2025 Nelsen Corporation Catalog - Catalog - Page 421
National Secondary Drinking Water Regulations 17
National Secondary Drinking Water Regulations (NSDWRs
or secondary standards) are non-enforceable guidelines for
contaminants that may cause cosmetic effects (such as skin
or tooth discoloration) or aesthetic effect (such as taste,
odor or color) in drinking water. EPA recommends secondary
standards to water systems but does not require systems to
comply. However, states may choose to adopt them as
enforceable standards.
Note: This document addresses the United States Environmental
Protection Agency National Primary Drinking Water Regulations in
effect at its time of publication. These regulations are continually
being reviewed and updated at the federal level. Accordingly, this
list of recognized treatment technologies will be reviewed and
amended periodically.
Contaminant
SMCL,MG/l+
Treatment Methods
Alkalinity
(measured as calcium
carbonate, CaCo )
No federal limit
Low alkalinity -
300
mg/L
Raise alkalinity by feeding 1.5 mg/L of soda ash for each on mg/L of alkalinity
needed or calcite filtration;
Lower alkalinity by feeding white vinegar (acetic acid), citric acid or any acid;
add carbon dioxide; ion exchange dealkalization; reverse osmosis; distillation or
electrodialysis
Aluminum (Al +3)
on case-by-case
0.05 to 0.2 depending
circumstances
Chloride (C1 -1)
250
3
Color
15 color units
Portable Cation
Exchange
Distillation
Ultrafiltration
Reverse Osmosis
Electrodialysis
Deionization
Reverse Osmosis
Distillation
Deionization
Anion Exchange
Electrodialysis
Anion Exchange
Reverse Osmosis
Filtration
Activated Carbon
Distillation
Chlorination
Ozonation
Note: Color units are based on the APHA recommended standard of 1 color unit being equal to 1 mg/L of platinum or chloroplatinate ion.
Reverse Osmosis
Copper (Cu +2)
1.0
Corrosion Control
Distillation
Cation Exchange (2090%)
Calcite or Calcite/Magnesium Oxide (Magnesia)
Soda Ash Chemical Feed
Polyphosphate Feed
Corrosivity
Non-corrosive
Sodium Silicate Feed
Remove all hydrogen peroxide
Reduce TDS via Reverse Osmosis (partial, split stream treatment)
Coatings
Insulating Unions with Ground straps around all insulating breaks in metal pipe
Fluoride (Fl-1)
Activated Alumina
2.0
Foaming agents (MBAS)
0.5
Hard Water
(measured as calcium
carbonate CaCO3)
No federal limit
Soft -
180
Electrodialysis
Reverse Osmosis
Bone Char Carbon
Chlorination
Reverse Osmosis
Activated Carbon
Distillation
Distillation
Ozonation
Remove all calcium and magnesium ions with a cation exchange water softener
(general limit is 1710 mg/L total hardness. Above 70 grains per gallon, install two
softeners in a series.
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17 - 1
Technical & Engineering
Recognized Treatment Techniques
for Meeting the National Secondary Drinking Water Regulations
with the Application of Point-Of-Use Systems
