Winning the War in Nutrient Removal: Case Study for SuperBiomedia in Trickling Filters
Biological nutrient removal (BNR) is necessary in the wastewater treatment process to protect local ecosystems after treated water is discharged. As the concentration of nutrients, namely nitrogen and phosphorus, increases in surface water, ecosystems are damaged in return. Algal blooms are a result of the increased nutrient concentration, which deplete dissolved oxygen, kill fish, and suffocate plants in local ecosystems. The facility upgrades needed to reduce nutrient concentrations to safe levels can be costly, requiring significant improvements to the treatment process to create anoxic zones for nitrogen removal. In a case study conducted at a municipal wastewater treatment plant in Ohio, Water Warriors SuperBiomediaTM reduced the overall nitrogen-ammonia (NH3-N) effluent concentrations on average by 42%, even in colder temperatures. Additionally, SuperBiomediaTM reduced the overall biochemical oxygen demand (BOD5) and overall chemical oxygen demand (COD) by 67%, and 60% respectively. The total phosphorus (TP) and total suspended solids (TSS) concentrations were not impacted in comparison to rock media. Based on the Velz equation, a depth of only 1.15 ft of SuperBiomediaTM with a recycle ratio of 0.232 was calculated to meet the existing exit BOD5 and NH3-N concentrations. A retrofit of existing trickling filters will prevent the need for a major process upgrade, reducing operating costs while also increasing the efficiency of nutrient removal.
At a municipal wastewater treatment plant in Ohio, the effectiveness of SuperBiomediaTM was compared to rock media in a trickling filter. Figure 1 shows the trickling filter used in this case study.
The city’s Division of Water reclamation has been treating wastewater since 1929 and uses a system of 20 trickling filters with all rock media. The trickling filters are each 165 ft in diameter, and 7 ft deep with a calculated volume of 149,697 ft3 per trickling filter. Each trickling filter is constructed of four arms that rotate over a circular area containing filter media. Influent consistently exits through two arms, whereas the remaining two arms are used when recirculation flow is added. The influent to the plant averages between 48-50 million gallons per day (MGD) and is combined with a recirculated flow after passing through the trickling filters. The recirculated flow combined with new influent into the plant totals to approximately 90 MGD. The recirculation rate is a fixed at an average of 35 MGD but may be changed manually. The recirculation flow is divided over the 20 trickling filters, where half of the flow is sent to the 10 filters on the East Bank, and the other half flows to the 10 filters on the West Bank.
Methods The test bed was a concrete well inside the bed of rock media. This concrete well allowed for testing of other trickling filter media without disrupting the operations of the plant. The dimensions of the test bed are 49 inches length, 39 inches wide, and 78 inches deep. The total volume of the test bed is 149,058 in3 , making the test bed 1 /12 the scale of the entire trickling filter. Figure 1 below shows the test bed containing SuperBiomedia.
SuperBiomediaTM pieces were packed into a mesh bag and then placed into the concrete test bed, which remained open to atmosphere. Wastewater flowed through the media before exiting through the bottom. A funnel and open container were positioned below the test bed to collect samples after passing through the SuperBiomediaTM. Collected samples were periodically withdrawn over several months from this container and analyzed by an EPA-approved laboratory located in Ohio. Samples were collected from April 3rd , 2019 until February 12th, 2020 to compare performance during varying temperature conditions.