Variation of the element composition of municipal sewage sludges in the context of new regulations on phosphorus recovery in Germany

Environmental Sciences Europe

Table 2 Average matrix element contents in g/kg (of all samples) in sludges of 9 wastewater treatment plants (WWTPs)

WWTP	a	b	c	d	e	f	g	h	i
n	11	10	13	10	12	12	9	12	12
C¹	428.0	218.4	183.4	170.1	338.1	315.5	397.4	178.5	324.4
Ca	24.0	152.1	205.4	235.5	12.4	18.9	9.9	191.7	29.9
H¹	64.6	37.0	33.5	33.2	52.7	53.4	61.7	31.8	50.9
N¹	42.5	27.7	18.4	19.4	55.4	47.9	70.8	19.1	50.0
P	21.1	23.7	20.6	17.5	24.8	23.9	20.1	18.0	23.3
Fe	38.4	44.0	49.8	36.4	23.6	10.6	20.6	41.3	32.8
Al	3.5	14.1	5.5	4.5	26.9	59.2	7.4	9.0	21.1
S	16.1	9.5	7.1	18.7	5.5	5.0	6.2	4.0	9.7
Mg	2.5	9.0	8.5	6.8	3.7	5.1	3.5	6.0	6.2
K¹	1.6	3.3	1.9	1.6	4.7	5.1	4.8	2.2	3.9
Na	0.7	0.9	0.6	0.9	1.0	1.3	0.6	0.6	0.6
Zn	0.6	0.8	0.5	0.4	1.0	1.1	0.7	0.6	0.8
Mn	0.3	0.3	0.3	0.2	0.3	0.3	0.2	0.3	0.8
Cu¹	0.4	0.2	0.2	0.2	0.2	0.2	0.2	0.2	0.3
o.c	80%	40%	30%	26%	65%	62%	73%	26%	60%
\(\frac{\mathrm{C}}{\mathrm{o}.\mathrm{c}.}\)	54%	55%	60%	65%	52%	51%	55%	70%	54%
\(\frac{{\mathrm{P}}_{\mathrm{NAC}}}{\mathrm{P}}\) ²	80%	91%	93%	95%	90%	76%	70%	91%	84%
\(\frac{Fe+Al}{P}\)	1.2	1.7	1.6	1.4	1.8	3.1	1.0	1.8	1.8

n number of samples; o.c. organic content as loss of ignition (550 °C)
¹Number of analyzed samples for C, H, N, K and Cu is lower than n in some WWTPs (n = 7–11). For detailed information check the Additional file which contains measurement data for each sample per WWTP a-i (Additional file 1: Fig. S1–S9)
²Share of phosphorus load which is NAC-extractable (average of one to three samples per WWTP) and molar ration of phosphorus and precipitation agents iron and aluminum (average of all samples), also check Additional file 1: Fig. S10 for more information