A priest has the option of doing the purification at the credence table, instead of the altar.
I think a deacon is required to do the purification at the credence table.
For Mass with a deacon, from the 2002 GIRM:
“183. When the distribution of Communion is completed, the deacon returns to the altar with the priest and collects the fragments, if any remain, and then carries the chalice and other sacred vessels** to the credence table, where he purifies them** and arranges them in the usual way while the priest returns to the chair.”
For Mass without a deacon:
“163. … Upon returning to the altar, the priest collects any fragments that may remain. Then,
standing at the altar or at the credence table, he purifies the paten or ciborium over the chalice then purifies the chalice, saying quietly, Quod ore sumpsimus (Lord, may I receive), and dries the chalice with a purificator.”
The credence table is preferred:
“279. The sacred vessels are purified by the priest, the deacon, or an instituted acolyte after Communion or after Mass, insofar as possible at the credence table.”
The 2002 GIRM can be accessed from
romanrite.com/girm.html .