Water Pollution
These include water quality standards ; pollution discharge permits ; mandatory best practices ; environmental impact assessments for certain farming activities ; buffer zones around farms ; restrictions on agricultural practices or the location of farms ; and limits on the marketing and sale of dangerous products .
However , the report acknowledges that well-known principles for reducing pollution , such as ‘ polluter pays ,’ are hard to apply to non-point agricultural pollution because identifying the actual polluters is neither easy nor cheap .
That means that measures that promote farmer “ buy in ” are critical to preening pollution at the source — such as tax breaks for the adoption of practices that minimize farm export of nutrients and pesticides or payments to for “ landscape maintenance .”
On the farm , a number of best practices can reduce the export of pollutants into surrounding ecosystems , for example : minimizing the use of fertilizers and pesticides , establishing buffer zones along watercourses and farm boundaries , or improving drainage control schemes .
Integrated pest management , which combines the strategic use of pest-resistant crop varieties with crop rotation and the introduction of natural predators of common pests is another helpful tool
On livestock operations , traditional techniques such as restoring degraded pasturelands and better managing animal diets , feed additives and medicines are needed — while more also needs to be done with new nutrient recycling techniques and technologies , such as farm waste biodigesters .
Agricultural water pollution : Numbers of note
• Irrigation is the world ’ s largest producer in volume of wastewater ( in the form of agricultural drainage ).
• Globally , around 115 million tonnes of mineral nitrogen fertilizers are applied to croplands each year . Around 20 percent of these nitrogen inputs end up accumulating in soils and biomass , whereas 35 percent enters the oceans .
• Worldwide , 4.6 million tonnes of chemical pesticides are sprayed into the environment every year .
• Developing countries account for 25 percent of world pesticide use in farming , but 99 percent of the world ’ s deaths due to pesticides .
• Recent estimates that the economic impact of pesticides on non-target species ( including humans ) is approximately $ 8 billion annually in developing countries .
• Oxygen-depletion ( hypoxia ) resulting from manmade nutrient overloading affects an area of 240 000 km2 globally , comprising 70 000 km2 of inland waters and 170 000 km2 of coastal areas
• Worldwide , an estimated 24 percent of the area under irrigation is affected by salinization
• Currently , more than 700 emerging pollutants , their metabolites and transformation products , are listed as being present in the European aquatic environment .
Some Common Types of Water Contamination
Sewage and wastewater
Used water is wastewater . It comes from our sinks , showers , and toilets ( think sewage ) and from commercial , industrial , and agricultural activities ( think metals , solvents , and toxic sludge ). The term also includes stormwater runoff , which occurs when rainfall carries road salts , oil , grease , chemicals , and debris from impermeable surfaces into our waterways
More than 80 percent of the world ’ s wastewater flows back into the environment without being treated or reused , according to the United Nations ; in some least-developed countries , the figure tops 95 percent . In the United States , wastewater treatment facilities process about 34 billion gallons of wastewater per day . These facilities reduce the amount of pollutants such as pathogens , phosphorus , and nitrogen in sewage , as well as heavy metals and toxic chemicals in industrial waste , before discharging the treated waters back into waterways . That ’ s when all goes well . But according to EPA estimates , our nation ’ s aging and easily overwhelmed sewage treatment systems also release more than 850 billion gallons of untreated wastewater each year .
Oil pollution
Big spills may dominate headlines , but consumers account for the vast majority of oil pollution in our seas , including oil and gasoline that drips from millions of cars and trucks every day . Moreover , nearly half of the estimated 1 million tons of oil that makes its way into marine environments each year comes not from tanker spills but from land-based sources such as factories , farms , and cities . At sea , tanker spills account for about 10 percent of the oil in waters around the world , while regular operations of the shipping industry — through both legal and illegal discharges — contribute about one-third . Oil is also naturally released from under the ocean floor through fractures known as seeps .
Africa Water , Sanitation & Hygiene • August 2018 15