Tabic 6. Abundance of Major Elements in Typical Sewage Sludge and Natural Sediments. 



Sewage Sludges 



Sedimentary Rocks 



as Element 



as Oxides 



Carbon-free* 



Shale 



Sandstone 





(percent) 





(percent) 



(percent) 



(percent) 



(percent) 



Si 



10.0 



SiO^ 



21.4 



63.6 



58.1 



78.3 



Ti 



0.25 



TiO^ 



0.4 



1.2 



0.65 



0.25 



Al 



2.5 



AI2O3 



4.8 



14.3 



15.4 



4.8 



Fe 



1.3 



FeO 



1.7 



5.0 



6.1 



1.3 



Mg 



0.6 



MgO 



1.0 



3.0 



2.4 



1.2 



Ca 



1.5 



CaO 



2.1 



6.2 



3.1 



5.5 



Na 



0.75 



Na^O 



1.0 



3.0 



1.3 



0.45 



K 



1.0 



K^O 



1.2 



3.6 



3.2 



1.3 



C 



31.0 



Organic 



56.0 



— 



0.80 







P 



0.55 



P2O5 



1.2 



— 



0.17 



0.08 



Chemical composition recalculated, and adjusted to 



100 percent after subtracting carbon and phosphorus content. 



after Gross, 1970 



58 



