Use of AFM in SWRO plants –
SWRO – Sea water reverse osmosis has found a great importance today as a technology for the reclamation of brackish water or sea water and making it potable enough for human consumption or industrial applications.
The most common schematics of a SWRO consists of a pre-filtration after a grit removal by a MGF/MMF followed by a disc filter and further to UF & RO. Sea water in most of the cases of has a large contamination of organics, bromine & other heavy metals. The most common biocide preferred for the use as a pretreatment for disinfection and sanitation to a SWRO is chlorine.
Chlorine in presence of organics, bromine & other heavy metal forms several chlorinated & disinfection byproducts including bromates which are no desirable in the SWRO plants. There are several instances which are brought to notice with contamination of the membranes in RO due to DBP’s & bromates.
UF and RO membranes work best when the membranes are new and clean. Fouling of the membranes by inorganic and organic contaminants as well as biofouling are some of the main issues effecting the performance and cost of running membrane water filtration systems.
AFM as a media instead of sand –
- Would remove organics & heavy metal from water.
- Reduce the SDI in the membrane.
- Increase the life span of the RO & UF membranes.
- Reduced downtime of membrane maintenance.
- Prevents biofouling and contamination in the membrane.
- Reduce load on the RO & UF by removing micron & submicron size particles.
Performance comparison of AFM with sand and UF
|AFM||Sand||UF at 0.03 microns|
|Remove dissolved silica||Yes||Can add free silica to water||No|
|Remove phosphate||Yes, when combined with NoPhos||no||No|
|Remove dissolved organics||Yes, especially when combined with APF precoagulation and flocculation using ZPM||After 6 months sand filters will be increasing organic load through autotrophic bacteria||No, UF cannot remove chemicals in solution.|
|Biofouling||No, AFM does not biofoul||Yes, 100% coverage of every grain of sand in 3 days||Yes, membranes need to be regularly cleaned|
|Prevention of RO membrane biofouling||Yes, because it removes phosphate and dissolved nutrients required by bacteria||No, sand is the perfect substrate to grow bacteria. Often solids load is higher on discharge than influent.||Phosphate, and dissolved nutrients will react the RO membranes|
|Scaling||No||Yes, with carbonates, calcite, struvite, ferric etc||Yes, with carbonates, calcite, struvite, ferric etc|
|Chlorination||Not required, AFM does not biofoul. So no chlorine reaction products such as THM`s, TCA, or hydrobromous acid||Yes, sand filters need to be chlorinated continuously or as part of a regular cleaning schedule.||May be required as part of the cleaning schedule|
|Filtration level||90% down to 0.1micron, approx. 80% down to 0.01micron||All sand filters will channel, so membranes are exposed to unfiltered water.||0.03 to 0.01 microns absolute, unless the membrane ruptures|
|Sustainable||100% sustainable, Circular Economy VIBES winner in the UK||No sustainable, needs to be replaced at 1 to 10 year intervals||Not sustainable, membranes need to be replaced at 1 to 10 year intervals|
|Operation costs||Can operate at 50% higher flow rates, so much lower capital cost than sand filtration||Lower capital cost than AFM and higher running, operation & maintenance costs||Much higher capital cost than AFM. Much higher pressures and running costs. Lower area required for installation|
Other AFM Application Areas
AFM® reduces the biological risk from bacteria and parasites as well as the chemical risk from water and air just above the surface. The result is a safer pool for children, a healthier work place for staff in public pools and a greatly improved swimming experience for everyone. Read More…
UF, RO membranes & DM plant resins work best when they are new and clean. Fouling of the membranes by inorganic and organic contaminants as well as biofouling are some of the main issues effecting the performance and cost of running water treatment systems.Read More…
Arsenic is often found in borehole / tube wells and ground water at varying concentrations depending upon the geology of the ground. In India western states along with certain locations in the south have fairly high contamination of Arsenic in the ground water. IN certain cases Arsenic is also found in the waste water effluent of certain industries. Read More…
Iron and manganese are often found in borehole / tube wells and ground water at varying concentrations depending upon the geology of the ground. Read More…
Chromium is occasionally found in ground water in trace amount from 1 to 10 ug/l however the occurrence of chromium is usually associated with pollution from industries such a leather tanning, wood preservation and textiles. Polluted ground water may have much higher concentrations. Read More…