FY 1982

Estimated discharge characteristics of a commercial nodule mining operation

Ozturgut, E., J.W. Lavelle, and B.H. Erickson

Mar. Mining, 3(1/2), 1–17 (1981)

Assessment of environmental impacts of deep-ocean manganese nodule mining requires data on the concentration, discharge rates, and physical-chemical characteristics of the discharged material. Estimates of those quantities and discharge characteristics have been made here for commercial mining operations by extrapolating the discharge data obtained during pilot-scale mining tests and by using the information provided by the mining industry on future commercial mining systems. During a commercial mining operation, it is estimated that the solid fraction of the mining effluent, consisting mainly of bottom sediments and some abraded nodule material, will be discharged at rates of 1.4 × 10⁴ g/s at the surface and at 5.5 × 10⁵ g/s near the sea floor. The liquid fraction of the surface discharge will be bottom water with a salinity of 34.7‰ and temperature ~7°C; the bulk density of the surface discharge will be approximately 1.06 g/cm³. As suggested by data from the pilot-scale mining tests, the ratio of nodule material to sediments in the mining discharge will be dependent upon the nodule-sediment separation system employed on the mining ship. Fe and Mn concentration, because of their enrichment in the discharge particulates, will be indicators of mining material.