Listen to the Waste Water Podcast: Pangea Podcast Episode 6: Waste Water Treatment

We explore sustainable liquid waste water treatment, focusing on greywater and blackwater systems utilized in Earthships and other sustainable building practices. It highlights the environmental and economic benefits of these systems, along with practical implementation guides and maintenance tips.

Key Ideas & Facts:

  • Greywater Re-use: Greywater, defined as “untreated wastewater which has not come into contact with toilet waste,” presents a significant opportunity for water conservation. “[On average] each person will use 80-100 gallons of water per day. The largest contributor to this use is flushing the toilet. Kitchen and bathroom sinks combined only use 15% of the water that comes into a home.” This system reduces potable water use by treating and reusing greywater for flushing toilets and irrigation.
  • Earthship Liquid Waste Water Treatment: Earthships employ a closed-loop system, treating greywater in interior botanical cells (indoor planters) and blackwater in exterior botanical cells. This allows for multiple uses of water, reduces strain on municipal sewer systems, and facilitates on-site, self-contained wastewater treatment.
  • Botanical Treatment Cells: These act like constructed wetlands, mimicking natural filtration processes. They comprise layers of rocks, soil, and carefully selected plants. “The botanical cells are lined and filled with large rocks, smaller rocks, dirt, topsoil and are sloped with a deeper well at one end.” The system can be completely bypassed with valves, allowing for connection to conventional septic systems for regulatory compliance and flexibility.
  • Plant Selection & Transpiration: Plants play a crucial role in these systems, utilizing, cleaning, and transpiring water. The document emphasizes the importance of plant selection based on water requirements, treatment capabilities, and companion planting principles. “Transpiration is the loss of water from plant leaves…The volume of water lost in transpiration can be very high…An acre of forest transpires even more.”
  • Construction and Maintenance: The document provides detailed instructions for constructing and maintaining both interior and exterior botanical cells, emphasizing conventional plumbing practices and the importance of observation and regular maintenance.
  • Economic and Environmental Benefits: Implementing these systems leads to lower freshwater consumption, reduced strain on municipal systems, and the reclamation of valuable nutrients in wastewater. The document argues that these benefits translate into tangible energy and cost savings while promoting sustainable water management practices.
  • Challenges and Future Outlook: While legal hurdles and the lack of widespread adoption pose challenges, the document remains optimistic. Growing awareness of water scarcity and the economic viability of greywater systems, exemplified by the City of Austin’s reclaimed water initiative, suggest a promising future for these sustainable solutions.

Quotes:

  • On the benefits of greywater systems: “The use of greywater results in lower fresh water use, less strain on failing septic tanks or treatment plants, less energy and chemical use, reclamation of otherwise wasted nutrients.”
  • On the design of botanical cells: “The design and layout of this plumbing system is completely conventional. The system is set up (via valving) creating loops which have the planters within them.”
  • On plant selection and transpiration: “Data is known for how much water certain types of plants will use, process, oxygenate and transpire.”
  • On the importance of maintenance: “Generally, maintenance in a sustainable home with the outlined liquid waste water system is less than a conventional home.”

Further Research:

  • Conduct a comparative analysis of different greywater system designs (e.g., evapotranspiration systems, shallow trench systems).
  • Investigate the legal landscape surrounding greywater use in different jurisdictions and explore potential solutions for overcoming regulatory barriers.
  • Analyze the economic viability of greywater systems in various contexts, considering factors like installation costs, water savings, and maintenance expenses.