Simulating the impact of water demand management options on water consumption and wastewater generation profiles

Figures & data

Figure 1. Components and principle of the simulation tool

Table 1. Calculation of greywater stored in the storage tank, the flow of water consumption and wastewater discharge

(a) Acronyms (and their descriptions) used for the calculation of greywater stored in the tank and the flows of water consumption and wastewater discharge
	Acronyms/Abbreviations	Description
1	$n$	Time interval
2	$G{W}_n$	Amount of greywater (GW) discharged from hand basins, showers and baths
3	$W{C}_n$	Amount of water consumption from toilets
4	$TK{1}_n$	Amount of greywater (GW) stored at the end of the first sub-period
5	$TK{2}_n$	Amount of GW stored at the end of the period
	$TK{1}_{n-1}$	Amount of GW stored at the beginning of the period n
6	$Full$	Maximal amount of GW that can be stored in the storage tank
7	$TopU{p}_n$	Amount of mains top-up
8	$Ov{F}_n$	Amount of wastewater discharged from hand basins, showers and baths that goes to the sewer
(b) Greywater stored in the tank and the flows of water consumption and wastewater discharge specific to Scenario ‘Very efficient’ during the period n
Beginning of the period n: $TopU{p}_n=0andOv{F}_n=0$
End of the first sub-period (filling stage)
Storage level vs greywater intake	Greywater stored in the tank $TK{1}_n$	Overflow $Ov{F}_n$
Stored greywater volume is sufficient $G{W}_n\le Full-TK{2}_{n-1}$	$TK{2}_{n-1}+G{W}_n$	0
Stored greywater volume is not sufficient $G{W}_n>Full-TK{2}_{n-1}$	$Full$	$G{W}_n-\left(Full-TK{2}_{n-1}\right)$
End of the period n (discharging stage)
Storage level vs toilet usage	Greywater stored in the tank $TK{2}_n$	Mains top-up $TopU{p}_n$
Stored greywater volume is sufficient $W{C}_n\le TK{1}_n$	$TK{1}_n-W{C}_n$	0
Stored greywater volume is not sufficient $W{C}_n>TK{1}_n$	0	$W{C}_n-TK{1}_n$

Table 2. Water savings resulting from the installation of different water use (saving) appliances in the Scenario ‘Efficient’

Appliances	Measures	Whole group	1-occupant	2-occupant	3-occupant	4-occupant
(a) Dual-flush toilets (3.6 l/use)	Water saving in m^3/day	28.3	4	8.0	7.0	9.6
	Water saving in l/person.day	28.3	38	40.0	23.3	23.9
	% of the standard water consumption	22.1	18	26.2	20.3	22.8
(b) Low-flow taps (3.6 l/min)	Water saving in m3/day	5.2	0.7	1.2	1.4	1.9
	Water saving in l/person.day	5.2	6.8	6.1	4.8	4.7
	% of the standard water consumption	4.1	3.2	4.0	4.2	4.4
(c) Efficient bathtubs (60 litres/use)	Water saving in m3/day	6.4	1.7	1.2	1.6	2.0
	Water saving in l/person.day	6.4	16.7	5.8	5.2	4.9
	% of the standard water consumption	5.0	7.9	3.8	4.5	4.7
(d) Shower restrictors (flow rate: 3 l/min)	Water saving in m3/day	5.4	0.7	1.1	1.9	1.6
	Water saving in l/person.day	5.4	6.7	5.6	6.5	4.1
	% of the standard water consumption	4.2	3.1	3.7	5.6	3.9
(e) Washing machines (42 l/use)	Water saving in m3/day	4.8	0.9	1.1	1.2	1.5
	Water saving in l/person.day	4.8	9.2	5.7	4.0	3.9
	% of the standard water consumption	3.7	4.3	3.7	3.5	3.7
(f) Dishwashers (13 l/use)	Water saving in m3/day	0.7	-	0.2	0.2	0.3
	Water saving in l/person.day	0.7	-	1.0	0.8	0.7
	% of the standard water consumption	0.6	-	0.7	0.7	0.7

Figure 2. Diurnal variations of water consumption for the whole group when the following WSAs are installed: (a) dual-flush toilets; (b) low-flow taps; (c) water-efficient baths; (d) shower restrictors; (e) water-efficient washing machines; and (f) water-efficient dishwashers

Figure 3. Water consumption breakdown based on different water use appliances in Scenario ‘Efficient’ for the whole group when the following WSAs are installed: (a) dual-flush toilets; (b) low-flow taps; (c) water-efficient baths; (d) shower restrictors; (e) water-efficient washing machines; and (f) water-efficient dishwashers

Table 3. Water savings resulting from the installation of GWR systems with different sizes of storage tanks

Appliances	Measures	Whole group	1-occupant	2-occupant	3-occupant	4-occupant
(a) Only GWR tank capacity: 10 l	Water saving in m^3/day	24.49	2.88	10.78	6.21	10.78
	Water saving in l/person.day	24.49	28.78	53.91	20.70	26.95
	% of the standard water consumption	20%	14%	35%	18%	26%
(b) Only GWR tank capacity: 50 l	Water saving in m^3/day	43.77	5.66	12.76	10.63	15.09
	Water saving in l/person.day	43.77	56.56	63.79	35.42	37.72
	% of the standard water consumption	34%	27%	42%	31%	36%
(c) Only GWR tank capacity: 100 l	Water saving in m^3/day	45.14	6.03	12.76	11.14	15.23
	Water saving in l/person.day	45.14	60.29	63.79	37.14	38.08
	% of the standard water consumption	35%	28%	42%	32%	36%
(d) Only GWR tank capacity: 150 l	Water saving in m^3/day	45.14	6.03	12.76	11.14	15.23
	Water saving in l/person.day	45.14	60.29	63.79	37.14	38.08
	% of the standard water consumption	35%	28%	42%	32%	36%
(e) GWR (storage tank: 100 l) when all the saving devices are installed	Water saving in m^3/day	67.61	9.97	17.59	17.50	22.55
	Water saving in l/person.day	67.61	99.68	87.95	58.35	56.37
	% of the standard water consumption	53%	47%	58%	51%	54%

Figure 4. Diurnal variations of water consumption for the whole group with: (a) no GWR nor WSDs; (b) only GWR (tank capacity: 10 l); (c) only GWR (tank capacity: 50 l); (d) only GWR (tank capacity: 100 l); (e) only GWR (tank capacity: 150 l); and (f) GWR (tank capacity: 100 l and all WSAs)