CITY OF OMAHA TRICKLING FILTER IMPROVEMENT PROJECT MISSOURI RIVER WASTEWATER TREATMENT PLANT

Trickling filters have been used for over 100 years for treating wastewater. A reduction of the rotational speed of the distributor arms has increased the instantaneous application rate of wastewater to the media. This has shown to produce better performance of the trickling filter resulting in the development of the SK value. There are three objectives to slowing down the rotational speed of the distributor:Improve BOD5 and ammonia removal.Remove excess biomass attached to the media.Drive organic food materials into the lower level of the media.The Missouri River Wastewater Treatment Plant is one of two plants servicing the City of Omaha, Nebraska. There are two circular trickling filters, 145 feet in diameter by 40 feet tall. The media is cross-flow plastic that is 20.5 feet in depth. Between 1988 and 1996, each trickling filter had experienced a bearing failure, media collapse, and an infestation of beggiatoa. The daily flushing cycle required to assist in the sloughing of the biomass was labor intensive and performed opposite of the criteria to receive optimum results. The trickling filters were determined to be a major source of odor, allowing for 75% of the emissions to be fugitive.An improvement project was undertaken in 1996 to retrofit the trickling filters with a mechanical drive system and to cover each filter with an aluminum dome. Installation of the mechanical drive system has increased operational flexibility and efficiency. The treatment plant has maintained compliance with the NPDES permit. The growth of biomass on the media surface is better controlled resulting in a healthy media appearance, decreased production of hydrogen sulfide and a decrease in the filter fly population. The domes provide capture of hydrogen sulfide emissions resulting in less odor complaints and improved relations with the surrounding neighborhoods.