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Water Quality

Water Quality Criteria for Nitrogen (Nitrate, Nitrite, and Ammonia)

Overview Report

Prepared pursuant to Section 2(e) of the
Environment Management Act, 1981

R. N. Nordin Ph.D.
L. W. Pommen M.Sc. P.Eng.
Resource Quality Section
Water Management Branch
Ministry of Environment and Parks (now called
Ministry of Water, Land and Air Protection)

Original signed by Ben Marr
Deputy Minister
November 12, 1986

Updated: August 7, 2001


Table of Contents

Tables

Preface

Recommended Guidelines

Application of the Guidelines


NOTE: The marine ammonia criteria found in this document have been replaced by newer values found in the document Ambient Water Quality Guidelines for Ammonia to Protect Marine Aquatic Life.


Tables

Table 1. Summary of Water Quality Criteria for Nitrogen

Water Use
Nitrate
mg/L as Nitrogen
Nitrite
mg/L as Nitrogen
Ammonia (total)
mg/L as Nitrogen
Drinking Water
10 mg/L (maximum)
1 mg/L (maximum)
None proposed
Fresh Water Aquatic Life - maximum
200 mg/L (maximum)
0.06 mg/L (maximum)
Fresh Water Aquatic Life - average
less than or equal to 40 mg/L (average)
0.02 mg/L (average) when the chloride is less than or equal to 2 mg/L - also see
Table 2
Marine Aquatic Life - maximum
None proposed
None proposed
2.5 mg/L (maximum)
Marine Aquatic Life - average
None proposed
None proposed
less than or equal to 1.0 mg/L (average)
Livestock Watering
100 mg/L (maximum)
10 mg/L (maximum)
None proposed
Wildlife
100 mg/L (maximum)
10 mg/L (maximum)
None proposed
Recreation and Aesthetics
10 mg/L (maximum)
1 mg/L (maximum)
None proposed


1. The average value is calculated from at least 5 weekly samples taken in a period of 30 days.

2. Where nitrate and nitrite are present, the total nitrate-nitrite nitrogen should not exceed these values.


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Table 2. Criteria for Nitrite for Protection of Freshwater Aquatic Life

Chloride in mg/L
Nitrite (maximum) mg/L as Nitrogen
Nitrite (average)
mg/L as Nitrogen
less than 2 mg/L
0.06 mg/L
0.02 mg/L
2 to 4 mg/L
0.12 mg/L
0.04 mg/L
4 to 6 mg/L
0.18 mg/L
0.06 mg/L
6 to 8 mg/L
0.24 mg/L
0.08 mg/L
8 to 10 mg/L
0.30 mg/L
0.10 mg/L
greater than 10 mg/L
0.60 mg/L
0.20 mg/L


The 30-day average chloride concentration should be used to determine the appropriate 30-day average nitrite criterion.

 

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Table 3. Maximum Concentration of Total Ammonia Nitrogen for Protection of
Aquatic Life (mg/L of Nitrogen)

