Key control handles in integrated urban wastewater systems for improving receiving water quality

Figures & data

Figure 1. BSM-UWS layout identifying different control strategies (in orange) used for the GSA study (modified from Saagi et al. (2017)). Note that the diagram for the valve after the rainwater storage tank (just before the primary clarifier) represents two valves (throttle valve for the storage tank and the bypass valve) and DO control includes three control handles (SP_DO2, K_La₁gain, K_La₃gain).

Table 1. Catchment characteristics and sewer storage volumes for the BSM-UWS layout.

Sub-catchment	Area (ha)	PE	DWF (m^3.d^−1)		Storage (m^3)
			DOM	IND
1	99	15,920	2390		5000
2	21	3920	590	2500	1000
3	29	2960	440
4	71	9600	1440		4400
5	71	7840	1180		3600
6	249	39,760	5960		8100
Total	540	80,000	12,000	2500	22,100

DWF: Dry weather flow; DOM: Domestic; IND: Industrial

Table 2. List of input factors (control handles) for the GSA study.

Section		Input factor	Description	Default value
Sewer	1	Qpump,ST1	Max. pump capacity for ST1 (m^3.d^−1)	25,000
	2	Qmax,ST2	Max. throttle flow rate for ST2 (m^3.d^−1)	20,500
	3	Qpump,ST4	Max. pump capacity for ST4 (m^3.d^−1)	5000
	4	Qthrottle,ST4	Max. throttle flow rate for ST4 (m^3.d^−1)	63,600
	5	Qmax,ST5	Max. throttle flow rate for ST5 (m^3.d^−1)	22,500
	6	Qmax,ST6	Max. throttle flow rate for ST6 (m^3.d^−1)	187,200
WWTP	7	Qmax,RST	Max. throttle flow rate for RST (m^3.d^−1)	187,200
	8	QBP1	Max. flow rate after BP1 (m^3.d^−1)	90,000
	9	QBP2	Max. flow rate after BP2 (m^3.d^−1)	70,000
	10	Qr	Sludge recycle rate (m^3.d^−1)	20,600
	11	Qw	Sludge wastage rate (m^3.d^−1)	450
	12	Qintr	Internal recirculation rate (m^3.d^−1)	61,900
	13	KLa1gain	Gain for oxygen transfer coefficient (AER1) (-)	1.5
	14	SPDO2	Dissolved oxygen set point for AER2 (g.m^−3)	2
	15	KLa3gain	Gain for oxygen transfer coefficient (AER3) (-)	0.5

Figure 2. Influential control handles for sewer and WWTP performance criteria (1-year evaluation period) – V_ovf (a), OQI (b), EQI (c) and OCI (d). Sewer control handles in blue and WWTP control handles in green.

Figure 3. Influential control handles for river water quality using 1-year evaluation period in terms of T_exc,NH3 (a) and T_exc,DO (b). Sewer control handles in blue and WWTP control handles in green.

Figure 4. Comparison of GSA results for sewer performance criteria (V_ovf (a) and OQI (b)). The µ* values from three different 15-days evaluation are compared with 1-year evaluation.

Figure 5. The GSA results for WWTP performance (EQI (a) and OCI (b)) from 1-year evaluation compared with those from three 15-days simulations.

Figure 6. GSA results comparison for river water quality criteria T_exc,NH3 (a) and T_exc,DO (b).

Table A1. Weights used for the calculation of criteria OQI, EQI and OCI.

OQI/EQI – pollutant (kg.d^−1)	Weight	OCI – component	Weight
TSS	2	Aeration (kg O2.d^−1)	1
COD	1	Mixing (kWh.d^−1)	1
BOD5	2	Pumping (recycle) (m^3.d^−1)	0.008
TKN	30	Pumping (wastage) (m^3.d^−1)	0.05
NO3	10	Pumping (internal recirculation) (m^3.d^−1)	0.004
Porg	100	Sludge handling (kg TSS.d^−1)	5
Pinorg	100	Chemicals (carbon) (kg.d^−1)	3

Figure A1. An example wedge plot using the µ and σ values obtained from Morris screening.

Figure A2. Rainfall data for the three different return periods (0.5 year (a), 2 years (b) and 5 years (c)).

Table A2. Complete list of sensitivity indices for all the input factors using 1-year evaluation period. Influential control handles in bold text.

S.No	Control handle	Sensitivity index (µ*) for evaluation criteria
		Vovf	OQI	EQI	OCI	Texc,NH3	Texc,DO
1	Qpump,ST1	0.042	0.037	0.009	0.003	0.004		0.042
2	Qmax,ST2	0.023	0.022	0.007	0.001	0.004		0.015
3	Qpump,ST4	0.008	0.004	0.002	0.001	0.001		0.007
4	Qthrottle,ST4	0.228	0.201	0.038	0.012	0.008		0.195
5	Qmax,ST5	0.002	0.001	0.000	0.000	0.000		0.038
6	Qmax,ST6	0.882	0.826	0.173	0.031	0.041		0.208
7	Qmax,RST	0	0	0.104	0.031	0.035		0.283
8	QBP1	0	0	0.104	0.034	0.028		0.213
9	QBP2	0	0	0.139	0.075	0.056		0.186
10	Qr	0	0	0.310	0.239	0.498		0.034
11	Qw	0	0	0.658	0.850	0.550		0.482
12	Qintr	0	0	0.143	0.029	0.139		0.030
13	KLa1gain	0	0	0.134	0.080	0.185		0.048
14	SPDO2	0	0	0.225	0.102	0.397		0.169
15	KLa3gain	0	0	0.149	0.026	0.197		0.202

Table A3. Complete list of sensitivity indices for all the input factors using a 5-year return period rainfall event. Influential control handles in bold text.

