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Tasmania, Australia
River water
Potable water
Taswater
60 m3/hr
INTRODUCTION
challenges
- High consumption of chemicals and consequently production of a large volume of sludge to be treated and disposed of.
- Clarifiers and media filters take up a large foot print.
- Generation of disinfection by-products: Trihalomethanes (THM’s), Haloacetic Acids (HAA’s) and bromate
- Requirements for micro biological safety are becoming more strict, especially with regards to viruses and cysts
- Some feed water sources observe a decrease in water quality (browning) and are becoming more and more difficult to treat
- High pressure membrane technology, such as nanofiltration
- Extensive pretreatment required, discharge of concentrate with increased hardness - Low pressure membranes, assisted with coagulation
- Addresses only micro biology, organics removal similar to conventional technology - Ion exchange
- Does not address micro biology, discharge of brine solution
Methods
Pentair X-Flow started development of a new hollow fiber nanofiltration membrane. The following goals have been set for development of this new membrane:
- Single step reduction of dissolved organics without the need for coagulant dosing.
Target is >50% removal of NOM and >70% of color - Robust barrier for micro biology
Target is >99.99% removal of bacteria and viruses - Versatile and easy to clean membrane
Target is a backwashable, chlorine tolerant membrane with open channels that do not block
Pentair X-Flow did identify a material (modified Poly Ether Sulphon) that allowed for a single step spinning process of a membrane without a thin film top coating. The mechanical stability of this material allowed for production of unsupported hollow fibers with excellent mechanical properties (high burst and collapse pressure).
The membrane has been validated under NSF61 and NSF419. Size exclusion for all microbiology, including viruses.
An additional benefit is the very low retention for dissolved inorganics: typical retention for hardness is 20%. Valuable minerals are not being removed from the potable water, furthermore it facilitates concentrate discharge.
This hollow fiber nanofiltration is marketed by Pentair X-Flow as HFW1000 Membrane Element. The figure below shows a comparison of TOC retention of UF, assisted with coagulation and hollow fiber NF, for different process settings.
Comparison
results
The water treatment plant is co-located with an irrigation scheme. This allows for a shared river water intake, furthermore NF backwash waste is reused as irrigation water, thus eliminating the need for wastewater treatment or a sewer connection.
- Feed strainer to protect the membranes from ingress of harmful matter
- Granular Activated Carbon to remove small organics
- CO2 dosing and calcite contactors for control of corrosiveness
- UV treatment as second microbiological barrier
- Chlorine and fluoride dosing for transport safety and dental protection
Impression of location
nanofiltration performance summary
| units | feed water | HFW PERMEATE | final outlet | |
| Turbidity | NTU | 1.3 - 1.4 | 0.020 - 0.027 | 0.06 - 1 |
| Color (true) |
Hazen | 45 - 50 | 2 | |
| pH |
- |
6.0 - 6.5 | same |
7.8 - 8 |
| DOC |
mg/l | 5 | < 450 |
1 |
| Total THM |
mg/l | < 80 | < 5 |
CONCLUSIONS
This new Hollow Fiber Nanofiltration membrane allows for chemical free one-step production of potable water from surface water high in organics and micro biology. Especially in environmentally sensitive locations, where handling and discharge of chemicals is restricted, the hollow fiber nanofiltration provides significant benefits
Besides the first operational plant another two full scale plants that employ Hollow Fiber Nanofiltration for potable water production are currently under construction in Tasmania.
Related products
The X-Flow HFW1000 hollow fiber nanofiltration membranes provide superior removal of organic matter and color components in the treatment of surface water and WWTP effluent, with a limited reduction of bivalent salts.
Pentair X-Flow HFNANO Solution: a chemical free water treatment with one-step nanofiltration.
