Harmful algal blooms are a growing concern in the US, they are caused by nutrient (nitrogen and phosphorus) accumulation in bodies of water. As a result, stricter effluent restrictions are being placed on nutrient point sources, including wastewater treatment plants. Tertiary nitrification is a solution to meet these new restrictions.

Figure 1: A beach that has been closed due to a harmful algal bloom at Moreau Lake State Park, New York

• Tertiary treatment is the final process in wastewater reclamation where nutrients and other inorganic chemicals are removed before the water is discharged to the receiving water body. This helps to reduce the nutrient load on the receiving body of water.

• Nitrification, is a tertiary treatment process where ammonium is converted to nitrate as follows:

𝑁𝐻4+ + 𝑂2 → 𝑁𝑂2

− + 3𝐻+ + 2𝑒−

𝑁𝑂2− + 𝐻2𝑂 → 𝑁𝑂3

− + 2𝐻+ + 2𝑒−

• Traditional suspended growth nitrification methods require costly downstream processing to remove the suspended growth from the now clean water.

• Attached film growth technology, like an MBBR, which grows nitrifying bacteria on the surface of carriers (shown below) reduces costly downstream processing by reducing biomass production.

Capstone Design | December 9, 2019

Design and Construction of a Pilot Scale MBBR for Tertiary Nitrification

Jeffrey Crandall | Dylan Ellis | Brayden Llewellyn | Dr Ron Sims | Mark Biesinger

Theoretical DesignIntroduction

Future Work

•WesTech-Inc supplied the reactor, carriers, pumps, air compressor, and other equipment• Goal of 6 hour hydraulic retention time.o Temperature and the breaker tripping from

space heaters caused varying retention times resulting in sporadic removal efficiencies.

o Heat trace and PVC pipes were used to insulate pipes and keep them from freezing.

• DO, pH, temperature, and ammonia levels in the influent and effluent were measured.Figure 2: Carriers used in the MBBR provided by WesTech-Inc

ResultsNitrification started on November 12, 2019 and sampling occurred through December 6, 2019. Influent and effluent levels are shown in Figure 4. Alkalinity was measured at 362 mg/l at the influent and 340 mg/l at the effluent, well above the necessary range. DO and pH of the reactor ranged from 8.6 to 12.3 mg/l and 6 to 7 respectively.

Removal efficiencies ranged from 6.7% to 96.8%. Sporadic removal efficiencies were caused by different hydraulic retention times (HRT) from flow rates changing as temperature caused pipes to freeze as well as other issues with retention time.

Design requirements

• Flow rate: 1.5 million gallons per day

• BOD: reduce from 225 mg/l to 30 mg/l

• TKN: reduce from 45 mg/l to 5 mg/l

• TSS: reduce from 250 mg/l to 30 mg/l

• Operating temperature: 15 – 22 C

• 5000 ft elevation

• DO concentration of 6 mg/l

• Specific surface area 800 /m

• Carrier fill ratio = 0.6

Using methods from Metcalf and Eddy, WEF Manual of Practice 8, and Suncam Online Course, design calculations were performed, and a sizing script was created in python.

Design Calculations

• Tank volume:

o 15 C = 424 m3

o 22 C = 286 m3

• Hydraulic retention time:

o 15 C = 68.9 min

o 22 C = 46.4 min

• Aeration requirements: 5546 m3air/day

• Equipment prior: Primary clarifier

• Equipment after: Phosphorus Removal and Denitrification along with a secondary clarifier to remove any biomass from solution

Figure 3: Flow diagram of the pilot scale MBBR showing bacterial growth on carriers. Bacteria take up ammonium and perform nitrification by using it as an energy source for cell metabolism and biomass growth. By doing this the cell converts the ammonium into nitrate, removing the it from the water.

Pilot Scale MBBR

➢ Repeat pilot study at Logan Lagoons with more controlled flow rate and temperature to determine the effects of HRT and temperature on nitrification.

➢ Investigate technology as a potential to be used as secondary treatment (BOD removal).

Additional Studies

Acknowledgements

We would like to thank the USU department of biological engineering, WesTech-Inc., and Mark Biesinger for their extensive help in supporting this project.

Figure 4: Pilot influent and effluent concentrations over time. The space heaters were installed on Nov. 15 and stopped working on Nov. 18, and Nov 27. The latter resulted in the system freezing.