Sources of Nitrogen Pollution

The abatement of nitrogen pollution must be based upon a knowledge of the quantities of nitrogen from the various sources. Mass balances must be set up for ecosystems and for entire regions. Table 1.1 gives an example. The estimated nitrogen loadings for the San Francisco Bay Basin (from "California ", 1974) are shown. The mass balance shows clearly that major problems are rooted in the discharge of waste water and nitrogen from dairies and feedlots. The abatement should therefore concentrate primarily on these sources of nitrogen emissions.

Table 1.2 gives the nitrogen balance for Denmark, which is a country characterized by intensive agriculture and many food processing industries. The balance shows that a comprehensive reduction of the nitrogen emission requires that the non-point sources are included in the abatement scheme. It is, however, in most cases more difficult to find good solutions to the reduction of nitrogen emission from non-point sources than from point sources. Some of the ecotechnological methods briefly touched upon in part B may be applied effectively to reduce these sources, but a wide spectrum of methods, which include planning and legislation, is needed in practical environmental management to achieve an acceptable result.

It would be going too far in this context to present these methods in detail in this context, but it should be mentioned that the following components have been included in the management of nitrogen pollution in Denmark:

1. Legislation concerning manure application schemes and storage capacity for surplus manure.

2. Use of wetlands close to sensible aquatic ecosystems.

3. Legislation on the needs for green fields during the winter season.

4. Encouragement of limited use of fertilizers. Were this not be successful, the imposition of a tax on the use of fertilizers will be considered.

5. Financial support for erection of biogas-plants for treatment of manure and other animal wastes.

Table 1.1.

Estimated nitrogen loadings for the San Francisco Bay Basin*)

Nitrogen source t per year Percent of total

Municipal waste water

26 000

49

Industrial waste water

16 000

30

Dry deposition

590

1.1

Wet deposition

390

0.8

Urban run-off

1 400

2.7

Non-urban run-off

1 900

3.6

Nitrogen from irrigated

agricultural land

900

1.7

Nitrogen from dairies

and feedlots

6 000

11.1

Total

53 000

100

*) Source "California", 1974.

*) Source "California", 1974.

The methods for nitrogen removal presented in Parts B and C are aimed at the reduction of nitrogen in the effluents from industries and municipalities, i.e., the point sources. The few ecotechnological methods, mentioned in Part B can be used for both point sources and non-point sources. These methods are defined as the application of ecologially sound engineering methods for restoration of ecosystems. They are included in this volume, as they are based on the same principles as the other methods, presented in Part B. All the methods presented otherwise can be considered as environmental technological methods.

Table 1.2.

Source

Nitrogen loadings for Denmark *) 1000 t N / yr.

Municipal Waste water Villages, summer houses without sewage systems Industries Run-off

24.1

Fertilizers

Animal waste, manure Dry and wet deposition Biological nitrogen fixation

115-130 45-109 12-30 10-28

Removed by harvest Denitrification

Run-off, agriculture (difference) 42-124

115-130 25-43

Total loadings of nitrogen

75-157

') Sources: SJVF (1985) and Miljestyrelsen (1984).

0 0

Post a comment