Filtration Station: Optimizing a Hydroponics System Using Diversified Natural Filters

Overview

Purpose: This experiment examined which ratio of filtration materials—pebbles, sand, and charcoal—effectively purifies water to maximize lettuce growth in a hydroponic system compared with an equal-parts control filter. It was hypothesized that one part sand, one-part pebbles, and two parts charcoal would yield the greatest growth. Procedure: Four filters with varying material ratios were constructed. A total of 60.57 L of lake water was collected and filtered into four hydroponic systems. Turbidity and pH levels were recorded before and after filtration. Lettuce growth was measured weekly for 4 weeks. Results: Compared to the Equal Parts control filter which grew 17.58 cm, the Double Charcoal filter produced the highest average plant growth, with a 31.97% increase (23.2 cm) over four weeks. The Double Sand filter followed with 28.16% growth (22.53 cm), while the Double Pebbles filter showed 11.04% growth (19.52 cm). pH levels remained constant at 7.0 across all systems. Turbidity decreased from an initial range of 25–50 NTU to 5–10 NTU for all filters. Results calculating non-surviving seedlings were considered secondary. Discussion: Filters containing higher amounts of charcoal were most effective, consistent with research showing charcoal’s strong purifying ability due to its porosity. While turbidity decreased equally among filters, plant growth varied, suggesting charcoal improved water quality beyond clarity. Limitations include using plant height as the sole growth indicator, minor material loss during filtration, variations in light exposure, and partially treated lake water. Conclusion: The Double Charcoal filter most effectively supported plant growth, supporting the hypothesis that increased charcoal improves water quality in hydroponic systems

Competition history

• CSEF 2026 Environmental Engineering (Junior Division) · Entry J-11-39

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