As communities across the country look for ways to reduce household waste, Waltham will host its annual Zero Waste Day on Saturday, April 18, from 9 a.m. to 2 p.m. at Nipper Maher Park, 65 Dartmouth St. The event offers residents a free opportunity to recycle hard-to-dispose-of items such as clothing, electronics, car tires, books and metal. A paper shredding service will also be available.