Sustainable Wastewater Treatment for Homes & Communities

Greywater Reed Bed Systems & Blackwater Biodigesters

Whether you're building a new home, designing a residential complex, or just looking to reduce your water footprint, treating your wastewater sustainably is not only possible—it’s essential. In this article, we break down two simple and effective solutions you can implement on-site:  Greywater treatment using reed bed systems and Blackwater treatment using a bio digester septic tank

If you landed here after watching our reel, welcome! This blog continues where the video left off, giving you all the details you need. If you’re here for the first time—read on. You’re in the right place.

Understanding the Basics: Greywater vs. Blackwater

Before diving into treatment systems, it’s important to know the difference:

• Greywater is the relatively clean wastewater from bathrooms, sinks, showers, and washing machines. It contains soap and organic matter but not human waste.

• Blackwater is the waste that comes from toilets (water closets)—a mix of liquid and solid human waste.

Each type of water requires a different treatment approach.

Greywater Treatment Using Reed Bed Systems

Reed bed systems use natural filtration through gravel, plants, and sunlight to clean greywater, making it reusable for gardening and groundwater recharge. They are odor-free, low-maintenance, and incredibly efficient when designed correctly.

How the System Works

Cross section of a horizontal reed bed system

1. Pre-Treatment to remove particles, fats and solids. 

Grease Trap – Captures fats and oils from kitchen water. It can be installed for bathwater too if there is a usage of oil applications etc in lifestyle. 

Chamber top of grease trap

Grease trap inside chamber

Inside the grease trap

Baffle Tank – Is the first level of cleaning, slows down flow and separates solids; can be built with Kadapa stone slabs or waste granite as baffles.

Top of baffle tank

Inside the baffle tank

2. Reed Bed – This is the heart of the system, filled with layers of graded gravel (jelly stones) and planted with water-loving species like Canna indica or Phragmites, Cyperus Rotundus, Alocasia etc. This can be either a constructed tank or it could be made with reused containers of suitable sizes. 

   
   
   
   

   

   Reedbed and baffle tank constructed with masonry

3. Polishing Tank – An open tank where treated water is exposed to sunlight, further cleaning it and reducing pathogens. The polishing tank ca be covered with a steel mesh lid to prevent leaves, other debris from falling in. 

   
   
   
   

   

   Polishing tank with mesh lid made of MS

   
   

System Design: Key Considerations

• Sizing: Size of reed bed -  A general thumb rule is 1 sft of reedbed space for every 20 litres of grey water input into the bed. The exact size depends on daily greywater output from all the sources at the residence. Size of the baffle tank can be roughly one third the size of reed bed. The polishing tank size can be as to accommodate the total volume generated in one day or two days at the most.   

• How to calculate the volume of grey water output: A general thumb rule for this could be 120 to 150 litres of water per person in the household.

• Horizontal vs. Vertical Flow:

  • Horizontal flow is better for homes due to lower maintenance.

  • Vertical flow requires more precision but is more compact.

    
    

Material & Construction Tips

• Excavation: Depth of ~2–3 feet for each tank. Make sure there is atleast one foot of the tank above the natural ground level outside.

• Wall Construction: Use masonry or ferrocement plaster to prevent seepage. Waterproofing can be done too for the plaster.

• Filling Layers: Start with 120mm jelly at the base, 40mm jelly in the middle, and finer gravel or 20mm jelly near the top.

• Plants: Choose hardy species that thrive in wet, nutrient-rich environments and don’t clog the system. Canna indica, Phragmites, Cyperus Rotundus, Alocasia etc. can be used. Few people have experimented with banana plants as well but edible tuber varieties are not recommended for usage of the tubers.

  
  

Polishing Tank Guidelines

• Size it based on your total greywater outflow. You will need 1 cft of tank space for every 28 litres of grey water treated and let out.

• A submersible pump can be used to either pump the water up to reuse for flushing in water tanks or can be used directly to water the garden using a hand pump or submersible pump. 

• Treated water must be reused or discharged within 2 days to avoid mosquito breeding and odor.

• Keep the tank shallow, open to sunlight, and optionally add floating plants for aesthetics and added purification. Guppy fish can be added too to prevent mosquitoes but the system needs to be designed to accommodate the submersible pump in a different partition inside the tank.

Blackwater Treatment Using a Biodigester

Blackwater is traditionally managed using septic tanks, soak pits, or dry compost toilets—all of which have their challenges. But there’s now a better way.

What Is a Biodigester?

Originally developed by DRDO (Defence Research & Development Organisation), the biodigester is a sealed tank that uses bacterial cultures called bioenzymes to break down human waste anaerobically—without smell, without maintenance, and without ever needing to be emptied. The solid output is converted into water that is pure enough to be used for gardening or for recharging the ground water table. 

Biodigester made in RCC

Why Choose a DRDO-Approved Biodigester?

• No odor, no sludge removal

• No need for pumping or suction machines

• Can be safely recharged into the ground

• Cleared by Pollution Control Boards

• Licensed vendors manufacture and install these across India

Recommended Size

For a family of up to 10 people, a 3’ diameter x 4’ deep tank is typically sufficient. It can be buried underground, connected directly to your toilets.

Where and how to buy a Bio-Digester

You can find out more about the Biogester here. Biodigester link of DRDO govt of India for those who want to know more

https://www.drdo.gov.in/drdo/bio-digester 

Here is the list of approved Licensee vendors by Govt. Of India. You can look up the nearest suppliers for your location in the country. All India Approved manufacturers and Licensee list for those interested in buying.

http://drdoficciatac.com/biodigester/activetot.aspx 

Can You Use Regular Cleaning Products?

Although biodigesters are resilient to everyday use, it’s best to avoid harsh chemicals.

• OK: Mild soaps, biodegradable cleaners

• Use sparingly: Dishwashing liquids, floor cleaners

• Avoid: Acids, bleach, phenyl, and heavy-duty toilet cleaners

We strongly recommend switching to natural, toxin-free alternatives. For recipes and easy, economical options, read our next blog:

Toxin-Free Cleaning for a Healthy Home & Planet (Coming Soon)

Closing Thoughts

Integrating reed bed systems for greywater and biodigesters for blackwater is one of the most impactful things you can do for your home and the environment. These systems don’t just help you reuse and recharge water—they align your lifestyle with nature’s flow.

If you’re designing or upgrading your home, now is the time to plan for sustainable waste management. Got questions? Drop a comment or message us. Let’s make conscious living the new normal.

Here are a few pictures of a garden thriving with treated waste water. 

Don’t forget to:

• Save this blog for later

• Share it with someone building a home

• Check out our upcoming post on toxin-free housekeeping!