Ryther (1977) compare the pollution problems of secondary sewage treatment and 

 those of ocean outfalls. They conclude that the problems should be reexamined with 

 appropriate scientific and engineering evaluations. Since the essential plant nutrients 

 are largely unaffected by secondary sewage treatment, the biological cycle in the sea 

 recreates the organic matter that was removed in the treatment process. The location 

 of the maximum impact will depend on the characteristics and vigor of the circula- 

 tion, and an offshore outfall may be preferable to sewage treatment with the release 

 of the effluent within the estuary. Clearly, untreated sewage should not be discharged 

 into harbors and estuaries, but offshore disposal has not been clearly shown to have 

 significant effects except in very localized areas (Gameson, 1975; Eppley et al., 1971; 

 Thomas et al., 1974). Sinderman ( 1976) discusses the effects of coastal pollution on 

 fish and fisheries. He finds that it is very difficult to establish a cause and effect 

 relationship except in confined and highly polluted waters. 



SUMMARY AND CONCLUSIONS 



The discharge of domestic pollution into coastal waters can cause beneficial or 

 detrimental effects. Disposal operations should be designed in ways that will pro- 

 duce the maximum benefit and cause the least deterioration of the environment. 



Sewage is frequently discharged into the confined waters of the estuary where 

 secondary treatment for the removal of organic material is essential to reduce the 

 biological oxygen demand of the effluent and to avoid local putrefaction and anoxia. 

 Secondary treatment does not, however, remove the essential plant nutrients, 

 primarily nitrogen and phosphorus, from the effluent. In the natural biological cycle, 

 the phytoplankton assimilate these nutrients and produce an amount of organic 

 carbon approximately equal to the amount that was removed in the treatment plant. 

 When conditions within the estuary are not favorable for photosynthesis, the 

 production of organic material will be delayed and maximum accumulation of 

 organic material will be displaced downstream by a distance that is determined by 

 the vigor of the circulation. 



Within the Hudson Estuary, for example, excessive turbidity limits photosynthe- 

 sis. After the polluted water reaches the coastal area of the New York Bight, phyto- 

 plankton photosynthesis is high over a wide area nourished, at least in part, by the 

 nutrients added in pollution. 



While this high production in the coastal water does not generally have a detri- 

 mental effect, wide areas of anoxia developed in the New York Bight in 1976 with 

 associated extensive fish kills. Studies were undertaken to evaluate the cause of this 

 event. The results have been described in a volume edited by Swanson and Sinderman 

 (1979). Several contributing phenomena are described, including unusual meteoro- 

 logical conditions, an extensive bloom of the dinoflagellate Ceratiwn tripos, and 

 high nutrients resulting in part from pollution. All may have contributed to the 

 development of the anoxic conditions, but no single cause could be identified. The 

 anoxic event demonstrates, however, how delicate the balance is between the high 

 production in this area and the potential depletion of the oxygen content in the 

 waters. 



When sewage is discharged directly into coastal waters with an active circulation, 

 it is questionable whether or not secondary treatment is desirable. The dangers of 

 localized anoxia are minimized in coastal waters since the effluent is rapidly diluted 

 and dispersed by the active circulation. The natural processes of the ocean serve as a 

 sort of treatment resulting in fertilization of the marine environment and increased 

 productivity. 



The basic principles that should provide guidance in designing the discharge of 

 sewage to the marine environment are well established. After appropriate dispersion 

 and dilution, the nutrient concentrations in the environment should not permit the 

 development of more organic material than can be decomposed by the available oxy- 

 gen in the system. In a simple quantitative sense, these relationships are well known. 



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