Q:

Is my question on safety practices for WWTP plant visits salvageble? 

This question of mine was closed as to broad.  Reasons given where that a good answer would be beyond the scope of SE.  Since then there's also a request for reopening, not by me (reopen-voter, speak up!).  Is it salvageable?  How? 
I'm not 100% convinced by the close reason.  My previous employer had a sheet of paper with 5 bullet points as 'best practices' for similar plants, obviously not a great example.  Seminars on plant safety (not WWTP, similar) I attended dealt to 80% with legal issues and Quality assurance.  So I'm not 100% convinced that that there are no meaningful yet short answer possible. 
To be sure, I'm not in any role where I'm responsible for anyone's safety beyond mine.  There may be a difference in the legal obligations consultant engineers have between Germany and elsewhere, maybe this misunderstanding is part of the problem?  
P.S. Not that his has bearing on the discussion here, but two things I will do is hunt down safety manuals of the plants I visit and pursue my employer about this issue.   
P.P.S While my employer offers seminars on safet around the office once a year, on-site practices are not covered.  They are in trouble when something happens to one of us, but that's nothing I want to see happen. 

A:

I have two general issues with the question.   Only one really relates to the site.  The other one is more of an "industry" concern. 
Site Issues
The problem with asking about general site safety is that there is always something more to think about in order to be safe.  Everyone could add all of their thoughts.  These could even be bullet points from very specific safety training or plant safety manuals.  At the end, there is going to be something that has not been covered. 
Are you worried about meteors?  badgers?  power outage?  earthquake?  tidal wave?  plane crash?  Those are all safety issues, but the likelihood of each of them are not the same.  Where does the list stop? 
Also, do the "general" things need to be on the list?  Does the list need to include first aid?  not licking the walls?  slips trips and falls?  oxygen tanks?  lock out tag out?  eye protection?  hearing protection? 
These are reasons why asking for a list can not possibly be answered completely on this site. 
Industry Issues
This is where I point out that having to ask on a site like this about safety issues scares me.  Your employer should be training you in everything that you need to know.  Even the plant should be sure that you have the required training before setting foot on site.  If none of this has happened, that scares me. 
I believe that you are in a different country (and the laws are likely very different), but in the USA, the government agency that handles industry safety is OSHA.  They have volumes of rules that are required to be followed.  And as is usually the case, ignorance of these rules doesn't protect you from being punished for not following them. 
Can the question be saved? 
The items above are about the question as it stands now.  That doesn't mean that it can't be saved.   You will have to narrow it down somehow to make it work though.