I have two environments locl and UAT, both have asp.net 2.0, when I access System.Data.SqlDbType.Structured on local it works fine whereas on UAT it throws an error saying
System.Data.SqlDbType.Structured is not part of System.Data.SqlDbType
When I looked into versions of System.Data on local it is 2.0.50727.3053 and on UAT 2.0.50727.832.
Any idea how this can be fixed...
That was added in one of the various service packs - I think 2.0 SP2 (and has been there since at least 2008, so your server seems quite unusually unpatched...).
The easiest way to fix this is to install .NET 3.5 and all service packs (taking usual "upgrading a server" precautions into account).