Bacterial biofilm attachment to sustainable carriers as a clean-up strategy for wastewater treatment: A review

Wastewater treatment using biofilm technology with sustainable carriers contributes towards the circular bioeconomy. The use of renewable biological materials and wastes as novel biofilm supports promotes material valorisation and reusability, decreasing the depletion of natural resources and the generation of waste and emissions. This manuscript presents a comprehensive review of the sustainable bacterial biofilm carriers used in biological wastewater rehabilitation. They include organic and inorganic materials from natural sources such as clays, volcanic rocks, stones, bamboo and luffa fibers and waste-based materials as wood husk, coconut husk, corncob, waste tire rubber, cigarette filter rods, textile wastes, among others. The material characteristics and application performance as sustainable bacterial biofilm carrier to remove several toxic pollutants and nutrients typically found in domestic or industrial effluents, in batch experiments and biofilm reactors were analyzed. Cell attachment and biofilm formation mechanisms are discussed. Processing approaches and surface modifications of the referred materials are presented. The review emphasizes the economic and environmental benefits of sustainable carriers compared to traditional ones. This survey is in tune with the need to explore materials that are included within the principles of circular economy, allowing the application of a more environment friendly and cost-effective water treatment.