A Numerical Guide to Volume 2 of the Guidelines and Practical Advice on how to Transpose them into National Standards

[INTRODUCTION] In 2006, the World Health Organization published the third edition of the Guidelines, in collaboration with FAO and UNEP. The third edition consist of four volumes; volume 2, explained in this guidance note, addresses methods, procedures and guideline values for the safe use of wastewater in agriculture. In essence, the Guidelines are a code of good management practice. Volume 2 aims to ensure that health risks associated with the use of wastewater for irrigating crops (including food crops that are or may be eaten uncooked) are assessed and managed. Other than the 1989 second edition, this new edition therefore offers much more than a set of guideline values.

The new approach will challenge programme managers and engineers responsible for wastewater treatment and use who need to know how to use the recommended methods and procedures to design wastewater use systems that do not adversely affect public health. They will have to learn about and understand in detail the ‘numerical’ recommendations in the Guidelines so that the wastewater use systems they design are safe. However, it is not straightforward for these professionals to comprehend these numerical recommendations simply by reading the Guidelines − it requires a considerable amount of study and there are several concepts (for example, disability-adjusted life years) and topics (quantitative microbial risk analysis) with which few are familiar. They need a ‘Guide to the Guidelines’. The purpose of this Guidance Note is to provide programme managers and engineers with a succinct overview of new concepts and topics.