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Case Studies

Case Study: City of Miner, Missouri

Dirty Discharge

Miner, Mo., population 980, is a quaint rural community located halfway between St. Louis and Memphis, Tenn. The 20-year-old Miner 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,” said chief operator Marvin Hatton. Miner needed to clean up its discharge to comply with Missouri Department of Natural Resources (DNR) and U.S. Environmental Protection Agency (EPA) regulations. The plant’s staff and City of Miner Engineer Norman Lambert 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. They decided a brand new plant should replace the old one.

“It would have been just as cheap to have a new [plant] put in [than] to have it cleaned out and put back in service,” Hatton said. “To be honest, it was just time to update.” 

Downsizing to Upgrade
Lambert selected EDI to design and implement a new lagoon treatment plant for Miner. EDI proposed an Intermittently Decanted Extended Aeration Lagoon, or IDEAL™. The solution focused on eliminating solids, oxygen demand and ammonia in Miner’s wastewater. The IDEAL is able to provide full nitrification while removing a majority of total nitrogen through denitrification. The overall IDEAL Process uses two ponds; the IDEAL for advanced treatment followed by a partial mix basin with a settling zone for sludge storage and solids separation, thereby shrinking the size of Miner’s plant while improving its efficiency and effectiveness. The IDEAL aerates influent for two hours for BOD removal and nitrification before entering an anoxic settling and decant phase (one hour each), which provides denitrification, retains biomass, and discharges 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 that are not trapped in the partial mix zone settle; allowing clear water to flow out of the pond and to UV disinfection. Finally, the treated wastewater is discharged into the North Cut Ditch.

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

Major improvements
When construction for the IDEAL Process was fully completed in November 2012, Hatton said EDI representatives spent a week training his staff on the new equipment and processes.

A joint effort between the City of Miner and EDI tracked the plant’s effectiveness during the record-cold winter of 2013/2014. Hatton and his staff gathered composite samples from the influent and effluent of the plant twice a week, while monitoring temperature in the IDEAL. Those samples were sent to Environmental Analysis South in Jackson, Mo., where the level of total suspended solids, ammonia, BOD, nitrate, nitrite, and total nitrogen were tested. Consistently, analysis of incoming and outgoing nutrient removal has been very positive. Ammonia levels, for example, have averaged 27 mg/L in wastewater 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 in the IDEAL dropped below 3°C. Similarly, BOD drops 230 mg/L to 4.5 mg/L and suspended solids fall 104 mg/L to 5.3. Total nitrogen drops 66% from 32 mg/L to 11 mg/L.

Hatton said a site visit from Missouri DNR state officials where samples were taken and tested also yielded enthusiastic feedback. He credited the improved water quality to the more effective and efficient process of the IDEAL. Installing the IDEAL brought Miner’s wastewater treatment plant well within DNR regulatory requirements.

Ongoing Partnership
Hatton said the IDEAL was easy to install and is low-maintenance with highly favorable outcomes. However, to garner further maintenance support with its new water treatment system, Miner is entertaining a maintenance contract agreement with EDI. The city of Miner Board of Aldermen will vote on the proposal to provide the Miner Wastewater Treatment Plant additional maintenance assistance from EDI. Should Miner and EDI develop a maintenance agreement to ensure sustained success of the IDEAL solution, Hatton said he would welcome occasional EDI service visits. 

“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,” he said. “They’ve been really good with us.”

Case Study: City of Grantsville, Utah

Utah Wastewater Facility Meets Discharge Requirements with EDI Aeration System

Discharge Dilemma
Originally designed for a 0.75 MGD capacity, the Grantsville Wastewater Treatment Plant receives residential wastewater from almost 10,000 residents in Grantsville, Utah, just west of Salt Lake City. In 2009, the plant was having significant trouble meeting the city’s discharge requirements for ammonia, TSS, and BOD. According to Ron Griffin, the plant’s operator, treated wastewater would violate discharge requirements so regularly that he had to withhold it six months out of the year to limit violations.

“Something within every six months was a problem — either our ammonia or our BOD,” Griffin said. “So, I was only discharging six months out of the year. I would discharge for three months, hold for three months, discharge for three and then hold for three.”

Identifying the Cause
The cause of the problem could be traced to a surface aerator in the plant’s primary treatment pond. The aerator created an aerobic zone in the top 4-ft or 5-ft of the pond and maintained an anaerobic zone throughout the rest of the 10-ft column. According to Griffin, the anaerobic process was slow and sluggish, and the by-products, hydrogen sulfide and methane, caused odor. The plant needed a more efficient system that would allow a continuous discharge of treated effluent and have the capacity to meet future requirements for ammonia removal. The plant had two options: convert existing non-aerated ponds to aeration, or construct new ponds that met state requirements.

Selecting a Solution
For Griffin, there was one obvious answer: “It was much more cost-effective to use our existing footprint and ponds and just add the [aerators].” Upon further evaluation, Environmental Dynamics International (EDI) proposed using an Intermittently Decanted Extended Aeration Lagoon, or IDEAL™.  IDEAL is a lagoon-based extended aeration system that treats raw wastewater using a batch reactor process. The IDEAL Process allows continuous inflow of raw wastewater, which then undergoes a sequenced aeration reaction/mixing phase, followed by a settling phase. Finally, the water is decanted and discharged to polishing ponds.

After removing the existing surface aerator from the primary pond, construction workers installed the IDEAL. Equipment required for the upgrade included EDI’s floating lateral aeration system with FlexAir 88S assemblies paired with Magnum fine bubble diffusers, a BioReef™ BioCurtain, and four 24-inch diameter decant pipes with electric actuated valves, system control panel, and three 220HP turbo blowers. During construction, workers were met with a significant challenge: A 4-ft sludge blanket in the bottom of the cells. “We had to pull about 30 different blocks that held the old surface aerators in place, and they had to be eliminated so we could put in these deep, fine bubble diffusers.” 

“We had to pull about 30 different blocks that held the old surface aerators in place, and they had to be eliminated so we could put in these deep, fine bubble diffusers.” 

Improved Treatment Process
The system went online in July 2010. With the new treatment process, wastewater comes in through the head works to remove all of the large particles. It goes to the primary cell, comprised of the IDEAL. “The system has big air pumps that [aerate] from the very bottom of the pond, so it turns the entire 10-ft of the elevation into an aerobic zone,” Griffin said. The aerobic treatment process is much more aggressive and robust. Since air is applied at the bottom of the lagoon, instead of top-down, it’s a more efficient process. Because the by-products are carbon dioxide and water vapor, it eliminates odor. 

After this process, the water is decanted from the first cell, traveling through two partially mixed cells and one quiescent cell. It is disinfected with a UV light before discharge. The water is then discharged into Blue Lakes — a small wildlife area north of the plant — and is mostly used for irrigation of pasture.

Quality Results
The system upgrade has resulted in increased plant capacity, now 1.5 MGD, and the quality of the effluent has drastically improved. “With the upgrade, the ammonia went down to less than 1 mg/L and non detect on the BOD. I’m literally getting a non detect on my report about 80% of the time on my BOD, TSS and ammonia, and even E. coli. It’s made a real fine quality of water,” Griffin said.

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