Dr. Vaccari’s research encompasses three major phases; Biological Processes, Physiochemical Processes and System Modeling. His work in Biological Processes involves; Control theory applied to the activated sludge process, Modeling of compression in gravity thickening of sludge, Nonlinear time-series analysis for system identification of secondary clarification, Development and marketing of software product for activated sludge process simulation and control, and Long-term and ultimate biodegradability of solid materials, including consumer product testing.

Physiochemical research provides for advancement in; Air-stripping for removal of volatile organics, Adsorption hysteresis in groundwater, Responsible for design and testing of packed-column air-stripping equipment for the removal of volatile organic compounds from drinking water and wastewater, Developing new technologies for solvent recovery from air, and for point-of- use and point-of-entry removal of VOCs from drinking water, and Recovery of potable water from combustion gases.

His System Modeling research includes; Nonlinear time-series analysis and correlation (Multivariate Polynomial Regression, or MPR), Modeling and optimization of complex integrated systems, including integrated modeling of bioregenerative life support systems for long-term space travel, and Modeling of stream hydrology and water quality, including development of Total Maximum Daily Load (TMDL).

Dr. Vaccari is a member of Licensed Professional Engineer, New Jersey, 1989, holds an S-4 Wastewater Treatment Plant Operator's License, Stationary Engineer (High Pressure Boiler Operator's License), and has received the International Assoc. on Water Quality USA National Committee Founders Award for outstanding paper in Water Research by an US author.

He has been the recipient of honors and awards such as the Water Environment Federation (Technical Practice Committees for Wastewater Biology Manual of Practice and for Instrumentation and Control), American Academy of Environmental Engineers, Engineering Education Committee, Participation as Accreditation Visitor, American Water Works Association, Association of Environmental Engineering Professors, International Association of Water Quality (Specialist Group on Computing), ABET Accreditation Visitor for Bachelor of Environmental Engineering and Bachelor of Engineering Technology in Environmental Engineering, and the ABET Alternate Representative to the Technology Accreditation Commission.