Bubo Coroman (X) (asker) Sep 4, 2010:

thanks again Psi... what confused me is, if the second item is rainwater as per both answers (thank you answerers!), then what would be the point of including this in the list at all given that in the U.K. the separation of the two is automatic and follows through the system. As you mentioned this automatic separation does not apply in Spain, that would explain why the point is mention-worthy.
It also seems clear from your explanation that "tratamientos de aguas" is not what the writer actually meant, and I think what the answerers suggested makes sense.

psicutrinius Sep 3, 2010:

I have seen your link... ...and it gets worse: This is a gas station, so not much treatment of whatever here. The only possibilities are (a) they run surface water and effluent through separate networks (but this does not make sense if -as most usually happens- the municipal network it is plugged into does not run separate systems) and (b) they separate the "soft" effluent from the "hard" one and they recycle the first (say, for flushing toilets, for watering the "jardinería", etc), but I still cannot see any treatment here (less than before, in fact), unless this separation and re-use of soft effluent is the "tratamiento" they have in mind (which might be, but this a rather curious use of the word).

Best procedure: check

Bubo Coroman (X) (asker) Sep 3, 2010:

Psi... many thanks... what would you say to "separate drainage systems for foul water, and rainwater sent to the potable water treatment plant?" (assuming that was what they meant)

psicutrinius Sep 3, 2010:

that's a bit confusing... The original, I mean. It actually says that the networks separate sewage "and water for treatment". I do not see how you could do that: "Water for treatment" is the raw water coming from whatever reservoir for its use (which requires pretreatment), but this is the water "flowing in", and it is thus perfectly separated from any effluent, or from any "flowing out", such as effluent and rainwater.

As MPGS correctly points out, these two end up mixed (usually), which is not an efficient way of using the rainwater. This is where you can separate (two networks), but the original carries no mention whatsoever of "rainwater" (which will need treatment also, if mixed with the "water in"), and that's where it becomes confusing.

Besides, you also treat effluents (at the "EDAR", Estación de Depuración de Aguas Residuales"), so more confusion here.