Cascade method of wastewater treatment using various natural sorbents Alexey Ovchinnikov, Viktor Bocharnikov, Olesya Bocharnikova, Maria Denisova, Olga Kozinskaya, Evgeny Pustovalov and Tatiana Repenko E3S Web of Conf., 539 (2024) 01024 Published online: 17 June 2024 DOI: 10.1051/e3sconf/202453901024