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Whether for agricultural, industrial, recreational or environmental use, we rely on water for almost all our everyday activity, especially the planet’s fresh water resources.

The earth’s water supplies exist as salt water (97%) and fresh water (3%). More than two thirds of this is frozen in glaciers and the polar ice caps. The remainder of the unfrozen freshwater is found mainly as groundwater, with only a small fraction present above ground or in the air.

WATER POLLUTION

Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater) and occurs when pollutants are directly or indirectly discharged without adequate treatment to remove harmful substances. It affects the plants and organisms living in contaminated bodies of water.

In agriculture, pollution from farms is caused by surface runoff from fields during rainstorms. It is a major source of pollution, which includes:

Sediment runoff: Excess sediment, from soil washed off fields, causes high levels of turbidity in water bodies, which can inhibit growth of aquatic plants and animals. Erosion controls can help to reduce runoff and retain soil.

Nutrient runoff: Nitrogen and phosphorus, from commercial fertilizer, animal manure, or municipal or industrial wastewater (effluent) or sludge, are key pollutants found in runoff.

Pesticides: The appearance of pesticides in surface water is caused by direct application (e.g. aerial spraying or broadcasting over water bodies), runoff during rainstorms and aerial drift (from adjacent fields).

Vegetable washing water: Washing vegetables produces large volumes of water contaminated by soil and vegetable pieces. Low levels of pesticides used to treat vegetables may also be present, together with moderate levels of disinfectants such as chlorine.

Silage liquor: Fresh or wilted grass, or other green crops, can be made into a semi-fermented product called silage, which is stored and used as winter forage for cattle and sheep. Silage production can involve the use of an acid conditioner. Its production frequently produces a yellow-brown strong smelling liquid that is very rich in simple sugars, alcohol, short-chain organic acids and silage conditioner. This liquid is one of the most polluting organic substances known.

Point source pollution: Livestock and poultry farms can be a major contributor of point source wastewater. Known as concentrated animal feeding operations or confined animal feeding operations, these facilities are increasingly subject to government regulation.

Animal wastes: Animal wastewater typically has a strong organic content – much stronger than human sewage – and includes solid waste, nitrate, phosphorus and parasites, antibiotics, synthetic hormones, cryptosporidium and giardia spores, as well as human pathogenic bacteria.

Whilst solid manure heaps can give rise to polluting wastewaters from runoff, this type of waste is usually relatively easy to treat. Animal slurries are usually treated by containment in lagoons before disposal by spray or trickle application to grassland. Application of slurries to land overlying aquifers can result in direct contamination or, more commonly, elevation of nitrogen levels as nitrite or nitrate.

Piggery waste: Comparable to other animal wastes. However, piggery wastes often contain elevated levels of copper that can be toxic in the natural environment. Ascarid worms and their eggs are also common in piggery waste and can infect humans.

Milking parlour (dairy farming) and slaughtering wastes: Although milk is an important and valuable food product, its presence in wastewaters is highly polluting because of its organic strength, which can lead to rapid de-oxygenation of receiving waters. These waste products are often treated in admixture with human sewage, in a local sewage treatment plant, to ensure that disinfectants and cleaning agents are sufficiently diluted and amenable to treatment.

WATER STEWARDSHIP

Increasing the transparency of water usage, pollution and treatment will support the agricultural industry’s desire to improve its reputation and inform consumers about the impact final products have on the environment and social responsibility.

The industry’s preferred way to achieve this transparency is through a stakeholder-inclusive process that involves site and catchment actions. Good water stewardship means understanding water usage, catchment context and shared risk – in terms of water governance, water balance, water quality and important water-related areas. A good water steward can assess and implement this on their own estate and then engage in meaningful individual and collective actions that benefit people and nature.

Read more articles of our Seed and Crop Newsletter - February 2014.

For further information, please contact:

Bruno Widmer
Agriculture Audit & Certification Manager
SGS Geneva
1 places des Alpes
1211 Geneva
t: + 41 (22) 739 94 68