Reuse of plastic waste as bio-carriers for domestic wastewater treatment – An approach towards circular economy

With the rapid growth of economic development, the circular economy has been raised in many internationalenvironmental and socio-economic conferences and forums nowadays. The recycling of plastic waste was oneof those aspects. This paper studied the potential of directly reusing plastic bottle caps as bio-carriers in movingbed bioreactors without further waste processing. As the caps had lower surface areas than the commercial carriers, total bacteria communities on the commercial carriers (K3) were 3-4 times higher than those on the bottle caps at different counting magnitudes. Nevertheless, the bottle caps could accommodate similar nitrogen-based bacteria (ammonia-oxidizing bacteria - AOB and nitrite-oxidizing bacteria - NOB density), which promotes well for the nitrification and denitrification processes. The COD and N-NH4 removal efficiencies were 92% and 86% on average, respectively. The high pollutant removal capacity reveals the very promising potential of bottle caps as bio-carriers for domestic wastewater treatment, promoting waste reduction and treatment expenses and presenting an excellent example of economic circular.