Student - October 5, 2006

Big savings from new tapioca waste treatment

Wastewater from tapioca production in Vietnam can be treated using bacteria in an anaerobic reactor. According to Vietnamese PhD graduate Huynh Ngoc Phuong Mai, this form of ecological treatment is cheaper and reduces greenhouse gas emissions considerably.

Tapioca, a starchy product made from processed and dried cassava root, is used as a thickening agent in food in tropical countries. Most of the world’s tapioca is produced in Asia. The production process uses a lot of water, and the wastewater is often discharged into rivers and lakes.

Mai designed a wastewater treatment system based on the anaerobic UASB-reactor developed in Wageningen: ‘An important advantage of this technology is not only that it is space-saving, but that it uses far less energy, as it produces biogas.’

Despite the fact that the wastewater contains toxic cyanide, the results of laboratory tests were very encouraging. The small-scale pilot version of the technology, which was introduced at the start of this year in the province of Binh Phuoc, produced good results as well after some adjustments.

The technology would save an average tapioca factory, with a production capacity of 100 to 120 tons of starch per day, about a thousand dollars a day in energy costs, Mai calculated. An additional potential source of income is the considerable reduction in carbon dioxide emissions, which can be traded in the form of emissions rights under the Kyoto Protocol.

Under the new system, the treated wastewater can also be used for irrigation or aquaculture. According to Mai, it is ‘an almost perfect system for treating tapioca wastewater’ and it will be usable in other countries too. / Gert van Maanen

Huynh Ngoc Phuong Mai received her PhD on Tuesday 3 October. She was supervised by Professor Gatze Lettinga, emeritus professor of Anaerobic Treatment Technology.

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