The Solution for High Solids Removal in Wastewater
High concentration of colloidal solids (suspended sub-micron solids) are commonly encountered in industrial wastewater treatments, such as pH adjustment and processes involving coagulants/flocculants.
The WTS employs either cTMF
(depending on application needs) in the system to achieve an effective filtration. Common applications include:
- Pre-filtration with coagulants for SWRO and BWRO
- Cooling tower blowdown water
- Heavy metal removal
- Mop water
- Semiconductor and photovoltaic wastes
- Fluoride and high solids removal
- Tumbler deburring slurries
cTMF, a coiled tubular membrane filter, has a ½” tube used in cross-flow mode for ultrafiltration. The innovative design of cTMF resourcefully generates a secondary flow called Dean Flow to prevent foulants from building up on the membrane surface through its hydrodynamic advantage. As shown in the accompanied chart, by allowing particles in the processed fluid to settle on the membrane surfaces, (and halting the operation for two days between Week 1 and Week 2) the test data indicates there is more than a 20% difference in flux rate. Note, both filters showed a significant drop of flux at the onset of Week 2. However, the flux of the cTMF was able to resume and follow its original curve after several hours into the operation. By comparison, the straight TMF had very limited improvement and remained gap-down in the curve.
The cTMF comes with two coil diameters (based on OD, Outside Diameter), i.e. 3.5” and 5.5”. As shown in the figure, a 72” tube can be transformed to a 3.5” x 6.5” coil. This improvement not only accommodate shipping and handling, but also reduces the installation footprint. With the improved dimensions and robust tube construction, it is practical to use a cTMF without a housing. The 5.5” coil is designed so the 3.5” coil can be inserted into this center space to increase flow. With the cTMF, unhoused modules
can be practically created and fit into a tank. The FIT (filters in tank) design is compact, cost-effective, and ideal to be installed at the point of use.
cTMF is developed based on Porex’s tubular membrane filter (TMF
), which has polyvinylidene difluoride (PVDF) membrane casted on the inside surface of an ultra-high molecular weight polyethylene (UHMWPE) tube.
This provides the cTMF membrane with excellent chemical resistance (pH 0-14) and its structure with excellent impact strength and abrasion resistance. As with TMF
, cTMF is capable of handling solids with a concentration as high as 50,000 mg/liter and particle size as large as 125 µm without any additional pretreatment. With pore size rated at 0.02/0.05 µm, cTMF allows only water and dissolved matter to pass, rejecting everything that is undissolved. For highly challenged surface water treatments, the permeate turbidity of <0.1 NTU is constantly attainable. With its capability to produce high effluent quality from high solids influent, it is effective to remove precipitants generated in processes involving coagulants and flocculants. All these characteristics make cTMF an ideal choice for applications such as RO pretreatment and SDI reduction. Some common areas of applications are: Heavy metal removal, e.g. wastewater from plating processes, printed circuits; wastewater treatment from vibratory tumblers, silica wafer die sawing, fluoride removal; flue gas desulfurization (FGD) wastewater and cooling tower blowdown, etc.
Tubular membrane filters (TMF) are membrane filters in tube format.
The TMF provided by FSI has a PVDF membrane cast onto the inside surface of a UHMWPE substrate. Two diameters, ½” and 1”, are available. The cross section of the tubes are as shown in the sketch. The available membrane pore sizes are 0.02 µm. 0.05 µm, and 20 µm. With an open channel and robust structure, TMF is superior to Hollow Fiber and Spiral Wound filters for many high solids applications. The TMFs from FSI are featured with
- High Flux – Typical operation flux rate 300 - 500 lmh (liter/m2/hr) or 175-300 gfd (gaal/ft2/day)
- High Solids Concentration – up to 5% by weight
- Large Particle Size – up to 1/10 the tube diameter, e.g. 1.25 mm for ½” tube
- Minimum Pretreatment (Most applications do not require pretreatment)
- Extremely Durable
- Excellent Chemical Resistance – pH 0 to 14
Because of its capability for high solids and chemical resistance, TMFs are ideal for industrial wastewater treatment. Many industrial wastewaters are most efficiently processed with proper chemical pretreatment. The chemical treatment may take the form of precipitation, adsorption, chemical reduction/oxidation, pH adjustment and microbial control. These treatments usually generate high solids in the processes that can be effectively and efficiently separated through TMFs.
Taking advantage of the superb physical properties of TMF, FSI has developed a coiled TMF (cTMF
). This proprietary design generates a secondary flow called Dean Flow through the coiled flow path to achieve self-cleaning of the filter. Since there are no moving parts and no additional mechanical components required in the design, cTMF
is truly low maintenance, energy efficient, and highly reliable. A cTMF
can easily further improve the already favorable flux and service life of a typical TMF by more than 20%.
The compact size and robust construction of cTMF make it practical to be used without a housing. The cTMF comes with two coil diameters (based on OD, Outside Diameter), i.e. 3.5” and 5.5”. Available unhoused modules are shown in the accompanied Table. The unhoused modules can be mounted under the cover of a working tank to further improve space utilization. The integrated units with several prescribed capacities are provided by FSI as its FIT product line. A PCT Application (Serial No. PCT/US17/16353) has been filed. US Patent as well as several other international patents are pending. FIT
FIT (Filters in Tank) takes the advantage of the compact and light weight of unhoused cTMF modules to have them installed inside a tank under a tank cover to create a filtration system with minimum piping and fittings. The FIT product line is designated as FIT Tank Volume (Gallons)/Number of Filter Modules. For example, FIT 5/4 cTMF 3 x 7 is set up with four 3 x 7 cTMFs fit into a 5 gallon tank. Some FIT arrangements are shown below.
FIT 80/8 cTMF 5 x 40 FIT 5/1 cTMF 3 x 7 (Demo Unit)