Classes of Water Polluting Contaminants
- Oxygen Demanding Wastes are predominantly organic compounds that are easily degraded by bacteria, originating from domestic sewage, industrial wastes, feedlot runoff and food processing wastes that can create hypoxia/anoxia, fish kills and reduce habitat value. These contaminants are typically monitored by tracking dissolved oxygen and biological oxygen demand (BOD).
- Infectious Agents are pathogenic organisms such as bacteria, viruses, protozoa, parasitic worms, typhoid, cholera, and dysentery that enter water from sewage and pasture runoff or come from natural sources. The agents are commonly monitored through the measurement of fecal coliform. A lack of clean drinking water and a lack of sanitation cause 80% of diseases in developing countries and kills 10 million people annually with an average of 27,000 premature deaths per day (more than half of them children under 5 years old).
An indicator to assess water quality is the number of colonies of coliform bacteria (E. Coli) present in a 100 mL (0.1 qt.) sample of water. Zero colonies per 100 mL for drinking water and 200 colonies (max) per 100 mL for swimming pools.
- Plant Nutrients include compounds such as nitrogen and phosphorus, which are limiting factors in the growth of plants. High levels of these substances can originate from natural or human-induced sources (treated sewage, nonpoint source pollution, etc.) and may lead to algal blooms, increased turbidity and low dissolved oxygen levels. Nutrient levels are monitored by direct analysis and through the use of dissolved oxygen or chlorophyll studies.
- Petrochemical Compounds are complex mixtures of hydrocarbons that can have both acute and chronic environmental impacts. Common sources of petrochemical compounds include spills, exploration, discharge from refineries, leakage at transfer stations, and waste oils.
- Synthetic Organic Compounds are a group of pollutants, which include organophosphates, chlorinated hydrocarbons and PCBs, which produce both acute and chronic toxicity. These compounds are extremely resistant to biochemical breakdown and are very persistent. Sources include nonpoint source (NPS) pollution, spills, industrial and household wastes.
- Inorganic/Mineral Substances include salts, mineral acids, and metal compounds, which are generated as byproducts of industry, agriculture and may alter the acidity, salinity, and toxicity of an ecosystem. These substances can be monitored either directly or through the measurement of pH, conductivity, or biotoxicity.
- Sedimentation or Suspended Solids occur as a natural process of wind or water erosion. However, agricultural/construction runoff and dredging often create an excess of sediments, which can negatively impact habitats. These impacts often include the smothering of plants and animals, increased turbidity, and decreased aesthetics. Sedimentation is the biggest class of water pollutants.
- Thermal Pollution results in several industrial processes, which use water as a heating/cooling medium or to generate steam. Releases of thermally enhanced water can produce a reduction in oxygen solubility, increase the rate of chemical reactions/metabolism, and cause harm to organisms with limited thermal tolerance ranges. Thermal pollution lowers dissolved oxygen.
- Radioactive Materials are byproducts of modern technology, and include power reactors, medical wastes and nuclear fallout. The impacts may be acute or chronic. Relatively, the severity of these impacts worsens in more complex (higher) organisms.