Temperature (T) in degrees Celcius

pH
T = 0.0
T = 1.0
T = 2.0
T = 3.0
T = 4.0
T = 5.0
T = 6.0
6.5
27.7
28.3
27.9
27.5
27.2
26.8
26.5
6.6
27.9
27.5
27.2
26.8
26.4
26.1
25.8
6.7
26.9
26.5
26.2
25.9
25.5
25.2
24.9
6.8
25.8
25.5
25.1
24.8
24.5
24.2
23.9
6.9
24.6
24.2
23.9
23.6
23.3
23.0
22.7
7.0
23.2
22.8
22.5
22.2
21.9
21.6
21.4
7.1
21.6
21.3
20.9
20.7
20.4
20.2
19.9
7.2
19.9
19.6
19.3
19.0
18.8
18.6
18.3
7.3
18.1
17.8
17.5
17.3
17.1
16.9
16.7
7.4
16.2
16.0
15.7
15.5
15.3
15.2
15.0
7.5
14.4
14.1
14.0
13.8
13.6
13.4
13.3
7.6
12.6
12.4
12.0
11.9
11.9
11.7
11.6
7.7
10.8
10.7
10.5
10.4
10.3
10.1
10.0
7.8
9.26
9.12
8.98
8.88
8.77
8.67
8.57
7.9
7.82
7.71
7.60
7.51
7.42
7.33
7.25
8.0
6.55
6.46
6.37
6.29
6.22
6.14
6.08
8.1
5.21
5.14
5.07
5.01
4.95
4.90
4.84
8.2
4.15
4.09
4.04
3.99
3.95
3.90
3.86
8.3
3.31
3.27
3.22
3.19
3.15
3.12
3.09
8.4
2.64
2.61
2.57
2.54
2.52
2.49
2.47
8.5
2.11
2.08
2.06
2.03
2.01
1.99
1.98
8.6
1.69
1.67
1.65
1.63
1.61
1.60
1.59
8.7
1.35
1.33
1.32
1.31
1.30
1.29
1.28
8.8
1.08
1.07
1.06
1.05
1.04
1.04
1.03
8.9
0.871
0.863
0.856
0.849
0.844
0.839
0.836
9.0
0.703
0.697
0.692
0.688
0.685
0.682
0.681


Temperature (T) in degrees Celcius

pH
T = 7.0
T = 8.0
T = 9.0
T = 10.0
T = 11.0
T = 12.0
T = 13.0
6.5
26.2
26.0
25.7
25.5
25.2
25.0
24.8
6.6
25.5
25.2
25.0
24.7
24.5
24.3
24.1
6.7
24.6
24.4
24.1
23.9
23.7
23.5
23.3
6.8
23.6
23.4
23.1
22.9
22.7
22.5
22.3
6.9
22.5
22.2
22.0
21.8
21.6
21.4
21.3
7.0
21.1
20.9
20.7
20.5
20.3
20.2
20.0
7.1
19.7
19.5
19.3
19.1
18.9
18.8
18.7
7.2
18.1
17.9
17.8
17.6
17.4
17.3
17.2
7.3
16.5
16.3
16.2
16.0
15.9
15.7
15.6
7.4
14.8
14.7
14.5
14.4
14.2
14.1
14.0
7.5
13.1
13.0
12.9
12.7
12.6
12.5
12.4
7.6
11.5
11.4
11.3
11.2
11.1
11.0
10.9
7.7
9.92
9.83
9.73
9.65
9.57
9.50
9.43
7.8
8.48
8.40
8.32
8.25
8.18
8.12
8.07
7.9
7.17
7.10
7.04
6.98
6.92
6.88
6.83
8.0
6.02
5.96
5.91
5.86
5.81
5.78
5.74
8.1
4.80
4.75
4.71
4.67
4.64
4.61
4.59
8.2
3.83
3.80
3.76
3.74
3.71
3.69
3.67
8.3
3.06
3.03
3.01
2.99
2.97
2.96
2.94
8.4
2.45
2.43
2.41
2.40
2.38
2.37
2.36
8.5
1.96
1.95
1.94
1.93
1.92
1.91
1.91
8.6
1.58
1.57
1.56
1.55
1.55
1.54
1.54
8.7
1.27
1.26
1.26
1.25
1.25
1.25
1.25
8.8
1.03
1.02
1.02
1.02
1.02
1.02
1.02
8.9
0.833
0.832
0.831
0.831
0.832
0.834
0.838
9.0
0.681
0.681
0.681
0.682
0.684
0.688
0.692


