The discharge has killed huge volume of fish in the north central province of Thanh Hoa in the lower reaches of the river.
Besides, the company has been suspended in six months and required to solve the problem.
Before resuming operation, it must build wastewater treatment system which will be attested to meet standards by authorized agencies. The company will face heavier penalty if repeating violation.
Previously, the plant has taken responsibility for releasing wastewater into the river damaging fish famers and promised to compensate over VND1.4 billion (US$63,000) for the damage.