Table 7.

Selected physicochemical parameters of galvanic wastewater before and after treatment.

Parameter *	Before Treatment	After Treatment by Using Na2CS3 (pH 9.7, Na2CS3 533 mg/L, Time 23 min) **	Removal, % ***	After Treatment by Using NaOH (Alkalization up to pH 11)	Removal, % ***	After Treatment by Using 15% Suspension of Ca(OH)2 (Alkalization up to pH 11)	Removal, % ***	After Treatment by Using 15% Suspension of CaO (Alkalization up to pH 11)	Removal, % ***
pH	3.4 ± 0.1	9.7 ± 0.1	-	11.0 ± 0.1	-	11.1 ± 0.1	-	11.1 ± 0.1	-
Copper (Cu), mg/L	59.0 ± 5.90	0.12 ± 0.01	99.80	2.50 ± 0.25	95.76	2.9 ± 0.29	95.08	2.8 ± 0.28	95.25
Cadmium (Cd), mg/L	4.50 ± 0.45	0.10 ± 0.01	97.78	0.8 ± 0.08	82.22	0.50 ± 0.05	88.89	0.42 ± 0.04	90.67
Zink (Zn), mg/L	22.70 ± 2.27	0.05 ± 0.01	99.78	4.6 ± 0.46	79.74	2.1 ± 0.21	90.75	2.2 ± 0.22	90.31
∑Cu,Cd,Zn, mg/L	86.20 ± 8.62	0.27 ± 0.03	99.69	7.90 ± 0.79	90.84	5.50 ± 0.55	93.97	5.42 ± 0.54	93.71

* Parameter value ± the measurement uncertainty for an extension factor k = 2; for pH, the uncertainty was ±0.1; for Cu, Cd, Zn the uncertainty was ±10%; ** in optimal conditions; *** Removal = $\frac{\left(C1-C2\right) \times 100\%}{C1}$, where c₁—concentration of metal in raw wastewater, c₂—concentration of metal in treated wastewater.