CIBATH Biofilter

Overview

A DIY biofilter designed to remove micro- and nanoplastics from tap water using biological filtration media — a practical, home-scale approach to a growing environmental health concern.

Problem

Micro- and nanoplastics are present in tap water worldwide. Commercial filters aren’t designed to target particles at the nanoscale. There’s no affordable, accessible home solution.

Approach

• Design a gravity-fed or low-pressure biofilter using layered biological media
• Biofilms on sand/gravel media act as “irreversible traps” for nanoplastics
• Test before/after water quality (within the limits of home testing)
• Iterate on media types and flow rates

Open Questions

• What filter media candidates for v1? (Sand, activated carbon, biochar?)
• What “success” measurement is feasible at home?
• Flow rate vs. filtration efficiency tradeoff
• Maintenance schedule — how often to clean/replace media?
• Safety — is the filtered water safe to drink, or demonstration-only?

Research Plan

Research Question

Can a gravity-fed layered biofilter using sand, gravel, and biochar achieve measurable reduction in micro- and nanoplastic concentrations in Swiss tap water at the home scale?

Milestone 1 — Literature Review & Hypothesis

Goal: Formalize existing research into a structured review, define the experimental plan.

• Synthesize research notes into a proper literature review covering:
  • Nanoplastic composition and behavior in tap water
  • Biological filtration mechanisms (biofilm adhesion, enzymatic degradation)
  • Existing pilot projects (BIOFOS Copenhagen, Eawag Switzerland)
• Define a testable hypothesis and scope (what the filter targets, what it doesn’t)
• Identify measurement strategy:
  • Home instruments: turbidity meter, TDS meter, particle counter
  • Professional: contact Eawag or a local Swiss lab for before/after water sample analysis
  • Be explicit about what home measurements can and cannot prove
• Write up experimental methodology (media selection rationale, test protocol, data collection plan)

Publish: Blog post — open lab notebook with literature review, hypothesis, and experimental plan Video: “I’m building a biofilter to remove nanoplastics — here’s what the science says”

Milestone 2 — Filter Design & Build (v1)

Goal: First working prototype.

• Select and justify media stack from literature (sand, gravel, activated carbon, biochar)
• Design housing: gravity-fed, food-safe container, 3D-printed manifolds for inlet/outlet
• Document full BOM, CAD files, assembly process
• Begin biofilm conditioning (weeks of flowing water to establish biological layer)
• Log conditioning progress (visual changes, flow rate over time)

Publish: Open design files (CAD, BOM, assembly guide) on GitHub Video: “Building the biofilter v1” — design decisions, science behind each media layer, biofilm timelapse

Milestone 3 — Baseline Testing

Goal: Establish what the filter measurably does.

• Run before/after measurements over several weeks as biofilm matures:
  • Turbidity (NTU)
  • Total dissolved solids (ppm)
  • Flow rate (mL/min)
  • pH, temperature
• Send paired water samples (unfiltered + filtered) to a professional lab for particle analysis
  • Budget for 2-3 lab tests across the project lifecycle
• Log all data systematically (timestamped, raw values, conditions)
• Be transparent: state clearly what home instruments measure vs. what they don’t

Publish: Raw data on GitHub, blog post with methodology and initial results Video: “Does the biofilter actually work?” — testing process, explaining what each measurement means, honest about limitations

Milestone 4 — Iteration & Optimization

Goal: Improve filtration performance based on data.

• Build a second filter to enable A/B testing
• Vary one parameter at a time:
  • Media composition and layer depth
  • Flow rate (adjust head height)
  • Biofilm maturity (age of filter)
• Track maintenance: clogging rates, backwash frequency, media replacement intervals
• Document failure modes (channeling, biological contamination, flow bypass)
• Send second round of lab samples after optimization

Publish: Updated dataset, iteration log with before/after comparisons Video: “What went wrong and what I changed” — real engineering iteration, failure modes, improvements

Milestone 5 — Formal Write-Up & Publication

Goal: Compile findings into a publishable paper.

• Structure: introduction, methods, results, discussion, limitations, conclusion
• Frame the contribution as citizen science methodology for home-scale water filtration assessment
• Preprint first on Zenodo or OSF (gets a DOI immediately)
• Target journals:
  • Citizen Science: Theory and Practice
  • PLoS ONE
  • JOSS (if significant software/tooling is produced)
• Include all raw data and design files as supplementary material

Publish: Preprint → journal submission Video: “I published a research paper on my DIY biofilter” — the story of doing independent research, the process, what was learned

Notes

• Timeline estimate: ~12 months total alongside other projects. M1-M2: ~2-3 months. M3: ~2 months (data collection takes time). M4: ~3 months. M5: ~2 months.
• Key credibility move: Professional lab analysis. Even 1-2 tests bridge the gap between home-instrument proxies and real nanoplastic measurement.
• Eawag connection: They are doing exactly this research in Switzerland. A cold email explaining the citizen science angle may open doors for collaboration, equipment access, or at minimum guidance on measurement methodology.
• Videos are not a separate track. The camera rolls during the research. Each milestone naturally produces both a publication artifact and video content.
• Safety: Until professional lab results confirm safety, all filtered water is for demonstration and measurement only — not drinking.

References

Log