Table 24. Length of Ocean Outfall for Secondary- Treatment 

 Effluent That Can Be Constructed at Cost of Conversion to 

 Advanced Wastewater Treatment (Source: Adapted from 

 Reference 97) 



^For secondary treatment effluent. 

 Cost equal to cost of advanced treatment for same volume of wastewater flow. 



4.10.4 Improved Treatment Systems 



Extended treatment may be required for sewage disposed in estuaries in 

 the future because the assimilative capacities of estuaries are so low that 

 they would be overwhelmed by discharge from secondary treatment plants. _ 



Advanced, or tertiary treatment requires moving beyond the simple 

 mechanical and biological methods employed in primary and secondary_ 

 treatment to incorporate more advanced techniques, such as coagulation- 

 sedimentation, adsorption, electrodialysis chemical oxidation, 

 nitrification-dentrification or a combination of these [100] (Figure 34). 



An effective alternative to dumping sewage effluent into coastal 

 water bodies is land application of wastewater. The feasibility of this 

 approach is demonstrated by the more than 500 municipalities in the United 

 States that use some form of land application for disposal or treatment of 

 wastes [102]. 



In the land application system, wastewater is applied by spray 

 irrigation or overland flow to a land surface, where it is cleared by 

 biological, chemical, and mechanical processes and/or filters through the 

 soil as it travels over a vegetated surface. Finally, it either filters 

 into the groundwater or is collected for discharge to a water body, 

 depending on the system used. In an optimum treatment system with 



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