What is the relationship between water treatment and water in the context of the input sentence. Choose an answer from: product/material produced; manufacturer; distributed by; industry; position held; original broadcaster; owned by; founded by; distribution format; headquarters location; stock exchange; currency; parent organization; chief executive officer; director/manager; owner of; operator; member of; employer; chairperson; platform; subsidiary; legal form; publisher; developer; brand; business division; location of formation; creator.

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.

Answer: product_or_material_produced