Temperature (T) in degrees Celcius

pH
T = 14.0
T = 15.0
T = 16.0
T = 17.0
T = 18.0
T = 19.0
T = 20.0
6.5
24.6
24.5
24.3
24.2
24.0
23.9
23.8
6.6
23.9
23.8
23.6
23.5
23.3
23.3
23.2
6.7
23.1
23.0
22.8
22.7
22.6
22.5
22.4
6.8
22.2
22.0
21.9
21.8
21.7
21.6
21.5
6.9
21.1
21.0
20.8
20.7
20.6
20.5
20.4
7.0
19.9
19.7
19.6
19.5
19.4
19.3
19.2
7.1
18.5
18.4
18.3
18.2
18.1
18.0
17.9
7.2
17.1
16.9
16.8
16.8
16.7
16.6
16.5
7.3
15.5
15.4
15.3
15.2
15.2
15.1
15.1
7.4
13.9
13.9
13.8
13.7
13.6
13.6
13.5
7.5
12.4
12.3
12.2
12.2
12.1
12.1
12.0
7.6
10.8
10.8
10.7
10.7
10.6
10.6
10.5
7.7
9.37
9.31
9.26
9.22
9.18
9.15
9.12
7.8
8.02
7.97
7.93
7.90
7.87
7.84
7.82
7.9
6.79
6.75
6.72
6.69
6.67
6.65
6.64
8.0
5.71
5.68
5.66
5.62
5.61
5.60
5.74
8.1
4.56
4.54
4.53
4.51
4.50
4.49
4.49
8.2
3.65
3.64
3.63
3.62
3.61
3.61
3.61
8.3
2.93
2.92
2.92
2.91
2.91
2.91
2.91
8.4
2.36
2.35
2.35
2.35
2.35
2.35
2.36
8.5
1.90
1.90
1.90
1.90
1.90
1.91
1.92
8.6
1.54
1.54
1.54
1.55
1.56
1.56
1.57
8.7
1.25
1.25
1.26
1.26
1.27
1.28
1.29
8.8
1.02
1.03
1.03
1.04
1.05
1.06
1.07
8.9
0.842
0.847
0.853
0.861
0.870
0.880
0.891
9.0
0.698
0.704
0.711
0.720
0.729
0.740
0.752

 

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Table 4. Average 30-Day Concentration of Total Ammonia Nitrogen for Protection of Aquatic Life (mg/L of Nitrogen)

Temperature (T) in degrees Celcius

pH
T = 0.0
T = 1.0
T = 2.0
T = 3.0
T = 4.0
T = 5.0
T = 6.0
6.5
2.08
2.05
2.02
1.99
1.97
1.94
1.92
6.6
2.08
2.05
2.02
1.99
1.97
1.94
1.92
6.7
2.08
2.05
2.02
1.99
1.97
1.94
1.92
6.8
2.08
2.05
2.02
1.99
1.97
1.94
1.92
6.9
2.08
2.05
2.02
1.99
1.97
1.94
1.92
7.0
2.08
2.05
2.02
1.99
1.97
1.94
1.92
7.1
2.08
2.05
2.02
1.99
1.97
1.94
1.92
7.2
2.08
2.05
2.02
1.99
1.97
1.94
1.92
7.3
2.08
2.05
2.02
1.99
1.97
1.94
1.92
7.4
2.08
2.05
2.02
2.00
1.97
1.95
1.92
7.5
2.08
2.05
2.02
2.00
1.97
1.95
1.92
7.6
2.09
2.05
2.03
2.00
1.97
1.95
1.93
7.7
2.09
2.05
2.03
2.00
1.98
1.95
1.93
7.8
1.78
1.75
1.73
1.71
1.69
1.67
1.65
7.9
1.50
1.48
1.46
1.44
1.43
1.41
1.39
8.0
1.26
1.24
1.23
1.21
1.20
1.18
1.17
8.1
1.00
0.989
0.976
0.963
0.952
0.942
0.932
8.2
0.799
0.788
0.777
0.768
0.759
0.751
0.743
8.3
0.636
0.628
0.620
0.613
0.606
0.599
0.594
8.4
0.508
0.501
0.495
0.489
0.484
0.479
0.475
8.5
0.405
0.400
0.396
0.381
0.387
0.384
0.380
8.6
0.324
0.320
0.317
0.313
0.310
0.308
0.305
8.7
0.260
0.257
0.254
0.251
0.249
0.247
0.246
8.8
0.208
0.206
0.204
0.202
0.201
0.200
0.198
8.9
0.168
0.166
0.165
0.163
0.162
0.161
0.161
9.0
0.135
0.134
0.133
0.132
0.132
0.131
0.131


