple as connecting a garden hose to it and flushing the line. If this does not solve the problem, it may be necessary to remove screen for cleaning. Simply turn off the flow of water to the filter. Drain the filter completely. Loosen and disconnect the rubber couplings on the inlet and outlet lines, tilt the filter back so the beads slide away from the sludge valve and unscrew the sludge valve assembly. After cleaning the screen, apply Teflon tape or thread sealant to the threads and screw the sludge valve assembly back into the filter. Note after restarting the filter it may be necessary to backwash the unit multiple times to release any trapped beads from the charge chamber.
B. If your system is heavily loaded and the screen clogs frequently you can remove it and operate the system without a sludge screen. However, you should be aware that if you operate the system without a sludge screen you may experience a small amount of bead loss during sludge removal.