Hexavalent Chromium is known to be:

Hexavalent chromium, also known as chromium VI, is recognized for its harmful effects on the environment and public health, making it toxic. It can cause serious damage to ecosystems, including aquatic life, and poses significant risks if it contaminates water sources. Chromium VI is a carcinogen, meaning it is known to cause cancer in humans, which underscores its environmental toxicity.

The other choices do not accurately reflect the properties or impacts of hexavalent chromium. It is not beneficial for treatment in wastewater processes and is not considered non-toxic to aquatic life. Additionally, it is generally not cost-effective, as specialized methods are required to remove or reduce its concentration in wastewater due to its hazardous nature. Overall, understanding the toxicity of hexavalent chromium is crucial for wastewater management and environmental protection.