Filter Our Future: How Biochar Can Save the Bay of Quinte

Transcript: Excess phosphate in the Bay of Quinte causes algae overgrowth and threatens ecosystems and surrounding communities. My project studied the main source of phosphate pollution and explored a technical solution to reduce the phosphate loads. I conducted field surveys of five tributaries—Trent, Moira, Salmon, Napanee River and Wilton Creek. Water samples were collected at upstream and mouth of each tributary, before and after rain. Multiple water quality parameters, including phosphate, were tested. Results showed the Trent River accounted for 90% of the total phosphate load in the Bay of Quinte. I then explored biochar adsorption as a possible phosphate reduction method. A multi-media filter containing gravel, sand, and varied quantities of biochar reduced phosphate up to 53%. My results show that this is an effective, scalable approach to reduce phosphate pollution in the Bay. My future work involves implementing this solution on the Trent River and confirming economic and ecological feasibility.

Last summer, my family and I took a road trip and visited Lake on the Mountain. The water was so clear, even the deepest parts were visible. After, I went on the Glenora Ferry in the Bay of Quinte (BOQ) and the water beneath was completely green, filled with algae. I was concerned why it looked that way. From my research, I learned that the Bay has been struggling with water quality for decades, and that the algae overgrowth was caused by excessive amounts of nutrients like phosphate.

The BOQ is not only essential for tourism and local businesses, but it also provides drinking water for the 200,000+ residents in the greater BOQ region. The Bay of Quinte Remedial Action Plan has upgraded sewage waste treatment plants and regulated agricultural runoff, but the algae overgrowth could get worse as the Bay continues to be subjected to phosphate loadings from population increase, land use development and climate change. Water quality is an important topic to me, and I wanted to help.

My project focuses on two objectives: identifying which of the five major tributaries—Trent River, Moira River, Salmon River, Napanee River, and Wilton Creek—contributes the most phosphate to the Bay, and to explore a solution to reduce these phosphate loads.

My solution can help clean the Bay so surrounding communities can have cleaner drinking water and beaches.

Objective: Identify which tributary contributes the most phosphate and test a solution to reduce it.

Hypothesis: The Trent River will have the highest phosphate levels, and biochar will reduce them effectively.

Variables:

Independent: treatment type, biochar amount/type.

Dependent: phosphate levels.

Controlled: testing environment, equipment, and test solutions.

Field sampling and testing:

Sampling sites were identified along five tributaries. At each site, two 200 mL water samples were collected. This process was repeated 48 hours after rainfall to compare conditions. At each sampling location, pH, total dissolved solids (TDS), and water temperature were measured on site. Water samples were stored in a cooler and later analyzed in a controlled environment. For phosphate testing, 10mL of each sample was placed into a cuvette and analyzed using a Hanna Checker, following manufacturer instructions. Tap water was used as a control in all tests.

Biochar experiments:

Calcium-enhanced biochar was prepared by removing inner membranes from clean eggshells, boiling for 10 minutes, baking at 120°C for 15 minutes, and crushing finely.

Because winter conditions made bay water unrepresentative, a synthetic phosphate solution was created by dissolving 1.15g of 20-20-20 Miracle-Gro fertilizer in 1 L of tap water to achieve ~490 ppm phosphate. A diluted test solution (~1 ppm phosphate) was then made by mixing 5mL of this stock solution with 2 L of tap water.

Multi-media filters were constructed using drilled 500 mL–1 L plastic bottles. Each filter was layered with approximately 2.5 cm of aquarium-safe gravel, filter sand, and varied amounts of biochar (15g, 30g, or 60g), repeated as needed.

Before testing, each filter was rinsed with tap water. Once drained, 300 mL of test solution was poured through the filter. After all the water passed through the filter, phosphate levels were measured. Each condition was repeated for consistency.

Conclusion:

My field sampling in summer 2025 confirmed Trent River is the biggest contributor to the phosphate loads in the Bay, it contributes 89.56% of phosphate out of all the tributaries into the Bay, which helps me to focus on Trent River for phosphate reduction, because it is the biggest source.

