Captain Rufus Dreher SENN (abt. 1824–1898), Commanding, Post Guard, Columbia, SC, was a grocer in Columbia. He operated a store in partnership with Henry Muller at 249 Richardson Street, and his residence was at the corner of Richardson and Gervais Streets. He enlisted at Columbia on 9 May 1863, and was paroled at Chester, SC, on 5 May 1865. He died on 15 November 1898, and is buried in Elmwood Cemetery, Columbia, SC. Senn previously served as commissary for the 3d Battalion SC Infantry.

Probably not the same officer who enlisted your ancestor, but at least you now know who he was.