Temperature (T) in degrees Celcius

pH
T = 7.0
T = 8.0
T = 9.0
T = 10.0
T = 11.0
T = 12.0
T = 13.0
6.5
1.90
1.88
1.86
1.84
1.82
1.81
1.80
6.6
1.90
1.88
1.86
1.84
1.82
1.81
1.80
6.7
1.90
1.88
1.86
1.84
1.83
1.81
1.80
6.8
1.90
1.88
1.86
1.84
1.83
1.81
1.80
6.9
1.90
1.88
1.86
1.84
1.83
1.81
1.80
7.0
1.90
1.88
1.86
1.84
1.83
1.81
1.80
7.1
1.90
1.88
1.86
1.84
1.83
1.81
1.80
7.2
1.90
1.88
1.86
1.85
1.83
1.81
1.80
7.3
1.90
1.88
1.86
1.85
1.83
1.82
1.80
7.4
1.90
1.88
1.87
1.85
1.83
1.82
1.80
7.5
1.91
1.88
1.87
1.85
1.83
1.82
1.81
7.6
1.91
1.89
1.87
1.85
1.84
1.82
1.81
7.7
1.91
1.89
1.87
1.86
1.84
1.83
1.81
7.8
1.63
1.62
1.60
1.59
1.57
1.56
1.55
7.9
1.38
1.36
1.35
1.34
1.33
1.32
1.31
8.0
1.16
1.15
1.14
1.13
1.12
1.11
1.10
8.1
0.922
0.914
0.906
0.899
0.893
0.887
0.882
8.2
0.736
0.730
0.724
0.718
0.714
0.709
0.706
8.3
0.588
0.583
0.579
0.575
0.571
0.568
0.566
8.4
0.471
0.467
0.464
0.461
0.458
0.456
0.455
8.5
0.377
0.375
0.372
0.370
0.369
0.367
0.366
8.6
0.303
0.301
0.300
0.298
0.297
0.297
0.296
8.7
0.244
0.243
0.242
0.241
0.241
0.240
0.240
8.8
0.197
0.197
0.196
0.196
0.196
0.196
0.196
8.9
0.160
0.160
0.160
0.160
0.160
0.161
0.161
9.0
0.131
0.131
0.131
0.131
0.132
0.132
0.133


Temperature (T) in degrees Celcius

pH
T = 14.0
T = 15.0
T = 16.0
T = 17.0
T = 18.0
T = 19.0
T = 20.0
6.5
1.78
1.77
1.64
1.52
1.41
1.31
1.22
6.6
1.78
1.77
1.64
1.52
1.41
1.31
1.22
6.7
1.78
1.77
1.64
1.52
1.41
1.31
1.22
6.8
1.78
1.77
1.64
1.52
1.42
1.32
1.22
6.9
1.78
1.77
1.64
1.53
1.42
1.32
1.22
7.0
1.79
1.77
1.64
1.53
1.42
1.32
1.22
7.1
1.79
1.77
1.65
1.53
1.42
1.32
1.23
7.2
1.79
1.78
1.65
1.53
1.42
1.32
1.23
7.3
1.79
1.78
1.65
1.53
1.42
1.32
1.23
7.4
1.79
1.78
1.65
1.53
1.42
1.32
1.23
7.5
1.80
1.78
1.66
1.54
1.43
1.33
1.23
7.6
1.80
1.79
1.66
1.54
1.43
1.33
1.24
7.7
1.80
1.79
1.66
1.54
1.44
1.34
1.24
7.8
1.54
1.53
1.42
1.32
1.23
1.14
1.07
7.9
1.31
1.30
1.21
1.12
1.04
0.970
0.904
8.0
1.10
1.09
1.02
0.944
0.878
0.818
0.762
8.1
0.878
0.874
0.812
0.756
0.704
0.655
0.611
8.2
0.703
0.700
0.651
0.606
0.565
0.527
0.491
8.3
0.564
0.562
0.523
0.487
0.455
0.424
0.396
8.4
0.453
0.452
0.421
0.393
0.367
0.343
0.321
8.5
0.366
0.365
0.341
0.318
0.298
0.278
0.261
8.6
0.296
0.296
0.277
0.259
0.242
0.227
0.213
8.7
0.241
0.241
0.226
0.212
0.198
0.186
0.175
8.8
0.197
0.198
0.185
0.174
0.164
0.154
0.145
8.9
0.162
0.163
0.153
0.144
0.136
0.128
0.121
9.0
0.134
0.135
0.128
0.121
0.114
0.108
0.102


