Quality control of wastewater for irrigated crop production. (Water reports - 10)

Table of Contents Página 1 de 3 Quality control of wastewater for irrigated crop production. (Water reports - 10) Table of Contents D.W. Westcot Environmental Program Manager California Regional Water Quality Control Board Sacramento, California, USA FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1997 ISSN 1020-1203 The designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. M-56 ISBN 92-5-103994-1 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying or otherwise, without the prior permission of the copyright owner. Applications for such permission, with a statement of the purpose and extent of the reproduction, should be addressed to the Director, Information Division, Food and Agriculture Organization of the United Nations, Viale delle Terme di Caracalla, 00100 Rome, Italy. FAO 1997 This electronic document has been scanned using optical character recognition (OCR) software and careful manual recorrection. Even if the quality of digitalisation is high, the FAO declines all responsibility for any discrepancies that may exist between the present document and its original printed version. http://www.fao.org/docrep/w5367e/w5367e00.htm

Table of Contents Página 2 de 3 Table of Contents Preface Acknowledgements Chapter 1 - Introduction Chapter 2 - Health risks associated with wastewater use Types of pathogens present in wastewater Pathogens that reach the field or crop Pathogen survival under agricultural field conditions Relative health risk from wastewater use Agronomic conditions that minimize disease spread when wastewater is used for irrigation Guidelines for public health protection during wastewater use Chapter 3 - Implementing health protection measures for wastewater use Wastewater treatment to lower health risks Lowering risk of direct human exposure in areas using wastewater Lowering risk to consumers through crop restrictions Chapter 4 - Developing a programme to promote safe production Phase I: Development of a sound information base Selection of study areas to determine safe production zones Parameters used for measurement of microbial contamination Analytical methods which can give acceptable results Laboratory selection Field sampling techniques Criteria used to select field monitoring sites Phase II: Organization and analysis of the information Historical sources of data Sampling frequency and criteria used to evaluate the data Database, mapping systems Phase III: Certification programmes and institutional and policy issues Certification programmes Policy considerations for certification Developing a water quality certification programme http://www.fao.org/docrep/w5367e/w5367e00.htm

Table of Contents Página 3 de 3 Institutional and policy issues Water certification Policy issues for development of safe production areas Chapter 5 - The case study of Chile Planning for controlling the quality of irrigation water destined for vegetable production in Chile References http://www.fao.org/docrep/w5367e/w5367e00.htm

Chapter 1 - Introduction Página 1 de 3 Chapter 1 - Introduction The use of domestic wastewater for crop production has been practised for several centuries in one form or another. Prior to the 1940s, most wastewater use occurred on "sewage farms" or areas specifically designated for such use. One of the oldest in the world is the Werribee Farm which serves the City of Melbourne, Australia. This large well-managed farm was established in 1897 and is still in operation today, irrigating some 10 000 ha with wastewater. The impetus for these "sewage farms" was to minimize or prevent pollution in rivers and conserve water and nutrients to improve agriculture (Shuval, 1991). Few of these "sewage farms" still exist today; most were ill-conceived, inadequately funded and poorly regulated, and were eventually abandoned because of public health concerns. In the mid 1940s, domestic wastewater use again gained increased attention, especially in arid and semi-arid areas that suffer from insufficient overall water supplies. Although the same early motivations for wastewater use remained, the newer areas using wastewater were focused on ensuring they minimized or prevented potential public health problems. The principal concern was use of wastewater on crops normally eaten raw. The change in focus was driven by a better understanding of public health problems and the desire to improve public health standards. The need to improve public health protection prompted a number of state health departments in the United States to establish guidelines and regulations to control the public health aspects of wastewater use in agriculture. These initial guidelines provided a rational basis for continuing wastewater use by agriculture while meeting strict public health criteria. One important criterion was to restrict the use of partially treated sewage to crops that are generally cooked before being consumed and allow only water that has gone through advanced wastewater treatment and microbial disinfection to be applied to crops normally eaten raw. Many nations adopted the very strict microbial standards for wastewater use that were developed in California (USA) and elsewhere. In reality these microbial standards were almost unattainable in most wastewater treatment systems, therefore many poorer or developing countries abandoned plans for wastewater use (Shuval et al., 1986a). The primary reason was the realization that producing effluent with a microbial quality sufficient for unrestricted irrigation required costly sophisticated treatment technology. Some of these countries shifted their focus in wastewater use to unrestricted areas of use coupled with crop restrictions. Most, however, did not have a strong institutional structure to control cropping. The result has been little improvement in public health conditions associated with wastewater use. Untreated or partially treated wastewater continues to be used directly for unrestricted irrigation or is discharged to surface water channels where unintended use by agriculture occurs when water is appropriated for irrigation use. Over the past 20 years there has been a strong revival of interest in the controlled use of wastewater for crop irrigation. In addition to consumer health protection, the main reasons are: http://www.fao.org/docrep/w5367e/w5367e03.htm

