They are referred to as SLAD reactors, old school wastewater treatment
For all the basic info on SLAD reactors and wastewater you should try this web site
http://mtac.sws.uiuc.edu/mtacdocs/fi...inalReport.pdf
They are easy to build, and in terms of aquarium literature try
Here
http://mars.reefkeepers.net/USHomePa...torSoufre.html
Here
http://mars.reefkeepers.net/USHomePa...Denitrator.htm
And here for a DIY design (which I would modify per my comments below)
http://mars.reefkeepers.net/USHomePa...ionSoufre.html
For a discussion of its use in aquariums try this link
http://aqualinkwebforum.com/eve/ubb....2/m/3536050522
The SO4 build up is not as much a problem as you would think given that levels of sulfur in mixes are lower than sulfur levels in seawater.
Mix the sulfur and the limestone (Aragonite) in a column followed by a pure aragonite column. The mix in the first chamber helps keep the ph up throughout the "sulfur" column (low ph reduces denitrtrfication rates)
Hope this helps