Microbiological Evaluation of the Effectiveness of Sewage Sludge Sanitization with Solar Drying Technology

Table 2

Average results of physicochemical analyses of sewage sludge in summer cycles.

		Average results for summer cycles (replications number = 3)
Parameter	Unit	Sampling terms for the research (days)
		0	7	14	21	28
Dry matter of sludge after centrifuge	%	16.22 (±0.16)*	—	—	—	—
Dry matter of sludge in the pile	%	—	40.30 (±4.00)	47.20 (±10.68)	69.90 (±10.81)	86.40 (±13.01)
Organic substance	% D.M.	66.90 (±0.71)	67.00 (±0.71)	66.60 (±0.90)	65.70 (±1.45)	65.30 (±1.71)
pH	—	6.70 (±0.16)	6.70 (±0.16)	6.69 (±0.13)	6.70 (±0.16)	6.70 (±0.18)
Total nitrogen content	% D.M.	4.08 (±1.27)	4.05 (±1.28)	3.60 (±1.19)	3.30 (±1.04)	3.20 (±1.04)
Ammonium nitrogen content	% D.M.	0.19 (±0.09)	0.16 (±0.10)	0.17 (±0.06)	0.15 (±0.02)	0.15 (±0.02)
Total phosphorus	% D.M.	2.14 (±0.99)	2.12 (±0.98)	2.12 (±0.98)	2.05 (±0.94)	2.12 (±0.98)
Calcium content (Ca)	% D.M.	1.13 (±0.14)	1.12 (±0.15)	1.12 (±0.15)	1.13 (±0.14)	1.13 (±0.14)
Magnesium content (Mg)	% D.M.	0.43 (±0.03)	0.43 (±0.03)	0.43 (±0.03)	0.43 (±0.03)	0.43 (±0.03)
Heavy metals
Lead (Pb)	mg/kg D.M.	31.50 (±0.58)	31.50 (±0.58)	31.50 (±0.58)	31.50 (±0.58)	31.51 (±0.53)
Cadmium (Cd)	mg/kg D.M.	2.41 (±0.09)	2.42 (±0.07)	2.40 (±0.11)	2.41 (±0.09)	2.41 (±0.09)
Mercury (Hg)	mg/kg D.M.	1.03 (±0.60)	1.00 (±0.57)	1.00 (±0.57)	1.00 (±0.57)	1.00 (±0.57)
Nickel (Ni)	mg/kg D.M.	16.30 (±3.90)	16.31 (±3.76)	16.30 (±3.90)	16.30 (±3.90)	16.31 (±3.75)
Zinc (Zn)	mg/kg D.M.	1100.00 (±84.97)	1100.00 (±84.97)	1100.00 (±84.97)	1100.00 (±84.97)	1100.00 (±84.97)
Copper (Cu)	mg/kg D.M.	240.50 (±19.05)	240.50 (±19.05)	240.52 (±20.17)	240.51 (±20.15)	240.50 (±19.05)
Chromium (Cr)	mg/kg D.M.	38.37 (±23.56)	38.30 (±23.58)	38.37 (±23.56)	38.36 (±23.55)	38.37 (±23.56)

*Standard deviation.