ROOF WATER-FARM Greywater Hydroponics & Aquaponics Research Project

Summary

ROOF WATER-FARM was a German research project (roughly 2013–2018, led by TU Berlin with partners) that explored how buildings can treat their own wastewater streams and reuse them for urban food production. Its demonstration and test site at Block 6 in Berlin-Kreuzberg — a housing block with an ecological water concept dating back to the 1987 International Building Exhibition — treated the greywater of ~250 tenants to bathing-water quality in an on-site water-processing house, then used the reclaimed water in a rooftop/courtyard "water-farm" greenhouse for hydroponic vegetable cultivation and aquaculture/aquaponics (fish rearing), and produced liquid fertilizer from blackwater for hydroponic plant production. Research components included hygienic-quality testing of reclaimed water, analysis of micropollutants (pharmaceutical residues such as diclofenac, ibuprofen, carbamazepine), and development of procedural data, sustainability assessments, and operator models for commercial and non-commercial rooftop replication. The project is a reference case for the water–energy–food nexus in cities: it showed that building-integrated greywater recycling can supply hydroponic and aquaponic food production, and it spawned a broader scientific literature on greywater-fed hydroponics, including health-risk assessments of lettuce grown on treated greywater.

Guiding Principles

Circular Economy: The project's core is closing urban water and nutrient loops at building scale — greywater becomes irrigation water, blackwater becomes fertilizer, and food is produced where people live.
Modularity: The demonstration site was designed to generate transferable "ROOF WATER-FARM technology" components and operator models replicable on other rooftops and courtyards.
STEM Integration: The test track explicitly produces procedural and static data for engineering, water chemistry, and sustainability analysis — an interdisciplinary research infrastructure spanning environmental engineering, horticulture, and urban planning.

Learning Outcomes & Transferable Skills

For researchers and advanced students, the project builds Water Chemistry expertise (treatment quality, micropollutant fate, hygienic assessment), Systems Thinking (coupling building water management with food production), Data Literacy (long-term monitoring of the demonstration system), and Sustainability Literacy around urban resource loops. For communities, it demonstrates a concrete Food Production pathway that does not compete for freshwater.

How to Replicate or Build On It

Start at roofwaterfarm.com (English/German) for the Block 6 demonstration-site description, technology components, and project timeline.
Read the follow-on peer-reviewed literature for transfer detail: e.g., Eregno, Moges & Heistad (2017), "Treated Greywater Reuse for Hydroponic Lettuce Production in a Green Wall System" (MDPI Water 9(7):454), and "From shower to table" (IWA Blue-Green Systems, 2024) on micropollutants in greywater hydroponics.
Replication at small scale: a treatment column (e.g., Filtralite + activated carbon) feeding a flush-and-drain hydroponic bed; nutrient supplementation (the literature used stored urine or commercial solution) is necessary — raw treated greywater alone does not sustain crop growth.
Check local water-reuse regulation first (e.g., EU Regulation 2020/741 categories for reclaimed water contact with food crops).

Considerations & Constraints

Cost: High — the Berlin site was a federally/state-funded research installation; building-integrated plumbing (dual greywater piping, treatment house) is a capital project, not a hobby build.
Skill Level: Advanced — requires wastewater treatment, plumbing, and horticultural competence; suitable for universities, municipalities, and experienced practitioners.
Space/Climate: Demonstrated on temperate-climate rooftops/courtyards with greenhouse protection; building plumbing retrofits are a prerequisite.
Tools Required: Greywater treatment train (filtration columns, activated carbon), pumps, hydroponic beds, water-quality lab access for hygienic verification.
Ongoing Maintenance: High — continuous treatment-system operation, water-quality monitoring, and regulatory hygiene checks.
Access Barriers: Project concluded; website is archival in nature. Full engineering detail lives in project reports and journal papers (some paywalled); food-safety rules for greywater-grown produce vary by jurisdiction and may prohibit certain uses.

Prerequisites

Foundational understanding of hydroponics and water quality; see ARC Climate-Smart Agriculture Training Manual (South Africa) for water-scarcity framing and classroom-scale alternatives before attempting building-scale reuse.

Primary Source

ROOF WATER-FARM project website: http://www.roofwaterfarm.com/en/