What is the distinction between the terms detrivores, decomposers, saprotrophs and saprozoic organisms?
Detritivores consume (eat) detritus.

Saprotrophs feed on dead organic matter by the means of extracellular digestion.

Saprozoic organisms are protozoans that are saprotrophs. This actually comes from an obsolete classification of plants and animals where bacteria and fungi were grouped with plants and were therefore called saprophytes if they are saprotrophic. Protozoans were considered animals; so saprozoic. 

Decomposer is a broad class including both detritivores and saprotrophs.

Scavengers also consume dead organisms. They are distinct from detritivores because the former consumes a relatively larger amount of dead matter. Often, scavengers are the first to consume dead organisms; the leftovers are processed by decomposers.


I could not find any authoritative source for these definitions. A peer-reviewed article by Getz (2010) attempts to classify organisms based on their eating habits.