Several standards for the reuse of wastewater for agricultural and landscape irrigation, both restricted and unrestricted, have been issued in Saudi Arabia. Initially, the Ministry of Agriculture and Water (MAW) issued several draft and tentative standards (MAW, 1986 and MAW, 1989), all of which were stringent, and prevented agricultural use of the treated effluent (Abu-Rizaiza, 1999). In 2003, the Ministry of Municipal and Rural Affairs (MMRA) issued new standards (MMRA, 2003), which were replaced in 2006 by the latest standards (MWE, 2006a), set by the Ministry of Water and Electricity (MWE). Table 2 shows the maximum allowable contaminant levels for both MWE and MMRA standards for the reuse of wastewater for agricultural irrigation. The MWE is currently responsible for issuing the standards pertaining to water and wastewater.
| Parameter | Unit | Unrestricted irrigation | Unrestricted irrigation | Restricted irrigation | Restricted irrigation |
| 2003-MMRA | 2006-MWE | 2003-MMRA | 2006-MWE | ||
| Physical parameters | |||||
| Floatable materials | Absent | Absent | Absent | ||
| Total suspended solids (TSS) | mg/L | 10 | 10a | 40 | 40b |
| pH | 6–8.4 | 6–8.4 | 6–8.4 | ||
| Turbidity | NTU | 5 | 5 | ||
| Chemical parameters | |||||
| Organic chemicals parameters | |||||
| Biochemical oxygen demand (BOD5) | mg/L | 10 | 10a | 40 | 40b |
| Chemical oxygen demand (COD) | mg/L | 50 | |||
| Total organic carbon (TOC) | mg/L | 40 | |||
| Oil and grease | mg/L | Absent | Absent | Absent | |
| Phenol | mg/L | 0.002 | 0.002 | 0.002 | |
| Inorganic chemicals parameters | |||||
| Heavy metals | |||||
| Arsenic (As) | mg/L | 0.1 | 0.1 | 0.1 | |
| Cadmium (Cd) | mg/L | 0.01 | 0.01 | 0.01 | |
| Chromium (Cr) | mg/L | 0.01 | 0.1 | 0.1 | |
| Copper (Cu) | mg/L | 0.2 | 0.4 | 0.4 | |
| Cyanide (Cn) | mg/L | 0.05 | |||
| Lead (Pb) | mg/L | 5 | 0.1 | 0.1 | |
| Mercury (Hg) | mg/L | 0.001 | 0.001 | 0.001 | |
| Nickel (Ni) | mg/L | 0.02 | 0.2 | 0.2 | |
| Zinc (Zn) | mg/L | 2 | 4 | 4 | |
| Aluminum (Al) | mg/L | 5 | 5 | 5 | |
| Barium (Ba) | mg/L | 1 | |||
| Manganese (Mn) | mg/L | 0.2 | 0.2 | 0.2 | |
| Silver (Ag) | mg/L | 0.5 | |||
| Selenium (Se) | mg/L | 0.02 | 0.02 | 0.02 | |
| Molybdenum (Mo) | mg/L | 0.01 | 0.01 | 0.01 | |
| Boron (B) | mg/L | 0.75 | 0.75 | 0.75 | |
| Vanadium (V) | mg/L | 0.1 | 0.1 | 0.1 | |
| Lithium (Li) | mg/L | 2.5 | 2.5 | 2.5 | |
| Beryllium (Be) | mg/L | 0.1 | 0.1 | 0.01 | |
| Iron (Fe) | mg/L | 5 | 5 | 5 | |
| Cobalt (Co) | mg/L | 0.05 | 0.05 | 0.05 | |
| Chemical compounds | |||||
| Total dissolved solids (TDS) | mg/L | 2000 | 2500c | 2000 | 2500d |
| Chloride (Cl2) | mg/L | 100 | |||
| Sulfate (SO4) | mg/L | 600 | |||
| Ammonia (NH3–N) | mg/L | 5 | 5 | 5 | |
| Nitrate (NO3–N) | mg/L | 10 | 10 | 10 | |
| Free residual chlorine | mg/L | 0.2 | 0.5e | 0.5e | |
| Fluoride (F) | mg/L | 1 | 1 | ||
| Biological parameters | |||||
| Fecal coliforms per 100 mL | 2.2f | 2.2g | 1000h | 1000b<comma>h | |
| Intestinal nematodes per litre | No./L | 1i | 1i | 1j |
a Monthly average BOD5, and TSS should not exceed 10 mg/L each. Weekly average BOD5, and TSS should not exceed 15 mg/L each.
b Monthly average of BOD5, and TSS should not be more than 40 mg/L, and Fecal coliforms 1000 colonies/100 mL.
c Tertiary treated effluents with TDS more than the stated concentration can be used if dilution with a water of less TDS is possible, or if it will be used for irrigating crops insensitive for high TDS.
d Secondary treated effluents with TDS more than the stated concentration can be used if dilution with a water of less TDS is possible, or if it will be used for irrigating crops insensitive for high TDS.
e Free residual chlorine should not be less than 0.2 mg/L if chlorine is used as a disinfectant.
f Fecal coliform organisms in the effluent should not exceed 2.2/100 mL (MPN method or equivalent).
g The wastewater effluent shall be considered adequately disinfected for unrestricted irrigation if the average fecal coliform organisms in the effluent do not exceed MPN 2.2/100 mL (or equivalent) as determined from the bacteriological test results of the last 7 days, and the number of fecal coliform organisms does not exceed MPN 23/100 mL (or equivalent) in any sample.
h Colonies.
i One live intestinal nematodes per litre.
j Secondary
treated effluents with intestinal nematodes more than the stated number can be
used if precautions for workers and consumers can be taken.
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References: http://www.sciencedirect.com/science/article/pii/S1018363910000024
http://www.sawea.org/pdf/2009/Session%20D/Wastewater%20Reuse%20Regulations.pdf