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Bacteria and Heavy Metal Pollutants Found
in River Basins in Baskongadak

Mila Parot Zubimendi

The basins of the rivers Oiartzun, Artibai, Deba, Bidasoa, Urumea, Uroa, Oria, Oka, Barbadun, Butron, Lea, Urola and Nervion are polluted, according to a report of the regional government of Baskongadak's Environment Department released this week. The basin of the Nervion River has the highest level of contamination. The coastal waters of Gipuzkoa has maintained the same high level of heavy metal pollution for the last five years. The Department insists that human excreta and hydrocarbons are the major sources of contamination in this region with a strong industrial sector.

According to the Department, bacteria and heavy metal pollution are still present in the following rivers:

Deba: bacteria and heavy metal pollution. High concentrations of lead, zinc, cooper, nickel threatens fauna.

Nerbioni: shows highest concentration of heavy metals.

Bidasoa: the estuary zone frequently shows hypoxia, especially in the summer, fron fecal discharge which transports a variety of bacteria that threatens human health.

Oiartzun: since raw sewage was diverted to the Murguita cala in summer 1996, a slightly increase of oxygen was noted in the area of Lezo. However, the coastal zone of Mungita continues to deteriorate.

Urumea: the Tximistarri area is less contaminated while Mompas is more polluted with bacteria as the major source.

Oria: is thought to be the river basin with the lowest level of contamination. Estuary sediments still show heavy metal pollution.

Urola: mollusks show low level of heavy metal contamination. Pollution from bacteria is high.

Deba: High concentration of heavy metals remain a serious threat to fauna.

The regional head of Environment, Patxi Ormazabal, said on Wednesday that installation of sewage treatment plants by 2005 in areas with more than 2,000 inhabitants will reduce pollutants. Currently only 50 percent of the population in Baskongadak has sewage treatment plants.

However, sewage treatment plants do not significantly reduce all pollutants and eliminate the problem of pathogens. To eliminate human pathogens the water discharged from sewage treatment plants is sometimes treated with chlorine, which reacts with organic chemicals to form carcinogenic chlorinated hydrocarbons. The sludge produced by sewage treatment can also pollute water, unless it is further treated and incinerated or properly applied to land. Moreover, where sewer systems are combined with storm drainage sytems, storm water may overwhelm storm drainage systems and flow into sewer systems, mixing with sewage and discharging into the receiving river, lake, or coastal water body.

Freshwater polluted by metals and industrial or agricultural chemicals requires expensive, technologically advanced treatment. Preventing pollutants from entering groundwater or surface waters can reduce treatment costs and downstream damage.

Finally, reducing industrial pollution must be a government priority. Companies that undertake waste-reduction programs often save money by using materials and energy more efficiently or by reducing the costs of conventional pollution control and waste disposal.

Freshwater pollution: sources, effects, and measures

The land area drained by rivers and its tributaries, known as a river basin, is the basic unit for understanding the sources and effects of freshwater pollution as well as the ecological relationships between terrestial and aquatic systems.

As water circulates from the atmosphere to the watershed and oceans and back into the atmosphere (hydrological circle) it is vulnerable to pollution from many sources. First, airborne dust, nutrients, metals, and other chemicals may fall as dry deposition or adhere to and fall with raindrops and snowflakes on both land and water. Second, as it flows over or filters through the soil, precipitation may dissolve nutrients and chemical residues, metals, and other pollutants. Eventually, some of the water may enter tributary streams and rivers, into which a third source of pollution, sewage and industrial wastewater, is discharged directly. At their mouths, rivers disgorge their loads of sediment and pollutants into coastal estuaries, where they may remain for many years.

Human settlements, industrial development, agriculture, deforestation, have significantly altered they physical and ecological features of many river basins.

Industry and mining are the principal sources of heavy metals and synthetic organic chemicals in freshwater. Industrial sources of heavy metal pollution include dust from smelting and metal processing; discharge of heavy metal solutions used in plating, galvanizing, and picling; use of metals and metal compounds in paints, plastics, batteries, and tanning; and leaching from solid waste dumps.

Most synthetic organic chemical pollution comes from industrial sources, including chemical and petrochemical refineries, pharmaceutical manufacturing, iron and steel plants, wood pulp and paper processing, and food processing. Like heavy metals, synthetic organic compounds such as PCBs and certain pesticides concentrate at higher levels of the food chain. Some increase the rish of cancer and reproductive abnormalities in fish, aquatic mammals, and humans.

Costs of freshwater pollution from synthetic organics include reduced productivity of fisheries, restrictions on consumption of fish from contaminated areas, and contamination of drinking water.

In addition to producing chemical pollution, human activities affect aquatic ecosystems in a variety of ways. When cities are built, grasslands, forests, and wetlands are converted to impermeable surfaces such as roads, parking lots, and roofs, greatly altering streamflow patterns. In cities, on farms, and in logging operations, removal of streamside vegetation can promote streambank erosion and subsequent smothering of freshwater animals and plants by sediments. Dams for power or irrigation impede fish migration and alter water chemistry and temperature in downstream areas.

Agriculture is the leading nonpoint source for water pollutants such as sediments, pesticides, and nutrients, principally nitrogen and phosphorus.

Inadequately treated sewage from human settlements introduces large quantities of nutrients, pathogens, heavy metals, and synthetic organic chemicals into surface waters. In industrial countries, much of the sewage generated in urban areas is collected by sewer systems and treated to varying degrees before being discharged into rivers, lakes, or coastal waters. Primary (physical) and secondary (biological) treatment of sewage may remove 35 and 85 percent of pollutants in sewage, respectively, but they remove only 30 percent of the phosphorous, 50 percent of the nitrogen, and 70 percent of the most toxic compounds. Advanced sewage treatment plants that can further reduce specific pollutant levels cost twice as much to build and four times as much to operate as secondary treatment plants. Without regular maintenance and proper operation, primary, secondary, and advanced sewage treatment plants will operate well below their intended standards.

Freshwater polluted by metals and industrial or agricultural chemicals requires expensive, techonologically advanced treatment. Preventing pollutants from entering groundwater or surface waters can reduce treatment costs and downstream damage. Some existing, small-scale measures can also salvage nutrients for use in raising food and creating habitat for wildlife.

Tighter government regulation would increase private business spending on pollution control and waste management which will make industry seek to reduce the amount of waste it generates.

Throughout a river system, pollution of groundwater, surface waters, and ultimately coastal waters can directly and indirectly damage human health and economic activities, as well as aquatic plant and animal communities. Once polluted, freshwater, especially groundwater, is expensive to cleanse for human use. Waterways degraded by development or pollution suffer decrease diversity and reduced abundance of fish and the invertebrates upon which fish and other animals feed. Furthermore, metals and inorganic chemicals may accumulate in aquatic organisms to levels well above those in the water itself, as the contaminants are passed up the food chain from prey to predator, including humans who consume fish. Finally, erosion resulting in sedimentation of water ways can impede navigation and require expensive dredging. Pollution by upstream users can significantly reduce the quality of water available to downstream users and ecosystems at little or no cost to polluters. This greatly complicates efforts to maintain or restore water quality.

Most sources of pollution have been identified and technologies or processes have been devised to reduce each pollutant. Where watershed pollution continues, it is usually because of a lack of political will, intergovernmental coordination, or inadequate funding.

February 2000

Mila Parot Zubimendi is a law student and an environment activist. She's currently living in Miarritze.