My multi-media filter prototype with 15 g ultra fine biochar successfully reduced the phosphate levels by ~25%. In the 2x scale-up test, the multi-media filter with 30 g ultra fine biochar successfully reduced the phosphate levels by ~35%. In the 4x scale-up test with 60 g of biochar, it increased the phosphate reduction rate to ~53%. I compared the percentages of phosphate reduction with the amount (g) of biochar in the filter and confirmed that there was a very linear correlation (R²=0.9993). Calcium-enhanced biochar didn’t improve the phosphate reduction efficiency compared with biochar, therefore I decided to focus on only using biochar in the rest of the experiments.

Besides phosphate, at each sampling point, pH, water temperature, and total dissolved solids (TDS) were measured before and after rainfall. These parameters were analyzed to identify potential relationships with phosphate levels. When plotted against phosphate data, no linear correlation was observed, and no other clear relationships were identified within the dataset.

Discussion:

After rainfall, phosphate levels at the Trent River mouth decreased by 33%. This is unusual, as rainfall typically increases phosphate through runoff. A possible explanation is that increased water volume and flow during rainfall flushes stagnant water from the area, where phosphate tends to accumulate. This flushing effect may replace higher-phosphate water with fresher, lower-phosphate inflow, resulting in the observed decrease after rainfall.

At the Belleville Sewage Treatment Plant, phosphate levels increased by 240% after rainfall. This may be linked to the adjacent Belleville Turtle Pond, where sediments such as algae and sludge accumulate under normal conditions. Rainfall likely disturbs and releases these sediments. Because the pond is connected to the bay, phosphate-rich water may be flushed into the sampling area, elevating phosphate concentrations after rain.

At the Napanee River mouth, phosphate levels increased ~140% after rainfall, while only a 40% increase occurred upstream. This may result from converging water flows: Bay water flows downstream from the West meeting Napanee river coming from the East, then mixing at the Napanee mouth. This convergence likely accumulates phosphate, leading to higher concentrations after rainfall.

The purpose of this project was to identify which of the five tributaries in the Bay contributed the most to the phosphate loads and to propose an effective solution to reduce phosphate in the Bay.

Based on the results, I found that Trent River was, by far, the biggest contributor to phosphate loads in the Bay, contributing almost 90% of all the phosphate from the five tributaries. This supports my hypothesis because I speculated Trent River would be the biggest contributor due to its size, which was proven so.

In addition, a multi-media filter with approximately 2.5 cm each of gravel, sand, and varied quantities of biochar is the most effective solution to reduce phosphate in water. 15 g biochar reduces the total phosphate up to 25%. I doubled the biochar amount to 30 g, which successfully reduced phosphate up to 35%. Using 60 g of biochar, it increased the reduction to around 53%. I compared the percentages of phosphate reduction with the amount (g) of biochar in the filter and confirmed that there was a very linear correlation (R²=0.9993).

When I performed my biochar experiments, the Bay was frozen and its water was not representative, so I created a synthetic phosphate solution by mixing fertilizer containing phosphate into tap water. As a next step, I will repeat the experiments using real Bay water to confirm the effectiveness of my solution. My next scale-up will involve testing on a small creek near a farm where agricultural runoff drains in, using a multi-media filter to reduce phosphate levels. If successful, I will evaluate potential implementation at a dam near the Trent Water Treatment Plant on the Trent River.

Thank you!

To my family for supporting me, driving me to locations, helping me when I had questions and needed equipment.

To my friends who always encouraged me and asked me questions.

To my QRSTF judges and special awards sponsors - City of Belleville and SHAD Community Changemakers.

To Quinte Conservation, for providing me with resources and guidance in my project.

And lastly, sincere thanks to my CWSF delegates who volunteered their time to mentor Team Quinte.

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IMAGES

[13] Utah State University Extension. (n.d.). [Diagram explaining eutrophication process] [Online image]. Utah State University Extension. https://extension.usu.edu/waterquality/research/eutrophication

[14] University of Minnesota Extension. (n.d.). [Agricultural drainage pipe discharging into a creek] [Photograph]. University of Minnesota Extension. https://extension.umn.edu/agricultural-drainage/how-agricultural-drainage-works

[15] Canva. (2026). [Conceptual illustration of a multimedia filter installed on a dammed river] [AI-generated image]. Canva Magic Media. https://www.canva.com/

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[17] Quinte Conservation. (n.d.). [Quinte Conservation logo] [Photograph]. Quinte Conservation. https://www.quinteconservation.ca/

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