Pretreatment programs are implemented by the municipal authorities operating the sewage collection systems and sewage treatment plants, commonly referred to as publicly owned treatment works or POTWs. These programs are needed to eliminate potentially serious problems that can occur when industrial wastewaters are discharged into sewage systems.

• Toxic industrial pollutants may pass through the treatment plant, polluting a receiving water body and posing a threat to aquatic life, and, through the food chain, to human health.
  
  
• Industrial wastes may interfere with the operation of the treatment plant, rendering treatment of other wastes less effective.
  
  
• Industrial wastes containing high levels of toxic metal or organic compounds can contaminate biosolids, making disposal options more expensive and more limited.
  
  
• Industrial wastewater can corrode the pipes and equipment in the sewage collection system and the treatment plant.
  
  
• Highly volatile wastes can explode, causing considerable damage.
  
  
• Some wastes may interact to produce toxic gases, which pose health hazards to workers in the sewers and the treatment plant.