July 2010, Volume 1, No. 1
International Journal of Chemical and Environmental Engineering
Onsite Greywater Treatment Using Septic Tank
Followed by Intermittent Sand Filter- A Case Study
of Abu Al Farth Village in Jordan
Almoayied K. Assayed*, Sahar S. Dalahmeh, Wael T. Suleiman
Royal Scientific Society-Environmental Research Centre Al-Jubaiha Jordan
* Corresponding Author email: [email protected]
Abstract
This paper aims at presenting a case study of onsite greywater treatment in small rural community in Jordan using septic
tank followed by intermittent sand filter. A 1 m3 septic tank followed by 6m2 intermittent sand filter of 1m in depth were
used to treat an average flow of 150L/Day of greywater effluent from single household in Abu Al Farth Village in the
Badia of Jordan. The raw greywater has a total BOD5 of about 1149mg/L, total suspended solids TSS of 606mg/L, COD
of 1952mg/L and E.coli of 9400MPN/100mL. The treatment efficiency of BOD5, COD, total suspended solids and E.coli
were 95%, 93%, 95% and 90% respectively. The treated greywater has average BOD5 of 59 mg/L, TSS of 31 mg/L,
COD of 161 mg/L and E.coli of 227 MPN/100mL. The quality of treated greywater complies with the Jordanian
Standards JS (893/2006) for the Reclaimed Wastewater reuse for restricted irrigation.
1. Introduction
Greywater is commonly defined as wastewater
without input from toilets and kitchen. Separation of
domestic wastewater at source is wide spread practice in
many of the rural communities in Jordan; blackwater from
toilets discharged to cesspools and septic tanks, while
greywater is directly discharged to the environment or
used for irrigation without treatment [1]. This indigenous
practice of source separation provides a potential for
development of sustainable greywater management
systems [2] based on the principle of ecological sanitation
or what so called "Ecosan" [3].
Greywater can be considered an alternative that
provides non-potable water for household usage, and thus
reduces the per capita water use by 50% [4]. For this
reason it provides an attractive and sustainable low cost
water source especially in the arid and semiarid areas due
to the water scarcity and fluctuation in the rainfall patterns
[5].
The issue of greywater management is gaining
importance especially in low and middle income countries
where inadequate wastewater management has
detrimental impacts on public health and environment. In
the recent years, greywater has been linked not only to
environmental degradation and serious health risks, but
has also been increasingly identified as a valuable source
of water that if properly used for irrigation can reduce the
agricultural use of freshwater and increased food security
as well as improves public health [6].
In 1997 reclaimed wastewater was officially
approved in the national strategy of Jordan as a non
conventional water source that shall be managed and
treated to a standard level that allows its use for non
domestic use [7].
Greywater management is a critical issue that not
only depends on the technical feasibility of the treatment
system, but also depends on human issues such as public
perceptions and health [8]. According to Nolde (1999)
and (2005), greywater reuse after treatment shall satisfy
four criteria: Hygienic safety, aesthetics, environmental
tolerance and technical and economical feasibility [9, 10].
Treatment technologies for making greywater safe for
indoor use or for irrigation are many and diverse and they
vary from simple systems in single household to advanced
systems for large scale reuse. Course filtration with
disinfection represents the most common technology used
for greywater treatment in many places in the world [8].
Septic tank followed by sand filter is an alternative for
greywater treatment [11]. Septic tank, acts as a settling
basin for the wastewater in which heavy materials settle
down to the bottom of the tank whereas water and other
materials are found above the sludge, while soap and
grease form a floating scum layer [12]. Intermittent sand
filters provide unsaturated downward flow of wastewater
Onsite Greywater Treatment Using Septic Tank Followed by Intermittent Sand Filterthrough mineral sand, so as to provide biodegradation or
decomposition of wastewater constituents by bringing the
wastewater into close contact with a well developed
aerobic biological community attached to the surfaces of
the filter media [12].
Intermittent sand filters are proposed as an efficient
and economic treatment technology for domestic-strength
wastewater, and can produce an effluent with low organic
and pathogenic content [13].
Standard Methods for the Examination of Water and
Wastewater [14].
