Table 2.

Viral detection and quantification in wastewater and sludge by various countries.

.Country	Sample source	Sample type (grab or composite)	Sampling pretreatment	Concentration method	Sample volume (mL)	Concentration (copies/L)	Recovery (%)	Positive percentage (%)	Detection technique	Sampled virus	Reference
Australia	Raw sewage	Composite	→Centrifugation →pH adjustment	→Ultrafiltration →Electronegative membrane	100	0-120	NA	22%	RT–qPCR	SARS-CoV-2	(Ahmed et al., 2020)
Canada	Primary sludge	Composite	→Settled at 4°C for an hour	→Precipitated with polyethylene glycol →Centrifugation	250	1.7 × 103 -3.8 × 105	9.3 ± 4.9%	90%	RT-qPCR	SARS-CoV-2	(D'Aoust et al., 2021)
Chile	Raw sewage	Grab	NA	→Ultracentrifugation →Phosphate buffered saline →pH 7.4	36	4.4 × 103-2.3 × 107	47%	81%	RT-qPCR	polyomavirus JC	(Levican et al., 2019)
Czech Republic	Raw sewage	Composite	→Storage at 5oC	→Flocculation →Beef extract solution →Centrifugation	500	NA	35.5±13%	11-27%	RT-PCR	SARS-CoV-2	(Mlejnkova et al., 2020)
Ecuador	River water	Grab	→1 N HCl →Storage at 4oC	→Skimmed Milk Flocculation method	2000	2.07 × 105- 3.19 × 106	NA	100%	RT-qPCR	SARS-CoV-2	(Guerrero-Latorre et al., 2020)
Egypt	Raw sewage	Grab	NA	→Viradel protocol →Filtration →Organic flocculation	5000	3.9 × 104 to 3.3 × 108	NA	94%	RT-PCR	Pepper mild mottle virus	(Hamza et al., 2019)
Egypt	Raw sewage	Grab	NA	→Viradel protocol →Filtration →Organic flocculation	5000	1.5 × 104 and 1.5 × 107	NA	94%	RT-qPCR	Adenovirus	(Hamza et al., 2019)
France	Raw sewage	Composite	NA	→Centrifugation	11	5 × 104 - 3 × 106	NA	100%	RT-qPCR	SARS-CoV-2	(Wurtzer et al., 2020)
Germany	Raw sewage	Composite	→Centrifugation	→Ultrafiltration →Centrifugation	45	3 × 103 - 2 × 104	NA	100%	RT-qPCR	SARS-CoV-2	(Westhaus et al., 2021)
India	Raw sewage	Composite	→Filtration →Centrifugation	→PEG precipitation	50	3.5 × 102	57%	0-100%	RT-PCR	SARS-CoV-2	(Kumar et al., 2020b)
Italy	Raw sewage	Composite	→Viral inactivation treatment at 56°C	→Two-phase (PEG-dextran) separation method →Centrifugation	250	2.4 × 104 - 5.6 × 104	2.04 ± 0.70%	45-65%	RT-qPCR	SARS-CoV-2	(La Rosa et al., 2021)
Italy	Raw sewage	Composite	→PEG-dextran	→Filtration	250	NA	NA	100%	RT-PCR	SARS-CoV-2	(La Rosa et al., 2020)
Japan	Raw sewage	Grab	NA	→PEG-dextran precipitation →Centrifugation	100	1.2 × 104 -3.5 × 104	45%	47%	RT-qPCR	SARS-CoV-2	(Hata et al., 2020)
Netherlands	Raw sewage	Composite	→Centrifugation	→Ultrafiltration	250	7.9 × 105 - 2.2× 106	73±13%	NA	RT-qPCR	SARS-CoV-2	(Medema et al., 2020)
Spain	Raw sewage	Grab	→Centrifugation	→Adsorption precipitation	200	0-5× 105	NA	11%	RT-PCR	SARS-CoV-2	(Randazzo et al., 2020)
Spain	Raw sewage	Composite	→Centrifugation	→Ultrafiltration →PEG-dextran precipitation	100	NA	NA	100%	RT-qPCR	SARS-CoV-2	(Balboa et al., 2020)
UAE	Raw sewage	Composite	→Thermal deactivation	→Ultrafiltration →Centrifugation	250	2.86 × 102 -2.90 × 104	NA	85%	RT-qPCR	SARS-CoV-2	(Hasan et al., 2021)
USA	Primary sewage sludge	Composite	→Storage at -80oC	→RNeasey PowerSoil Total RNA Kit	40	1.7 × 106 - 4.6 × 108	NA	20-60%	RT–qPCR	SARS-CoV-2	(Peccia et al., 2020)
USA	Raw sewage	Composite and grab	→Centrifugation	→Ultrafiltration →Electronegative membrane	1000	0-7.5 × 103	54-56%	29% (2/7)	RT-PCR	SARS-CoV-2	(Sherchan et al., 2020)