Effect of ozone pre-treatment on sludge production of aerobic digestion processes

Figures & data

Figure 1 Experimental set-up.

Figure 2 Evolution of COD and TSS during batch ozonation at different ozone dose: pH = 7, (A) [O₃] _i  = 0.00025 O₃/g TSS, (B) [O₃] _i  = 0.0010 g O₃/g TSS, (C) [O₃] _i  = 0.0015 g O₃/g TSS and (D) [O₃] _i  = 0.022 g O₃/g TSS.

Table 1 Experimental results obtained for different sequential processes.

#	Process	Time, O3 (min)	Time, bio (h)	[TSS] i (g/l)	[COD] i (mg/l)	[TSS] f (g/l)	[COD] f (mg/l)	ΔO3, g O3/g TSS	% COD	% TSS
1	O3 + bio1 + O3 + bio2 + O3 + bio3	5	24	3.70	452	3.14	398	0.0014	11.9	15.0
2	O3 + bio1 + O3 + bio2 + O3 + bio3	5	24	4.74	444	2.75	230	0.039	48	42
3	O3 + bio1 + O3 + bio2 + O3 + bio3	10	24	3.93	480	2.10	230	0.055	52.0	46.6
4	O3 + bio1 + O3 + bio2 + O3 + bio3	10	24	3.43	480	1.99	230	0.101	52.0	42.1
5	O3 + bio1 + O3 + bio2	5	24	4.74	428	2.99	217	0.010	30.6	36.8
6	O3 + bio1 + O3 + bio2	5	Bio1 = 24, bio2 = 96	4.74	428	2.66	245.6	0.011	42.6	44
7	O3 + bio1 + O3 + bio2	5	24	4.24	444	3.39	368	0.0017	17	20
8	O3 + bio1 + O3 + bio2	5	Bio1 = 48, bio2 = 96	4.75	428	3.21	303	0.0017	29	32.3
9	O3 + bio1 + O3 + bio2 + O3 + bio3 + O3 + bio4 + O3 + bio5	10	Bio1 = 4, bio2 = 4, bio3 = 24, bio4 = 96, bio5 = 96	4.52	632	2.45	1040	0.075	–64.6	45.9
10	O3 + bio1 + O3 + bio2 + O3 + bio3	10	Bio1 = 4, bio2 = 20, bio3 = 4, bio4 = 24	4.91	480	2.85	240	0.054	50	42

Figure 3 Evolution of COD and TSS during the sequential process (A) ΔO₃ = 0.014 g O₃/g TSS, (B) ΔO₃ = 0.015 g O₃/g TSS, (C) ΔO₃ = 0.099 g O₃/g TSS and (D) ΔO₃ = 0.141 g O₃/g TSS.

Table 2 Operational conditions and removal efficiencies for sludge mixing experiments.

#	Process	Time, O3 (min)	Time, bio (h)	[TSS] i (g/l)	[COD] i (mg/l)	[TSS] f (g/l)	[COD] f (mg/l)	ΔO3	% COD	% TSS
1	O3 + bio1 + O3 + bio2	20	Bio1 = 24, Bio2 = 96	3.70	452	1.65	194.36	0.024	57	44
2	O3 + bio1 + O3 + bio2	5	Bio1 = 48, Bio2 = 96	4.75	428	1.32	214	0.015	50	47.4
3	O3 + bio1 + O3 + bio2	20	24	4.24	744	1.949	226.8	0.010	48.9	32.3
4	O3 + bio1 + O3 + bio2 + O3 + bio3	5	Bio1 = 48, Bio2 = 24, Bio3 = 96	4.20	352	0.429	209	0.015	40.5	67.7

Table 3 Effect of the ozonation process and sequential processes on the sludge settlement.

Process	g O3/g TSS	TSS (g/l)	% Sludge settled in 30 min
Sludge 1
O3 ^a	0.005	3.70	40
O3 + bio^b	0.005	3.30	48
O3 + bio+O3	0.010	2.85	37
O3 + bio+O3 + bio	0.010	2.90	40
O3 + bio+O3 + bio+O3	0.024	3.19	38
O3 + bio+O3 + bio+O3 + bio	0.024	2.94	49
Sludge 2
O3 ^c	0.024	2.76	18
O3 + bio^b	0.024	3.58	28
O3 + bio+O3	0.061	2.50	20
O3 + bio+O3 + bio	0.061	3.91	33
O3 + bio+O3 + bio+O3	0.101	4.79	32
O3 + bio+O3 + bio+O3 + bio	0.101	2.09	40
a Ozonation time 10 min.
b Biological time 24 h.
c Ozonation time 20 min.

Figure 4 Protein test during sequential processes.