2.2Design Calculations
a.
Septic tank
Vliq = Q× HRT
Vsl =
1.1 Study area
Integrated wastewater management policies and
technologies in the marginal communities on Jordan,
2003-2007" is a development research project focuses on
greywater management in the rural communities in the
North-eastern Badia of Jordan. Two pilot scale treatment
units were constructed in two villages in the North-eastern
Badia of Jordan. Selection of villages where the treatment
plants were constructed based on a selection criteria took
into consideration: 1. current wastewater management
practices (existing greywater separation and household
agriculture), 2. social acceptance & favourability for
treatment, operation and maintenance of the treatment
system and 3. potential for replication in other similar
communities in terms of environmental conditions,
practices, and building/housing style [11].
Abu Al Farth village is one of the two villages that
met community selection criteria where septic tank
followed by intermittent sand filter pilot unit was
constructed to serve single household in the village. The
household is inhibited by 9 people with the monthly
income ranges from US$ 185 to US$420. The blackwater
of the household is diverted to cesspool while the
greywater is used to irrigate the olive trees. The average
consumptive use of water of this family is about
40L/Capita.day [1].
Q × CTSS × RTSS × 365
Csl .
Vscum = Hscum × AST
VST = (Vliq + Vsl. + Vscum) + 0.2 × (Vliq + Vsl. + Vscum)
Where: Vliq is the volume needed for the liquid (m3);
Q is the flow rate (m3/d); HRT is the hydraulic retention
time (d); Vsl is the volume needed for the sludge (m3);
CTSS is the concentration of TSS (kg/m3); RTSS is the
percentage removal of the TSS; Csl. is the concentration of
the sludge (kg/m3); Vscum is the volume needed for the
scum (m3); Hscum is the height of the scum layer (m); AST
is the surface area of the septic tank (m2); VST is the
volume of the septic tank (m3); OLR is the organic
loading rate [15].
Intermittent sand filter
Area (A) = Flow (Q) / Organic Application rate
A=
Q × BOD5
0.024kgBOD5 / m 2 .d
Table (1) shows the design criteria of the sand filter.
Filter Media
Sieve analysis of the filter media was done to find the
effective size and uniformity coefficient. The sieve
analysis was done According to ASTM procedures C136,
2006 and C117 2004.
2. Materials and Method
2.3 Layout and Effluent Distribution System
The sand filter was laid out based on the area, length
and width of the sand filter. Number of lateral pipes was
decided taking into consideration the spacing
requirements based on design criteria in Table (1).
Spacing between orifices was designed based on design
criteria in Table (1).
Flow /dose = Daily Flow/ Dosing Frequency
Flow /Lateral /Dose = (Flow /Dose) / Number of Laterals
Number of Orifices = (Flow/Lateral/Dose) / Flow in
Orifices
Flow in Orifice = 2.45 C (D2) (2ghn) 1/2 (Metcalf, 1991)
Where 2.45 is a conversion factor, C is an orifice
discharge coefficient, D is diameter of orifice (m), g is
gravitation acceleration (m/s2), and hn is the head loss in
orifice (m).
2.1Quality and Quantity Measurements
Greywater quality and quantity was monitored for
seven months before the construction of the septic tankIntermittent sand filter system, from March 2005 to
September 2005. 14 greywater samples were collected
and analyzed from three sampling points in the
household; kitchen sink, washing machine & bath tub and
hand washing basin & moping basin. Composite
greywater samples were collected over 24 hrs using
barrels that were previously graduated over the height for
the purpose of flow measurement. Contents of the barrels
were mixed thoroughly before sampling. Collected
samples were transferred to Royal Scientific Society RSS
labs and analyzed for pH, Electrical Conductivity (EC),
Total Suspended Solids (TSS), Biological Oxygen
Demand (BOD5), Chemical Oxygen Demand (COD),
Total Phosphorus (T-P), Ammonia (NH4), Fat, Oil and
Grease (FOG), total and faecal coliform and E.coli. All
chemical analyses were carried out according to the
2.4 Head Loss in Laterals
Hlfp = 10.5 L (Q/C) 1.85 D –4.87 (Metcalf, 1991)
Where Hlfp is the head loss in pipe through orifice (m), Q
68
Onsite Greywater Treatment Using Septic Tank Followed by Intermittent Sand Filteris the pipe discharge (m3/s), C is Hazen Williams
discharge coefficient (150 for plastic pipes) and D is the
diameter of the pipe (m).