Chapter 2 - Health risks associated with wastewater use Página 1 de 16 Chapter 2 - Health risks associated with wastewater use Types of pathogens present in wastewater Pathogens that reach the field or crop Pathogen survival under agricultural field conditions Relative health risk from wastewater use Agronomic conditions that minimize disease spread when wastewater is used for irrigation Guidelines for public health protection during wastewater use There are agronomic and economic benefits of wastewater use in agriculture. Irrigation with wastewater can increase the available water supply or release better quality supplies for alternative uses. In addition to these direct economic benefits that conserve natural resources, the fertilizer value of many wastewaters is important. FAO (1992) estimated that typical wastewater effluent from domestic sources could supply all of the nitrogen and much of the phosphorus and potassium that are normally required for agricultural crop production. In addition, micronutrients and organic matter also provide additional benefits. There are many successful wastewater use schemes throughout the world where nutrient recycling is a major benefit to the project (Pescod and Arar, 1988; FAO, 1992). Rarely, however, is a scheme laid out or planned on the basis of nutrient recycling. The primary constraint to any wastewater use project is public health. Wastewater, especially domestic wastewater, contains pathogens which can cause disease spread when not managed properly. The primary objective of any wastewater use project must therefore be to minimize or eliminate potential health risks. In most developing countries direct wastewater use projects are normally centred near large metropolitan areas. These schemes often only use a small percentage of the wastewater generated. The result is that indirect use of wastewater prevails inmost developing countries. Indirect use occurs when treated, partially treated or untreated wastewater is discharged to reservoirs, rivers and canals that supply irrigation water to agriculture. Indirect use poses the same health risks as planned wastewater use projects, but may have a greater potential for health problems because the water user is unaware of the wastewater being present. Indirect use is likely to expand rapidly in the future as urban population growth outstrips the financial resources to build adequate treatment works. Where indirect use occurs, the primary objective must also be to ensure that it is in a manner than minimizes or eliminates potential health risks. The health hazards associated with direct and indirect wastewater use are of two http://www.fao.org/docrep/w5367e/w5367e04.htm

Chapter 3 - Implementing health protection measures for wastewater use Página 1 de 6 Chapter 3 - Implementing health protection measures for wastewater use Wastewater treatment to lower health risks Lowering risk of direct human exposure in areas using wastewater Lowering risk to consumers through crop restrictions The discussion to this point has centred on defining the risk of disease transmission. All wastewater contains pathogens and these pathogens do pose a risk. As discussed in Chapter 2, that risk can be defined. The focus now shifts to evaluating what can be done to minimize or eliminate that risk. The water is the means that allows an infectious pathogen to move to a new host. The intermediate step in this process is crop production which can provide a route of infection. There are two approaches to developing a regulatory programme for health protection. The first is to focus on lowering the risk from the water. This is normally done by wastewater treatment or treatment and disinfection. Where the treated water does not meet health protection standards for unrestricted irrigation, the focal point for risk reduction shifts to the point of water use (irrigation). Here agricultural restrictions can lower the potential health risks. The point of water use is usually where the route of infection shifts to the soil and crop; therefore, these become the primary focus of management or regulatory strategies. There are numerous agronomic practices that can assist in lowering the risk from wastewater use but most of these are individual site decisions that are normally made by the farmer to increase agricultural production and not to lower the overall disease infection risk. Farmers cannot be expected to implement a programme that focuses on individual cultural practices since the farming goal is agricultural production. Any regulatory approach must be institutional and have a primary focus on the type of crop grown. Such an approach avoids the regulation process being involved with the way a particular crop is grown. The following sections briefly describe the two levels of approach: wastewater treatment and control at the field level. The latter is divided into the steps needed to prevent worker safety problems and those needed to prevent infection of the consumer of the crop. Wastewater treatment to lower health risks The water is the vehicle for movement of any pathogenic organism in wastewater. Any regulatory programme must first focus on intercepting these pathogens and rendering them harmless. The first option is to provide treatment of the http://www.fao.org/docrep/w5367e/w5367e05.htm

