Water used for irrigation should not contain microorganisms or substances harmful to consumer health. There can be three groups of microorganisms in water: proper water bacteria and soil bacteria - usually harmless to humans, sewage microorganisms, including pathogenic bacteria for humans. The most important gastrointestinal diseases transmitted by pathogenic bacteria living in the water environment include typhoid fever, dysentery and typhoid fever. Viruses that cause infectious hepatitis have also been found in surface waters. It can be dangerous for consumers of fresh fruits and vegetables irrigated with water containing pathogenic bacteria. An indicator of biological contamination of water is the detection of Escherichia coli bacteria, which can cause diarrhea. The presence of this bacteria in the water indicates that the water is contaminated with fecal matter and indicates the potential danger of pathogenic bacteria. The coliform index is the number of coliform bacteria in 100 milliliters of water. In drinking water, this index should not exceed 0. The coliform index in irrigation water for vegetables and berries consumed fresh should not exceed 10. Instead of the coliform index, the so-called coliform titer is often given, which determines the smallest amount of water in which one bacterium is found. Appropriate analysis should be carried out at a unit authorized to do so, such as a sanitary-epidemiological station.
https://www.gov.pl/web/gis/stacje-sanitarno-epidemiologiczne
No less important is also the content in water of elements and chemical compounds that are harmful to humans and easily accumulate in plants (this applies mainly to heavy metals, phenols, detergents, etc.). (Table 1).
Table 1. permissible contents of certain elements in irrigation water according to the national standard PN-84 (c-04635)
| Element | Permissible amount [mg/l] |
|---|---|
| Arsenic (As) | 0,2 |
| Boron (B) | 0,5 |
| Chlorides (Cl) | 400 |
| Zinc (Zn) | 2,0 |
| Fluorine (F) | 1,5 |
| Aluminum (Al) | 5 |
| Cadmium (Cd) | 0,1 |
| Nickel (Ni) | 1,0 |
| Lead (Pb) | 0,1 |
| Mercury (Hg) | 0,01 |
| Sulfides (S) | 0,1 |
| Total heavy metals | 1,0 |
A very important aspect is also the pesticide content of irrigation water. Unfortunately, more and more often not only surface water but also deep-sea water contains pesticides. Unknowingly using such contaminated water for irrigation can cause certification laboratories to show the content of pesticides in even facilities where they have never been used. Chemical analyses of water for the content of pesticide residues in water can be carried out in the accredited laboratory of the Food Safety Research Department of the Institute of Horticulture - PIB in Skierniewice