and 797 mg/L respectively. These concentrations are very
high, and attributed to the low consumptive use of water
in the household (<40L/ca.day) as well as to hygienic
behaviours of household inhabitants, types of detergent
used by households (locally manufactured), amount of
detergent used, food style and meals patterns.
Average BOD5/COD ratio was 0.48 and BOD5 Filtered
/BOD5 ratio was about 0.3 which means that most of the
suspended solid in the greywater was organic. Thus, pretreatment using septic tank is necessary and will
considerably enhance the quality of the greywater.
In addition, high pathogenic counts at 2.85× 104
MPN/100 ml were found for greywater samples. Faecal
input from hand washing after defecation and babies
washing in hand washing basin were the key factors for
this high numbers of E.coli. Table (2) shows greywater
quality parameters of the household in which septic tank
and sand filter treatment unit was constructed.
2.5 Efficiency & Performance of the Treatment System
Efficiency of treatment system was measured by
analyzing greywater samples from three locations:
1. Collection tank: Gives the quality of untreated
greywater,
2. Outlet of septic tank: Gives the quality of
greywater treated in septic tank
3. Outlet of Sand Filter: Gives the quality of
greywater treated in the sand filter.
19 samples from the each of the above mentioned three
sampling points were collected over 14 months from
March 2006 to May 2007. The samples were analyzed for
the physical, chemical and microbiological parameters
mentioned earlier according to the Standard Methods for
the Examination of Water and Wastewater [14].
3.2 Size of Septic Tank and Sand Filter
1 m3 septic tank with retention time of 5 days was
designed and constructed. A sand filter with overall
surface area of 6 m2 (2x3) and 1m depth was designed and
constructed. The filter media consisted of 3 layers; top
layer of 10 cm of (11 mm) gravel, intermediate layer of
10 cm of (5mm) fine gravel and filtering sand of 60 cm of
effective size of (0.32 mm). The sand layer was under laid
by 10 cm fine gravel and another 10 cm of under drain.
Greywater was distributed over the sand filter using 5
laterals each of 12 orifices. Fig. 1 shows schematic
diagram of the septic tank and sand filter units.
Table 1 Design criteria of sand filter
Treatment
components
Intermittent
sand filter
Media
Specifications
Distribution
system
Dosing
Parameters
Value/criteria
Ref.
BOD loading rate
Hydraulic loading
rate
BOD removal
efficiency
COD removal
efficiency
Dosing rate
24 g/m2.d
44 L/m2.d.
[16]
Filter
medium
Material
Effective size
Uniformity
coefficient
Depth
Application Rate
Pipe size
Orifice size
Head on orifice
Lateral spacing
Orifice spacing
Frequency
Washed
durable
granular material
0.25-0.75 mm
<0.4
Volume/orifice
0.6L/orifice/dose
90%
80%
12 times/day
450-900 mm
80-200 L/m2/day
25- 50 mm
3-6 mm
1-2 m
0.3- 1.2 m
0.3- 1.2 m
12- 48 times/day
[12]
Table .2 Greywater Quality Parameters of greywater
effluent from household subject of the study
[12]
Parameter
[12]
1
3. Results and discussion
3.1Greywater Characteristics
Greywater generation in the targeted household
fluctuates from day to day according to the indoor
activities. Hence, it varied from 52L/day to 345L/day,
with average flow of 150L/day; Average of 60L/day was
generated in the kitchen basin, 80L/day was from washing
machine and bath tub and 10L/day was from hand
washing basin.
