Table 727 Important Wastewater Contaminants Based On Potential Effects And Concerns In Treatment


Reason for Importance

SS SS can lead to the development of sludge deposits and anaerobic conditions when untreated wastewater is discharged to the aquatic environment.

Biodegradable Composed principally of proteins, carbohydrates, and fats, biodegradable organics are commonly measured in organics terms of BOD and COD. If discharged to the environment untreated, their biological stabilization can deplete natural oxygen resources and cause septic conditions.

Pathogens Communicable diseases can be transmitted by pathogenic organisms in wastewater.

Nutrients Both nitrogen and phosphorus, along with carbon, are essential nutrients for growth. When discharged to the aquatic environment, these nutrients can lead to the growth of undesirable aquatic life. When discharged in excessive amounts on land, they can also lead to groundwater pollution.

Priority These pollutants include organic and inorganic compounds selected on the basis of their known or suspected pollutants carcinogenicity, mutagenicity, teratogenicity, or high acute toxicity. Many of these compounds are found in wastewater.

Refractory These organics tend to resist conventional wastewater treatment. Typical examples include surfactants, organics phenols, and agricultural pesticides.

Heavy metals Heavy metals are usually added to wastewater from commercial and industrial activities and may have to be removed if the wastewater is to be reused.

Dissolved Inorganic constituents such as calcium, sodium, and sulfate are added to the original domestic water supply inorganics as a result of water use and may have to be removed if the wastewater is to be reused.

Source: Metcalf and Eddy, Inc., 1991, Wastewater engineering, 3d ed. (New York: McGraw-Hill, Inc.).

and crayfish usually indicates relatively clean water; while communities of sludge worms, air breathing snails, midges, and aquatic earthworms indicate the presence of oxygen-consuming materials and deteriorating conditions.

Toxicity tests, the second category of biomonitoring, are less expensive and labor intensive than ecological surveys. Toxicity tests use indicator organisms in a controlled situation to examine water and effluent toxicity. The toxic effects of concern are death, immobilization, serious inca-pacitation, reduced fecundity, or reduced growth. Toxicity tests can be used to assess acute or chronic toxicity. Acute toxicity is a severe toxic effect resulting from a brief exposure, while chronic toxicity results from prolonged exposure. Tests for acute toxicity can be conducted within

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