A homemade recipe for a completely sustainable sewage treatment process

by Gastón Gertner

How to treat wastewater in an environmentally friendly and cost effective manner.

 

This summer, I got to know Violeta Reynal and Ezequiel Bella in Villa La Angostura, on the shores of Nahuel Huapí Lake in Argentina. Thirty-something, married, and fed up with the chaos of Buenos Aires, they decided on a change of lifestyle after a year of living in India.

So they built their home in the middle of Patagonia, using clay for the floor and walls and cypress trunks for the beams. Despite the seemingly basic nature of these materials, the design of the house takes even the smallest detail into account, from the natural way the temperature is controlled to measuring energy consumption.

But what left me speechless was the fact they had implemented an individual waste water treatment system that was completly sustainable . With their own hands! This home is undoubtedly the dream of supporters of sustainable development eager to find ways to mitigate the effects of climate change. Do you want to know more about how a house like this works?

 

A bed massage for treating greywater

The water treatment system built by Violeta y Ezequiel is an eco-friendly septic water system that makes use of reed bed technology. 

Think of reeds and rushes being planted on soil for infiltration, and the soil being filled with stones (gravel). On coming into contact with the flow of greywater, this reed bed treats the waste water four ways :

1. The purifying action of millions of bacteria and microorganisms living in the reed bed ecosystem “digest” the waste.
2. The spaces between the small stones allow filtration to take place.
3. The reeds and rushes act as oxygen-carrying vessels and allow the microorganisms to do their job.
4. The roots of the plants themselves purify the water by absorbing excess nutrients.

 

The water treatment system: step by step

Waste water from the shower, clothes washing and the kitchen is taken via pipes to the biodigester. This is an “enhanced septic tank,” in the shape of a cone, that is placed below ground level and has a red tube sticking above the surface to allow gases to escape.

The function of the biodigester is to help separate solid waste matter in the water (such as food or soap remains), forming a sludge base at the bottom and a floating crust on the surface . The solid remains are removed every two years as part of the maintenance routine for the chamber.

The biodigester also aids in the digestion of solid matter, reducing the pollution potential of the waste before the treatment of the greywater begins.

The water flow then follows toward the inspection chamber. The condition of the

water coming out of the biodigester is assessed at this stage, and an extra barrier to any fats or grease is added so as to prevent their entering the reed bed.

The bed lies in a space filled with layers of stones that are some 70 centimeters deep. On top of the bed, reeds and rushes grow, along with  a nice-looking myrtle plant (luma apiculata) in the middle. A nylon sheet is placed under the stones to prevent the waste water filtering into the groundwater.

The water effluent enters the bed from the inspection chamber through a pipe, filtering into the spaces between the pebbles. The remains of organic materials are separated out of the water and settle between the roots and the stones. At this stage, bacteria and microorganisms break down any pollutants.

Finally, on leaving the reed bed, the effluent continues its journey to the pond that is positioned next to a rich community of reeds, whose roots extend all the way to the bottom. The water then reaches a third stage of natural treatment in which the natural vegetation completes the process of breaking down nitrates within a life-giving ecosystem for birds, plants, and insects.

When it leaves the pond via a natural overflow, the treated water naturally irrigates native trees and plants, which enjoy very high growth rates. As a future improvement to the system, Ezequiel and Violeta are working on installing a wind turbine that will power an air compressor, with the aim of oxygenating the pond for the “fishes that will come.”

Ezequiel, who has a degree in Software engineering  from the University of Buenos Aires, summarizes the system in a natural way: “The roots of the plants and the bacteria digest most of the waste. This treatment of dirty water completes its cycle by itself and is 100 percent sustainable.”

 

The profile behind a leader in sustainability

Studying the evidence is a basic requirement for self-taught proponents of sustainable development. “I read all the documents you might imagine before starting,”  Ezequiel explains. “I began to research reed beds, and I discovered that they were the best way to complement the action of the septic tank before returning the water to its natural course.”

However, the engineering skills and know-how needed to design this cost-effective system aren’t the only requirements. They must be complemented with an appropriately sustainable lifestyle. Besides the maintenance tasks, the system also requires dedication.

“We don’t use any conventional detergents, bleaches, shampoo, toothpastes, or soap powder for washing clothes. We use biodegradable white soap to wash our clothes, with natural essences for fragrance and vinegar to remove any fats,” Violeta emphasizes.

The responsibility also comes at a price, as maintenance of the reed bed exposes people to viral and bacterial vectors. So appropriate immunization and frequent health check-ups are recommended.

Responsible use of water is really important for these individual solutions. The night they invited us to dinner ended up being a wonderful evening. Like any good guests, my girlfriend and I offered to wash the dishes. We didn’t get to wash three pieces of cutlery before our hosts took over the job from us because  of our unintentionally inefficient and waste use of the water.

A lesson learned: the sustainable use of water needs to be constant, even when on vacation.

Thanks to @mekiwerner for her patience in taking the photos.

 

Gastón Gertner is a consultant in the Office of Strategic Planning and Development Effectiveness at the Inter-American Development Bank. At the IDB, he supports the design and implementation of impact evaluations and surveys in different areas, including social protection, human development, and water and sanitation projects addressing child nutrition, early childhood development, drinking water systems in rural areas, and mechanisms incentives for connecting households to sewer systems. Gastón earned a Masters in Public Affairs from Princeton University, where he specialized in development studies. @GastonGertner