The average values of BOD5, COD and TSS of the
total generated greywater were 1149 mg/L, 1952 mg/L,
69
Washing
machine
& Bath
Tub (1)
Hand
washing
basin &
Moping
basin
(2)
Kitchen
sink (3)
weighted
average
(1) & (2)
weighted
average
(1), (2) &
(3)
7.41
1456
798
8.29
1756
797
PH
EC
TSS
TDS
7.30
1286
810
793
8.30
2812
698
1271
5.60
1357
410
918
TSS
TS (g/d.ca)
BOD5
BOD5Filtered
1603
14.3
657
298
1969
2.2
650
168
1328
8.8
1092
551
656
284
1517
25.29
1030
391
COD
BOD/COD
NO3
1466
0.45
2.20
1906
0.34
2.10
2039
0.53
2.70
1515
0.43
2.19
2138
0.48
2.97
NH3
MBAS
76
53.0
152
43.0
82
36.0
84
51.9
103
56.4
E.coli
2.30E+04
4.70E+04
1.90E+04
2.57E+04
2.85E+04
Onsite Greywater Treatment Using Septic Tank Followed by Intermittent Sand FilterMBAS and E.coli were 95%, 93%, 95%, 95%, 53%, 98%,
5% and 90% respectively with concentration of 59mg/L,
161mg/L, 31 mg/L, 8mg/L, 12 mg/L, 1mg/L, 50 mg/L
and 227MPN/100 ml in the same order.
The septic tank followed by intermittent sand filter
has achieved a level of treatment that exceeded the
requirement of Jordanian standards JS (893/2006) for the
reclaimed wastewater reuse for fodder, industrial crops
and vegetable eaten cooked.
The septic tank-sand filter overall removal
efficiencies of BOD5, COD, TSS, FOG, NO3, NH4,
MBAS and E.coli were 95%, 93%, 95%, 95%, 53%, 98%,
5% and 90% respectively with concentration of 59mg/L,
161mg/L, 31 mg/L, 8mg/L, 12 mg/L, 1mg/L, 50 mg/L
and 227MPN/100 ml in the same order.
The septic tank followed by intermittent sand filter
has achieved a level of treatment that exceeded the
requirement of Jordanian standards JS (893/2006) for the
reclaimed wastewater reuse for fodder, industrial crops
and vegetable eaten cooked.
a. Top view
Fig 1 (a&b). Schematic diagram of septic tank and sand filter
treatment unit
Table.3 Performance of Septic tank/sand filter
treatment unit
Parameter
BOD5 mg/l
COD mg/l
TSS mg/l
FOG mg/l
MBAS mg/l
NO3-N mg/l
NH3-N mg/l
E.coli
MPN/100ml
b. Sectional view
3.3Performance of Septic Tank and Sand Filter
The performance data of BOD5, COD, TSS, Fat-OilGrease (FOG), NO3, NH4, T-P and E.coli for both septic
tank and sand filter are shown in Table (3).
The septic tank allowed solids to separate from
liquid, while encouraged oils and fats to float at the
surface of liquid. The accumulated solids have undergone
into biological degradation that resulted in reducing the
BOD5, COD and TSS by 63%, 58% and 66%
respectively. FOG was reduced 89% by floating on the
surface of water in septic tank. The anaerobic condition in
the septic tank has resulted in de-nitrification of 95%
NO3-N into (NH4-N); as a result, higher concentrations of
NH4-N were measured at the outlet of the septic tank than
in raw greywater. Storage of greywater and presence of
organic materials in the septic tank has resulted in the
reproduction of E.coli in the septic tank by 2.4 logs.
The partially clarified greywater in septic tank was
vertically distributed into the sand filter on intermittent
bases. 87% of the BOD5, 83% of the COD and 85% of
TSS were removed by both physical and biological
processes within the filter media. 50% of NH4 entering
the sand filter was removed by being assimilated into cell
tissues of the biomass in the top layer of the sand filters.
68% of synthetic detergents (MBAS) were removed by
biodegradation. 3.4 log reduction in E.coli was estimated
in the sand filter which was accomplished by physical
filtration in the sand bed.
