Nitrogen pollution is a worldwide environmental issue, which has serious adverse effects on aquatic ecosystems. Ammonium, the major form of nitrogen presented in the wastewater, is conventionally treated via a biological energy-intensive aeration process. It also comes with great emission of greenhouse gas (nitrous oxides). We aim to remove ammonium using bioelectrochemical systems (BESs), where the nitrifying bacteria could shuttle electrons from ammonium to electrode under anaerobic condition and simultaneously generate electricity. This project will focus on understanding the bacteria shuttling capacity for ammonium oxidation and increasing the practical applicability of BESs on ammonium removal towards a cost-effective and sustainable technology.