DIY Domestic Greywater Treatment

We had plumbing repaired in May and that also became the opportunity to find a way to treat domestic wastewater so that it can be diverted into the garden. Since sewage systems aren’t centralised in our village, it is important that we treat our wastewaters locally and in a way that is responsible.

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Above: Some of the drawings and plans we made to help build our greywater treatment systems.

In households in our village, domestic blackwater goes into a septic tank whilst greywater goes into the nearest empty plots. We have our own septic tank and our greywater went into a concrete water feature in the garden. This water feature often flooded especially in the rainy season, and wastewater just filtered into the ground. What we wanted was a system that not only filtered greywater, but also diverted it to good use in the garden. Additionally, we decided to separate kitchen greywater and bathroom greywater to lessen the load on our selected methods of treatment.

Treating Kitchen Greywater

Kitchen greywater goes though a pipe and gets filtered in a DIY grease trap (refer to links to resources below to learn how to make a Grease Trap). From the grease trap, the water pours into a constructed wetland – or what may be called an infiltration planter – built next to the rainwater fishpond. The infiltration planter is filled with layers of gravel, a fine mesh netting, sand and soil. Plants are grown in the infiltration planter to help treat the greywater. As greywater filters down the planter, excess water flows out into a lower bed of plants.

View of the Grease Trap.
Grease Trap – bucket with strainer on top to filter out food debris. Refer to links below on how to make a Grease Trap.
Accumulated grease in the Grease Trap.
Internal construction of the Grease Trap – elbow and pipe sealed with Epoxy.
Grease Trap is cleaned next to the compost pit.

Treating Bathroom Greywater

Bathroom wastewater consists of water from the shower and the bathroom sink. This water goes through a pipe and flows out over a gravel path with cement lining to prevent the water from seeping directly into the ground. The gravel path goes along the house, into the garden and down to the duck pond, some 10 or so meters away. The assumption is that the greywater – along with rainwater during the rainy season – would be filtered appropriately by the time it reaches the duckpond, at the same time reducing soil erosion, since the ground slopes naturally towards the duckpond.

Ground has natural slope and the Gravel Path Filter is dug up in the direction of the slope towards the duck pond.
After digging, the path is cemented to prevent water from seeping into the ground along the house. The water needs to flow and get filtered by the gravel and ultimately flow into the duck pond.
Gravel placed into the path. The orange pipe is the bathroom greywater outlet.
A closer view of the Gravel Path Filter. The reservoir/pond catches rainwater runoff from the roof of the house and overflows into the Gravel Path Filter.
At the end of the Gravel Path Filter is the duck pond. Rocks are placed at the mouth of the Path to filter out larger debris.

 

The results

After nearly 3 months of use, together with the onset of the rainy season, our constructed wetlands are working beautifully! Plants are growing well in the infiltration planter, the gravel path has done away with mud and soil erosion in a large area along that side of the house. Some plants and grass have even started growing amongst the gravel. There is some odour coming from the infiltration planter but this is not irritating and the odour disappears very quickly. As more plants grow in the planter, we hope the odour will be further minimized. The DIY grease trap – a 5 gallon/10-liter capacity -requires some cleaning only every 2 months. The grease and debris collected is dumped into the compost pit.

Note that if any edible plants are placed in the infiltration planter, they should not be eaten.

Resources

If you are interested in building a constructed wetland system for greywater treatment in your own home, check first with local ordinances. Some municipalities, for example, that have centralised wastewater treatment facilities will not allow domestic greywater treatment because centralised wastewater (especially blackwater) treatment needs sufficient amounts of greywater for proper treatment.

If you are sure that constructed wetlands are allowed in your location, you can find basic information, designs, principles and examples of ecologically responsible wastewater treatment systems through the following resources. Our home set-up was inspired by these resources. Good luck!

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