Página 1 de 49 Chapter 4 - Developing a programme to promote safe production Phase I: Development of a sound information base Phase II: Organization and analysis of the information Phase III: Certification programmes and institutional and policy issues As discussed in Chapter 3, adopting a crop restriction programme as a means of health protection where wastewater is used for irrigation requires a strong institutional framework. It also requires the capacity to monitor and control compliance with regulations and to enforce them. In reality, if the wastewater is not used in a defined and restricted area and the use of that water is not centrally controlled, enforcement of a crop restriction programme at the field level will not be easy to accomplish. The key to any effective programme is the farmer. Maintaining cooperation of the farmers involves ensuring that there is a strong market for the crops allowed and ensuring that there are negative market pressures for the restricted or high-risk crops. Developing farmer cooperation and the correct economic pressures is an alternative approach to crop restrictions. Farmers want the greatest economic advantage possible. Vegetable and other high-risk crops often present large economic returns, especially if production is done close to urban centres. These are often high-disease risk areas because of urban wastewater disposal practices. There is mounting evidence that the use of contaminated water to irrigate vegetables and certain fruits near urban areas is one of the chief means of gastrointestinal disease spread including cholera (Shuval, 1993). This has increased the urgency for health officials to restrict such production in these heavily contaminated areas. This in turn has increased the urgency to use economic incentives to develop safe production areas to meet national production needs. Developing a programme to promote safe production areas is an alternative to crop restrictions and can be done with a three-phased process. Each phase depends upon the successful completion of the previous phase. The first phase is to develop a sound information base (water quality monitoring phase) that can be used to evaluate the existing levels of contamination (water quality) in the water being used for production. This phase includes selection of contamination indicators, establishing field sampling methods, defining acceptable laboratory analytical methods, selecting participating laboratories, selecting the field monitoring sites and conducting a field water quality monitoring programme. A full discussion of these steps is in the following section of this report. The second phase involves evaluating the water quality data collected in the first phase and developing procedures to assess the levels of contamination (data

Chapter 5: The case study of Chile Página 1 de 5 Chapter 5 - The case study of Chile Planning for controlling the quality of irrigation water destined for vegetable production in Chile Planning for controlling the quality of irrigation water destined for vegetable production in Chile The outbreak of cholera in Chile in April of 1991 made it urgently necessary to control the use of contaminated irrigation water used on vegetable crops that are normally eaten raw. The Ministry of Health began a major programme to restrict such production in heavily contaminated areas. This increased the urgency for the Servicio Agrícola y Ganadero (SAG) of the Ministry of Agriculture to evaluate the extent of irrigation water contamination and to develop methods to promote production in safe areas. FAO together with SAG developed a one-year international project (Oct 1992 - Sept 1993) to evaluate the impact of microbial contamination in irrigation water. The project counterpart was the Department of Natural Resource Protection (DEPROREN) of SAG. The principal objectives of the project were to evaluate the existing levels of contamination, develop a database that could be used as a basis to control contaminated water use in vegetable production and to propose a certification system that could be used to promote safe production areas for both internal and international markets. The project was operated in three distinctly different phases: Phase 1 (Water Quality Monitoring Phase) In developing and conducting the water quality monitoring, the project reviewed whether the procedures had national and international recognition, formed a legal basis for follow-up actions and whether SAG could use the procedure and results to promote safe production. Monitoring was conducted in only two pilot areas; the Metropolitan and V Regions of Chile. These areas represented 50 percent of the population and 49 percent of the total vegetable production in the country. In addition, the two Regions contain 80 percent of the production of the 14 crops identified by the Ministry of Health as high-risk crops. The project used faecal coliform count as the contamination indicator. This indicator is recognized internationally by WHO, PAHO and other organizations in Latin America. Faecal coliform count is also used in regulations in Chile that deal with wastewater and how it can be used on crops (NCh 1333/1978) and is within the capability of all public and private laboratories in Chile to determine on a routine basis. The project recommended the continued use of this indicator until http://www.fao.org/docrep/w5367e/w5367e07.htm

References Página 1 de 4 References APHA. 1992. Standard Methods for Examination of Water and Wastewater. 18th Edition. American Public Health Association. Washington DC. Arthur, J.P. 1983. Notes on the design and operation of waste stabilization ponds in warm climates of developing countries. World Bank Technical Paper No. 6. World Bank, Washington DC. Bartone, C.R. 1991. International perspective on water resources management and wastewater reuse: appropriate technologies. Water Science and Technology 23(10/12): 2039-2047. Blum, D. and Feachem R.G. 1985. Health Aspects of Nightsoil and Sludge Use in Agriculture and Aquaculture. Part III: An Epidemiological Perspective (Report No. 05/85). International Reference Center for Waste Disposal. Dubendorf. Blumenthal, U.J., Strauss, M., Mara, D.D. and Cairncross S. 1989. Generalized model of the effect of different control measures in reducing health risks from waste reuse. Water Science and Technology 21(6/7): 567-577. Bordner, R. and Winter, J. (eds.). 1978. Microbiological methods for monitoring the environment: water and wastes. US Environmental Protection Agency Report No. EPA-600/8-78-017. 338 p. Cifuentes, E., Blumenthal, U., Ruiz-Palacios, G. and Bennett, S. 1991/92. Health impact evaluation of wastewater use in Mexico. Public Health Review 19:243-250 Duron, N.S. 1985. Mexican experience in using sewage effluent for large scale irrigation. In: Treatment and Use of Sewage Effluent for Irrigation (1988). M.B. Pescod and A. Arar (eds). Butterworth, London. FAO. 1985. Water quality for agriculture. R.S. Ayers and D.W. Westcot. FAO Irrigation and Drainage Paper 29, Rev. 1. FAO, Rome. 174 p. FAO. 1992. Wastewater treatment and use in agriculture. M.B. Pescod. FAO Irrigation and Drainage Paper 47, FAO, Rome. 125 p. FAO. 1993. Control de Aguas de Riego Destinadas a la Producción Hortofrutícola: Chile. Technical Report of Project TCP/CHI/2251(A). FAO, Rome. 69 p. Feachem, R.G., Bradley, D.J., Garelick, H. and Mara, D.D. 1983. Sanitation and Disease: Health Aspects of Excreta and Wastewater Management. John Wiley, Chicester. Geldreich, E.E. 1976. Fecal coliform and fecal streptococcus density relationships in waste discharges and receiving waters. CRC Critical Reviews in Environmental Control. 349 p. http://www.fao.org/docrep/w5367e/w5367e08.htm

