60-Second Science

Low-Tech Wastewater Treatment Recipe Features Onions

Powdered onions sopped up most of the lead, iron and tin in wastewater samples laden with the metals. Christopher Intagliata reports

Onions and garlic add pizzazz to your cooking. But they can also do a more distasteful job: onions and garlic can suck heavy metals from industrial wastewater. So finds a study in the International Journal of Environment and Pollution. [Rahul Negi et al., Biosorption of heavy metals by utilising onion and garlic wastes]

Good recipes start with the right ingredients. So Indian researchers rounded up onion and garlic peels from the canning industry, and dried and powdered them. They got industrial runoff from an electric motor factory in Delhi, laced with pollutants like arsenic, iron, lead, nickel and tin. They spiked that runoff with even more heavy metals. And then added a pinch of onion powder.

In just half an hour, the onion gunk mopped up nearly 70 percent of the lead, iron and tin in the wastewater. It might work because onions and garlic contain a dietary fiber called inulin, which can bond with metal ions.

Conventional wastewater treatment is pricey—small industries in developing countries can't afford it. So low-tech solutions like this might help clean up waterways like India's Yamuna River—a waterway so polluted that it might be freshened by onions and garlic.

—Christopher Intagliata

[The above text is a transcript of this podcast,]

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