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Additional Information 
Q: What is pH

pH is measured in the field to determine if water has the potential to be corrosive to metals (low pH, “free” hydrogen ions), or has a bitter taste (high pH, lower proportion of free hydrogen ions to the substances that want to bind them), or has a possibility to form scale (which means that the predominant substance in the water that wants to bind hydrogen is carbonate, or sulfite, or sulfate). pH scale goes from 0 to 14, 7 being neutral. pH 7 means have an equal concentration of the free hydrogen ions to substances that want to bind them. Substances that want to bind hydrogen ions are called bases. The pH scale is a tool for judging what to do with the water. In the field, if pH is below 7, there is excess free hydrogen and you want to raise it you need to add something that wants them (e.g., carbonate from calcium carbonate – lime). If you have pH above 7 you have more alkaline substances than free hydrogen ions, and need to add something like citric acid to bring the pH down.

Q: Common Filtration Types
Q: What is Silt Density Index (SDI)?
Nearly all feed water sources contain varying levels of suspended solids from sources such as bacteria, iron, clay, clarification chemicals and other colloidal and particulate matter. Under certain conditions, the presence of these materials can result in membrane fouling characterized by decreased permeate flux, increased operational pressure, and/or reduced salt rejection. Silt Density Index (SDI) is a simple field test used to predict the degree of membrane fouling and expected frequency of cleaning when operating a reverse osmosis unit on a particular water supply.
Q: Selecting the Right Softener

First thing we start with is determining the hardness of your water. The illustration to the left shows how this can vary by region. Usually a simple water test will determine the make-up of your incoming water. The second determination is size. This is based upon your volume needs. Volume is based upon absolute gallons needed. This can be measured by daily use, peak demand or say eight-hour shift. The last determination is involves the type of sophistication (manual, metered or timed) and if it will be operating with other equipment such as a RO unit.

Selecting the right Softener

Q: What is fouling?

 Fouling occurs when material is passed through the RO and caught in the membrane resulting in decreased performance. Fouling may be bio/organic or inorganic. Each type presents different challenges to the integrity of the RO membrane and the operation of the entire water system. Some indications of membrane fouling are: a 10-15% decrease in normalized permeate flow; a 10-15% decrease in normalized permeate quality; a 10-15% increase in normalized pressure drop as measured between the feed and concentrate headers. Often times a simple pre-treatment can lessen or remove any incidents of fouling. UIS offers both chemical and mechanical (softener/carbon) treatment in front of a reverse osmosis system

Q: What are the laboratory grades of water?

Are You Using the Right Quality of Water? 

Different levels of quality are required for a vast range of applications, therefore different grades of water must be purified and utilized to match the required procedures or appliances.

Grade of Water Resistivity (M-cm) TOC (ppb) *Bacteria(CFU/ml) **Endo-toxin (EU/ml) Typical Applications
Type 1+ 18.2 < 5 <1 < 0.03 GF-AAS, ICP-MS, trace metal detection
Type 1 > 18 < 10 < 10 < 0.03 High Performance Liquid Chromatography (HPLC), GC, AAS, Immunocytochemistry, mammalian cell culture, plant tissue culture
Type 2+ > 10 < 50 < 10 NA General laboratory applications requiring higher inorganic purity
Type 2 > 1 < 50 < 100 NA Feed to ultra pure type 1 systems, feed to clinical analyzers, electrochemistry, sample dilution, media preparation, radioimmunoassay
Type 3  > 0.05 < 200 < 1000 NA Feed to ultra pure water type 1 systems, feed to washing machines, dishwashers, autoclaves

Grades of Water pdf

Q; What is Source Water


Typical Properties of Source Waters

 Source Turbidity NTU Color  TOC TDS SDI
River High, with seasonal variation Moderate Moderate to High Low  > 5
Lake/Pond Low, with seasonal variation High, with seasonal variation High Low  > 5
Well Low Low Moderate Low to high  < 5
Municipal Low to moderate Low Low to moderate Low to moderate  > 5 or < 5
Brackish Low Low Low to moderate Moderate to high  > 5
Seawater Low to moderate Low Low High  > 5

Definition of Characterization

Parameter/Values Low Moderate High
Turbidity -NTU 1-10 10-25 >25
Color -PtCO <10 15-30 >30
TOC -ppm <1 2-10 >10
TDS -ppm 10-150 150-2500 >2500 - Brackish

What is your source water? pdf

Q: Effects of Water Temperature?

Effects of Water Temperature

High Temperature (25-30 C)

  • Design For Lower Pressure = Smaller Pump
  • Warm water has lower viscosity

Lower Temperature (<20 C)

  • Design For Higher Pressure
  • Large Pump
  • LE Elements (CW Option)
  • Cold water has higher viscosity

Does your water temperature change +/- 10 C or more?

Adjust pressure to maintain consistent permeate Flow Variable Frequency Drive (VFD).

Effects of water temperature

Q: Dissolved Ions Effect
Dissolved Ions that Form Scale
  Foulant / Scale Pretreatment and Cleaning
 Calcium Carbonate Control with pH reduction and/or anti-scalant. Easy to clean
Calcium Sulfate Control with anti-scalant. Difficult to clean.
Barium Sulfate Control with anti-scalant. Impossible to clean.
Strontium Sulfate Control with anti-scalant. Difficult to clean. Not Common.
Calcium Phosphate Control with anti-scalant and pH reduction. Easy to clean.
Iron Assuming No Oxidation (Air, CI2). Control with anti-scalant. Easy to clean.
Manganese Assuming No Oxidation (Air, CI2). Control with anti-scalant. Easy to clean. 
Aluminum Control with pH reduction and anti-scalant. Easy to clean (not Aluminum Silicate).
Silica Assuming no colloidal silica. Control with anti-scalant. Adjust the pH up or down can help. Impossible to clean.

Dissolved Ions that form scale pdf

Q: Feed Water Guidelines
RO Feed Water Quality Guideline
Parameter Typical Limits
Turbidity Prefer < 0.2 NTU, 1.0 Max
SDI15 Prefer < 3, Up to 5 accepted
Iron < 0.05 ppm
Manganese < 0.05 ppm
Aluminum < 0.1 ppm
TOC < 3 ppm
Silica < 40 ppm
pH TFC (5.0 - 9.0)
Temperature 55-85F (12.7 - 30C)
LSI Run anti-scalant program
Barium Run anti-scalant program
Strontium Run anti-scalant program
Phosphate Run anti-scalant program

Feed Water Guideline pdf