References Página 2 de 4 Gerba, C.P., Wallis, C. and Melnick, J.L. 1975. Fate of wastewater bacteria and viruses in the soil. Journal of the Irrigation and Drainage Division, American Society of Civil Engineers 28:987-991. Hespanhol, I. and Prost, A.M.E. 1994. WHO guidelines and national standards for reuse and water quality. Water Research 28(1): 119-124. IRCWD. 1985. Health aspects of wastewater and excreta use in agriculture and aquaculture: The Engleberg Report. International Reference Center For Waste Disposal (IRCWD) News 23: 11-18. Kittrell, F.W. and Kurfari, S.A. 1963. Observations of coliform bacteria in streams. Water Pollution Control Federation 35(11): 1379. Mara, D. and Cairncross, S. 1989. Guidelines for the Safe Use of Wastewater and Excreta in Agriculture and Aquaculture: Measures for Public Health Protection. World Health Organization, Geneva. 187 p. Pescod, M.B. and Arar, A. (eds). 1988. Treatment and use of sewage effluent for irrigation. Proceedings of the FAO Regional Seminar on the Treatment and Use of Sewage Effluent for Irrigation. Nicosia, Cyprus 7-9 October 1985. Butterworths, London. 380 p. Rose, J.B. 1986. Microbial aspects of wastewater reuse for irrigation. CRC Critical Reviews in Environmental Control 16(3): 231-256. Shuval, H.I. 1991. Health guidelines and standards for wastewater reuse in agriculture: historical perspectives. Water Science and Technology 23(10/12): 2037-2080. Shuval, H.I. 1993. Investigation of typhoid fever and cholera transmission by raw wastewater irrigation in Santiago, Chile. Water Science and Technology 27(3/4): 167-174. Shuval, H.I., Adin, A., Fattal, B., Rawitz, E. and Yekutiel, P. 1986a. Wastewater irrigation in developing countries: health effects and technical solutions. Technical Paper Number 51. World Bank, Washington DC. 324 p. Shuval, H.I., Yekutiel, P. and Fattal, B. 1986b. An epidemiological model of the potential health risk associated with various pathogens in wastewater irrigation. Water Science and Technology 18(10): 191-198. Strauss, M. 1985. Health Aspects of Nightsoil and Sludge Use in Agriculture and Aquaculture. Part II: Pathogen Survival (Report No. 04/85). International Reference Center for Waste Disposal. Dubendorf. Strauss, M. 1991. Human waste use: health protection practices and scheme monitoring. Water Science and Technology 24(9): 67-79. US EPA. 1973. Water Quality Criteria. National Academy of Sciences Report to the United States Environmental Protection Agency. Washington DC. pp. 350-366. WHO. 1973. Reuse of effluents: methods of wastewater treatment and health http://www.fao.org/docrep/w5367e/w5367e08.htm

References Página 3 de 4 safeguards: Report of a WHO Meeting of Experts. WHO Technical Report Series No. 517. World Health Organization, Geneva. WHO. 1989. Health guidelines for the use of wastewater in agriculture and aquaculture: Report of a WHO Scientific Group. WHO Technical Report Series 778. World Health Organization, Geneva. 74 p. Witt, V.M. and Reiff, F.M. 1991. Environmental health conditions and cholera vulnerability in Latin America and the Caribbean. Journal of Public Health Policy 12(4): 450-463. FAO TECHNICAL PAPERS WATER REPORTS 1. Prevention of water pollution by agriculture and related activities, 1993 (E S) 2. Irrigation water delivery models, 1994 (E) 3. Water harvesting for improved agricultural production, 1994 (E) 4. Use of remote sensing techniques in irrigation and drainage, 1995 (E) 5. Irrigation management transfer, 1995 (E) 6. Methodology for water policy review and reform, 1995 (E) 7. Irrigation in Africa in figures/l'irrigation en Afrique en chiffres, 1995 (E/F) 8. Irrigation scheduling: from theory to practice, 1996 (E) 9. Irrigation in the Near East Region in figures, 1997 (E) 10. Quality control of wastewater for irrigated crop production, 1997 (E) Availability: June 1997 Ar - Arabic C - Chinese E - English F - French P - Portuguese S - Spanish Multil - Multilingual * Out of print ** In preparation The FAO Technical Papers are available through the authorized FAO Sales Agents or directly from Sales and Marketing Group, FAO, Viale delle Terme di Caracalla. 00100 Rome, Italy. This document discusses the use of wastewater for irrigated crop production. It reviews wastewater standards and proposes an interim approach to be applied in areas using wastewater, which promotes safe production areas for crops such as vegetables. The approach is to assess the quality of water actually being used for irrigation against a known standard. It is proposed that the World Health Organization (WHO) guidelines for wastewater treatment plant design be used as irrigation water standards in making this assessment. In view of the fact that the http://www.fao.org/docrep/w5367e/w5367e08.htm

