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Table 7

Comparison of the composition of the clogging material sampled in the irrigation pipeline and of the precipitates formed in the aeration/sedimentation tanks after 30 days of treatment, determined by EDS analyses (atomic percentages)

ParameterClogging material from irrigation pipelinePrecipitates collected from the aeration tanks
Control (no aeration)
16.5 L/(h Lreactor) aeration
33 L/(h Lreactor) aeration
% content% contentpt-testa% contentpt-testa% contentpt-testa
63 ± 3 60 ± 3 3.0·10−1 67 ± 3 2.1·10−1 66 ± 3 3.2·10−1 
Ca 20 ± 1 22 ± 1 8.0·10−2 17 ± 1 1.7·10−217 ± 1 1.7·10−2
7.7 ± 0.4 3.1 ± 0.2 4.3·10−51.4 ± 0.1 9.8·10−61.5 ± 0.1 1.1·10−5
Mn 3.5 ± 0.2 b 4.1·10−6b 4.1·10−6b 4.1·10−6
Si 3.5 ± 0.2 3.3 ± 0.2 2.2·10−1 b 4.1·10−6b 4.1·10−6
Al 1.0 ± 0.1 b 6.5·10−5b 6.5·10−5b 6.5·10−5
Mg 0.84 ± 0.08 0.39 ± 0.04 1.1·10−30.44 ± 0.04 1.9·10−3b 6.5·10−5
Fe 0.35 ± 0.04 b 6.5·10−5b 6.5·10−5b 6.5·10−5
b 0.29 ± 0.03 6.5·10−5b c b c 
b 0.18 ± 0.02 6.5·10−5b c b c 
Ni b 0.48 ± 0.05 6.5·10−5b c b c 
ParameterClogging material from irrigation pipelinePrecipitates collected from the aeration tanks
Control (no aeration)
16.5 L/(h Lreactor) aeration
33 L/(h Lreactor) aeration
% content% contentpt-testa% contentpt-testa% contentpt-testa
63 ± 3 60 ± 3 3.0·10−1 67 ± 3 2.1·10−1 66 ± 3 3.2·10−1 
Ca 20 ± 1 22 ± 1 8.0·10−2 17 ± 1 1.7·10−217 ± 1 1.7·10−2
7.7 ± 0.4 3.1 ± 0.2 4.3·10−51.4 ± 0.1 9.8·10−61.5 ± 0.1 1.1·10−5
Mn 3.5 ± 0.2 b 4.1·10−6b 4.1·10−6b 4.1·10−6
Si 3.5 ± 0.2 3.3 ± 0.2 2.2·10−1 b 4.1·10−6b 4.1·10−6
Al 1.0 ± 0.1 b 6.5·10−5b 6.5·10−5b 6.5·10−5
Mg 0.84 ± 0.08 0.39 ± 0.04 1.1·10−30.44 ± 0.04 1.9·10−3b 6.5·10−5
Fe 0.35 ± 0.04 b 6.5·10−5b 6.5·10−5b 6.5·10−5
b 0.29 ± 0.03 6.5·10−5b c b c 
b 0.18 ± 0.02 6.5·10−5b c b c 
Ni b 0.48 ± 0.05 6.5·10−5b c b c 

Application of a t-test (significance level 0.05) to assess statistical differences between compositions.

aProbability that there are no statistically significant differences between the % content of each monitored element in the precipitates formed in the aeration/sedimentation tanks after 30 days and the corresponding % content in the clogging material sampled in the irrigation pipeline. The probabilities lower than the significance level (0.05), corresponding to statistically different % contents, are indicated with an asterisk.

bBelow detection limit.

ct-test not applicable.

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