1. The average of the measured values must be less than the average of the corresponding individual values.

2. Each measured value is compared to the corresponding individual values. No more than one in five of the measured values can be greater than 1.5 x the corresponding criteria values.


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Preface

The MINISTRY OF ENVIRONMENT, LANDS AND PARKS (now called Ministry of Water, Land and Air Protection) develops province-wide ambient water quality guidelines for variables that are important in the surface waters of British Columbia. This work has the following goals:

  1. to provide guidelines for the evaluation of data on water, sediment and biota
  2. to provide guidelines for the establishment of site-specific ambient water quality objectives

Ambient water quality objectives for specific waterbodies will be based on the guidelines and also consider present and future uses, waste discharges, hydrology/limnology/oceanography, and existing background water quality. The process for establishing water quality objectives is more fully outlined in Principles for Preparing Water Quality Objectives in British Columbia, copies of which are available from the Water Quality Section of the Environmental Quality Branch.

Neither guidelines nor objectives which are derived from them, have any legal standing. The objectives, however, can be used to calculate allowable limits or levels for contaminants in waste discharges. These limits are set out in waste management permits and thus have legal standing. The objectives are not usually incorporated as conditions of the permit.

The definition adopted for a guideline is:

A maximum and/or a minimum value for a physical, chemical or biological characteristic of water, sediment or biota, which should not be exceeded to prevent specified detrimental effects from occurring to a water use, including aquatic life, under specified environmental conditions.

The guidelines are province-wide in application, are use-specific, and are developed for some or all of the following specific water uses:

  • raw drinking, public water supply and food processing
  • aquatic life and wildlife
  • agriculture (livestock watering and irrigation)
  • recreation and aesthetics
  • industrial (water supplies)


The guidelines are set after considering the scientific literature, guidelines from other jurisdictions, and general conditions in British Columbia. The scientific literature gives information on the effects of toxicants on various life forms. This information is not always conclusive because it is usually based on laboratory work which, at best, only approximates actual field conditions. To compensate for this uncertainty, guidelines have built-in safety factors which are conservative but reflect natural background conditions in the province.

The site-specific water quality objectives are, in most cases, the same as guidelines. However, in some cases, such as when natural background levels exceed the guidelines, the objectives could be less stringent than the guidelines. In relatively rare instances, for example if the resource is unusually valuable or of special provincial significance, the safety factor could be increased by using objectives which are more stringent than the guidelines. Another approach in such special cases is to develop site-specific guidelines by carrying out toxicity experiments in the field. This approach is costly and time-consuming and therefore seldom used.

Guidelines are subject to review and revision as new information becomes available, or as other circumstances dictate.


The guidelines apply to the ambient raw water source before it is diverted or treated for domestic use.

The Ministry of Health regulates the quality of water for domestic use after it is treated and delivered by a water purveyor.

