7.5 What quality of wastewater/effluent and soil is acceptable for irrigation?
Wastewater and effluent quality standards for irrigation should ideally be clearly outlined within national regulations and standards. In cases where such domestic regulations and standards are insufficient or absent, it becomes essential to turn to internationally recognised guidelines and standards.
The guidelines aim to protect public health and prevent environmental degradation.
Depending on the country and purpose, the requirement for wastewater reuse can vary. If no national standards are present, the WHO standards can be applied. To illustrate what the standards and regulations can look like, the irrigation standards for Morocco and Jordan can be found in the Materials tab.
In addressing hygienic indicators for agricultural wastewater reuse, WHO categorises them based on reuse conditions, exposed groups, and irrigation methods, as outlined in the following matrix.
| Category | Reuse Condition | Exposed Group | Irrigation Method | Helminth’s eggs/L | Faecal coli / 100mL |
|---|---|---|---|---|---|
| A | Unrestricted: Crops eaten uncooked, sports fields, public parks | Workers, consumers, public | any | ≤ 0.1 | ≤ 103 |
| B | Restricted: crops eaten cooked, cereals, industrial crops, fodder, pasture, and trees | Workers >15 years old | Spray/sprinkler | ≤ 1 | ≤ 105 |
| Workers >15 years old | Flood/furrow | ≤ 1 | ≤ 103 | ||
| Workers including children, nearby communities | any | ≤ 0.1 | ≤ 103 | ||
| C | Localised irrigation of crops in category B if exposure of workers and the public does not occur | None | Trickle, drip, or bubbler | Not Applicable | Not Applicable |
For most crops, the target is to have less than or equal to one helminth egg per litre of irrigation water. However, for crops that are eaten uncooked, the threshold is less than 0.1 egg per litre.
Additionally, maximum allowable soil concentrations for various chemicals are specified and summarised in the table below.
| Inorganic Compounds | Soil (mg/kg) | Organic Compounds | Soil (mg/kg) |
|---|---|---|---|
| Ag | 3 | 2,4-D | 0.25 |
| As | 8 | 2,4,5-T | 3.82 |
| B | 1.7 | Aldrin | 0.48 |
| Ba | 302 | Chlordane | 3 |
| Be | 0.2 | Dieldrin | 0.17 |
| Cd | 4 | Lindane | 12 |
| F | 635 | DDT | 1.54 |
| Hg | 7 | PAHs | 16 |
| Mo | 0.6 | PCDs | 0.89 |
| Ni | 107 | PCDDs | 0.00012 |
| Pb | 84 | Benzene | 0.14 |
| Sb | 36 | Chlorobenzene | 211 |
| Se | 6 | Toluene | 12 |
| Tl | 0.3 | Phthalate | 13 733 |
| V | 47 | Pyrene | 41 |
| Styrene | 0.68 | ||
| Toxaphene | 0.0013 |
Please note that the industry mainly generates heavy metals and toxic organic compounds in wastewater, which are of less concern in a refugee camp setting. However, some sources of heavy metals and organic pollutants in wastewater may still exist in refugee camps, from batteries, paints, detergents, and pharmaceuticals.
No specific groundwater or environmental protection guidelines are provided due to local variations, which complicate creating a universal guideline.
However, the WHO guidelines also offer various control measures to mitigate environmental impacts, detailed in the following table.
| Problem | Suggested Control Measure |
|---|---|
| Nitrogen excess | – Removal through treatment – Dilution with fresh water – Limitation of wastewater quantity applied |
| Organic matter | – Removal through treatment – Resting time between irrigation for soil to biodegrade |
| Salinity | – Avoid the use of water with TDS 500mg/L – 2,000mg/L, depending on soil type and drainage – Dilution of water – Increase soil washing, improve ground drainage, apply soil amendments (compost or manure) |
| Chlorides | – < 100mg/L for sprinklers – < 350mg/L for flood irrigation – Irrigate at night |
| TSS | – Removal through treatment – Plough soil when clogged |
For further information, please click on the Materials tab at the top of the page.
Further Reading:
- Proposed national standard for treated domestic wastewater reuse for irrigation (Link)
- WHO Guidelines for the safe use of wastewater, excreta and greywater (Link)
- JRC Minimum quality requirements for water reuse in agricultural irrigation and aquifer recharge (Link)
- FAO Water Quality in Agriculture (Link)
Examples of Irrigation Standards:
- Irrigation standards with wastewater in Jordan (p.19-20) (Link)
- Irrigation standards with wastewater in Morocco (Link)
