Performance appraisal of the A2/O process in domestic wastewater treatment replacing the anaerobic unit with UASB

Peer review under responsibility of Housing and Building National Research Center.

Figures & data

Fig. 4 COD removal efficiency along the whole experiment duration.

Fig. 1 The experimental setup.

Table 2 Runs schedule.

Run No.	OLR	HRT	IR
1	1	1	1
2	1	2	2
3	1	3	3
4	2	1	2
5	2	2	3
6	2	3	1
7	3	1	3
8	3	2	1
9	3	3	2

Table 1 Tested operational parameters and the levels of testing.

Factor	Level 1	Level 2	Level 3
OLR (g/m^3)	<500	500–1000	>1000
HRT (h)	15	12.5	10.50
IR (%)	100	200	300

Fig. 2 The organic loading rate along the experiment duration for the UASB and the activated sludge.

Table 3 Raw water characteristics during the Low organic loading runs.

Variable	Unit	Min	Average	Max
pH	mg/L	7.15	7.32	7.45
Alkalinity	mg/L as CaCO3	220.00	282.22	370.00
COD	mg/L	248.00	436.44	955.00
BOD	mg/L	144.00	346.56	845.00
TSS	mg/L	155.00	357.89	1200.00
VSS	mg/L	112.00	244.56	800.00
NH4-N	mg/L	11.80	14.29	17.60
NO3-N	mg/L	0.80	1.89	3.70
TN	mg/L	4.87	5.27	5.64
TP	mg/L	5.13	8.57	12.00

Table 4 Low organic loading runs results.

Variable	Units	Raw water (average)	UASB reactor				Final effluent				Average system efficiency
			Min	Average	Max	Average efficiency	Min	Average	Max	Average efficiency
pH	mg/L	7.32					7.26	7.44	7.95
Alkalinity	mg/L as CaCO3	282.22					200.00	297.78	610.0
COD	mg/L	436.44	111.0	134.00	170.0	70.07	24.00	93.22	205.0	78.12	78.64
BOD	mg/L	346.56					18.00	66.67	164.0	79.29	80.76
TSS	mg/L	357.89	65.00	80.00	67.27	55.03	25.00	84.44	240.0	74.77	76.40
VSS	mg/L	244.56					17.00	63.33	170.0	71.25	74.10
NH4-N	mg/L	14.29	12.00	13.33	14.00	4.51	4.32	5.81	8.00	59.49	59.34
NO3-N	mg/L	1.89					6.80	14.02	23.50
TN	mg/L	15.80	13.41	13.91	14.40	12.02	9.51	10.19	10.81	35.37	35.52
TP	mg/L	8.57	7.67	8.93	10.20	5.00	2.50	3.44	4.50	19.44	59.89

Table 5 Raw water characteristics during the low organic loading runs.

Variable	Unit	Min	Average	Max
pH	mg/L	6.56	7.42	7.45
Alkalinity	mg/L as CaCO3	220.00	300.22	420.00
COD	mg/L	510.00	901.11	1200.00
BOD	mg/L	172.00	567.56	1185.00
TSS	mg/L	260.00	948.33	1900.00
VSS	mg/L	180.00	645.56	1310.00
NH4-N	mg/L	14.00	22.84	32.50
NO3-N	mg/L	0.20	2.89	3.70
TN	mg/L	20.60	54.53	86.67
TP	mg/L	5.88	12.78	24.17

Table 6 Medium organic loading runs results.

Variable	Units	Raw water (average)	UASB reactor				Final effluent				Average system efficiency
			Min	Average	Max	Average efficiency	Min	Average	Max	Average efficiency
pH	mg/L	7.42					7.12	7.67	8.80
Alkalinity	mg/L as CaCO3	300.22					160.0	300.22	400.0
COD	mg/L	901.11	90.00	164.75	240.00	69.39	47.00	95.11	120.0	88.35	89.45
BOD	mg/L	567.56					24.00	65.00	109.0	84.03	88.55
TSS	mg/L	948.33	112.0	203.00	440.00	73.32	21.00	59.67	85.00	90.94	93.71
VSS	mg/L	645.56					14.00	47.22	70.00	89.57	92.69
NH4-N	mg/L	22.84	16.00	17.06	18.11	19.03	0.13	5.79	10.00	74.12	74.64
NO3-N	mg/L	2.89					1.30	10.58	25.00
TN	mg/L	54.53	4.38	12.80	52.40	29.25	9.82	11.15	13.04	74.52	79.55
TP	mg/L	12.78	6.67	11.77	16.87	13.15	2.52	3.53	4.77	67.49	72.37

Table 7 Raw water characteristics during the low organic loading runs.

Variable	Unit	Min	Average	Max
pH	mg/L	7.31	7.53	7.80
Alkalinity	mg/L as CaCO3	160.00	270.00	400.00
COD	mg/L	940.00	1828.33	2635.00
BOD	mg/L	680.00	1091.78	140.00
TSS	mg/L	564.00	1094.89	1800.00
VSS	mg/L	400.00	774.78	1000.00
NH4-N	mg/L	13.40	28.78	87.00
NO3-N	mg/L	1.20	2.84	5.40
TN	mg/L	36.35	81.96	113.20
TP	mg/L	7.67	41.67	96.67

Table 8 High organic loading runs results.

Variable	Units	Raw water (average)	UASB reactor				Final effluent				Average system efficiency
			Min	Average	Max	Average efficiency	Min	Average	Max	Average efficiency
pH	mg/L	7.53					7.36	7.79	8.31
Alkalinity	mg/L as CaCO3	270.00					180.0	252.22	370.00
COD	mg/L	1828.33	325	311.98	1365.0	52.70	86.00	134.39	181.54	91.93	92.65
BOD	mg/L	1091.78					42.00	91.22	140.00	91.52	91.64
TSS	mg/L	1094.89	88	231.59	291.00	54.64	45.00	91.44	150.00	90.54	91.65
VSS	mg/L	774.78					45.00	65.11	100.00	92.02	91.60
NH4-N	mg/L	28.78	10.2	14.05	16.10	22.01	2.50	10.39	21.00	58.42	63.90
NO3-N	mg/L	2.84					1.20	16.45	37.50
TN	mg/L	81.96	12.87	50.47	98.50	71.86	12.87	22.47	30.00	71.86	72.59
TP	mg/L	48.89	5.67	2.90	47.33	18.62	4.50	12.22	24.67	24.23	75.00

Fig. 3 UASB TSS removal efficiency.

Fig. 5 TN removal efficiency along the experiment duration.

Fig. 6 TP removal along the experiment duration.

Fig. 7 The variation of phosphorus concentration with C/P feeding ratio in the process.