Algal Biofilm Ammonia Removal Under Light Cycles

ISEF Category: Environmental Engineering

Subcategory: Bioremediation  ·  Difficulty: Intermediate  ·  Setup: School Lab  ·  Time: 1 to 2 Months

The Hook

Wastewater does not vanish after the toilet flushes. Small treatment systems still need ways to remove ammonia before water leaves the site. A tiny biofilm reactor gives you a chance to test how light affects that cleanup. You get a real engineering question, and you can measure the answer with simple water tests.

What Is It?

This project studies a mixed community of algae and bacteria growing as a biofilm. A biofilm is a slimy layer of microbes that stick to a surface and work together. In your reactor, the algae use light to make energy, and the bacteria help break down nitrogen compounds such as ammonia. Think of it like a tiny work crew on a wall, where each worker does a different job.

Ammonia matters because high levels can harm aquatic life and signal poor treatment. In septic polishing, the last treatment step cleans water before it returns to the environment. You are testing whether changing the light and dark pattern changes how fast the system removes ammonia. That gives you a clear link between biology, chemistry, and practical water treatment.

Why This Is a Good Topic

This is a strong science fair topic because you can vary one clear factor, the light and dark cycle, and measure one clear result, ammonia removal. The project connects to real problems in decentralized wastewater treatment, especially in homes, cabins, and small communities. You can learn reactor design, water testing, control setup, and data analysis without needing a university lab.

Research Questions

• How does the length of the light cycle affect ammonia removal rate in an algal-bacterial biofilm reactor?
• What is the effect of light to dark ratio on nitrate buildup during ammonia polishing?
• Does intermittent lighting improve total nitrogen removal more than constant lighting?
• To what extent does LED color change ammonia removal in the reactor?
• Which reactor flow pattern gives the most stable ammonia reduction over time?
• How does biofilm thickness affect ammonia removal under the same light cycle?

Basic Materials

• Fish tank pump or small aquarium air pump.
• Clear plastic tubing.
• Small clear container or jar reactor vessel.
• LED grow light.
• Aquarium test kit for ammonia, nitrite, and nitrate.
• Dechlorinated water.
• Fish food or household ammonia source for safe model testing, if approved by your teacher.
• Nonreactive surface or mesh for biofilm growth.
• Digital kitchen scale, 0.1 g accuracy.
• Thermometer.
• Notebook or spreadsheet for data logging.

Advanced Materials

• Peristaltic pump.
• Dissolved oxygen meter.
• pH meter.
• Spectrophotometer.
• Ammonium ion selective electrode or colorimetric reagent kit.
• Nitrate and nitrite analysis kits.
• Microscope for biofilm imaging.
• Slides or coupon materials for biofilm attachment.
• Light meter or PAR sensor.
• Incubator or temperature-controlled chamber.
• Membrane filters and filtration setup.
• Autoclave or sterile supplies, if your lab requires them.

Software & Tools

• Google Sheets: Organizes measurements, graphs trends, and compares treatment groups.
• ImageJ: Measures biofilm coverage and image-based changes over time.
• Python: Helps you run statistics, make plots, and test whether the cycles differ.
• RStudio: Supports cleaner statistical analysis and publication-style charts.
• NIH ImageJ documentation: Explains basic image measurement methods and calibration steps.

Experiment Steps

1. Define the treatment question you will test, then choose one light cycle variable and keep the rest fixed.
2. Design a reactor setup that keeps flow, surface area, and mixing as consistent as possible across trials.
3. Build a measurement plan that turns ammonia readings into a removal rate, not just a one-time concentration.
4. Plan controls that separate light effects from temperature, aeration, and starting ammonia level.
5. Decide how you will track biofilm growth, water chemistry, and cycling pattern together in one dataset.
6. Set your analysis plan before you start, including replicates, graphs, and the statistical test you will use.

Common Pitfalls

• Letting light also warm the reactor, which makes temperature changes look like a lighting effect.
• Changing starting ammonia levels between trials, which breaks fair comparison of removal rates.
• Letting the pump rate drift, which changes how long the water stays in contact with the biofilm.
• Using cloudy or dirty samples, which makes color-based ammonia readings hard to trust.
• Measuring only the final ammonia value and missing the full removal pattern across the cycle.

What Makes This Competitive

A competitive version goes beyond a simple before-and-after test. You would compare multiple cycle designs, keep strong controls, and report removal as a rate with replicates and statistics. You could also pair chemistry data with biofilm imaging, which gives a deeper explanation of why one setup works better. Strong entries often answer a practical engineering question and a biological question at the same time.

Project Variations

• Test whether red, blue, or white LED light changes ammonia removal more in the same reactor setup.
• Compare synthetic wastewater with diluted aquarium water to see how the microbial community changes performance.
• Measure how biofilm thickness or carrier material changes ammonia polishing under the same light cycle.

Learn More

• USGS Water Science School: Search for pages on nitrogen, ammonia, and water quality basics.
• NOAA Water Topics: Search for background on nutrient pollution and aquatic ecosystem impacts.
• NASA Earth Observatory: Search for articles on algal growth, eutrophication, and water quality.
• PubMed: Search review articles on algal-bacterial consortia, biofilm reactors, and nitrification.
• Environmental Engineering textbooks from your school library or OpenStax: Look for chapters on wastewater treatment and nitrogen removal.
• MIT OpenCourseWare: Search for environmental engineering or biological wastewater treatment lecture notes.