The 20-year-old Miner (Mo.) Wastewater Treatment Plant faced a number of technical issues in 2012. The town’s old three-cell 0.302 mgd aerated lagoon had high levels of suspended solids. Its ammonia and nitrogen concentrations were above their targets.

“There was quite a bit wrong with the plant,” says Marvin Hatton, chief operator. The city needed to clean up its discharge to comply with Missouri Department of Natural Resources (DNR) and U.S. EPA regulations.

The plant’s staff and Norman Lambert, city engineer, decided it was time for a full-service upgrade. They called in Environmental Dynamics International (EDI) to assess the issues and develop a rehabilitation plan, ultimately choosing to replace the plant with a brand new facility.

Essential to the new process is an Intermittently Decanted Extended Aeration Lagoon (IDEAL) system. The solution has successfully reduced effluent ammonia, BOD and TSS and enabled the plant to meet DNR requirements.

Downsizing to upgrade

Miner (population 980) is a rural community halfway between St. Louis and Memphis, Tenn. Its old plant would have needed significant work to be able to comply with tightening effluent standards. “It would have been just as cheap to have a new plant put in as to have the old one cleaned out and put back in service,” Hatton says. “To be honest, it was just time to update.”

Lambert selected EDI to design and implement the new lagoon treatment plant with the IDEAL solution, which focuses on eliminating solids, oxygen demand and ammonia in the effluent. The process can provide full nitrification while removing a majority of total nitrogen through denitrification.

The overall process uses two ponds: the IDEAL system for advanced treatment followed by a partial mix basin with a settling zone for sludge storage and solids separation. This shrinks the footprint of the plant while improving its efficiency and effectiveness.

The IDEAL process aerates influent for two hours for BOD removal and nitrification. The wastewater then enters an anoxic settling and decant phase (one hour each), providing denitrification, retaining biomass and discharging clear water.

Supernatant and stabilized waste sludge are partially mixed in the second pond to maintain a positive level of dissolved oxygen to digest solids and prevent ammonia rebound. A small portion of the secondary pond is a dedicated quiescent zone where solids not trapped in the partial mix zone settle. This allows clear water to flow out of the pond and to UV disinfection. Finally, the effluent discharges to the North Cut Ditch.

“It’s a pretty good little plant,” Hatton says. “Our numbers have been really good. I mean, really good.”

Major improvements

When construction for the lagoon process was complete in November 2012, EDI representatives spent a week training the staff on the new equipment and processes. Later, a joint effort between the city and EDI tracked the plant’s effectiveness during the record-cold winter of 2013-2014.

Hatton and his staff gathered composite influent and effluent samples twice a week while monitoring temperature in the IDEAL pond. Those samples were sent to Environmental Analysis South in Jackson, Mo., and tested for TSS, ammonia, BOD, nitrate, nitrite and total nitrogen.

Consistently, analysis of incoming and outgoing nutrient levels has been strongly positive. Ammonia levels, for example, have averaged 27 mg/L entering the plant and drop to less than 0.05 mg/L by discharge. Not one sample has come in above the method detection limit of the analysis, even when the temperature dropped below 3 degrees C.

Similarly, BOD dropped from 230 mg/L to 4.5 mg/L and TSS from 104 mg/L to 5.3 mg/L. Total nitrogen dropped 66 percent, from 32 mg/L to 11 mg/L. A site visit from DNR officials in which samples were taken and tested also yielded enthusiastic feedback.

Continuing partnership

Hatton notes that the process was easy to install and requires little maintenance. To obtain maintenance support for the new system, the city explored a maintenance agreement with EDI. “If I have any problem I can call and they’ll do a little troubleshooting on the phone, and if that doesn’t take care of it, they’ll come down,” says Hatton. “They’ve been really good with us.”

About the author

Tim Canter of Environmental Dynamics International works on development of advanced wastewater treatment systems for earthen basins. He can be reached at Tim.Canter@wastewater.com.