Prof. Kroiss received his Master and Ph.D at Vienna University of Technology. From 1987 to 2012, he was full professor for water quality management at the Institute for Water Quality, Resource and Waste management at Vienna University of Technology. From 1994 to 1998, Prof. Kroiss was dean of the Faculty of Civil Engineering and 2004 to 2010 vice chair of the Senate. In 2021, for his contribution in water research, he was awarded the Prechtl Medal, the highest scientific award by TU-Wien.

Prof. Kroiss has been appointed the Member of the IAWQ and IWA Board of Directors for many years. He was the chief editor of WST and the chair of the IWA publishing committee from 2010 to 2014, IWA president for the period 2014 to 2016, IWA immediate past president 2016 to 2018. Prof. Kroiss was awarded IWA Distinguished Fellow since 2008.

His main research fields included urban and industrial wastewater treatment design and operation, development from lab scale to full scale plant design and operation, and he focused on the role of nutrients for surface, ground, and coastal waters in river basin management.

Prof. Kroiss mainly engaged in basic and advanced education in Water Quality Management and doctoral programs. He Enhanced the continuous flow of knowledge and experience from research to full scale operation (professional training), and he was awarded by Dunbar Medal 2005.

For his international teaching and consulting with special emphasis on Europe and Asia, Prof. Kroiss was awarded the Honorary member of WEF (US), DWA (Germany), BWA (Bulgaria).