I didn't see the programme and have no TV but I fear from the occasions I have seen documentaries on technical subjects, anything beyond the producer's or presenter's immediate comprehension is discreetly ignored; and any stretching the viewer intellectually is to be avoided.
I can understand not showing what happens when things go wrong though. The water company involved was probably very nervous of showing that thing can and do go wrong. We are engineers – we know they can and do; but I fear most of the public, the Press and politicians are not and do not. They imagine you just Create a Policy, press [Enter] and Hey Presto! all complete, fully-working and any breakdown is automatically by fault of the Chairman and the lowest-paid staff-member.
The lack of showing the tight environmental control though, seems suspicious. Could be just typical media-studies ignorance as above, but perhaps the documentary company wanted to make viewers think it does not take place.
That first "no mention" though reminds me of a major repair of a local sewer years ago now. The poor blokes working in a pit several feet deep, in thick, sticky clay mixed with a good deal of pink-flecked cess, were probably accustomed to it, but certainly earned their money.