Chemical composition of sludges

Some of the undesirable components found in sewage sludge are shown in Table 3.67. This table refers to sludge from a primary settler, although many of the same components are found in secondary settler sludges [9]. 

Component Level, ppm by dry weight unless otherwise stated 

Faecal coliforms (digested sludge) 4 x 10 viable cells/100 ml  

A considerable proportion of the sludge dry matter is that ascribed to lipids (ether and petroleum-ether extractable substances), consisting of free fatty acids, their esters and substances incapable of undergoing saponification. The content of fatty acids in sludge is a value which is useful for characterizing the biochemical conditions in the anaerobic process of sludge stabilization. 

Other important components of sludges are polysaccharides (celluloses, hemicelluloses, starch). 

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Fortescue,). A. C., Silvester, M. D., Abercrombie, F. N., The Chemical Composition of Sludge from Six Sewage Plants in the Niagra Penninsula, Ontario, Canada as Determined by Atomic Absorption and Emission Spectroscopy Using an Inductively Coupled Plasma Source , Proceedings of the 9th Annual Conference on Trace Substances in Environmental Health, Columbia, Missouri, June, (1975). 

Table 10.11 shows the different residual sludges and their characteristics after the SCWO process. Based on characteristics presented in Table 10.11, the chemical composition of sludge residue from SCWO can be disposed of at any sanitary landfill. 

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