Now that the chunky chowder has been sieved, strained, bubbled, and mixed to remove 85% of the wastes (garbage, liquids, and solids), the remaining broth, mostly liquid, gets a last fix from the "reverse" chefs.   The final step in treating the liquid portion of wastewater is disinfection or the selective destruction of pathogenic organisms in wastewater to protect the health of people and other animal life.  Disinfection is considered an advanced treatment technology that compliments conventional treatment methods at the primary, secondary, or tertiary levels of treatment.  Several types of disinfection are available--the addition of chemicals, especially chlorine, is the most widely used type of disinfection.

Wastewater treatment plants in coastal areas of New Jersey use chlorination along with secondary treatment.

• the most widely used type of disinfection, primarily due to its availability and cost effectiveness
• has detrimental effects on marine life, including: reduced growth, acute toxicity (effects will depend on the organism and the concentration of chlorine)
• organic compounds found in wastewater can react with chlorine to produce chloro-organic compounds, which are potential carcinogens (cancer-causing), mutagens, and toxins
• chlorine produced oxidants (CPO) are highly reactive compounds that contain chlorine and are the sum of the total amount of chlorine and bromine in the water.   In NJ, after the treatment process has completed, all treatment plants that discharge effluent into the ocean must test for CPO in their treated wastewater.   However, currently, there are no limits on allowable concentrations of CPO in effluent.
• a process that must be considered in the future to address problems associated with chlorination is dechlorination, which involves the removal of chlorine after the chlorination process, but before effluent reaches its outfall destination in the ocean.

OZONATION

• the byproducts and aspects of this alternative are safer than chlorination
• the strength of ozonation requires a small amount of ozone and a shorter period of disinfection
• costly
• energy intensive, requiring 16-24 kilowatt hours of electricity per kilogram of ozone
• a mode to prevent the regrowth of microorganisms after ozonation does not exist

ULTRA VIOLET IRRADIATION

• up-and- coming technology which is effective and has safe residues
• relatively easy to maintain and operate
• relatively inexpensive
• its efficieny sometimes may be reduced by the presence of certain chemicals in effluent
• a mode to prevent the regrowth of microorganisms after ozonation does not exist