Anaerobic Codigestion of Municipal Wastewater Treatment Plant Sludge with Food Waste: A Case Study

Table 6

Digestate heavy metals concentration in mL/g at the end of the experiment (after six HRT cycle of 20 days).

Parameter	1% PF	2% PF	5% FW	1% GT	2% GT	100% SS	Limit (mg/kg)
Ca
Mg
Ca hardness
Mg hardness
Al
As	<1	<1	<1	<1	<1	<1	20
Cd	<0.1	<0.1	<0.1	<0.1	<0.1	<0.1	1
Cr							400
Cu							100
Fe
Pb	<0.5	<0.5	<0.5	<0.5			300
Hg	<1	<1	<1	<1	<1	<1	1
Ni							60
Zn							200
Si
Si-SiO2
S
S-SO4

Heavy metal screening of the digestate samples was carried out by a commercial laboratory (ALS Environmental Division: Water Research Group).
Contaminant upper limits for biosolids as grade C1 [30].