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Table 1 describes pollutant removal efficiencies and effluent concentration under continuous and intermittent feeding modes. It is clear that under continuous operation (drying-wetting cycle 0), pollutant removals were relatively low, especially for COD and NH4+-N. When the feeding days was extended, removal efficiency of NH4+-N continuously declined to 88.4 ± 0.9% under drying-wetting cycle of 1:3. In contrast, TN removal efficiency increased with the declining of the drying-wetting cycle. The possible reasons may be: prolonged feeding days led to increased denitrification rates both by increasing the oxygen consumption making conditions more suitable for denitrification and providing organic carbon needed in the denitrification process.

Table 1

Effluent quality under different drying-wetting cycles

Drying-wetting cycleCOD
BOD
NH4+-N
NO2-N
Effluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %
3:1 20.0 ± 8.0 93.3 ± 2.6 2.0 ± 1.0 99.1 ± 0.4 1.0 ± 0.2 95.3 ± 0.9 0.26 ± 0.05 13.3 ± 16.7 
2:1 14.0 ± 4.0 95.3 ± 1.3 5.0 ± 1.0 97.8 ± 0.4 1.0 ± 0.15 95.3 ± 0.7 0.27 ± 0.07 10.0 ± 23.3 
1:1 26.0 ± 5.0 91.3 ± 1.6 5.0 ± 1.0 97.8 ± 0.4 1.8 ± 0.2 91.6 ± 0.9 0.48 ± 0.03 60.0 ± 10.0 
1:2 32.0 ± 6.0 89.3 ± 2.0 9.0 ± 2.0 96.1 ± 0.9 2.0 ± 0.3 90.7 ± 1.4 0.42 ± 0.04 40.0 ± 13.3 
1:3 43.0 ± 3.0 85.7 ± 1.0 12.0 ± 1.0 94.8 ± 0.4 2.5 ± 0.2 88.4 ± 0.9 0.00 ± 0.00 100.0 ± 0.0 
60.0 ± 2.0 80.0 ± 0.7 15.0 ± 2.0 93.5 ± 0.9 5.0 ± 0.15 76.7 ± 0.7 0.05 ± 0.05 83.3 ± 16.7 
NO3-N
TN
TP
Drying-wetting cycleEffluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %
3:1 1.5 ± 0.10 50.0 ± 3.3 4.8 ± 0.3 80.8 ± 1.2 0.0 ± 0.0 100.0 ± 0.0   
2:1 1.2 ± 0.08 60.0 ± 2.7 4.3 ± 0.3 83.2 ± 1.2 0.0 ± 0.0 100.0 ± 0.0   
1:1 1.0 ± 0.05 66.7 ± 1.7 2.8 ± 0.2 88.8 ± 0.8 0.2 ± 0.1 95.0 ± 2.5   
1:2 0.8 ± 0.05 73.3 ± 1.0 2.6 ± 0.1 88.6 ± 0.4 0.2 ± 0.2 95.0 ± 5.0   
1:3 1.0 ± 0.05 66.7 ± 1.4 2.5 ± 0.4 89.6 ± 1.6 0.2 ± 0.1 95.0 ± 2.5   
0.5 ± 0.05 83.3 ± 1.2 6.4 ± 0.3 74.4 ± 1.2 0.2 ± 0.1 95.0 ± 2.5   
Drying-wetting cycleCOD
BOD
NH4+-N
NO2-N
Effluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %
3:1 20.0 ± 8.0 93.3 ± 2.6 2.0 ± 1.0 99.1 ± 0.4 1.0 ± 0.2 95.3 ± 0.9 0.26 ± 0.05 13.3 ± 16.7 
2:1 14.0 ± 4.0 95.3 ± 1.3 5.0 ± 1.0 97.8 ± 0.4 1.0 ± 0.15 95.3 ± 0.7 0.27 ± 0.07 10.0 ± 23.3 
1:1 26.0 ± 5.0 91.3 ± 1.6 5.0 ± 1.0 97.8 ± 0.4 1.8 ± 0.2 91.6 ± 0.9 0.48 ± 0.03 60.0 ± 10.0 
1:2 32.0 ± 6.0 89.3 ± 2.0 9.0 ± 2.0 96.1 ± 0.9 2.0 ± 0.3 90.7 ± 1.4 0.42 ± 0.04 40.0 ± 13.3 
1:3 43.0 ± 3.0 85.7 ± 1.0 12.0 ± 1.0 94.8 ± 0.4 2.5 ± 0.2 88.4 ± 0.9 0.00 ± 0.00 100.0 ± 0.0 
60.0 ± 2.0 80.0 ± 0.7 15.0 ± 2.0 93.5 ± 0.9 5.0 ± 0.15 76.7 ± 0.7 0.05 ± 0.05 83.3 ± 16.7 
NO3-N
TN
TP
Drying-wetting cycleEffluent mg/LRemoval %Effluent mg/LRemoval %Effluent mg/LRemoval %
3:1 1.5 ± 0.10 50.0 ± 3.3 4.8 ± 0.3 80.8 ± 1.2 0.0 ± 0.0 100.0 ± 0.0   
2:1 1.2 ± 0.08 60.0 ± 2.7 4.3 ± 0.3 83.2 ± 1.2 0.0 ± 0.0 100.0 ± 0.0   
1:1 1.0 ± 0.05 66.7 ± 1.7 2.8 ± 0.2 88.8 ± 0.8 0.2 ± 0.1 95.0 ± 2.5   
1:2 0.8 ± 0.05 73.3 ± 1.0 2.6 ± 0.1 88.6 ± 0.4 0.2 ± 0.2 95.0 ± 5.0   
1:3 1.0 ± 0.05 66.7 ± 1.4 2.5 ± 0.4 89.6 ± 1.6 0.2 ± 0.1 95.0 ± 2.5   
0.5 ± 0.05 83.3 ± 1.2 6.4 ± 0.3 74.4 ± 1.2 0.2 ± 0.1 95.0 ± 2.5   

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