References Página 4 de 4 present lever of water contamination in many countries already seriously exceeds the limits set in the guidelines, achieving the prescribed standards for vegetable production would be a major accomplishment towards improving health conditions in these countries. The document makes reference to procedures developed and studied in 1992 in an FAO project in Chile. Comments and suggestions for improvement of this approach for practical application in the field are invited and encouraged. http://www.fao.org/docrep/w5367e/w5367e08.htm

Chapter 5: The case study of Chile Página 2 de 5 changed by the Ministry of Health. TABLE 14: Distribution of faecal contamination in irrigated areas of the Metropolitan and V Regions, Chile % of the 120 000 ha sampled in the Metropolitan Region % of the 80 000 ha sampled in the V Region Faecal contamination level (Faecal coliforms/100 ml) <10 3 10 3-10 4 10 4-10 5 >10 5 8 25 41 26 27 65 8 0 The analytical method used by the project was the multiple-tube fermentation technique. This method was recommended for future programmes within Chile but the project felt strongly that SAG, the Ministry of Health and the University of Chile should attempt to adapt the membrane filtration method to use with Chilean irrigation waters. This would give SAG and others much more flexibility in sampling in remote rural areas and responding to emergency situations throughout the other regions. The project used the University and Public Health Institute (ISP) laboratories for analytical work. The main reason for using these laboratories was the lack of capabilities within SAG laboratories and the need to demonstrate a high level of credibility during the monitoring programme. The project recommended that SAG continue to strengthen its ties with the ISP laboratories until capabilities within SAG laboratories could be established. Two contamination sources were considered in setting the water quality monitoring sites: primary contamination that occurred in the rivers before the water is diverted into the irrigation system and secondary contamination that occurred within the irrigation system. The project developed guidelines for selecting monitoring sites based on these two contamination sources and complying with existing regulations as defined in NCh 1333/1978. The guidelines emphasized only monitoring potentially clean areas to promote safe production. This approach avoided using financial resources to monitor heavily contaminated areas that have little potential for future production of vegetables. The monitoring network set out by the project divided the Metropolitan Region into five irrigated zones. From December 1992 to March 1993, a total of 604 samples were collected from 120 sites within these five zones which cover approximately 120 000 hectares. The V Region was divided into seven irrigated zones. From January to April 1993, over 750 samples were collected from 150 sampling sites within the seven zones that cover approximately 80 000 hectares. Phase 2 (Data Analysis Phase) Based on the monitoring results, the project was able to make the estimates shown in Table 14. In order to evaluate the project results, the project assessed primary contamination. This contamination was generally due to discharges of untreated urban wastewater in amounts that were so large that often there was not sufficient http://www.fao.org/docrep/w5367e/w5367e07.htm

Chapter 5: The case study of Chile Página 3 de 5 natural river water to dilute the discharge to bring the faecal coliform levels below the 10 3 FC/100 ml standard designated in NCh 1333/1978. The project also assessed secondary contamination. Some of the causes of secondary contamination have been identified as discharges directly to the irrigation canals of domestic household wastewater and from animal confinement facilities. The choice of monitoring sites focused on detecting the presence of secondary contamination in channels that initially showed low levels of contamination at the river intakes. The selection of sites followed the guidelines shown in Figure 7. As shown in Table 14, the Metropolitan Region had the highest level of bacterial contamination. The main cause was the direct discharge of untreated urban wastewater to natural waterways before the water was diverted for irrigation (primary contamination) but secondary contamination sources did play a role. This results in only 8 percent of the irrigated area with a high potential to participate directly in a programme of water certification for safe vegetable production. Because of the extent of the primary contamination from discharges to the river, it is unlikely that the area available for vegetable production could increase significantly until the treatment works are in place for the urban wastewater. Because of the high initial levels of contamination, secondary contamination in such channels did not appear to be a significant factor with the exception of zones irrigated with well water or in areas not affected by large urban discharges. It can be seen in Figure 8 that 37 percent of the irrigated area of the Metropolitan Region initially was below the maximum defined in NCh 1333/1978 but this dropped to only 8 percent after secondary sources of contamination were examined. This decrease was followed by a rise in the percentage of area found in the intermediate range (10 3-10 4 ). The increase in percentage of the area contaminated was due to discharges directly to the canal system downstream of the intake. Figure 8 also shows that the percentage of area affected in the heavily contaminated areas (>10 4 ) did not vary significantly. These areas are affected by heavily contaminated discharges that were external to the irrigation system (primary contamination) and these high levels did not drop significantly as the water passed through the irrigation channels. In the V Region, almost 1/3 of the irrigated area tested had a high probability for direct participation in a certification programme for safe production areas. The most important cause of contamination in the V Region was secondary contamination. An additional 63 percent of the irrigated area tested could participate in a certification programme if the direct discharges to the canals were eliminated (Figure 16). Secondary contamination discharges were found to prevent a significant amount of the total irrigated area from immediately participating in a water certification programme. The sampling points for this programme were chosen to represent a large irrigated area and, as such, samples were often taken at intermediate points in the irrigation system. The extent of irrigated area that moves from the low (<10 3 ) to the intermediate range (10 3-10 4 ) or higher is likely to increase as water samples are collected closer to the individual fields. Thus solving the secondary contamination problem should not be overlooked as it may be a major constraint in developing safe (clean) production areas. http://www.fao.org/docrep/w5367e/w5367e07.htm

