Particle Size (nm) Surface charge concentration Duration Major Findings Reference
SiO2 80-100 (DI water) n/a 1, 50 mg/L 1 day, 50 days 50 mg/L NP led to: 1) inhibited N removal; 2) decreased NAR and NIR activities; 3) shift in microbial communities Zheng et al, 2012
SiO2 12, 151, 442, 682 (TEM) n/a 5-500 mg/L 20 minutes 1) Smaller NPs (< 151) are stronger inhibitors than larger NPs on oxygen uptake; 2)cell membrane damages Sibag et al, 2015
SiO2 30 (TEM) n/a 0-30 mg/L 300 days 1) Slight inhibition on COD & N removal; 2) significant inhibition on P removal; 3) increased ROS production and LDH release Li et al, 2017
MWCNT 40-60 nm (D), 5-15 mm (L) n/a 1, 20 mg/L 1 day, 180 days 1) No adverse effects from short-term exposure; 2) 20 mg/L long term led to decreased N removal, decreased AMO & NOR activities; and decreased abundance of PAOs; 3) 1 and 20 mg/L long-term led to decreased P removal, enzyme activities (PPX, PPK) and decreased abundance of AOBs, 4) 1 mg/L long term led to increased abundance of GAOs Hai, et al, 2014
MWCNT 2-6 nm (ID), 10-15 nm (OD), 0.1-10 um (L) n/a 0.64, 1.44, 2.16 and 3.24 g/L 3 hr 1) Dose-dependent inhibited respiration; 2) stronger effects on sheared sludge liquor Luongo et al, 2010
MWCNT-COOH
2-5 (ID), 2-8 (OD), 10-30 µm (L)
n/a
10, 30 mg/L
150 days
10 mg/L had no adverse effects, 30 mg/L inhibited ammonia removal, increased ROS production
Ma et al, 2019
MWCNT-COOH SiO2 TiO2 30-50 (OD) 0.5-2 µm (L) 80 10-30 n/a n/a n/a
0.5, 1, 2.5, 5 mg/L
overnight
1) MWCNT caused slight inhibition in oxygen uptake; & strong inhibition of BOD removal; 2) SiO2 caused slight change in BOD removal and oxygen uptake; 3)TiO2 caused significant inhibition on both BOD removal and oxygen uptake
Ergӧn-can et al, 2016
SWNT n/a n/a 270 mg/L Shock load, 18 days 1) No negative impact on sludge performance; 2) improved sludge setttleability and dewaterability Yin & Zhang, 2008
SWNT 1-2 nm (OD), 5.0-30 µm (L) n/a 250 mg/L 3 hr 1)Inhibition of respiration and release of biomacromolecules; 2) stronger effects of sheared sludge liquor Thakor et al, 2015
SWNT
1-2 (diameter), 5-15 µm (L)
n/a
219 mg/L
5 hr
SWNTs (not the impurities) caused significant change to microbal structures
Goyal et al, 2010
GO n/a n/a 10-300 mg/L 5 days 1) Inhibition of micriobial community metabolic activity; 2) decreased organic carbon removal; 3) 200 mg/L higher affected P removal; 4) enhanced ROS production Ahmed et al, 2013
Graphite n/a n/a 0.5 mg/L 3 hr 1) Inhibited nitrification; 2) damage to nitrifying bacteria; 3) dispersion of EPS Dong et al, 2017
GO 0-1 mg/mL 1) GO inhibited P. Putida growth; 2) cells lost membrane integrity but preserved metabolic activity Combarrous & Diaz, 2016
Graphene n/a n/a 0-300 mg/L 10 hrs 10 mg/L and higher led to 1) Decreased COD, N and P removal; 2) decreased abundance of AOB, AMO and PAOs Nguyen et al, 2017
GO & G n/a n/a 1, 5 mg/L 10 days 5 mg/L led to 1) reduction in COD, N and P removal after day 3; steady state reached after day 8; 2) shift in microbial community Nguyen et al, 2018
GO n/a n/a 60 mg/L 72 min, 235 min 1) No significant effects of denitrifying bacteria growth; 2) significantly improved the activities of nitrifying bacteria; 3) no significant effects on bacterial community change Guo et al, 2018
GO & Ag-GO
0.5-2 um (GO, TEM) 45.4 nm (AgNP, TEM)
n/a
10-100 mg/L
48 hr
1) Decreased nitrification; 2) LDH release, 3) ROS production
Ko et al, 2019
QDots PEI-coated; PMAO coated Pure culture study 1-10 nM 1) Nitrifiers more susceptible than nitrogen fixing bacteria and denitrifying bacteria; 2) toxicity came from the NP instead of the coating or released ion; Yang et al, 2012