Low Profile Gravity Sand Filter VS. Pressure Sand Filter

Filtration Equipment Required: 1. One (1) HEI Gravity Sand Filter

1. Influent Surge Tank
2. Influent Pressurization Pump
3. High Pressure Vessel
4. Pressure Sand Filter
5. Backflush Pump
6. Backflush Reservoir
7. Waste Backflush Surge Reservoir
8. Waste Backflush Return Pump
9. Pressure Sand Filter Controls
   
   1. Pressure Switch
   2. Pressure Guage
   3. Air Vent
   4. Compressed Air Media Scrubber
   5. Pressure Relief Valve
   6. Automatic Valves With Operators
   7. Valve Positioners
   8. Valve Position Indicators
      
10. Central Control System
    
    1. Motor Starters
    2. Disconnect
    3. PLC
    4. Switches

Continuous filtration with only a small continuous flow of backflush wastewater creates problem free performance. HEI’s trouble free units provide the following advantages:

• Eliminates equipment and tankage to store large volume of backwash water.
• With a small slip stream of backflush water, the wastewater treatment system does not need to be increased in size to accommodate large intermittent flows backflush water.
• Eliminates the pumps required for backflush.
• Eliminates electronic controls, PLC’s, motor starters, pressure switches, level controls required to control the filter and and process the backflush waste water.

Full automatic operation is achieved without operator assistance. The filter media is continuously backwashed at a rate controlled by simply adjusting the air supply to the air lift mechanism. This eliminates the batch operation common to pressure media filters backwashing. Since there are no moving parts or pumps required in the HEI gravity sand filter, the required operator attention is minimal.

The maximum height of the HEI gravity sand filter is only nine (9) feet, gravity flow from a conventional clarifier is readily achieved. Elevating the clarifier, recessing the sand filter or additional pump stations are not required.

The HEI gravity flow sand filter continuously cleans a slip stream of the contaminated media and redeposits the clean media on the filter bed. The filtrate continuously flows through clean media.

With the internal media backwashing design, capital cost of all external backwashing equipment including backwash influent storage tank, backwash effluent storage tank, high volume backwash pumps, and all related controls, is not required. The floor space required is limited to only the HEI low profile sand filter vessel. The overall cost of HEI’s self cleaning gravity flow media filter is significantly less than a pressure sand filter system, when all tanks pumps, controls etc. are considered.

HEI’s gravity flow media filter is shipped completely pre-assembled. Only influent, effluent piping, and air supply are required.

The HEI sand filter is manufactured in standard sizes varying from 10 sq. ft. (50 gpm) to 150 (750 gpm) sq. ft. of surface area in one unitized package. Multiple units may be manifolded together for larger flow rates.

Feed is introduced into the bottom of the filter, then flows upward through the inlet tube (H) and is evenly distributed into the sand bed through the open bottom of an inlet distribution hood (A). The influent flows upward, through the downward moving sand bed (B), with the solids being removed. The clean filtrate exits from the sand bed, overflows a weir (C), and is discharged from the filter (D). Simultaneously, the sand bed, along with the accumulated solids, is drawn downward into the suction of an airlift pipe which is positioned in the center of the filter. A small volume of compressed air is introduced into the bottom of the airlift (E). The air lifts the dirty sand up the airlift pipe, and air scours the sand at a rate of 100 to 150 SCFM/ft.2. The impurities are scoured loose from the sand during this violently turbulent upward flow. Upon reaching the top of the airlift (F), the dirty slurry spills over into the central reject compartment. The splash hood (Q) protects water coming over to the effluent weir (C). The sand is returned to the sand bed through the gravity washer/separator (G) which allows the fast settling sand to penetrate, but not the dirty liquid. The washer/separator is placed concentrically around the upper part of the air-lift and consists of several stages to prevent short circuiting. By setting the reject weir (J) below the filtrate weir (C), a steady stream flows upward, counter-current to the sand, through the washer section, over the sand distribution cone (P) and cleans the sand at a backwash loading rate of 50-100 gpm/ft.2. A continuous reject flow exits near the top of the filter (K), carrying away the dirt and impurities removed in the filter. Since the sand has a higher settling velocity than the dirt particles, it is not carried out of the filter. The clean sand is then redistributed after exiting the bottom of the gravity washer/separator. The sand bed is continuously cleaned while both a continuous filtrate and a continuous reject stream are produced.

The HGSF sand filter line was originally designed with the customer in mind. Hoffland Environmental, Inc. has overcome the height problem that all of its competitors have. By using its revolutionary patent pending inverse cone design, HEI can literally save the customer money by decreasing the height of the system.

Get it right and for less the first time with the HGSF line from Hoffland Environmental, Inc.

No need for clarifier stands to gain height for gravity flow.

No need for expensive lift stations.