Chapter 5: The case study of Chile Página 4 de 5 FIGURE 16: Changes in the extent of faecal contamination in the irrigation water of the V Region of Chile as a result of discharges into the irrigation system as compared to the initial level of contamination in the source of water used in the irrigation system (Source: FAO, 1993) The project recommended that SAG work with the Ministries of Health and Public Works to seek international assistance in developing and implementing methods to reduce or eliminate secondary contamination from areas showing high potential for safe vegetable production (areas <5000 faecal coliforms/100 ml). Phase 3 (Crop Certification Phase) The water quality data from Phase 1 and 2 were used to develop the concepts of a crop certification programme. The strong cholera eradication programme already instituted resulted in a heightened awareness of product quality by the consumer. The result was a number of labels used by producers that emphasize to the consumer the safety of the water used in production. In order to implement this programme, SAG needed to be prepared to develop and operate a nation-wide water quality monitoring programme to assess the extent of irrigation water contamination. To carry out this programme, it was recommended that SAG develop a staff who can plan, execute and interpret a water quality monitoring programme. The procedures used in this project were recommended for use as the guidelines for conducting such a programme. The project developed a five-step process for certifying clean production areas. The first three steps focus on water certification. The final two steps shift the focus of SAG to developing and applying a SAG label to vegetable production originating in safe production areas. The procedure for controlling the labelling of safe vegetable production was reviewed. It was recommended that, if resources are available, the certification of the water and the application of a SAG label should be controlled by direct contact with each producer. Control at this level ensures that certified water and safe production practices are used. Alternative and less intensive approaches considered were issuing labels on an area-wide basis or allowing groups of producers to control the labelling in SAG certified areas. The project also recommended that SAG and the Ministry of Health strengthen the role of the certification programme by using public education techniques to emphasize to consumers the need to buy only SAG certified produce. The scheme laid out by the project was considered a concept. The actual certification programme must consider several factors. There are four factors the project felt were extremely important to the success of any programme: that all public agencies agree that only one label is recognized as certifying production in safe areas. The use of alternative labels must be dealt with decisively and quickly; that SAG is prepared to apply the programme uniformly and nationwide as producers from other zones of the country will want the same economic advantages in selling their produce; http://www.fao.org/docrep/w5367e/w5367e07.htm

Chapter 5: The case study of Chile Página 5 de 5 that SAG is prepared to operate the programme fully in order to maintain a high level of credibility with both the producer and the consumer; and developing and operating a certification programme must be done with high standards and a high degree of credibility. http://www.fao.org/docrep/w5367e/w5367e07.htm

Página 2 de 49 analysis and evaluation phase). The overall goal of both Phases I and II is to ensure that the database can be used to define safe production areas. The database could also be used as a basis to control or regulate contaminated water use in vegetable or other high-risk production areas. This phase includes developing a reliable database and retrieval system, defining the methods used for analysis of the data and development of techniques that could be used to present the data. A discussion of the options available for analysis of the results is in the section Organization and analysis of the information of this chapter. The third and final phase of developing a programme to promote safe production areas is developing mechanisms to regulate the use of contaminated water on vegetable or other high-risk crops (crop or water certification phase). The focus here is to look at options other than crop restrictions that can be used to promote safe production areas. The discussion of certification programmes along with the range of policy options that needs to be considered are found in the sections Certification programmes and Institutional and policy issues of this chapter. Phase I: Development of a sound information base Selection of study areas to determine safe production zones Parameters used for measurement of microbial contamination Analytical methods which can give acceptable results Laboratory selection Field sampling techniques Criteria used to select field monitoring sites There is a need for an improved understanding of the extent of irrigation water contamination; therefore the first phase of any effort to define safe production areas should be to develop a programme to evaluate the quality of water being used for irrigation, both on a regional scale and on a production level. The goal of a water quality monitoring programme is to determine how extensive the irrigation water contamination is and at what level. Five principles should guide development of the water quality monitoring/evaluation programme: the results must provide the Ministry of Agriculture, the Ministry of Health or others with a sound legal and technical basis for any followup actions they choose to take; the results provide information needed to promote safe production; the procedure and parameters used for measurement must have national and international recognition; the procedure must be applicable to the entire country; and the procedure is within the resources of the Ministries and within the resources of the country to continue.

