DOMESTIC (HUMAN) WASTES 



The problems of the disposal of domestic pollution are global in extent, but the 

 impact on the environment is localized because of collection and release to a limited 

 area. Segar (in press) has compiled data for the release of contaminants in various 

 populated parts of the world. The estimated amounts of nitrogen and phosphorus 

 are shown in Table 2. The nitrogen contamination of these marine areas ranges from 

 8.000 to 33,000 tons per million population per year, and the range of phosphorus 

 contamination is from 900 to 3,600. Both of these vary by a factor of four but not in 

 parallel with each other; the Baltic Sea appears to receive an excessive amount of 

 nitrogen. Excluding the Baltic and the Seto Inland Sea, the ratio of nitrogen to phos- 

 phorus by weight ranges from 2.78 to 6.54 (6. 14 to 14.45 by atoms). The North Sea, 

 Seto Inland Sea. and the Baltic have an excess of nitrogen or an adequate amount to 

 meet the relative requirements of the phytoplankton. The New York Bight, the 

 Mediterranean, and the Irish Sea appear to be relatively deficient in nitrogen. The 

 Baltic Sea is the freshest of these coastal areas, and, like most fresh waters, it seems to 

 be deficient in phosphorus, relative to nitrogen, in terms of the needs of the phyto- 

 plankton populations. 



Table 2. Contaminant Inputs and N:P Ratios for Selected Ocean Regions 

 (after Segar, in press) 



Traditional sewage treatment was developed to achieve two major objectives: the 

 prevention of waterborne diseases and the removal of organic matter that contrib- 

 utes to the biological oxygen demand (BOD) and could thus lead to anoxic condi- 

 tions in the environment. These conventional treatment methods were not designed 

 to remove the essential plant nutrients from the effluent and they have, indeed, little 

 effect on them. The average concentrations of nitrogen and phosphorus in the ef- 

 fluent from a number of treatment plants is shown in Table 3A (Mancini et al., in 

 press) and the typical wastewater concentrations of these elements in comparison to 

 the BOD of the wastewater is shown in Table 3B. In comparison to the requirements 

 of the phytoplankton in the marine environment, all of these samples are clearly very 

 deficient in nitrogen relative to phosphorus. The ratio N:P by weight for all of these 

 samples ranges from 2.21 to 6.67 (4.90 to 14.73 by atoms). 



The low N:P ratio in wastewater can be considered, of course, either as a defi- 

 ciency of nitrogen or as an excessive amount of phosphorus. It has been estimated 

 that human wastes account for 30 to 50 percent of the phosphorus in modern domes- 

 tic wastewater. The balance is accounted for by the use of phosphorus-enriched 

 detergents (Mancini et al., in press). Mancini et al. present the data that are summa- 

 rized in Table 4 showing the effects of phosphorus detergent bans or phosphorus re- 

 moval on the phosphorus content of wastewater and on the N:P ratios of the ef- 

 fluents. The banning of detergents or removal of phosphorus in the treatment 

 process increases the N:P ratio in the effluent, but the effluent is still nitrogen-defi- 

 cient relative to the requirements of marine phytoplankton. 



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