Utilize the input text as a context reference, choose the right relationship between 'water treatment' and 'water' from the options.
Options: stock exchange, platform, product/material produced, employer

The joint venture is currently in negotiations on multiple projects, whereby large water treatment systems would be built based on LiqTech's proprietary silicon carbide technology and operated by the joint venture on the long-term water supply agreements with oil and gas producers.
product/material produced