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Table 6

Effect of the 15-day aeration post-treatment at different air flow rates on selected parameters of the TWW, and application of a t-test (significance level 0.05) to assess the statistical differences between the initial and final TWW composition in each treatment

ParameterInitial valueControl (no aeration)
16.5 L/(h Lreactor) aeration
33 L/(h Lreactor) aeration
FAO degree of restriction for TWW use for irrigationa
Value% variationbpt-testcValue% variationbpt-testcValue% variationbpt-testcLowSlight/moderateSevere
pH 7.44 ± 0.02 8.52 ± 0.02 +15% 3.1·10−78.53 ± 0.02 +15% 3.0·10−78.54 ± 0.02 +15% 2.9·10−7Normal range : 6.5–8 
Ca (mg/L) 139 ± 4 135 ± 4 −3% 3.0·10−1 127 ± 4 −9% 2.1·10−2147 ± 4 +6% 8.5·10−2 – – – 
HCO3 (mg/L) 576 ± 23 488 ± 20 −15% 7.2·10−3268 ± 11 −53% 3.0·10−5265 ± 11 −54% 2.9·10−592 92–519 >519 
Organic matter (mg/L) 150 ± 8 −100% 4.1·10−6−100% 4.1·10−6−100% 4.1·10−6– – – 
EC (dS/m) 3.55 ± 0.09 3.75 ± 0.09 +6% 8.9·10−2 3.65 ± 0.09 +3% 3.2·10−1 3.63 ± 0.09 +2% 4.1·10−1 <0.7 0.7–3.0 >3.0 
ParameterInitial valueControl (no aeration)
16.5 L/(h Lreactor) aeration
33 L/(h Lreactor) aeration
FAO degree of restriction for TWW use for irrigationa
Value% variationbpt-testcValue% variationbpt-testcValue% variationbpt-testcLowSlight/moderateSevere
pH 7.44 ± 0.02 8.52 ± 0.02 +15% 3.1·10−78.53 ± 0.02 +15% 3.0·10−78.54 ± 0.02 +15% 2.9·10−7Normal range : 6.5–8 
Ca (mg/L) 139 ± 4 135 ± 4 −3% 3.0·10−1 127 ± 4 −9% 2.1·10−2147 ± 4 +6% 8.5·10−2 – – – 
HCO3 (mg/L) 576 ± 23 488 ± 20 −15% 7.2·10−3268 ± 11 −53% 3.0·10−5265 ± 11 −54% 2.9·10−592 92–519 >519 
Organic matter (mg/L) 150 ± 8 −100% 4.1·10−6−100% 4.1·10−6−100% 4.1·10−6– – – 
EC (dS/m) 3.55 ± 0.09 3.75 ± 0.09 +6% 8.9·10−2 3.65 ± 0.09 +3% 3.2·10−1 3.63 ± 0.09 +2% 4.1·10−1 <0.7 0.7–3.0 >3.0 

aAyers & Westcot (1985).

b% variation in relation to the corresponding initial value.

cProbability that there are no statistically significant differences in the concentration of each compound or parameter between the initial TWW composition (2nd column) and the TWW composition after 15 days of post-treatment at different aeration intensities. The probabilities lower than the significance level (0.05), corresponding to statistically different values, are indicated with an asterisk.

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