Changes to Mexico’s industrial waste pretreatment program are awaiting approval by the Missouri Department of Natural Resources.

At its regular meeting on March 8, the City Council approved a resolution of support for the changes, which were made necessary by last year’s closure of the Teva Pharmaceuticals plant. There are currently six companies under the city’s pretreatment authority.

“Anytime change occurs we have to adjust load limits,” explained Public Works director Kinsey Russell. “Teva was one of the heavier users in terms of difficult chemicals.”

The pretreatment program requires certain industrial operations to reduce wastewater pollutants identified by the city before they reach Mexico’s wastewater treatment plant. These are called local limits and are established by calculating a number of factors, such as water quality criteria, the ability of the wastewater plant to remove certain chemicals and state environmental rules.

Setting local limits specific to the type and volume of pollutants discharged by each company in the program prevents the plant from being overwhelmed. The city’s plant is subject to its own limits for wastewater that is discharged into South For Salt River tributaries.

Changes before the Natural Resources department include adopting a new way of measuring chemical and other pollutants discharged by factories. Currently the city measures concentrate levels. Public Works prefers to consider “mass load,” or the actual weight of pollutants.

“That’s a technical thing, but we have to reallocate limits,” Russell said.

Teva discharged heavier chemicals into the water than many other industries, amounts that could be missed when measured as a concentrate amount.

Also included in the planned changes are the city’s enforcement response plan, incorporating methods for identifying what would be considered significant noncompliance by industries. Fines for late reports by companies were changed from $300 per day to up to $300 per day.

Pretreatment standards were originally established by the Environmental Protection Agency as part of the 1983 Clean Water Act.