Predication of Water Pollution Peak Concentrations by Hybrid BP Artificial Neural Network Coupled with Genetic Algorithm

Figures & data

Figure 1. Sampling stations of Sanxi and Pinshi WQAMS along Wujiang river.

Figure 2. Sanxi WQAMS online simulator and monitor panel.

Figure 3. Sampling stations of Sanxi and Pinshi WQAMS along Wujiang river.

Figure 4. Illustrative map of a typical 3-layer BPANN.

Figure 5. Schematic flowchart of hybrid GA-BPANN.

Figure 6. Model input and output structure.

Table 1. Descriptive statistics of calibration data from Oct. 2013 to July 2014.

Species	N	Min.	Max.	Mean	Std.	Skewness	Kurtosis
PS_Pb	304	0.50	21.51	2.15	2.40	3.78	20.2
SX_Pb	289	3.11	24.54	7.01	3.22	1.96	5.31
SX_WE	296	177	179.5	177	0.46	1.54	2.19
SX_Prep	304	0	71.5	3.24	8.76	4.37	23.8
SX_ pH	289	7.6	8.18	7.89	0.11	0.14	0.20
SX_Cond	289	281	412	355	24.9	−0.42	0.13
SX_Turb	289	2.00	383	21.9	38.9	5.15	34.2

Table 2. Descriptive statistics of predictive data from Aug. 2014 to Dec. 2014.

Species	N	Min.	Max.	Mean	Std.	Skewness	Kurtosis
PS_Pb	152	0.50	15.0	1.56	1.47	5.67	47.9
SX_Pb	152	3.25	11.6	5.03	1.18	2.07	8.81
SX_WE	152	177	179	177	0.28	2.12	5.93
SX_Prep	153	0	52.0	2.83	8.33	3.92	16.4
SX_ pH	153	7.57	8.24	7.87	0.13	−0.15	−0.04
SX_Cond	153	287	429	375	24.2	−0.55	0.93
SX_Turb	153	4.00	108	9.38	11.1	6.76	52.6

Figure 7. Calibration and prediction of DLC at Pinshi station by MLRM, BPANN and GA-BPANN.

Figure 8. Linear corelative analysis between observed and simulated DLC of Pingshi station at calibration phase.

Figure 9. Linear corelative analysis between observed and simulated DLC of Pingshi station at predictive phase.

Table 3. Simulated DLC(SDLC) and ARE by various models.

Date	DLC (ppb)	Modeled DLC (ppb)				MARE (%)
		MLRM	SMLRA	BPANN	GA-BPANN	MLRM	SMLRA	BPANN	GA-BPANN
2013/11/13	2.15	5.65	4.68	3.31	1.85	163%	118%	54%	14%
2013/12/17	11.97	7.97	8.19	11.04	11.95	33%	32%	8%	0%
2014/3/13	2.77	4.27	4.25	3.53	2.66	54%	54%	28%	4%
2014/4/1	14.03	9.58	9.40	10.19	14.03	32%	33%	27%	0%
2014/4/27	14.90	6.41	6.94	10.19	14.66	57%	53%	32%	2%
2014/5/13	5.53	4.48	4.45	3.88	4.52	19%	20%	30%	18%
2014/5/19	21.51	10.85	10.18	19.87	21.49	50%	53%	8%	0%
2014/5/23	11.17	9.02	9.07	9.50	11.10	19%	19%	15%	1%
2014/6/4	7.54	6.23	5.83	6.32	7.34	17%	23%	16%	3%
2014/6/11	9.77	7.15	7.28	5.69	9.78	27%	25%	42%	0%
2014/7/2	8.39	3.27	3.24	3.43	3.54	61%	61%	59%	58%
2014/8/20*	15.04	7.19	7.28	8.40	14.34	52%	52%	44%	5%
Min.	2.15	3.27	3.24	3.31	1.85	17%	19%	8%	0%
Max.	21.51	10.85	10.18	19.87	21.49	163%	118%	59%	58%
Average	10.40	6.84	6.73	7.95	9.77	48%	45%	29%	9%
R^2 in calibration phase	-					0.71	0.70	0.80	0.93
R^2 in verification phase						0.59	0.45	0.38	0.67

ppb means part per billion, is the unit of concentrations

Figure 10. Typical peak DLC process simulation by various models.

Figure 11. Typical peak DLC process simulation by various models.