129 



Sewage Sludge 



Sewage sludge is the waste solid byproduct of 

 municipal waste water treatment processes. 

 These solids can be further treated by di- 

 gestion, a process which allows accelerated 

 decomposition of the sludge to control odors 

 and pathogens. INIost sewage sludge is dis- 

 posed of on land or is incinerated. Kelatively 

 small amounts (4.5 million tons on a wet 

 basis) are currently dumped at sea, of which 

 almost 4.0 million tons are dumped off New 

 York harbor. (66) As of 1968, there were no 

 similar operations on either the Gulf or Pa- 

 cific Coasts, although sludge is being dis- 

 charged from Los Angeles by pipeline. 



Sewage sludge in digested or undigested 

 form contains significant quantities of lieavy 

 metals. A study by the FWQA indicated that 

 copper, zinc, barium, manganese, and molyb- 

 denum are present in sewage sludge. (9) 

 The concentrations and tyj^es of toxic mate- 

 rials vary because sludge is the residual of 

 waste water treatment and contains whatever 

 domestic and industrial contaminants have 

 entered the system. Table 7 shows the mini- 

 mum, average, and maximum values for three 

 heavy metals found in one analysis of sewage 

 sludge. 



Table 7. — Heavy Metals Concentrations in Sewage 

 Sludge (8,9, 36) 



(In parts per million) 



Sewage sludge also contains significant 

 amounts of oxygen demanding materials. In 

 1969, sludge dumped in the New York Bight, 

 encompassing the New York harbor and 



some adjacent coastal areas, had an oxygen 

 demand of about 70,000 tons. (15) These 

 wastes also include some bacteria that cause 

 diseases in man. 



Construction and Demolition Debris 



Only New York City disposes of debris at sea 

 in significant quantities because of the lack 

 of nearby available landfill. Sea disposal is 

 conducted Avith 3,000- to 5,000-ton capacity 

 barges that are towed some 9 miles offshore. 

 These materials are generally inert and non- 

 toxic. 



Solid Waste 



Solid waste, the byproducts and discards of 

 our society, amounts to approximately 5.5 

 pounds per capita per day collected by munic- 

 ipal and private agencies. (28) Although 

 these wastes total approximately 190 million 

 tons per year, ocean disposal accounted for 

 only about 26,000 tons. (66) Ocean dumping 

 of solid waste occurred exclusively on the 

 Pacific Coast, where they were generated by 

 cannery operations and commercial and naval 

 shipping operations. Other sources no doubt 

 exist, but the overall magnitude of the cur- 

 rent problem is minor. 



The composition of solid waste, ascertained 

 by sampling, is shown in Table 8. It is pre- 

 sented here to indicate the materials that 

 would be introduced into the marine environ- 

 ment if ocean dumping of solid waste be- 

 comes a common practice.) 



Solid waste disposed of in the ocean in- 

 teracts with the water, but the resultant chem- 

 ical products are difficult to determine. 

 Studies have been done on the interaction be- 

 tween solid waste and fresh water in sani- 

 tary landfills as the water percolates through 

 the waste materials. (The resultant mixture 

 of water and chemicals is called leachate.) 



