McCausland, Elizabeth D.  “Dirty Little Secrets: Realism and the Real in Victorian Industrial Novels,” The American Journal of Semiotics Vol. 9, Nos. 2-3 (1992): 149-165.
McCausland discusses the role of sewage and its resultant illnesses in Alton Locke.  Sewage or excrement is also a metaphor for the waste produced by the rich after they consume all the surplus value created by the toil of the working classes.  Sewage is “a sign of the suffering of the poor, all that is left of them after the rich have devoured them; this suffering is a result of the very system which claims to be creating a prosperous and civilized England” (158).

Alton Locke; Sewage; Social and Political Views.