The Influence of Sewage System on the Functioning and Quality of Krakow’s Watercourses

Table 7

Ranges of element concentrations (mg/kg) for relevant pollution classes of water drainage sediments [20].

Metal	Pollution classes of sediments
	Water drainage sediments			Sludge sewage
	1	2	3	In force
	Suggested
	<acceptable	Polluted	>unacceptable	Acceptable
Cd
g	<0.5	0.5–9	>9	10–50
d	<1	1–12	>12
Ni
g	<7	7–26	>26	100–500
d	<17	17–42	>42
Cr
g	<6	6–56	>56	500–2500
d	<11	11–61	>61
Cu
g	<51	51–129	>129	800–2000
d	<87	87–200	>200
Pb
g	<50	50–153	>153	500–1500
d	<120	120–234	>234
Zn
g	<229	229–729	>729	2500–5000
d	<434	434–1100	>1100

g: if <0.18 mm Fr. is <25% of weight, d: if <0.18 mm Fr. is ≥75% of weight.