Table 3: Permissible limits of some heavy metals in water in Wastewater Forum, WHO and Standard Organization of Nigeria.

Standard

(WWF)

(WHO)

(SON)

Mg/L

Lead, Pb

0.1

0.01

0.01

Cobalt, Co

 

0.005

 

Nickel, Ni

0.2

0.07

0.02

Chromium, Cr

0.01

0.05

0.05

Copper, Cu

0.2

2

1

Cadmium, Cd

0.01

0.003

0.003

Source: WWF: 2007; WHO: 2008 and SON: 2016