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What is Ultra filtration ?
Ultra filtration is a low pressure-driven mechanical process for separating and concentrating suspended solids, colloids and high molecular weight materials in aquious solution.
Ultra filtration membranes are tubular filters, which are designed and manufactured by a leading US supplier. They deflect metals, oils and grease while allowing water and some cleaning chemicals to pass through. The unique design uses the wash water to flow over the membrane surface at a precise flow rate and pressure, which keeps the surface clean from debris build up.
(Unlike conventional filters which dead end and clog up)
This process is referred to as "cross flow" the concentrated wastewater is referred to as "concentrate" while the clarified water produced for wash-up water recycle is referred to as "permeate".
2m3 per day ultra filtration unit
Prep-Tec UF system treating 2m3 per day Flexiographic Ink washup water at a Package printing company.
leaving PREP-TEC Works close up of 10,000ltr per day system
Prep-Tec 10,000 ltr per day UF System leaving Prep-Tec works 90% pre assembled for installation
at a paper sack manufacturing/printing company in Scotland.
Close up View of 36 membrane configuration on 10m3 System
2M3 Per day system with filter press 18 x 1 litre chamber Filter press
2 M3 Per day skid mounted system with filter press, for treating flexo ink waste water. System fully assembled and tested at our factory prior to delivery to customer. Close up view of filter press installed into system to process the concentrate ink waste , resulting in a dry cake for safe disposal to landfill.

40 tube UF system with filter press

40 tube UF System treating 70,000 Ltrs of Flexo ink and starch waste water per week. System is fully automatic & supplied with filter press reducing above to 18 off 500mm x 500mm x 25 thick solid cakes aprox 200KG for disposal to landfill . The majority of the clean filtered water is stored & re used for wash downs thus reducing the use and cost of fresh water.

4000 ltrs per day system

View of system to treat 4000 ltrs per day
System complete with 500 x 500 15 chamber filter press
for solids cake collection.
500 x 500 x 18 chamber filter press
Shown above is a 500mm x 500mm 18 chamber Filter press in operation. The tipping skip under effortlessly collects the dry cakes which are then transferred to a larger skip by means of a fork truck.
Available sizes of standard filter presses
Above are sizes of standard Filter presses which we can supply with our systems.

Filter Press bib outlet in operation
Opposite is a filter press in operation on Flexo Ink concentrate. With correct flocculation the water runs
off clear for safe disposal to sewer.

Each chamber retains the concentrated ink solids until a near dry solid cake is formed. These are then simply and effortlessly released for safe disposal to landfill.

Treating Flexographic ink
and Oily Waste Wash Waters with Ultrafiltration

Water samples
Oily wastewater generated from aqueous based metal degreasing plants presents operators with significant and costly disposal problems as does cleaning Flexiographic Presses, drums and mixing containers. As they contain unacceptable levels of colour, metal, and printing ink. In the past this would have been discharged direct into the sewers. However recent government effluent guidelines restrict at ever escalating costs or totally prohibit this practice, due to the high contamination, BOD, COD, and metal content of the wash water. example of water samples
Prep-Tec UF Systems offer the following benefits:
  • Fast payback time.
  • The backup of a leading US membrane manufacturer.
  • All systems are designed and manufactured in house.
  • Wastewater volume reduced by up to 96%
  • Clean recycled water can be re-used for wash up.
  • Low operation and payback costs.
  • Simple to operate and maintain.
  • No steam or compressed air required.
  • No Chemical additives or diatomaceous earth.
  • System operation can be fully automated.
diagram of Tubular UF Membrane
Prep-Tec Ultrafiltration systems work on any water based effluents or wash-up waters. The waste effluent is pumped through the tubular membranes, and is progressively concentrated until almost all the original water has been removed. Upon completion of a batch the membrane tubes are cleaned in position using the same process pump and a simple soap solution and returned back into service.

The membrane tubes are rugged and durable. Designed to withstand the rigors of an industrial environment. With proper care they can be used hundreds of times without maintenance or repair. All Prep-Tec systems are built in house to ISO 9002 standards and carry European CE markings.
Flexiographic Ink wastewater treatment with Ultrafiltration
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Mobile Ultrafiltration test rig. Now available for on site demonstrations and evaluations .Please ring for Details and availability . Flexiographic Ink waste water, before filtration
C.O.D. 20,000 mg/l
Suspended solids 6,000 mg/l
After Filtration
C.O.D. 1500 mg/l
S/S 0.05 mg/l

UF APPLICATION: Flexographic Ink Wastewater Treatment

a. Concentration for disposal and/or recycle of flexographic printing press washwater containing approximately 1% total solids consisting of
flexographic ink pigments, fillers, binders and vehicle.
b. Recovery for re-use and/or disposal of flexographic printing press washup water.


Typical ultrafiltration flexographic ink feed.
Total solids % : 0.5-2; average 0.75
Suspended solids (mg/1) : 300-10,000; average 5,600
PH : 5.6-9.3; average 7.5
Chemical Oxygen Demand : 8,000-80,000; average 4,000
Biological Oxygen Demand : 3,340 - 66,000; average 31,000


Typical practical concentrates of approximately 25% total solids can be achieved via Prep-Tec tubular ultrafiltration systems.
Final solids levels of > 30% total solids have been achieved at the expense of more intensive membrane cleaning procedures.


Typical ultrafiltration of flexographic ink permeates.
Total solids % : 0.6-0.615; average 0.6
Suspended solids (mg/1) : 4-40; average 23
PH : 4.6-9.3; average 6.8
Chemical Oxygen Demand : 8,00-9,300; average 3,700
Biological Oxygen Demand : 160-6,000; average 2,900


The ultafiltration process is a modified batch to batch operation. In the modified batch mode the ultrafiltration unit is fed flexographic ink washup
water from the equalization tank at a rate equal to the UF permeate rate. This mode will typically continue over a three to seven day period.
At the end of this period feed to the ultrafiltration is stopped and the UF process tank is batched down to the final concentrate by continuing
operation of the ultrafiltration unit. At the end of this batchdown period (approximately four to twelve hours), the ultrafiltration system is shut down
and cleaned. Concentrate is transferred out of the ultrafiltration process tank. Fresh UF feed is then transferred into the tank. Once the ultrafilter
is cleaned (approximately 2-4 hours), the modified batch to batch operation is repeated.


Average fluxes of 50 litres per m2 per hour are expected on Prep-Tec ultrafiltration systems on flexographic ink washup water where feed is
concentrated from 1% to 25% total solids. Good washup water quality (soft water) is also important in maintaining average design fluxes.


Based on extensive testing and experience, one-inch FEG moduled are the only accept configuration. Multi-tube, hollow fibre, and spirals are
not acceptable for this relatively aggressive ultrafiltration application. An on-site demonstration to evaluate your requirements can be arranged
using our test rig.
press here for membrane tubes press here for Filtration spectrum diagram
Press here for more info on the membrane tubes Press here for Filtration Spectrum Diagram
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