Msgr. Merdian has received Bachelor's of Art degree from Saint Mary's University in Winona, Minnesota, with a major in philosophy and a minor in psychology. He attended Mount Saint Mary's Seminary in Emmitsburg, Maryland, and graduated with a Master's of Arts in moral theology with a concentration in medical ethics. He received a Master's of Divinity and was ordained to the priesthood in 1993.
His first assignment was as an assistant pastor in Champaign, Illinois, where he was a member of the Covenant Hospital Ethics Board, which provided consultation to the hospital on medical–moral questions.
In 2001, he was appointed an ex-officio member of the Diocesan Ethics Committee to assist with promoting medical-moral issues to Catholic hospitals and medical facilities in Peoria, Illinois.
He was named a Chaplain to his Holiness in 2009, and in 2010 he was named Episcopal Vicar for Health Care.
In 2014 Msgr. Merdian was appointed a Pastor of St. Pius X Parish in Rock Island, and Vicar Forane of the Rock Island Vicariate.