Parts of Center City and South Philly will have twice-a-week trash collection days starting next month as part of the city’s larger efforts for cleaner streets. The additional garbage pick-ups will begin Monday, Dec. 2 from Callowhill Street to Pattison Avenue between the Schuylkill Expressway (30th Street) and Delaware Avenue. The Department of Sanitation says that increasing frequency in densely populated communities should help combat illegal dumping.