Floating Toilets

Wetlands Work!in Phnom Penh are Developing Plant-based Purifiers, Called Handy Pods

The natural instinct might be to make a deposit in the water. But that wouldn't be safe. Microbes in your feces would contaminate the water and could cause outbreaks of deadly diseases, like cholera.

A group of engineers in Cambodia wants to solve that problem for the floating villages ofTonle Sap Lake, the largest freshwater lake in Southeast Asia. Over a million people live on or around it. Exposure to wastewater spawns diarrhea outbreaks each year. In Cambodia, diarrheal diseases cause 1 in 5 deaths of children under age 5.

To help clean the lake's water, engineers at the companyWetlands Work!in Phnom Penh are developing plant-based purifiers, called Handy Pods. The pods are essentially little kayaks filled with plants. They float under the latrine of a river house and decontaminate the water that flows out.

Here's how it works. When a person uses the latrine, the wastewater flows into an expandable bag, called a digester. A microbial soup of bacteria and fungi inside the digester breaks down the organic sludge into gases, such as carbon dioxide, ammonia and hydrogen.

Some microbes in the waste survive that first step, but then they're washed into a pod filled with water hyacinth. The hyacinth roots have a large surface area to which the remaining bacteria stick. The water that runs off the roots into the lake is clean enough to play and swim in, Wetlands Work! founderTaber Handsays. But the water is still not safe enough to drink.

During a pilot project in 2013, Hand and his team gave pods to 35 houses in a village on Tonle Sap Lake. "The pods reduced E. coli in the ambient water by 50 percent," Hand says.

That wasn't as good as the pods' performance in lab tests, where they cut levels of E. coli by more than 99 percent. Hand thinks that's because real lakes have other sources of contamination besides latrines.

At the top of that list? Pigs. Pigsties around Tonle Sap Lake produce a tremendous amount of waste, Hand says.

"The floating communities of Tonle Sap Lake are one of the most challenging contexts for sanitation in the world," says environmental engineerJoe Brownof Georgia Tech, who isn't involved with the project. "Handy Pods are potentially a useful way for processing human excrement in this context."

But the floating toilets still have a ways to go before they are widely distributed.

For starters, Brown says, it's unknown whether the pods filter out viruses and parasites that cause diseases.Manmade wetlandsremove these pathogens, he says, so there's a possibility the hyacinth roots could also do it.

Source: NPR

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