Sources and microbial quality of irrigation waters and waters used in post-harvest processes

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1 Sources and microbial quality of irrigation waters and waters used in post-harvest processes Dr. Ir. Liesbeth Jacxsens Department of Food Safety and Food Quality Ghent University - Belgium Contributors: Philip Amoah, Liesbeth Jacxsens, Matthew Law, Mieke Uyttendaele, Pay Drechsel

2 Available guidelines and standards - Many guidelines and standards available about potential (micro)biological food safety impact of irrigation water (pre harvest) and post harvest use of water - E.g. Codex Alimentarius, (inter)national research organisations, NGOs, (legal framework), voluntary standards e.g. Global G.AP. - Good Agricultural Practices GAP pre harvest - Good Manufacturing Practices GMP post harvest - Avoid contamination = preventive measures - Eliminate or reduce contamination = interventions - Fresh produce interventions are limited preventive approach very important

3 Water quality - Source versus quality - In many guidelines and standards the source of water is inherent related to the quality of the water : - use of tap water = potable water - use of rainfall water = non potable water - Source : where does the water come from? - Quality : what is the (micro)biological load of the water? - However: - Different sources can supply to the same quality - Due to water treatment technology water quality can be influenced

4 Sources of water for fresh produce irrigation - Rain water or rain harvested water - Ground water (or bore hole water) - Surface water includes lakes, rivers, creeks, ponds and springs that come in contact to the surface - Run off water is water running of the fields after heavy rainfall. It can be collected in lakes, rivers or basins. - Sea water includes sea water, desalinated seawater, brackish groundwater - Wastewater - Reconditioned (treated) wastewater - Mixture of water from different sources (Micro)biological quality can be very different and can vary in function of time of the year (variability)

5 Quality of water for fresh produce irrigation - Many research papers available with information of the quality of the water literature study is made by ILSI : Rain water is generally of relatively good microbial quality, although it may vary and the quality is less than what is expected of potable quality, strongly influenced by the collection recipients. Ground water is generally of good microbial quality if infiltration of surface runoff is avoided. There can however be large variations between shallow ground water and water from deeper aquifers. Surface water sources have the most variable levels of contamination because they may be subject to temporary or intermittent contamination sources subject to discharges of (treated) wastewater, storm water runoff, livestock or wild life feces, etc. Wastewater is usually of very poor physico-chemical as well as microbial quality and consequently requires intensive treatment unless other safety measures are in place where treatment is not feasible

6 Country/region Water type Regulation/Guideline Criteria a, b Reference Australia & New Zealand c Guideline < 1000 E. coli/100 ml Australia & New Zealand Overview of guidelines/legalisation for irrigation water Irrigation water for non food crops (trees/flowers) - Secondary treatment or primary Treatment with lagoon detention Irrigation water for commercial crops raw or unprocessed (salads crops and spray irrigation) - Advanced treatment to achieve total pathogen removal required (eg secondary, filtration and disinfection) Australian Guidance for Water Recycling, 2006 Guideline < 1 E. coli/100 ml Australian Guidance for Water Recycling, 2006

7 Overview of guidelines/legalisation for irrigation water Country/region Water type Regulation/Guideline Criteria a, b Reference Australia & New Zealand e,f Irrigation water for commercial food crops - Secondary treatment with >25 days lagoon detention and disinfection Guideline < 100 E. coli/100 ml Australian Guidance for Water Recycling, 2006 WHO (2006)# Wastewater Guideline < 1000/100 ml fecal coliforms < 0,1 nematode egg/l Blumenthal & Peasey, 2002; WHO, many other regions e.g. Canada, US, Italy, Spain, Different indicators total coliforms fecal coliforms E. coli Different criteria for same type of water.

8 Irrigation method can influence transfer of pathogens to produce The agricultural practices regarding irrigation, types of crops produced, harvesting practices, washing processes and storage of fresh produce vary considerably from very simple manual practices in the developing countries to more sophisticated mechanical practices in the developed world. Different irrigation methods are used in different parts of the world and depending on the method, quality of the irrigation water and the type of crop irrigated consumers may be at risk.

9 Potential preventive measures pre harvest Literature overview was made to define the most appropriate preventive measures to avoid (micro)biological contamination during irrigation E.g. In case of the use of surface water Irrigation water from surface water Selection of proper sources of irrigation water. Do not use contaminated surface water. Avoid animal intrusion and animal debris. Restriction of livestock feeding, watering and grazing. Avoid contaminated water drainage into the surface water reservoir. Remove brush, bushes from canal banks and algae. Control surrounding vegetation and algae and run off. Regular sanitary survey of canals and ditches. Ditch construction, buffer strips, retention systems, drainage systems and ditches. Eliminate potential overflow points. Reparation of potential seepage. Lining of canals. Redirect contaminating water with diversion dikes, gradients, inlet/outlet control structures etc. Incorporate vegetation that is easy to maintain and supports water quality. Disinfection and decontamination treatments: Chlorination, peroxyacetic acid, UV radiation, ultrasound and filtration, ph shock, biological controls

10 Use of water post harvest activities Also at post harvest level water is applied :

11 Applied criteria in post harvest activities - Overall, the requirements for microbial water quality increase as the product progresses from field to final processing - In most guidelines/legal document potable water is demanded for post harvest activities (washing, transport, cooling activities) - According to Codex Code of hygienic practice for fruits and vegetables a differentiation is made between: - Clean water water that does not compromise food safety in the circumstances its use. - Potable water water which meets the quality standards of drinking water such as described in the WHO Guidelines for Drinking Water Quality. - The quality of water used should be dependent on the stage of the operation - clean water could be used for initial washing stages, whereas water used for final rinses should be of potable quality - potable water should be used in cooling systems where water or ice is in direct contact with fresh fruits and vegetables (e.g. hydro cooling, ice cooling).

12 Intervention at post harvest level : washing During washing of fresh(cut)produce to be considered : Monitoring temperature of the water solution Establishment of product/water volume ratio Establishment of number of washing steps Insert enough mechanical action to move the product In case of use of sanitizer : Monitoring of concentration of sanitizer, ph of water solution and organic matter Application of sanitizers in washing water = big discussion with pro and contras due to potential chemical risks

13 Conclusion and bottlenecks in defining the quality and source of water to be used pre or post harvest Most guidelines and regulations are now heavily based on microbial standards but other strategies for managing health risks may also be effective e.g. the latest guidelines by the World Health Organization for use of wastewater in agriculture have been revised substantially: The fecal coliform guideline has been replaced by health based targets defined through attributable risks and Disability-Adjusted Life Years (DALYs) Governments in developing countries have been given greater flexibility in achieving these targets (WHO, 2006). Requirements enabling the use of water for unrestricted irrigation (i.e. for crops that are to be eaten uncooked) are usually more stringent than those for restricted irrigation (i.e. crops that are not to be eaten uncooked).

14 Conclusion and bottlenecks in defining the quality and source of water to be used pre or post harvest The possible water sources and water quality in the fresh produce chain (farm level, processing level) should be clearly defined and linked towards the potential transfer of hazardous pathogens. A farm level, irrigation water and water applied for pesticide spreading should be controlled, along with run-off of rain water and irrigation practices. During processing, the wash methods should be optimized in reuse of water and saving big volumes of water. There are still immense differences in risk mitigation between high and low-income countries which are also affecting international trade of fresh produce or fresh-cut produce.