Removal of iron ore slimes from a highly turbid water by DAF

ABSTRACT

This paper addresses Dissolved Air Flotation (DAF) process variables, such as the flocculation parameters and the recycle water addition, as well as the pretreatment chemical variables (coagulation conditions), to determine the optimal values for the flotation of iron ore slimes found in a highly turbid water sample from the Gualaxo do Norte River, a tributary of the Doce River Basin in Minas Gerais, Brazil. This work was conducted using a flotatest batch laboratory-scale device to evaluate the effectiveness of DAF for cleaning the water polluted by the Samarco tailings dam leakage and determine the ability of DAF to reduce the water turbidity from 358 NTU to values below 100 NTU, aiming to comply with current legislation. The results showed that the four types of tested coagulants (PAC, ferric chloride, Tanfloc SG and Tanfloc SL) provided adequate conditions for coagulation, flocculation and flotation (in the range of 90–99.6% turbidity reduction). Although the process variables were optimized and low residual turbidity vales were achieved, results revealed that a portion of the flocs settled at the bottom of the flotatest columns, which indicated that the turbidity results represented removal caused by a combination of flotation and sedimentation processes simultaneously.

GRAPHICAL ABSTRACT

KEYWORDS:

• Dissolved air flotation
• coagulation
• flocculation
• recycle water addition
• iron ore slimes
• turbidity removal

Acknowledgements

The authors gratefully acknowledge the support by the Instituto Tecnológico Vale and the Laboratório de Tratamento Avançado e Reuso de Águas (LATAR) of the São Carlos School of Engineering at University of São Paulo -USP.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

L. M. Faustino http://orcid.org/0000-0002-0754-7063

A.S. Braga http://orcid.org/0000-0002-2558-276X

L.A. Daniel http://orcid.org/0000-0002-1765-4209

Additional information

Funding

This work was supported by the Instituto Tecnológico Vale.