It depend on type of heavy metals and their concentration. As to draw a equation various factors are needed.

Hi,

I assume that this paper could be quite helpful for your topic.

"Treated Greywater Reuse for Hydroponic Lettuce Production in a Green Wall System: Quantitative Health Risk Assessment" by Fasil Ejigu Eregno, Melesse Eshetu Moges and Arve Heistad. It was published in Water2017,9, 454; doi:10.3390/w9070454.

Best regards

Josephine

Thanks lot my dear Dr.