Nano-Scale Pollutants: Fate in Irish Surface and Drinking Water Regulatory Systems

Figures & data

Figure 1 Nanomaterial exposure model: Application of pharmaceutical, metal, and pathogen removal efficiencies in wastewater and drinking water treatment plants.

Table 1 Product/process categorization and wastewater release fractions.

	TiO2—Exterior	Ag—Food	CeO2—Diesel
Product/process	paints	packaging	fuel additives
Form	Liquid suspension	Embedded/Bound	Liquid suspension
Product nano-concentration (fraction)	PT1 = Uniform(0.001,0.025)	PA1 = Uniform(0.0001,0.01)	PC1 = Uniform(0.0001,0.001)
Total Irish market size (kg/yr)	MT1 = Normal(4 10^7,2.4 10^6)	MA1 = Normal(2 10^7,1.2 10^6)	MC1 = Normal(4.5 10^8,3 10^7)
Market penetration (fraction)	MT2 = 0.05	MA2 = 0.05	MC2 = 0.05
Direct release to WWTPs (fraction)	RT1 = Normal(0.025,0.0015) + Normal(0.1219,0.0296)	RA1 = Normal(0.05,0.003)	RC1 = Normal(0.005,0.0003)

Table 2 Pharmaceutical and metal removal efficiencies.

	Wastewater treatment	Pharmaceutical removal	Metals removal
WWTP stage	levels (%)	efficiency (fraction)	efficiency (fraction)
None	Tnone = 11	—	—
Preliminary & primary treatment	Tpre = 7	Ppharm = Normal(0.02,0.05)	Pmetal = Normal(0.40,0.0975)
Secondary treatment & additional	Tsec = 82	Spharm = Normal(0.57,0.08)	Smetal = Normal(0.48,0.121)

Table 3 Bacteria removal in WTPs.

	PWS	PuGWS	PrGWS	SPS
	probability	probability	probability	probability	Bacterial removal
	of stage	of stage	of stage	of stage	efficiency
WTP stage	implementation	implementation	implementation	implementation	(fraction)
Pre-treatment—	Pp,pws = 1	Pp,pugws = 1	Pp,prgws = 0	Pp,sps = 0	Fp,bac =
Roughing filters					Normal(0.725,0.136)
Coagulation/flocculation/	Pc,pws = 1	Pc,pugws = 1	Pc,prgws = 0	Pc,sps = 0	Fc,bac =
sedimentation—					Normal(0.6,0.18)
Clarification
Filtration—	Pf,pws = 1	Pf,pugws = 1	Pf,prgws =	Pf,sps = 0	Ff,bac =
Slow sand filtration			Binomial(1,0.067)		Normal(0.75,0.15)
Disinfection	—	—	—	—	Fd,bac = N/A (for nanomaterials)

Figure 2 Predicted annual nanomaterial ingestion through drinking water.

Table 4 Regulatory levels of concern—Varying model inputs.

	Model mean			Varied release			Varied WWTP			Varied release			Varied WTP
	predicted values			(fraction)			efficiency (%)			(fraction)			efficiency (%)
Model parameters	TiO2	Ag	CeO2	TiO2	Ag	CeO2	TiO2	Ag	CeO2	TiO2	Ag	CeO2	TiO2	Ag	CeO2
Initial release (fraction)	1	1	1	0.69	34.5	41.7	1	1	1	2.27	111	135	1	1	1
WWTP efficiency (%)	59.8	59.8	59.8	59.8	59.8	59.8	100	0	0	59.8	59.8	59.8	59.8	59.8	59.8
WWTP release quantity (kg a^−1)	1400	92.5	22.6	966	3189	942	0	154.7	37.8	1400	92.5	22.6	1400	92.5	22.6
Total surface water release quantity (kg a^−1)	4580	93.1	76.7	3159	3210	3195	3180	155.3	91.9	4580	93.1	76.7	4580	93.1	76.7
Surface water concentration (mg m^−3)	1.45	0.029	0.024	1.0 ^a	1.0	1.0	1.0	<1.0 (0.05)	<1.0 (0.03)	1.45	0.029	0.024	1.45	0.029	0.024
WTP efficiency (%)	96.95	96.95	96.95							96.95	96.95	96.95	93.1	0	0
Drinking water concentration (PWS) (μg m^−3)	44.1	0.90	0.74							100 ^b	100	100	100	<100 (29.5)	<100 (24.3)
Figures in bold: Varied release fractions and removal efficiencies
Figures in italics: Resulting surface water and drinking water concentrations