S.No	Control handle	Sensitivity index (µ*) for evaluation criteria
		Vovf	OQI	EQI	OCI	Texc,NH3	Texc,DO
1	Qpump,ST1	0.037	0.019	0.022	0	0.069	0.096
2	Qmax,ST2	0.034	0.032	0.021	0.001	0.017	0.087
3	Qpump,ST4	0.006	0.004	0.018	0.001	0.030	0.023
4	Qthrottle,ST4	0.119	0.153	0.089	0.004	0.050	0.085
5	Qmax,ST5	0.031	0.042	0	0	0.004	0.031
6	Qmax,ST6	0.974	0.959	0.579	0.006	0.120	0.252
7	Qmax,RST	0	0	0.088	0.002	0.190	0.140
8	QBP1	0	0	0.269	0.006	0.215	0.143
9	QBP2	0	0	0.450	0.018	0.585	0.506
10	Qr	0	0	0.216	0.219	0.131	0.028
11	Qw	0	0	0.194	0.982	0.022	0.008
12	Qintr	0	0	0.192	0.019	0.020	0.002
13	KLa1gain	0	0	0.098	0.049	0.067	0.018
14	SPDO2	0	0	0.226	0.086	0.126	0.068
15	KLa3gain	0	0	0.140	0.023	0.058	0.021

Table A4. Complete list of sensitivity indices for all the input factors using a 2-year return period rainfall event. Influential control handles in bold text.

S.No	Control handle	Sensitivity index (µ*) for evaluation criteria
		Vovf	OQI	EQI	OCI	Texc,NH3	Texc,DO
1	Qpump,ST1	0.023	0.037	0.024	0	0.06	0.094
2	Qmax,ST2	0.034	0.01	0.019	0.001	0.017	0.079
3	Qpump,ST4	0.005	0.003	0.018	0.001	0.029	0.029
4	Qthrottle,ST4	0.103	0.205	0.095	0.004	0.051	0.164
5	Qmax,ST5	0.024	0.022	0	0	0.004	0.045
6	Qmax,ST6	0.992	0.972	0.592	0.005	0.123	0.323
7	Qmax,RST	0	0	0.087	0.002	0.195	0.147
8	QBP1	0	0	0.282	0.006	0.228	0.145
9	QBP2	0	0	0.444	0.017	0.603	0.471
10	Qr	0	0	0.216	0.218	0.120	0.024
11	Qw	0	0	0.196	0.982	0.020	0.005
12	Qintr	0	0	0.198	0.02	0.021	0.002
13	KLa1gain	0	0	0.101	0.049	0.061	0.007
14	SPDO2	0	0	0.227	0.087	0.116	0.054
15	KLa3gain	0	0	0.141	0.023	0.059	0.058

Table A5. Complete list of sensitivity indices for all the input factors using a 0.5-year return period rainfall event. Influential control handles in bold text.

S.No	Control handle	Sensitivity index (µ*) for evaluation criteria
		Vovf	OQI	EQI	OCI	Texc,NH3	Texc,DO
1	Qpump,ST1	0.056	0.036	0.031	0.001	0.038	0.076
2	Qmax,ST2	0.034	0.046	0.015	0.001	0.008	0.038
3	Qpump,ST4	0.007	0.005	0.019	0.001	0.023	0.034
4	Qthrottle,ST4	0.191	0.152	0.095	0.003	0.072	0.138
5	Qmax,ST5	0.010	0.010	0	0	0.003	0.052
6	Qmax,ST6	0.922	0.950	0.618	0.004	0.114	0.461
7	Qmax,RST	0	0	0.111	0.002	0.176	0.172
8	QBP1	0	0	0.342	0.008	0.240	0.189
9	QBP2	0	0	0.442	0.018	0.627	0.486
10	Qr	0	0	0.196	0.217	0.088	0.015
11	Qw	0	0	0.178	0.982	0.015	0
12	Qintr	0	0	0.187	0.020	0.017	0.004
13	KLa1gain	0	0	0.094	0.050	0.063	0.013
14	SPDO2	0	0	0.208	0.087	0.092	0.048
15	KLa3gain	0	0	0.129	0.023	0.046	0.039

Saagi, R., X. Flores-Alsina, S. Kroll, K. V. Gernaey, and U. Jeppsson. 2017. “A Model Library for Simulation and Benchmarking of Integrated Urban Wastewater Systems.” Environmental Modelling & Software 93: 282–295. doi:10.1016/j.envsoft.2017.03.026.

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