OTTAWA — Ottawa University says its enrollment is up 16 percent this year. More than 500 new students registered for the university’s first fall session in its online programs and at its seven national campuses. Total undergraduate enrollment is slightly more than 2,100 students. The biggest increases were OU’s Wisconsin and Arizona campuses. At OU’s Ottawa campus, opening enrollment was virtually unchanged last year with 533 students even though the university tightened admissions standards. However, OU said the number of returning students increased 8 percent from last year.