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Table 5 Heavy metal concentrations in feedstock (t0) and digestate (tf)

From: Improved biofertilizer properties of digestate from codigestion of brewer’s spent grain and palm oil mill effluent by manure supplementation

Concentration (mg kg− 1)Initial concentration (t0)Final concentration (tf) 
A0B0C0D0AfBfCfDfPAS110
Lead4.0 ± 1.00b4.3 ± 0.l2b2.6 ± 0.10a2.3 ± 0.00aBDL3.6 ± 0.10cBDL2.3 ± 0.10b200
Nickel10.5 ± 0.10b11.3 ± 0.55b12.5 ± 1.00b6.3 ± 0.55a2.3 ± 0.10a4.4 ± 0.10d3.5 ± 0.20b5.3 ± 0.00c50
Zinc49.2 ± 1.10b51.3 ± 0.85c57.9 ± 1.01d45.5 ± 0.55a15.2 ± 0.32a27.2 ± 1.00b29.3 ± 0.63c40.1 ± 0.15d400
Copper3.7 ± 0.10b5.4 ± 0.10c4.0 ± 1.00b2.5 ± 0.20a0.9 ± 0.08b3.1 ± 0.10cBDLBDL200
ChromiumBDLBDLBDLBDLNDNDNDND100
MercuryBDLBDLBDLBDLNDNDNDND1.0
CadmiumBDLBDLBDLBDLNDNDNDND1.5
  1. Similar superscript letter means not significantly different in mean (p > 0.05), while different superscript letters mean significantly different (p < 0.05); PAS110 – Publicly available specification according to British Standard Institute [44]; BDL – Below detection level; ND – Not determined; A – D (Reactors). Minimum detection limit – 0.01 mg kg−1