The septic tank-sand filter overall removal
efficiencies of BOD5, COD, TSS, FOG, NO3, NH4,
A
1182
2248
609
159
27
47
53
2172
B
438
951
206
17
39
2
100
5.86
E+05
C
59
161
31
8
12
1
50
227
D
63
58
66
89
**
95
**
E
87
83
85
53
68
58
50
F
95
93
95
95
53
98
5
**
90
90
A: Raw greywater
B: Effluent from septic tank
C: Effluent from sand filter
D: Efficiency of septic tank %
E: Efficiency of sand filter %
F: Overall efficiency %
Greywater is generated by the use of soap products
and detergent, and it contains organic materials,
suspended solids and pathogens. Organic content of the
raw generated greywater from the household is higher
than raw greywater quality mentioned in literature. The
type of local manufactured detergent used by households,
amount of detergent used, food style and meals patterns as
well as the low consumptive of water are the key factors
that lead to the high organic loadings which all reflected
on the performance of the treatment system used [17]
Clogging of sand is still a problem in the sand
filtration processes. A risk of clogging was expected and
happened once after one year of operation. The clogging
depth of the sand layer was about 50 cm whereas the sand
layer depth is 60 cm. Therefore, depth of sand layer of
less than 60 cm will lead to more frequent clogging
events.
70
Onsite Greywater Treatment Using Septic Tank Followed by Intermittent Sand FilterThe high concentration of TSS in greywater entering
the sand filter is the main factor of clogging. Colonization
and growth of bacteria within the sand grains enhances
the removal of SS but at the same time it may increase the
risk of sand’s pores clogging.
[5] Al- Jayyousi. OR. 2003. Greywater reuse: towards
sustainable water management. Desalination, vol.
156, pp 181- 192.
[6] Eawag aquatic research, 2006. Greywater
management in Low and Middle Income countries.
Sandec Department of Water and Sanitation in
Developing Countries.
4. Conclusion
1.
2.
3.
4.
5.
The low consumption rate of water in the
household has resulted in high pollution loads of
the generated greywater, and this pollution
requires the greywater to be treated before use to
conserve environment and to protect health.
The composition and characteristics of greywater
significantly vary and very dependant on the
practices of household's inhabitants.
Septic tank followed by intermittent sand filter
was found very effective treatment system for
the highly polluted greywater with overall
efficiency of more than 90%.
The quality of the treated greywater is in
compliance with Jordanian standards for the
reclaimed wastewater reuse in restricted
irrigation.
Failure of sand filter due to clogging is the main
concern in the long term operation of the
treatment system.
[7] Al-Jayyousi, O.R. 2002. Focused environmental
analysis
for greywater
reuse in Jordan.
Environmental Engineering Policy, Vol 3, pp 67-74.
[8] Jefferson, B., Palmer, A., Jrffrey, P., Sturtz, R. and
Judd, S., 2004. Grey water characterization and its
impact on the selection and operation of technologies
for urban reuse. Water Science Technology Vol. 50
No. 2 pp 157 – 164.
[9] Nolde, E., 2005. Greywater recycling systems in
Germany- results, experiences and guidelines. Water
Science & Technology Vol 51 No 10 pp 203-210.
[10] Nolde, E. 1999. Greywater reuse for toilet flushing
in Multi-storey buildings-over ten years experience in
Berlin. Urban Water, Vol 1 pp 275-284.
[11] Dalahmeh, S., Assayed, M., Sulieman. W. 2006,.
Technical reports of integrated Wastewater
management policies and technologies of the
marginal communities of Jordan. 4th, 5th interim
technical report. Royal Scientific Society.
Acknowledgment
Authors would like to express their deep thanks for the
International Development Research Centre IDRC/
Canada, Ottawa for their financial support for the project
"Integrated wastewater management policies and
technologies of the marginal communities in Jordan",
under which this research has been done by
Environmental Research Centre of Royal Scientific
Society.
[12] Metcalf and Eddy (1991) Wastewater Engineering,
Treatment, Disposal, Reuse, 3rd ed., Mc-Graw Hill
Inc, New York.
[13] Healy, M.G., Rodgers, M., Mulqueen, J., 2007.
Performance of a stratified sand filter in removal of
chemical oxygen demand, total suspended solids, and
ammonia nitrogen from high-strength wastewaters.
Journal of Environmental management, 83 (4):409-415.
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