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Nitrates

The MCLG standards set by the EPA for nitrates is 10 parts per million (ppm) and nitrites is 1 ppm. Nitrates are very soluble and do not bind to soils and have a high potential to migrate to ground water. Because nitrates/nitrites do not evaporate, they likely remain in the water until consumed by plants or other organisms.

Nitrates are proving to be a far more immediate concern than arsenic pollution. The EPA is not lenient for excessive nitrates and will issue an immediate cease and desist order. The Municipal water treatment plants must immediately shut down non-compliant wells, representing millions of dollars of unused assets. Where arsenic related compliance is an issue, negotiations for remedies over time (or a future date for compliance) are sometimes negotiated. In the state of Washington alone, 18% of all wells have been closed due to nitrate contamination.

Table 5.  Nitrate Treatment Alternatives

 

Ion Exchange

Reverse Osmosis

Electrodialysis

Engineered Biological Treatment

Subsurface Biological

Treatment

Micronose dinitrification

US Installations

Many

Few

None is US.

Several in Europe

None in US.

Some in Europe

None

None

Pretreatment

Required

Sometimes

Sometimes

Sometimes

Sometimes

None

None

Cost

Moderate ($220/arce.f)

Moderate

High

High

Uncertain, but

likely low

low

Raw Water

Issues

Resin sensitive

to iron, manganese,

sulfate, organic matter,

and TDS

Process sensitive

to iron, manganese,

organic matter, TDS and turbidity

Membrane sensitive to iron, manganese, organic matter, and turbidity

Optimum pH

7-8.5.

Temperature:

5-30ºC

Optimum pH

7-8.5. Temperature:

5-30ºC

pH 7-8.5

Raw Water

Issues

Resin sensitive

to iron, manganese,

sulfate, organic matter,

and TDS

Process sensitive

to iron, manganese,

organic matter, TDS and turbidity

Membrane sensitive to iron, manganese, organic matter, and turbidity

Optimum pH

7-8.5.

Temperature:

5-30ºC

Optimum pH

7-8.5. Temperature:

5-30ºC

pH 7-8.5

Post

Treatment

pH adjustment

may be

required

Low TDS may

require

water

quality

adjustments

None Filtration,

disinfection,

and taste and

odor control

None

None

Waste Disposal

Salt brine and rinse water

Concentrate

Concentrate

Biological solids

None

None

Feasibility of

Automation

Good

Good

Good

Partial

Not required

 

Good

Process

Start-up

Minutes

Minutes

Minutes

Weeks (if new)

Undetermined

Minutes

 

 

 

Note: Areas in the United States with the highest risk of nitrate contamination of shallow ground water (shown in red on the map) generally have high nitrogen input, well-drained soils, and less extensive woodland relative to cropland. (USGS provides groundwater quality map for several states )