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Wastewater Treatment and Use in Agriculture is presented as a guide to the use of treated effluent for irrigation and aquaculture. This document presents the latest views on health risks, environmental hazards and crop production potential associated with the use of treated wastewater. It draws on the WHO Guidelines for health protection measures considered appropriate under various conditions. It explains the basis for conventional wastewater treatment processes and introduces natural biological treatment systems as viable alternatives in developing countries, particularly in hot climate regions. Recharge of aquifers as a means of treatment and indirect use of wastewater is covered in some detail.

An important chapter of this Irrigation and Drainage Paper concentrates on wastewater irrigation and deals with water quality requirements for optimum crop production and potential impacts on soils and crops. Principles of irrigation drawn from Irrigation and Drainage Paper 29 (Rev. 1) are applied to the specific use of wastewater for crop irrigation. Site and crop selection are discussed and irrigation system selection for treated wastewater delivery is reviewed.

As a by-product of conventional wastewater treatment, sewage sludge is introduced as a potential agricultural resource in combination with wastewater irrigation. Sludge characteristics and treatment are summarized and the limitations of land application are discussed. Potential effects on soils and crops are considered and suggestions made for planting, grazing and harvesting constraints as well as environmental protection.

One chapter of the document is devoted to wastewater use in aquaculture. The concept of aquatic food chains is introduced and appropriate fish species and aquatic plants for wastewater aquaculture are reviewed. This chapter deals in some depth with the environmental conditions and fish management in aquaculture ponds and develops the health aspects of fish culture.

A brief discussion concerning the economic, institutional and policy issues of wastewater use in agriculture is presented. The need for national planning is stressed so that advantage can be taken of the resource potential of wastewater and sewage sludge. Alternatives for managing effluent use schemes are discussed in the context of strict control and long-term sustainability.

The final substantive chapter of the document reviews wastewater use experience in seven countries under different conditions. The success with advanced wastewater treatment in California is contrasted with the use of stabilization pond treatment in Jordan. Soil-aquifer treatment research in Arizona provides yet another alternative for wastewater treatment in effluent use schemes. Success with the combination of conventional wastewater treatment and human exposure control in Kuwait is presented as an example of the results of careful national planning for wastewater use in agriculture. Long experience in Mexico with crop restriction as the sole control measure points out the benefits and risks of this approach to wastewater irrigation. Finally, the long-term record of wastewater-fed aquaculture in Calcutta is reviewed.

A comprehensive list of references is provided at the end of the document.

This Irrigation and Drainage Paper is intended to provide guidance to national planners and decision-makers, agricultural and municipal managers, field engineers and scientists, health and agricultural field workers, wastewater treatment plant operators and farmers. Consequently, it covers a broad range of relevant material, some in considerable depth but some more superficially. It is meant to encourage the collection, treatment and use of wastewater in agriculture in a safe manner, with maximum advantage taken of this resource. Informal, unplanned and unorganized wastewater use is not recommended, nor is it considered adviseable from the health or agricultural points of view.

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