Many years ago, I worked at a restaurant where they dumped the grease-trap into the sewer.
I'm willing to bet that that's the source of it: many restaurants doing it.
Somebody may be able to get the ones causing the problem, but it'd need either some analysis of exactly what's in that guck or someone becoming an informant, to stop the abuse of the Australian people's commonweath..
Nothing like wealth deeming everybody-else to be their toilet to hammer-home their "values", eh?
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