a biological filtration system includes a reservoir configured to receive an aqueous liquid , a multiplicity of polymeric container closures in the reservoir , a fluid inlet fluidically coupled with the reservoir , and a fluid outlet fluidically coupled with the reservoir . the fluid inlet is configured such that an aqueous liquid provided to the reservoir via the fluid inlet contacts the multiplicity of polymeric container closures . the polymeric container closures support biofilm growth . treating the aqueous liquid provided to the biological filtration system includes contacting the polymeric container closures with the aqueous liquid , growing biofilm on the polymeric container closures in contact with the aqueous liquid , thereby removing contaminants from the aqueous liquid to yield a treated aqueous liquid , and removing the treated aqueous liquid from the biological filtration system . the polymeric container closures may be reclaimed following consumer or industrial use , thereby conserving resources and reducing costs related to biofilm carriers .