Study of Nitrogen Removal Performance When Treating Low Carbon Sewage Using External Solid Carbon Sources in SBBR Systems

Table 1

Standard limit values for heavy metals according to the surface water environment quality standards (I and II), with the concentration of heavy metals released from corncob material into surrounding water.

Metal species	The level of I (mg/L)	the level of II (mg/L)	corncob (mg/L)
Cu	0.01	1.0	0.023
Zn	0.05	1.0	0.134
As	0.05	0.05	0.006
(+6) Cd	0.001	0.005	n.d.
Cr	0.01	0.05	0.02
Pb	0.01	0.01	0.006

n.d. means undetected.