Investigation of ultrasonic treatment of wastewater from iron compounds Liliia Frolova, Mykola Shapa, Tetiana Butyrina, Мariia Savchenko and Tetiana Hrydnieva E3S Web Conf., 168 (2020) 00027 Published online: 06 May 2020 DOI: 10.1051/e3sconf/202016800027