This morning we went to a wastewater treatment plant for a five-yearly inspection of the fixation bolts.
Because the sludge
is such a dense suspension of bacteries there is zero visibility.
Even when you put your hand on your mask you won’t be able to see it.
Yet Marie succeeded to inspect the 4 mixers by checking them by hands and spanner.
After about 90 minutes she finished the job and came above water.