1.5.1 Ensuring Safe Reuse: Meeting WHO Standards
When there are no national standards in place, the criteria for the quality of the treated liquid can be based on the guidelines set by the World Health Organization (WHO).
These standards primarily revolve around safeguarding the well-being of users who might reuse treated wastewater for activities like irrigation and fertilisation. Users must adhere to health safeguards, including protective gear, proper irrigation methods, and more.
The WHO Standards set strict limits for various disease sources, such as pathogens like helminths (worms) and Escherichia coli (E. coli), bacteria commonly found in our intestines and used as indicators for other bacteria that can cause disease.
Another crucial factor to consider is the type of irrigation, which the WHO classifies into two main categories: restricted and unrestricted. Unrestricted irrigation involves using treated wastewater to cultivate crops typically consumed raw. On the other hand, restricted irrigation pertains to using wastewater to grow crops not consumed raw by humans.
The following table contains recommended limits for E. coli and Helminth eggs according to the WHO.
| Type of irrigation | E. coli (cfu /100 mL) | Helminths (eggs/L) | Notes |
|---|---|---|---|
| Unrestricted | ≤1,000 | ≤1 | Root crops |
| ≤10,000 | Leaf crops | ||
| ≤100,000 | Drip Irrigation of high-growing crops | ||
| ≤1,000 | No recommendation | Drip Irrigation of low-growing crops | |
| Restricted | ≤10,000 | ≤1 | Labour intensive agriculture |
| ≤100,000 | Highly mechanized agriculture |
To ensure the safety of the reuse practice, the following Standard Operating Procedures (SOPs) need to be in place:
Effluent Quality Monitoring: Monitoring the treated wastewater’s quality regularly must be conducted. This includes testing for pathogens, contaminants, and other potential hazards to verify that the effluent meets the required safety standards and is also applicable for sampling, laboratory testing, documentation, and records.
Safe Management Plans: Developing and implementing plans that outline how the treated wastewater will be safely managed throughout the reuse process. This includes guidelines for handling, application, and protective measures.
Training and Awareness: Training sanitation workers, end-product users, and the community about safe practices when dealing with treated wastewater. This includes using personal protective equipment, following proper application techniques, and avoiding direct contact with the effluent.
Community Engagement: Involving the community in the decision-making process and sharing information about the benefits and risks associated with the reuse practice. This promotes transparency and helps build trust.
Regulatory Compliance: Ensuring the reuse practice adheres to local regulations, standards, and guidelines for wastewater reuse and environmental protection.
We will learn more about the safe handling of effluent with regard to irrigation in module 7.
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