The rehabilitation of 43 year old waste lagoons

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Courtesy of Reliant Water Technologies

In 1967 the City of Concordia, MO built a segmented lagoon system to handle the small town’s waste requirements. The main industry in Concordia is a Tyson renderings plant, and the lagoon system was designed to also handle that plant’s final waste and water polishing requirements. The lagoon system was a relatively standard design, consisting of an 18.7 acre primary lagoon, a 5.6 acre secondary, and a 3.2 acre final lagoon. All lagoons average 6 feet in depth, with the final outfall being received by a southeasterly flowing Panther Creek. A number of vertical spray aerators were placed in the primary lagoon in order to provide water turnover and dissolved oxygen (DO) to the system.

By 2003 the lagoon system began to exhibit outfall water quality that did not meet the state’s DEQ permit limits. The key parameters of concern were BOD and TSS, and the permit requirements carried a 30/30 limit. In an effort to assist the city through this period of required rehabilitation, the outfall requirements were raised to a 45/45 limit. The City Administrators began to work with Tyson in an effort to make sure that the plant’s waste was treated to such an extent that it did not produce an uncontrollable amount of untreated waste. Tyson was very cooperative in the requirements placed by the Administrators.

Also in 2003, a bio-augmentation program was begun in an effort to reduce the BOD/TSS outfall results. At first, this idea, while expensive, seemed to work, but it was soon realized that the added bacteria to the system worked fine, until the BOD and TSS both reduced to the low 40’s, at which time the results seemed to ‘hit a wall’ in contaminant reduction capability. From 2004 through 2009 more aerators were added to the primary lagoon and two other brands of bacterial additive products were tried. At one point the City installed constant dosing systems that were designed to automatically feed bio-augmentation product to the lagoon system. Through all of this time and effort, the ability to get the BOD at the outfall consistently below 45 PPM and the TSS even close to that number seemed to get more elusive. Other negative characteristics of the lagoons began to surface – first, there was the inability of the primary lagoon to ever hold more than 7 PPM of DO, no matter what environmental conditions existed; and in the summer months that lagoon was beginning to exhibit a very heavy, waxy algal ‘cap’ that not only looked bad, but had a tendency to emit odors. Neighbors downstream of the lagoons, on Panther Creek, began to complain over the increased TSS and algae that was apparent in the water.

By 2009 the DEQ began to put pressure on the City to make major changes to the lagoon system and to get back to the 30/30 limits of the original permit. A local engineering firm was brought on board to help Concordia’s Administrators deal with the added DEQ requirements, and develop a redesign of the lagoon influent structures. At the same time, I was introduced to a couple of new products, offered by Reliant Water Technologies out of New Orleans, which were designed to specifically deal with the rehabilitation of old waste lagoon designs. After talking with representatives of the company, and providing the characteristics of the lagoon system and our problems, an officer of the company came to Concordia to meet with our City Council, our engineers and our water/wastewater treatment specialists.

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