A new version of the WHO Guidelines for the Safe Use of Waste Water, Excreta and Greywater in Agriculture and Aquaculture has been released in 2006. These guidelines, among other things, establish criteria for the helminth ova content, considering them as one of the main targeted pollutants for developing countries. However, in spite of this breakthrough and the fact that helminth ova have been considered the main health risk when wastewater is reused for irrigation or aquaculture, relatively little information exists on how to remove and inactivate helminth ova from wastewater and sludge and, consequently, there are few technological options for controlling them. Moreover, it is still common nowadays to find recommendations on how technology can be applied to solving this problem based on data related to the inactivation of thermo-tolerant coliforms, even though it is well known that these are not indicators of helminth ova behavior. Furthermore, treatment methods are unable to produce treated wastewater and sludge with the low helminth ova content required by such criteria due to the high initial content found in the developing world. Due to the great need to apply adequate control methods in developing countries to address helminthiasis problems, this paper presents useful information for environmental and sanitary engineers concerning: (a) the general characteristics of the helminth ova; (b) the common helminth ova genus found in wastewater and sludge around the world; (c) the reason why common water and sludge disinfection methods are not effective at inactivating helminth eggs; (d) the main removal and inactivation mechanisms, (e) the processes that in practice have effectively removed or inactivated helminth ova and (f) how its content is measured in wastewater and sludge.

Bibliographic information

Jimenez-Cisneros, B. E. (2007). Helminth ova control in wastewater and sludge for agricultural reuse Chapter in Water and Health (editor: W. O. K. Grabow) in Encyclopedia of Life Support Systems (EOLSS), UNESCO, Eolss Publishers, Oxford, UK

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Food security and productive sanitation (WG5)Faecal sludge treatment processesEnglish

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