Página 3 de 49 In order to conduct a monitoring programme, several steps are necessary. The following sections discuss the principles involved in implementing each of these steps: selection of study areas to determine safe production zones; parameters used for measurement of microbial contamination; analytical methods which can give acceptable results; laboratory selection; field sampling techniques; and criteria used to select field monitoring sites. Selection of study areas to determine safe production zones Water quality sampling for microbial contamination is normally conducted by the health authorities. Their preliminary data often show extensive contamination of irrigation water supplies especially in developing countries (Table 6). The dilemma for the agricultural and health authorities is that the problem is often too widespread for the monitoring resources available, therefore priorities must be established on where data should be developed for decision making. Health and agricultural authorities often have different priorities. To help the agricultural authorities establish priorities and choose monitoring areas, the following factors should be considered: Availability of preliminary water quality data and data on cholera and other disease outbreaks: Preliminary information on the extent of microbial contamination in irrigation water would allow the monitoring programme to concentrate its efforts, otherwise an additional step would be needed to make this preliminary analysis. Where a preliminary reconnaissance is needed, the surface water supplies (rivers) should be sampled by river reach. The division between reaches should be based on the location of significant urban populations. Each river reach should be sampled as often as needed to develop a first approximation of the level of contamination. Figure 5 shows a hypothetical river basin which has been divided into reaches based upon major discharge points from urban areas. Location of major vegetable production areas in the country: Vegetable crops, especially those eaten raw, have been cited as a major mechanism of disease transmission. Vegetable production throughout the country should be reviewed but principally in the most contaminated regions as determined above. Four factors should be taken into account in evaluating the importance of vegetable production:? whether a crop quarantine programme is planned or underway in that region of the country;? extent of production of crops identified by the health authorities as high-risk crops;? extent of total vegetable production in that region of the

Página 4 de 49 country (all vegetable crops irrigated with contaminated water pose a high risk either from consumption or via worker health and safety); and? the likelihood that vegetable production would shift to a new area as further quarantines are implemented. Location of major population centres near vegetable production areas: Population centres pose a high risk to irrigation water quality because of untreated wastewater discharges. Significant population centres often exist upstream of vegetable production areas in developing countries. Availability of hydrologic information on the irrigation system: A major constraint to any water quality monitoring programme is a lack of understanding of the irrigation system hydraulics or the points of major discharge that affect the irrigation system. A primary reason that water quality monitoring programmes succeed is the availability of maps and information on the irrigation canal network as well as maps showing the points of major discharge that would affect irrigation water quality. Without these, a monitoring programme may struggle to set representative monitoring points and valuable time and sampling resources will be lost. The best available information is from the Water Division of the Ministry of Public Works or the Ministry of Irrigation. In those instances where detailed information is lacking, set up a preliminary assessment on the river network. That system should be divided into not more than six segments, and each segment should then be sampled 2-3 times. Based on this information then choices of irrigation systems to be sampled can be made. Crop production methods used are similar in other regions of the country: In the choice of study areas, consideration needs to be given to crop production methods and whether they are similar throughout the country. The principal concern is the method used to apply the irrigation water, especially for vegetable production. The highest risk occurs with sprinkler application of contaminated water. This method presents increased risk of crop contamination and worker health problems. Surface irrigation methods (flood, border, furrow, etc.) present a lower risk but there is still high risk for crops grown near or in contact with the ground. Drip or other forms of localized irrigation present the least threat for transmission of disease. Availability of a strong laboratory infrastructure that can perform the analyses within the project period: A major consideration in selecting a study or assessment area is the availability of reliable laboratories. A water quality monitoring programme is only as good as the laboratories used. Often the Agricultural Ministry does not have laboratories that can perform the needed microbial analyses on a routine basis. Microbial analyses of irrigation water and wastewater take a unique expertise that is often not found within the Agricultural Ministry. A major constraint for most public agency laboratories is they are not equipped to take on a new programme that produces a large number of samples in a relatively

