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Technical informationen for dimensioning filters with

Liquitech FOM
Removal of solids and turbidity in one process


FOM is a catalytic filter granulate which induces or remarkably intensifies reduction and oxidation processes (redox) in water and wastewater. The FOM media works within a wide range of pH 5.8 - 10.5. The required filter size depends mainly on the concentration of contaminants in the water. The higher the concentration of contaminants, and the finer the desired filtration sharpness, the longer the contact time of the FOM filter media with the water to be filtered should be. Generally, a flow rate in the filter media of 15 - 30 m/h applies.
The metal-oxide surface of the filter material is preferably once a week cleaned and regenerated by backwashing with PROTABS OXY LIQUID.

Comparison of filter materials used today and LIQUITECH FOM:

  FOM BIRM Greensand Plus
Contains Silica, Quartz No Yes Yes
Contains Silica, Tripoli No Yes Yes
Carcinogenic in humans No Yes Yes
Removes Iron at pH 6-9 Above pH 6,8 Above pH 6,8
Removes Manganese at pH 7 Yes No Yes
Removes Schwefelwasserstoff Yes, high capacity* No Limited
Removes Arsenic-III & V Yes** No Limited
Removes Uranium and Radium Yes No No
Removes Lead and Copper Yes*** No No
Bulk Density SI 1060 kg/m3 800 kg/m3 1425 kg/m3
Operational pH range 5,8 - 10,5 > 6,8 6,5 - 8,5
Tolerance to oxidizing agents High tolerance Only air Medium
Fine sediment filtration High performance,
Filtration down to 2-3µ
Not a filter No

* Needs dosing only for high contents of H2S.
** Needs dosing for effective oxidation of Arsenic-III.
*** Needs dosing for high concentration of contaminants.

LIQUITECH FOM solves filtration problems in one process

Oxygen contents of the water as important prerequisite:
LIQUITECH FOM is a catalytic filter granulate. It uses the oxygen dissolved in the water to form hydroxyl radicals (OH). The OH-radicals oxidize the contaminants to be removed, thus making them filtratable.
If the water does not contain enough oxygen (redox potential < 170 mV), this deficit must be compensated by dosing PROTABS OXY LIQUID. Accordingly, in case of higher contaminant loads, dosing must create an adequate oxidation potential.

Example:
Manganese contents Mn = 1.5 mg/l → required oxygen O2 = 3.0 mg/l
At sufficient oxygen contents the manganese contents will be reduced from Mn = 1.5 mg/l to < 0.01 mg/l.

Schaubild Filteranlage mit FOM Schaubild Filteranlage mit FOM

Fig.1: FOM-Filtration in normal operation

Fig.2: Cleaning the FOM-granulate by backwashing

Further dimensioning measures:
The catalytic oxidation and separation is a chemical process which decisively depends on the contact time of the water with the filter media:

Process Filtration rate Bed contact time Fe concentration at inlet
Catalytic Oxidation 20 BV/h 180 seconds 2 mg/l
10 BV/h 360 seconds 40 mg/l


Example: 20 BV/h → within one hour, 20 times the volume of Liquitech FOM filter granulate will be treated.

Also, the achievable filter sharpness of mechanic filtration depends on the filtration rate resp. contact time:

Process Filtration rate Bed contact time Filter performance estimated
Mechanic Filtration 40 BV/h 90 seconds 20 micron
30 BV/h 120 seconds 10 micron
20 BV/h 180 seconds 5 micron
Extreme case 12 BV/h 300 seconds ≤3 micron at 15 NTU

Dimensioning required size of a Liquitech FOM filter:
Desired flow rate Required volume of Liquitech FOM Required total filter vessel volume
4 l/min 0,25 m3/h 14 liters ½ sack 25 liters
8 l/min 0,5 m3/h 28 liters 1 sack 50 liters
12 l/min 0,75 m3/h 42 liters 1 ½ sacks 75 liters
16 l/min 1 m3/h 56 liters 2 sacks 100 liters
20 l/min 1,2 m3/h 70 liters 2 ½ sacks 120 liters
25 l/min 1,5 m3/h 98 liters 3 ½ sacks 150 liters
33 l/min 2 m3/h 112 liters 4 sacks 180 liters

With AOP filter technique through Liquitech FOM, a wide range of application is offered to engineers and users.

What makes LIQUITECH FOM extraordinary is its double effect:

Outstanding disinfection performance allows reliable control of microbial contamination without corrosive side effects

Outstanding filtration performance through strong active effect and high passive filtration rate


Construction and function of the required installation are easy and clear and offer high reliability of operation. With its high filtration capacity, the required size of the installation and thus the costs are reduced. Long exchange intervals for the filter media of 8 to 10 years lower operational costs. Any equipment already installed may be retrofit at low effort.

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