Please check the following link and PDF attachments.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5048648/

t contains vitamin B and a trace of vitamin C and also traces of iron and calcium. The outstanding characteristic of onion is its pungency, which is due to a volatile oil known as allyl-propyl disulphide. Onions compared with other fresh vegetable are relatively high in food energy, intermediate in protein content and rich in calcium and ribonflavin.

So, these components are available in the wastewater of industry approximately.

Thanks all for your replies.

Hope other would also give their valuable suggetions on it.

Regards