Página 5 de 49 short period of time. The laboratory needs to be able to operate on a seasonal basis because of the nature of the irrigation season. Testing during the irrigation season requires a large effort for only a 3 to 6 month period. One alternative approach is to utilize laboratories of the Ministry of Public Health and the universities. The decision to utilize such labs is often made because of cost, availability of analytical space and lack of a quality control programme for private laboratories in the country. In addition, the use of Public Health and university laboratories gives a higher level of creditability to the results over those that would be obtained through private laboratories. This is an important consideration when the information developed may be used to plan or restrict cropping patterns. Irrigation water contamination is a public health issue and it is valuable to have the expertise of the public health authorities or the university in interpreting results that a private laboratory would not have the capability to do within a reasonable cost. This is especially important because the laboratory will be working with two factors which are not routine in most private laboratories: contaminated water and irrigation water. The use of public health authority and university laboratories is recommended for the initial assessment but the private sector must be capable of carrying on a long-term programme or the Agricultural Ministry will find it necessary to build up this expertise. The analytical and operational costs will likely be higher in any public sector effort, and the Agricultural Ministry assumes a substantial risk to its reputation if analyses are not done correctly or are misinterpreted. Resources available for collection and analyses of samples. The ability to manage a sample collection and analysis programme in remote areas is a key factor in the choice of study areas. FIGURE 5: Division of a typical river basin into reaches based upon the location of major urban wastewater discharges

Página 6 de 49 CONTROL OF IRRIGATION WATER USED IN PRODUCTION OF VEGETABLE CROPS A programme to control vegetable production using a 3-phased approach was tried in Chile in 1992. Given below is the work plan from this project. A cholera outbreak and the high level of gastrointestinal diseases in Chile occurred because contaminated water was used to irrigate vegetables that are eaten raw (Shuval, 1993). Until a few years ago there was no programme to identify areas with high levels of contamination or to regulate production. Initial steps by Servicio Agrícola y Ganadero (SAG) of the Ministry of Agriculture and the Ministry of Health to control production in the worst contaminated areas significantly reduced disease transmission. There was, however, an urgent need for SAG to identify the level of contamination in other areas of the country and to develop programmes that promote or certify production in the safe areas to maintain national production needs. SAG and FAO developed a one-year project with the goal of defining the levels of contamination, preventing further contamination and, where needed, developing the procedures to regulate the use of the irrigation supply water to attain vegetable and fruit production that met the sanitary protection requirements for marketing at the national and international level. The work plan for the project was to: (a) develop a plan for systematic monitoring of the principal irrigation canals in selected zones in the country. This plan was to include the selection of indicators of

Página 7 de 49 contamination, field and laboratory methods to determine the values, and the logistics of conducting the plan. To establish this plan, the project needed to define the cost of operation, probable duration, the benefits and the ways to finance the programme; (b) establish a computer database with the needed systems of quality control for processing the raw data and define how the data should be analysed and presented. This database was to include both historical data and data generated in this project; (c) define a practical method to identify the geographic extent of contamination and define the priority for action to regulate cropping that uses contaminated water; (d) study the options for a programme of crop certification based on the level of contamination by district or irrigated region with the goal to reduce the spread of gastrointestinal diseases caused by contaminated vegetable products; (e) define an agreement for a crop certification programme with a system of regulations that conforms to the nature and levels of contamination; (f) define the practical standards for laboratories and their quality control that are applicable to determining irrigation water contamination with particular attention to the agents that cause the gastrointestinal diseases; and (g) define the basic elements of a national strategy to contain the origin of contamination of water used in agriculture. The work plan for the project had a variety of elements (described above) and conducting all simultaneously was beyond the resources of the project. It was decided that the project should be operated in three phases. The first phase was to develop a sound information base (water quality monitoring phase). The second phase was to evaluate the data collected and assess the levels of contamination (organization and analysis of the information). The third phase was to develop mechanisms to regulate cropping and use of contaminated water on vegetable crops (crop certification phase). Each phase of the project depended upon the successful completion of the previous one. The project counterpart was the Department of Natural Resource Protection (DEPROREN) of SAG along with strong assistance from DEPROREN in Quillota (V Region) and during the third phase on crop and water certification from the Department of Agricultural Protection of SAG. This project needed to consider a variety of issues from public health to irrigation systems and wastewater treatment. No one group, nor the project, could successfully complete the work plan without strong assistance and advice from a number of agencies. These agencies met periodically to review project results and offer guidance to the project team. Those agencies included: Dirección General de Aguas del Ministerio de Obras Publicas; Ministerio de Salud; Instituto de Salud Pública (Metropolitan and V Regions); Empresa Metropolitana de Obras Sanitarias (EMOS); Empresa de Servicios Sanitarios de Valparaiso (ESVAL); Departamento de Riego del Ministerio de Obras Publicas; Instituto de Investigaciones Agropecuarias (INIA); and Instituto de Desarrallo Agropecuario (INDAP). At the conclusion of the project a workshop was held on the project results along with the activities of the other agencies. The project had a full-time national irrigation expert who was responsible for the daily operation of each of the project phases. The project was also supported by international consultants in water quality, crop certification, laboratory methods for microbial testing of water and laboratory methods for microbial testing of food. (Source: FAO, 1993)