Approbation of the texture analysis imaging technique in the wastewater treatment plant

Figures & data

Table 1. Inlet and outlet wastewater quality parameters of Frogn WWTP

Variables	Mean	Min	Max	Standard deviation
Inlet flow, m^3/h	310.4	102.8	789.7	164.9
Inlet pH	7.4	6.7	8.0	0.3
Inlet turbidity, FNU	211.6	75.6	500.0	93.4
Inlet conductivity, μS/cm	758.9	400.3	1,154.5	174.7
pH after coagulant dosage	6.9	6.5	7.3	0.2
Outlet turbidity, FNU	3.8	1.1	21.1	4.3
Inlet total P, mg P/l	3.86	0.91	6.29	1.75
Outlet total P, mg P/l	0.18	0.10	0.29	0.05
Inlet total P, mmol P/l	0.12	0.03	0.20	0.06
Coagulant dose, ml/m^3	83.0	49.5	196.3	24.6
Coagulant dose, mmol Al/l	0.38	0.23	0.89	0.11
Ratio mol Al: mol P	3.65	2.07	8.38	1.92

Figure 1. (a) Schematic representation of the installation and (b) a photograph from the Frogn WWTP.

Figure 2. Graph showing the load changes in the Frogn WWTP during normal days and in rainy days. The images represent the typical floc structures for those particular days when the image analysis installation was functioning. Numbers within the each image mean the corresponding coagulant dosages in μl/l.

Figure 3. Scores plot of PCA, PC1 vs. PC2 for: (a) data with 9 GLCM textural features of the images of flocs; (b) data containing wastewater quality parameters, GLCM textural features and the coagulant dosage.

Table 2. FTI ranges for 3 classes in the data-set

FTIClass	Mean	Min	Max	Standard deviation
Normal conditions	7.97	4.63	11.89	2.25
Rain events	3.09	1.23	6.05	1.47
High inlet turbidity	2.48	1.57	3.90	1.24

Figure 4. Floc texture indexes and corresponding outlet turbidity for the obtained data-set

Table 3. Results of partial least squares regressions for the effluent turbidity prediction

Model, X variables	Number of factors	R^2 cal.	R^2c-val.	RMSEC	RMSECV
All inlet wastewater parameters QIN, TUI, PHI, CNI, Dose	2	0.805	0.793	1.919	2.013
All inlet WWP and FTI	2	0.829	0.81	1.795	1.885
QIN, TUI	1	0.797	0.789	1.96	1.998
QIN, TUI and FTI	1	0.837	0.828	1.755	1.795
QIN, TUI, Dose and FTI	2	0.841	0.812	1.732	1.885
QIN, TUI, Variance, Prominence, Correlation, Contrast	2	0.866	0.851	1.594	1.666

Figure 5. Comparison of two effluent turbidity prediction models: (a) TUO = f(QIN, TUI, CNI, PHI, Dose); (b) TUO = f(QIN, TUI, Variance, Prominence, Correlation, Contrast).