I can't resist saying:
You'll find the information you are looking for in WRc publication TR189.
Less facetiously:
It was updated in June 1997 to TT016
WRc ref TT016/09283-0
Any copying etc would breach copywrite, so I suggest you get on their web site and order a copy.
Addendum to my earlier response - the one you mention is for Water treatment sludge. There is a sewage sludge version (actually the original I believe) which was described a few years earlier in TR 185 (I think). As previously, ref their web site for details.
In general, I don't think you need worry about "copyrights". Most government publications are in the public domain and are not copyright-able ( if that's a word). I'm not a lawyer and don't want to be one. Just a long time government employee.