Guidelines relating to public health at bathing beaches are the same as those used by the Ministry of Health which regulates the recreation and aesthetic use.


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Recommended Guidelines

These criteria are based on a detailed analysis given in a technical document and are summarized in the Tables. The criteria are consistent with the Canadian Water Quality Guidelines (CCREM Guidelines) issued by the Canadian Council of Resource and Environment Ministers (1986), except as noted.

Nitrate, nitrite, and ammonia are the major inorganic nitrogen compounds occurring in surface waters. There is little environmental information on other compounds, both inorganic and organic, which are minor constituents or do not appear to affect water uses. These are therefore not included in the report at this time.


Drinking Water (Includes Food Processing Water)

For drinking water, high nitrate concentrations have been identified as a problem for infants. Nitrate can be converted to nitrite which combines with hemoglobin in the blood to form methemoglobin which does not absorb oxygen. With reduced capacity of the blood to absorb oxygen, death from lack of oxygen can result. Many agencies have specified maximum acceptable concentrations for nitrate or nitrate plus nitrite in drinking water and there is a general consensus that 10 mg/L (as N) represents a level of adequate protection. This well established level is proposed as the criterion for nitrate in drinking water for British Columbia.


The criterion for British Columbia which is proposed is a maximum of 10 mg/L nitrate + nitrite (as N).


There is also a general consensus with regard to nitrite among other agencies, and no recent scientific evidence to the contrary, that less than 1 mg/L nitrite (as N) represents a concentration which will provide protection against adverse effects in humans in drinking water supplies.


The criterion for British Columbia which is proposed is a maximum of 1 mg/L nitrate + nitrite (as N).


Establishing a criterion for ammonia in drinking water is more difficult. Although a number of other agencies have specified ammonia concentrations intended to provide acceptable drinking water, there now seems to be a very poor basis for the concentrations proposed. There does not seem to be sufficient data to define an ammonia concentration at which problems such as taste and odour, interference with chlorine disinfection, or any health effects occur. Consequently, no criterion for ammonia in drinking water supplies is proposed.


Aquatic Life (Freshwater, Marine and Estuarine)

In the literature, there has been a much more detailed examination of the response to nitrate, nitrite, and ammonia by freshwater biota, particularly fish, than by marine biota. Studies concerning estuarine biota are almost totally absent. As a consequence, the data on which to base criteria are much better for freshwater than marine water. Since virtually no data exist for nitrogen toxicity in estuarine environments, no specific criteria are suggested. It is proposed that the more stringent of freshwater and marine criteria should be used for estuaries. For these criteria the maximum concentration is designed to protect aquatic life against acutely toxic effects and the 30-day average against chronic effects. The 30-day average should be calculated from at least five weekly samples.

For freshwater studies there has been different amounts of research into the aquatic toxicology of the three forms of nitrogen. Nitrate has been the subject of few investigations due to its relatively low toxicity.


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Based on the information available, a criterion of 200 mg/L nitrate (as N) is recommended as a maximum concentration and 40 mg/L nitrate (as N) as a 30-day average.


There are no CCREM Guidelines for nitrate for freshwater aquatic life.

Nitrite has been shown to be quite toxic to some groups of fish, particularly salmonids, and consequently more investigations have been done.


On the basis of literature reports, a criterion of 0.020 mg/L (as N) is recommended as a mean concentration over a 30-day period for low chloride water, and a maximum concentration of 0.060 mg/L (as N) is recommended.


Allowable concentrations increase with ambient concentrations of chloride, as shown in the Tables. The CCREM Guidelines specify a maximum of 0.06 mg/L for all chloride concentrations. The recommended criteria vary with chloride concentration to reflect the marked influence of chloride on nitrite toxicity, and average criteria have also been recommended to provide adequate protection to the salmonids prevalent in British Columbia, particularly at low chloride concentrations.

