The Muldrow, Okla., wastewater treatment plant was having trouble complying with discharge limits until it began using a chemical treatment aid that helped reduce BOD, TSS and ammonia levels to within state-imposed limits.
Muldrow is a small community of approximately 3,000 people on the Oklahoma-Arkansas border just west of Fort Smith, Ark. Rated for 1 mgd, the plant typically processes 0.400 mgd to 0.600 mgd. The extended air plant operates both primary and secondary clarifiers, with an anaerobic digester.
Light industry in the area includes a chicken processing plant, which accounts for unusually high influent BOD, TSS, and ammonia levels. The wastewater treatment plant could handle the domestic waste stream, but the added industrial waste at times pushed the plant over permit limits. The plant was operating poorly and out of compliance during the summer months of 1997. Unsuccessful corrective measures included making mechanical repairs as well as bringing in a new operator to implement operational changes.
In August 1997, the BOD and TSS exceeded monthly permit limits (set at 20 for BOD and 30 for suspended solids) by more than 100 percent. BOD averaged 48 and TSS averaged 68. Foam covered the aeration basin and the secondary clarifiers would not settle.
At this point, Public Works Director Joe Shamblin brought in IMR Corporation of Tulsa, Okla. Dan Ward of IMR ran a series of tests at the plant, followed with the appropriate tests in the lab and made a recommendation to begin daily treatment with the company?s Aqua Treat 318 and Aqua Aide.
The two products were introduced in 1996 and work in tandem as a 100 percent natural physical flocculent and settling aid. They may be applied at the headworks, aeration basin or clarifier.
According to Lynn Kartchner, IMR chief chemist, Aqua Treat has a crystalline structure. Cations, bound on the outside of the crystal allow it to carry a positive charge in water, air or oil. Insoluble particles cling to the positively charged crystals and sink to the bottom. Aqua Treat 318 and Aqua Aide refloc repeatedly and continue to work until wasted out to the digester. The flow and the BOD determine the dosage of Aqua Treat 318. As flow and BOD levels fluctuate, the treatment level should be adjusted accordingly.
The new treatment began in late August 1997 with a BOD level of 48 and the TSS at 68. Table 1 shows the progress to compliance over a six month period.
During the winter and spring months of 1999 the city discontinued the program to see if the plant could run without the addition of the chemicals. The BOD and TSS levels began to creep upward until the city resumed using the products in April 1999.
In early 1999 the city learned that its discharge permit soon would limit ammonia levels. IMR requested monthly random tests of both raw influent and treated effluent to determine the ammonia removal effectiveness. Table 2 provides the results of those tests over a five-month period.
When the treatment was resumed in April 1999 the daily dosage was initially high, then gradually lowered over time until the plant was back to normal. The Muldrow plant continues to use a small amount of the product on a daily basis with very good results. BOD, TSS and ammonia levels have remained well below permit requirements.
?Now we don?t worry about being out of compliance,? Shamblin said.
A new eight-month series of random testing at the Muldrow plant began in January 2000. The results are expected to be available in September. Data Testing Inc., of Fort Smith, Ark., provided all testing conducted during the study.
