I think it may be possible. Actually, the dried agar is used as human food in east Asia, and is known to be a diet food in Japan. There exists many types of food from agar. No harmful bacteria or parasite inside as far as I know.
Hello Helena, this group from University of Porto, Portugal, published several articles on using agarophyte (Gelidium) extraction waste in effluent heavy metal treatments. Just one example: Vilar, V. J. P., Martins, R. J. E., Botelho, C. M. S., & Boaventura, R. A. R. (2009). Removal of Cu and Cr from an industrial effluent using a packed-bed column with algae Gelidium-derived material. Hydrometallurgy, 96(1–2), 42–46. doi:10.1016/j.hydromet.2008.07.015