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Table 4

Physical and chemical properties of the TWW before the aeration post-treatment, compared to the FAO recommendations on the degree of restriction for TWW reuse for irrigation and to the ISO 16075 standard

ParameterValue in the TWWFAO degree of restriction for TWW use for irrigationa
ISO 16075 guideline for TWW reuse for irrigationb
NoneSlight to moderateSevere
pH 7.44 ± 0.02 Normal range: 6.5–8  
EC (dS/m) 3.55 ± 0.09 <0.7 0.7–3.0 >3.0  
CO32− (mg/l)     
HCO3 (mg/l) 576 ± 23 <92 92–519 >519  
Ca2+ (mg/l) 139 ± 4     
Mg2+ (mg/l) 51 ± 2     
Cl (mg/l) 666 ± 26 <142c >142c   
Na+ (mg/l) 203 ± 6 <69c >69c   
K+ (mg/l) 45 ± 2     
NH4+ (mg/L) 1.8 ± 0.1     
P (mg/L) 0.90 ± 0.04     
NO3-N (mg/L) 55 ± 3 <5 5–30 >30  
Organic matter (mg/L) 150 ± 8     
5-day biochemical oxygen demand (mg/L) 12 ± 1    <35 
Total suspended solids (mg/L) 12 ± 1    <50 
Thermo-tolerant coliforms (n./100 mL) 60 ± 6    <10,000 
Total dissolved solids (mg/L) 2 595 ± 180 <450 450–2,000 >2,000  
ParameterValue in the TWWFAO degree of restriction for TWW use for irrigationa
ISO 16075 guideline for TWW reuse for irrigationb
NoneSlight to moderateSevere
pH 7.44 ± 0.02 Normal range: 6.5–8  
EC (dS/m) 3.55 ± 0.09 <0.7 0.7–3.0 >3.0  
CO32− (mg/l)     
HCO3 (mg/l) 576 ± 23 <92 92–519 >519  
Ca2+ (mg/l) 139 ± 4     
Mg2+ (mg/l) 51 ± 2     
Cl (mg/l) 666 ± 26 <142c >142c   
Na+ (mg/l) 203 ± 6 <69c >69c   
K+ (mg/l) 45 ± 2     
NH4+ (mg/L) 1.8 ± 0.1     
P (mg/L) 0.90 ± 0.04     
NO3-N (mg/L) 55 ± 3 <5 5–30 >30  
Organic matter (mg/L) 150 ± 8     
5-day biochemical oxygen demand (mg/L) 12 ± 1    <35 
Total suspended solids (mg/L) 12 ± 1    <50 
Thermo-tolerant coliforms (n./100 mL) 60 ± 6    <10,000 
Total dissolved solids (mg/L) 2 595 ± 180 <450 450–2,000 >2,000  

aAyers & Westcot (1985).

bValues corresponding to category C (irrigation of non-food crops) of the ISO 16075 standard (ISO 2015).

cRefers to the case of sprinkler irrigation.

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