MINNEAPOLIS (AP) — Minnesota regulators have unveiled the latest refinement to their proposal for revising the state’s water quality standards for protecting wild rice from sulfate pollution.

The document released Tuesday by the Minnesota Pollution Control Agency builds on more than 600 comments submitted about the agency’s original proposal after it was released last fall.

The state’s existing standard limits sulfate discharges into wild rice waters to 10 parts per million. The MPCA has been working on a different approach, using a complicated formula tailored to individual waters. It’s based on the interplay among sulfates, sulfides, iron and organic matter in sediments where wild rice grows.

The MPCA is taking feedback through Sept. 6, and citizens will have the opportunity to formally comment on the proposed standard during the rulemaking process next year.

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