AGP, the soybean processing plant on the northeast edge of Aberdeen, provided an update to the city council this week on hydrogen sulfide reduction efforts.

The news was encouraging, with both Water Reclamation Superintendent Peggi Badten and AGP Director of Environmental Compliance Kelly Jorgensen acknowledging lower readings in the system.

Jorgensen provided his update by phone at the beginning of Monday’s city council meeting. Badten was at the meeting.

AGP appeared before the city council during a special meeting March 11 to discuss rising levels of hydrogen sulfide, a corrosive and potentially explosive compound.

Wastewater discharge from AGP has continually exceeded the city’s allowed level of biochemical oxygen demand. That has not changed, and officials continue evaluate their system to find out how to reduce it to city-allowed levels.

Biochemical oxygen demand refers to the amount of oxygen needed to break down organic material in the water. If levels are too high, there isn’t enough dissolved oxygen available. That leads to the conversion of sulfites into sulfides and the creation of hydrogen sulfide gas.

Jorgensen said AGP continues to investigate why the biochemical oxygen demand is higher than it should be, but started a high-potency hydrogen peroxide treatment to the wastewater system to reduce the hydrogen sulfide.

Hydrogen peroxide is an oxidizer that reduces the development of hydrogen sulfide. It’s a short-term solution until AGP can permanently reduce biochemical oxygen demand levels in its wastewater discharge.

The treatment started March 13, and test results are showing lower levels of hydrogen sulfide, Jorgenson said.

Badten said water reclamation facility employees have tested gas levels recently, and those are showing levels of up to 200 parts per million. Previously, she said, levels were much higher. Monday morning tests showed 104 parts per million.

In an interview Wednesday, Badten said there really isn’t a safe level of hydrogen sulfide gas, as the human nose can smell the gas in concentrations of as little as 2 parts per million. What officials are concentrating on is reducing the liquid hydrogen sulfide within the system. Badten said as testing continues the city will be determining a target amount for the liquid hydrogen sulfide, but that amount has yet to be set.

Jorgensen said he will be at the March 23 Aberdeen City Council meeting to provide the next update. AGP has until March 20 to complete its compliance order. Jorgensen said that will be done on time.

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