You can try Regex for the same.
Iterate through the DataTable Rows and replace
string schoolName = Convert.Tostring( objDs.Tables[0].Rows[intCount][1]);
objDs.Tables[0].Rows[intCount][1] = Regex.Replace(schoolName,@"[\d-]",string.Empty);
And then ,
objDs.Tables[0].AcceptChanges();
Hope this helps