Ammonia has been the subject of intensive investigation and there is thus an excellent background on which to base a criterion. Because ammonia has been investigated for a long period, increasingly sophisticated and accurate criteria are being derived. Ammonia criteria have evolved from a single value to tabular criteria relating toxicity to important physical or other interactive factors which affect toxicity. Two factors which are important to the toxicity of ammonia to aquatic organisms are the pH and temperature of the water environment. The pH and temperature affect the amount of un-ionized ammonia which is the form most toxic to aquatic life.


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The Tables give the criteria recommended for maximum allowable concentrations of ammonia and for longer-term (30 day) allowable concentrations.


These criteria are similar to those developed by the US Environmental Protection Agency (EPA). The CCREM Guidelines adopted the EPA average criteria as maximum values, which in British Columbia's opinion is unnecessarily restrictive.

For marine studies, less information is available on which to base criteria. For nitrate and nitrite, insufficient data are available to propose any criteria.


NOTE: The marine ammonia criteria found in this document have been replaced by newer values found in the document Ambient Water Quality Guidelines for Ammonia to Protect Marine Aquatic Life.


For ammonia, a maximum concentration of 2.5 mg/L (as N) and a 30 day average concentration of 1.0 mg/L (as N) are recommended.



There are no CCREM Guidelines for marine aquatic life. For estuarine conditions, the freshwater criteria apply. Increasing salinity decreases ammonia toxicity to a slight degree so some marginal additional protection is afforded.


Irrigation and Livestock Watering

Water with excessive amounts of ammonia may affect agricultural uses such as irrigation or water supplied to livestock. Insufficient information is available to establish a criterion for nitrogen in irrigation water since an allowable concentration would be dependent on soil type, irrigation rate, and other factors. The proposed criteria for livestock watering exclude ammonia since few data exist.


For nitrate or nitrate plus nitrite, a maximum concentration of 100 mg/L (as N) is recommended and for nitrite alone a maximum of
10 mg/L (as N). The same concentrations are recommended for waters which might be used by wildlife as a drinking water supply.



There are no CCREM Guidelines for wildlife.


Recreation and Aesthetics

This is a water use for which high concentrations of nitrate, nitrite or ammonia are not likely to cause any direct problems in terms of body contact or visual deterioration. The more likely problem would be eutrophication-related problems when high concentrations of nitrogen (and accompanying phosphorus) cause heavy accumulations of algae. However, to protect recreational users who may ingest water, it is recommended that the drinking water criteria should apply to waters used for recreation.


The criteria for British Columbia which is proposed is a maximum of 10 mg/L nitrate + nitrite (as N). The criterion for British Columbia which is proposed is a maximum of 1 mg/L nitrite (as N).



There are no CCREM Guidelines for nitrogen for recreation.


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Application of Guidelines

Most of the criteria proposed require no additional explanation for their use. However, the table of ammonia criteria values for evaluation of chronic toxicity does require additional explanation for its application. The designated sampling period is 30 days and it is intended that at least five samples would be obtained. In addition to ammonia, each sample must be measured for pH and temperature. The temperature is that of the water in the field, and the pH is the laboratory pH at the time of analysis, although field pH is also acceptable if truly accurate measurements can be obtained.

The average measured concentration is calculated as an arithmetic mean. Using the individual temperature and pH values, the corresponding criteria values are obtained from the table. A mean of these criteria values is compared to the mean of the measured ammonia values. If the mean value for measured total ammonia exceeds the mean criteria value, the criteria would then be considered to be exceeded. If the mean value does not exceed the mean criteria value, it is still necessary to compare individual criteria to corresponding analytical results to ascertain whether or not more than 20% of the measured values exceed the mean criteria value by more than 150%. If more than 20% of the measured values do exceed the mean criteria by 150%, the criteria is exceeded even if the measured mean is less than the mean criteria value. This provision restricts the occurrence of fluctuating concentrations which can be more detrimental to aquatic life than a steady concentration.


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