Controls for water quality of irrigation

source water Regulations or Best Management Practices?

Water Quality Regulations:Advantage

• Creates arbitrary water quality standards• Convenient for govt.• Politically correct • Creates data of uses• Increases awareness of issue

Disadvantage

• Requires government support• Requires resources to fund,

administer and enforce.• Difficult to enforce - geographical

challenge of non-point source of contamination.• Only as good as resources put into

system. • Epidemiology of pathogens from

irrigation water not well understood

Best Management PracticesAdvantages

• A system that provides guidance to ensure source water is low risk of microbial contamination. • Financial incentives for good

practices.• Builds on shared learning. Examples - Commodity Specific Guidance for Leafy Greens, Melons and Tomatoes

Disadvantages• Volunteer compliance • A farmer needs to determine that it is in

their ‘economic interest’ to undertake the control measures. The farmer must clearly see the potential economic benefits from implementing management controls: i.e., erosion control measures to maintain soil fertility, less water usage (minimum tillage), drainage development, capital costs associated with improved manure handling and distribution, wetland construction, etc.

(Sagardoy, 1993).

Quantitative Microbial Risk Assessment Tool• A model that establishes a relationship between concentration of

pathogens in irrigation water and the probabilities of human illness. • Can be used for many variables - specific pathogen, water sources,

and agriculture management methods. Uses complex modeling to achieve a ratio of annual risk of infection, i.e., 1:10,000• Adopted by the WHO in developing guidelines for water related

diseases. • Limitations: currently only at laboratory scale, needs to be scaled up

to field, misses complex microorganisms processes of decay and persistence.

Constructed Wetlands - example• Constructed wetlands (on-site) can be a low-cost and effective

treatment methods for reducing nutrients and bacteria from irrigation waste water. • Factors: Importance of the design is key - to address, hydraulic

retention times, sedimentation and aquatic vegetation types. The shorter the hydraulic retention times, the better, as long treatment is achieved. (Sagardoy, 1993).

Recommendations: • Prevention management approach in best.• Water quality of source water needs to be of a potable standard.• Ensure no cross-connection within water distribution systems and install back-flow

prevention devices.• Prevent faecal contamination of produce on site.• Washing and sanitizing of produce before distribution – irradiation.• Supply chain management – refrigeration and limit people coming in contact with

produce. • Develop and implement a Water Safety Plan & Quantitative Microbial Risk

Assessment Tool Source: Lynch, et al (2009), Gelting, et al (2014)

Source: Pachepky, Y., et al. (2011). Irrigation Water as a source of pathogenic microorganisms in produce: A review

(Sagardoy, 1993).