Surface Water Treatment

Pall Aria™ Water Treatment Systems for Surface Water

概述

Governments around the world recognize the importance of safe drinking water – including water supplied by municipalities, housing developments, parks, rest stops, industry, and more. And when it comes to addressing this critical need, the road leads to 颇尔 Corporation!

Regulations such as the Safe Drinking Water Act in the US mandate that drinking water that comes from a surface source like a river, lake, or uncovered reservoir be treated to remove or neutralize pathogens that are resistant to chlorine, the most commonly used disinfectant. In the US, this is known as the Surface Water Treatment Rule (SWTR), and it specifically cites that parasitic cysts Giardia and Cryptosporidium be addressed.

Pall Aria Water Treatment systems with 0.1 micron hollow fiber Microza* microfiltration modules are designed to comply with these stringent regulations. The fine filters contain a mean pore size that is 1/20th the size of the smallest Cryptosporidium Oocyst.The state-of-the-art technology of Pall Aria systems offer the following results:

  • Reliable performance
    • Cyst Removal
      • Certified by ETV
      • Many other state certifications including California DHS
    • Up-time

  • Low cost
    • Capital
    • Installation
    • Operator attention
    • 维护
    • Consumable usage
      • 电源
      • 化学品
    • High ratio of water produced/water wasted

  • Safety in Use
    • Full System NSF 61 Listing
    • Automated operation
    • Absolute filtration via mechanical separation

There are many technologies currently in use to comply with federal and state regulations for surface water treatment. Pall Aria microfiltration membrane systems can be applied in a number of ways as a stand-alone option for surface water treatment rule compliance or in conjunction with other conventional and new technologies as part of an integrated treatment train. For more information or to contact a 颇尔 representative, click here.

 EPA Ground Water and Drinking Water

1) Application:原水

Raw surface water is water acquired directly from a pond, lake or river, and directly filtered by the Pall Aria system. In cases such as this, the only pre-treatment to the membrane is an intake screen and a 400 micron strainer or bag filter. It is particularly important to locate a suitable point from which to draw water from the body to avoid the plugging of screens and strainers by excessive rocks, earth or living creatures.

The quality of raw water varies unpredictably seasonally and with changing weather patterns such as rain, drought, and temperature swings. However, despite these variables, the quality of the effluent from the 颇尔 Microfiltration system will remain constant, assuring safe, cyst-free drinking water regardless of feedwater quality.

The table below outlines typical performance of the Pall Aria Microfiltration system when applied to raw surface water.

Raw Surface Water Application Table

Turbidity Avg. (NTU) TOC avg. mg/l Flux (Gallons/day/ft2) 回收率 (%)
<20 <3 75 97
<50 <5 53 94
高达 100 大于10000 32 90


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2) Application:Direct Coagulation

The addition of chemicals to coagulate contaminants in water for removal by filtration has long been a requirement for surface water treatment when used with conventional sand and mixed media filtration beds. With membrane filtration, this step is no longer needed to achieve removal of chlorine-resistant cysts from surface water. However there are other contaminants such as organics (TOC), arsenic, and phosphorous for which a coagulation step may significantly increase the removal efficiency of micro- or ultra- filtration membranes.

Recent new legislation in the US known as the EPA’s Stage 1 Disinfectants and Disinfection Byproducts (DBP) rule limits the amount of carcinogenic trihalomethanes (TTHM) and haloacetic acids (HAA5) allowed in drinking water systems. These carcinogens are formed when chorine is used to disinfect water containing organic materials.  By using an inexpensive coagulation step upstream of a microfilter, removalup to greater than 50% of the total organic carbon can be achieved in addition to the inherent cyst removal. Traditional chlorine disinfection can then be employed downstream, with reduced levels of these cancer-causing byproducts. The microfiltration membranes act as a cost-effective removal step compared to conventional sand or mixed media filters that require a settling tank or clarifier upstream to achieve similar removal. Coagulation with microfiltration is also less costly than using nanofiltration or reverse osmosis membrane systems that can be costly to operate, and difficult to keep in operation during the inevitable times of poor water quality.

Arsenic is another contaminant for which regulations are tightening. The EPA has mandated that arsenic concentration in drinking water cannot exceed 0.01 mg/L. With pH adjustment and the addition of inexpensive coagulant, the Pall Aria system achieves a level of .005 mg/L in the filtered water, even with influent concentration of arsenic greater than 50 mg/L. Microfiltration is also not selective in contaminant removal, so other constituents present in the feedwater won’t reduce the As removal efficiency, provided the coagulant dosage is adequate.

Direct Coagulation/Microfiltration - Surface Water Application Table

Turbidity(NTU) TOC Mg/L Coagulant Dose Mg/L Flux(Gallons/day/ft2) 回收率 (%)
<50 <5 <26 50 93
<50 大于10000 <51 42 92
高达 100 大于10000 <75 35 90


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3) Application:经凝结和沉降的水

For very large systems, applications with long periods of poor feedwater quality, or applications where a coagulation and sedimentation system is already present, it may be desirable to feed settled water to the Microfiltration system. By allowing much of the coagulated material and larger solids to settle out prior to feeding the supernatant to the Microfiltration system, higher flux can often be achieved compared to raw or direct coagulated feedwater. For large systems, the investment in settling equipment may be completely offset by the reduced number of modules required on the Microfiltration system. This arrangement would allow removal of pathogen cysts, and the contaminants that require upstream coagulation also (i.e. Arsenic, Organics, Metals, etc.)

Typical flux on settled water is 75 –100 gallons/ft2/day.

* Microza is a registered trademark of Asahi Kasei Corp., Ltd.


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