Philip Wachtler, principal of Wachtler Knopf Equities LLC, organized a blood drive for the tenants of 500 Bi-County Blvd., to mark the 6th anniversary of Sept. 11. "It's a way of giving back," said Wachtler, who was one of the first donors of the day. Jodi Staydar of the New York Blood Center, drew the real estate executive's blood. 500 Bi-County Blvd., managed by WKE, is one of the largest office complexes in the town of Babylon and an estimated 500 people work in the building. Established in 2005, Farmingdale, N.Y.-based Wachtler Knopf Equities is a property management and leasing company overseeing a portfolio of 10 Long Island office buildings totaling 579,000 s/f.