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Improving total nitrogen removal using a neural network ammonia-based aeration control in activated sludge process


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Figure 1:

BSM1.
BSM1.

Figure 2:

Feedback PI ABAC configuration.
Feedback PI ABAC configuration.

Figure 3:

Direct feedback NN ABAC.
Direct feedback NN ABAC.

Figure 4:

Flowchart of the proposed NN ABAC methodology.
Flowchart of the proposed NN ABAC methodology.

Figure 5:

Flowchart of the NN training process.
Flowchart of the NN training process.

Figure 6:

Flowchart of the LM algorithm.
Flowchart of the LM algorithm.

Figure 7:

The topological formation of the NN.
The topological formation of the NN.

Figure 8:

The implementation of NN ABAC control architecture in BSM1.
The implementation of NN ABAC control architecture in BSM1.

Figure 9:

Performances of the last 7 days of simulation using dry weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).
Performances of the last 7 days of simulation using dry weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).

Figure 10:

Performances of the last 7 days of simulation using rain weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).
Performances of the last 7 days of simulation using rain weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).

Figure 11:

Performances of the last 7 days of simulation using storm weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).
Performances of the last 7 days of simulation using storm weather with the PI (black line), PI-ABAC (red dotted line), and NN-ABAC (blue line).

Summary of recent research trend using ABAC control.

AuthorMethodsResults
PI ABACUprety et al. (2015)Feedback PID controller for ABAC to adjust DO in all aeration basins and zonesDecrease in supplemental carbon used for denitrification by 53% and overall decrease in energy consumption by 10%
Várhelyi et al. (2018)DO cascade, ABAC and combination of ABAC with the control of nitrate and return activated sludge recyclesABAC combination is the most cost-saving methods (reduction of about 43%)
MPC ABACSantín et al. (2015a)Fuzzy control and MPC (Feedforward ABAC)Total Nitrogen (Ntot) violations reduced by 11.04% and 100% elimination of SNH violations
Santín et al. (2016)Risk detection of effluent violation using artificial NN, fuzzy controller to improve denitrification/nitrification and MPC to improve DO trackingNtot violations reduced up to 97.63% and SNH violations reduced up to 68.29% (Ntot violation strategy) Ntot violations reduced up to 78.81% and 100% elimination of SNH violations (SNH violation strategy)

The effluent violations under dry, rain, and storm influent.

% of reduction
PIPI-ABACNN-ABACvs. PIvs. PI-ABAC
Dry
 Ntot violations (% of operating time)17.8611.9011.6134.99%2.44%
 Ntot violations (Occasions)75528.57%0.00%
 SNH violations (% of operating time)16.8216.5216.670.89%+0.91%
 SNH violations (Occasions)5550.00%0.00%
Rain
 Ntot violations (% of operating time)11.016.105.6548.68%7.38%
 Ntot violations (Occasions)53340.00%0.00%
 SNH violations (% of operating time)25.6022.9221.5815.70%5.85%
 SNH violations (Occasions)8880.00%0.00%
Storm
 Ntot violations (% of operating time)15.4810.8610.7130.81%1.38%
 Ntot violations (Occasions)75528.57%0.00%
 SNH violations (% of operating time)26.3425.1525.154.52%0.00%
 SNH violations (Occasions)7770.00%0.00%
 TSS violation (% of operating time)0.300.300.300.00%0.00%
 TSS violations (Occasions)2220.00%0.00%

Parameter used for LM training algorithm.

Maximum number of Epochs to train1,000
Performance goal0
Maximum validation failures6
Minimum performance gradient1e–7
Initial µu0.001
µu decrease factor0.1
µu increase factor10
Maximum µu1e10

Number of neurons suggested by the researcher and the corresponding MSE value

ResearcherMethodNumber of hidden neuronsMean square error (MSE)
Huang (2003)Nh=(m+2)N+2N/(m+2)750.0113080
Jinchuan and Xinzhe (2008)Nh=(Nin+Np)/L280.0052734
Shibata and Ikeda (2009)Nh=NiNo10.0089480

Comparison of five backpropagation algorithms.

BP algorithmFunctionMSEEpochR
Levenberg–Marquardttrainlm0.0057795230.99019
Scaled conjugate gradienttrainscg0.0073901270.98264
BFGS quasi-Newtontrainbfg0.0074205580.98849
Batch gradient descenttraingd0.054358010000.92262
Batch gradient descent with momentumtraingdm0.186900080.71436

The comparison of EQ, AECI, and Total OCI in dry/rain/storm weather.

% of reduction
PIPI ABACNN ABACvs. PIvs. PI ABAC
Dry
 EQI (kg poll.unit s/d)6,096.715,938.30215,978.31771.94%+0.67%
 AECI (kWh/day)3,697.573,769.5172,835.270323.32%24.78%
 Total OCI16,366.3016,500.99515,689.41974.14%4.92%
Rain
 EQI (kg poll.unit s/d)8,146.758,005.56478,029.17911.44%+0.29%
 AECI (kWh/day)3,671.703,786.55432,832.4722.86%25.20%
 Total OCI15,969.3516,133.867515,302.5044.18%5.15%
Storm
 EQI (kg poll.unit s/d)7,187.897,044.1157,079.70431.51%+0.51%
 AECI (kWh/day)3,720.763,830.84032,833.105423.86%26.04%
 Total OCI17,328.6717,403.953916,530.12044.61%5.02%

The comparison of AECI, EQI, OCI, and SNH and Ntot violations in similar studies.

Similar studiesProposed NN ABACHusin et al. (2020b)Husin et al. (2021b)
AECI (kWh/day)2,835.27033,641.693,749.24
EQI (kg poll.unit s/d)5,978.31776,081.465,975.75
Total OCI15,689.419716,366.3016,435.9
Ntot violations (% of operating time)11.6115.7713.8
SNH violations (% of operating time)16.6716.8216.07

Concentration thresholds of pollutants in the effluent.

VariablesNtot [g N/m3]CODt [g COD/m3]SNH [g N/m3]TSS [g SS/m3]BOD5 [g BOD/m3]
Max. values1810043010

The effluent quality limit.

Effluent averageSNH (<4 g N.m3)TSS (<30 g SS.m3)Ntot (<18 g N.m‒3)CODt (<100 g COD.m‒3)BOD5 (<10 g BOD.m‒3)
Dry
 PI2.478313.024816.890848.24702.7587
 PI ABAC2.548113.024415.862648.27362.7654
 NN ABAC2.911813.023315.351948.28882.7689
Rain
 PI3.157516.197014.715945.45873.4569
 PI ABAC3.129916.19714.180445.47023.459
 NN ABAC3.291816.195813.960645.473.4581
Storm
 PI2.995315.293515.834047.68753.2065
 PI ABAC2.996515.293515.131147.70433.2103
 NN ABAC3.238615.292314.819847.71193.2115
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Sprache:
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