TABLE 4.8 Options for Improving Coastal Waters Affected by a Wastewater Treatment Plant Discharge (Brooks 1988)

Assumed present system: primary treatment, short outfall.

Assumed ocean environment density stratification due to temperature and/or salinity variation with depth during most seasons of the year.

Water Quality Problem

Effective Remedial Action

Comments

1. Pathogens/coliform counts too high at target areas (swimming areas, shellfish beds)

• Longer diffuser

• Longer outfall(discharge farther offshore)

• Disinfection

• Higher initial dilution, possible submerged plume

• Increases travel time back to shore and die-off

•Some methods (e.g., chlorine) are injurious to marine organisms

2. Undesirable biostimulation due to excessive nutrients (e.g., algal blooms)

• Longer outfall

• Keep nutrients below photic zone

• Nutrient removal

•Improved dispersal to open ocean (nutrients less or not harmful)

•Submerged effluent plume in naturally turbid waters

• With some methods, increased sludge volume, requires larger disposal site

 

x Secondary treatment (not a remedy)

• Nutrients not significantly removed but may be more available

• Increased light penetration due to particle removal

3. Excessive turbidity or light extinction

• None, if turbidity is natural

• Increased removal of particles by chemical coagulation and/or secondary biological treatment

• Increased light transmission may increase biological growth

•Increased sludge production



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