Effect of structural difference on wastewater treatment efficiency in multi-soil-layering systems: Relationship between soil mixture block size and removal efficiency of selected contaminants

Figures & data

Figure 1  Structure and components of the five multi-soil-layering (MSL) systems (W50 cm × H60 cm × D10 cm) used for wastewater treatment. The size of the soil mixture block (SMB) is shown in parentheses (W cm × H cm × D cm).

Table 1 Top surface area (cm2), side surface area (cm2) and total volume (cm3) of the soil mixture blocks in the five multi-soil-layering (MSL) systems

	MSL systems
	1	2	3	4	5
Top surface area (cm^2)	1080	2160	2160	2160	4320
Side surface area (cm^2)	1920	1440	1920	4320	1920
Top and side surface area (cm^2)	3000	3600	4080	6480	6240
Total volume (cm^3)	8640	8640	8640	8640	8640

Table 2 Operation period, time, multi-soil-layering (MSL) systems, hydraulic loading rate (HLR) and temperature during the three experimental periods

Period	Experimental Time	Operation of MSL	HLR (L m^−2 day^−1)	Temperature (°C)
1	29 Oct.−3 Dec. 2003	1,2,3,4,5	1000	11–16
2	25 Dec.−30 Jan. 2004	1,2,3,4,5	2000	5–15
3	7 Apr.−13 Jun. 2004	1,3,4,5	3000	20–27

Figure 2  Concentration of (a) suspended solids (SS), (b) biological oxygen demand (BOD5) and (c) chemical oxygen demand (COD), and (d) the value of the oxidation–reduction potential (ORP) in the wastewater (WW) and in the treated water of the five multi-soil-layering (MSL) systems as affected by hydraulic loading rate. P, period; W, week.

Table 3 Average concentrations (mg L−1) and removal efficiency (%) of suspended solids (SS), biological oxygen demand (BOD5), chemical oxygen demand (COD), total phosphorus (T-P) and total nitrogen (T-N) in the multi-soil-layering (MSL) systems during the three experimental periods

	SS	BOD5	COD	T-P	T-N
	mg L^−1 (%)
Peroid 1 (n = 5)
WW (CV)	70.7 (13)	29.1 (19)	57.9 (16)	1.44 (18)	11.4 (13)
MSL 1	6.6 (90.6) a^†	3.6 (87.5) a	12.9 (77.7) a	0.60 (53.6) a	5.1 (55.2) a
MSL 2	5.0 (92.9) b	3.0 (89.7) ab	10.4 (82.0) b	0.50 (58.9) ab	5.2 (54.6) a
MSL 3	3.6 (94.9) b	3.0 (89.7) ab	10.5 (81.9) b	0.47 (61.1) b	4.9 (56.7) a
MSL 4	2.3 (96.8) c	2.3 (92.1) b	8.4 (85.5) c	0.42 (66.7) b	5.2 (54.9) a
MSL 5	2.0 (97.2) c	2.1 (92.6) b	7.5 (87.0) c	0.41 (67.1) b	5.3 (54.2) a
Peroid 2 (n = 4)
WW (CV)	73.3 (7)	29.6 (18)	51.3 (18)	1.20 (12)	10.0 (13)
MSL 1	9.4 (87.1) a	5.3 (82.2) a	20.4 (60.2) a	0.58 (51.9) a	6.7 (34.8) a
MSL 2	6.3 (91.4) b	4.4 (85.2) ab	16.6 (67.5) b	0.50 (57.3) b	6.8 (34.0) a
MSL 3	6.0 (91.8) b	4.0 (86.7) b	17.2 (66.5) b	0.49 (58.2) bc	6.4 (37.1) a
MSL 4	3.3 (95.5) c	2.7 (91.0) c	14.1 (72.6) c	0.43 (63.9) cd	6.0 (40.9) a
MSL 5	3.1 (95.8) c	2.7 (91.0) c	12.9 (74.9) c	0.42 (65.0) d	5.6 (44.5) a
Peroid 3 (n= 5)^‡
WW (CV)	72.7 (12)	38.5 (13)	65.0 (13)	0.99 (19)	8.7 (18)
MSL 1	9.2 (87.1) a	9.3 (75.7) a	24.3 (62.6) a	0.44 (50.6) a	5.4 (40.7) a
MSL 3	8.7 (88.0) a	7.2 (81.4) b	21.8 (66.5) b	0.40 (55.4) ab	5.0 (45.6) ab
MSL 4	7.5 (89.8) b	6.3 (83.7) c	20.2 (68.9) bc	0.39 (59.7) ab	4.0 (55.4) ab
MSL 5	5.7 (92.4) c	6.1 (84.1) cd	18.5 (71.6) c	0.39 (57.9) b	3.3 (62.7) b
^†Means with the same letter within the same column of the same period are not significantly different at P < 0.05, determined using Tukey's honestly significant difference test.
^‡Means were calculated for the first 5 weeks of Period 3 when the treatment efficiency was relatively stable.

Figure 3  Concentration of (a) total phosphorus (T-P), (b) -N, (c) -N and (d) total nitrogen (T-N) in the wastewater (WW) and treated water of the five MSL systems as affected by hydraulic loading rate. P, period; W, week.

Figure 4  Relationship between average removal rates of (a) suspended solids (SS), (b) biological oxygen demand (BOD5), (c) chemical oxygen demand (COD) and (d) total phosphorus (T-P) and the top plus side surface area of the soil mixture blocks (SMB).

Figure 5  Relationship between the average removal rates of (a) suspended solids (SS), (b) biological oxygen demand (BOD5), (c) chemical oxygen demand (COD) and (d) total phosphorus (T-P) and the top plus side surface area of the soil mixture blocks (SMB). P, period.