Robert Cameron, Penn State (IMAGE) Penn State Caption Penn State horticulturist Robert Cameron stands in front of a biofilter that uses plants roots, waste materials and bacterial colonies to clean wastewater as it trickles down the pipes. Credit Amitabh Avasthi Usage Restrictions Non commercial Use only License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.