I guess they kept doing whatever they did until then. In the thirties? They probably dumped everything into the nearest river.

If you asked 25 years ago I could have asked my grandfather.

Edit: I've re-read the question, mantained. It probably didn't last long enough.

Doubt there are records of something as mundane as sewage system, but in general revolutionary catalonia was still heavily relying on wage labor, commodity production, markets and so on. Of course, there was worker self-management but it was still capitalistic, and it's more than likely that public infrastructure was managed through it and being financed by local authorities

I suppose there already were workers maintaining it before the revolution. I guess they probably continued doing it, maybe some left, some newbies volunteered, but a core team probably already existed, and i see no reason to believe they all stopped doing the job they knew and were used to.

I expect it was probably pretty much the same as before, but with better labor conditions? Im just guessing.

We all have at least one 'nobody else wants to touch this' job we dont mind doing.