Open your table and add two fields and add 2 text (string) fields if you already haven't done so.
You python's 'split' function to cut the field into 2 based upon a common factor... that you have a ':' in the same place
We will denote your field as variable f.
Make the first field you want to add data to and we will get the 'Townhall' part of the string into it
Select the python parser, double click on your field name containing the original data and then append ' .split(":")[0] to the fields name so your expression should look like
"your original field".split(":")[0]
hit enter and the results should be there. repeat on the 2nd field using
"your original field".split(":")[1]
and you should have the facility types.
In pure python with a field named 'f' this would look like this
>>> f = "Townhall:Municipal Building"
>>>
>>> a = f.split(":")[0]
>>> b = f.split(":")[1]
>>> a
'Townhall'
>>> b
'Municipal Building'
>>>