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IMPROVED RURAL SANITATION CONCEPTS
By
Dhanesh GunatillekeSPECIALIST (SEWARAGE
DESIGNS)NWSDB
1st April 20141
2
1 Why wastewater treatment?
2 Policy on Wastewater Separation
3 Types of sanitation systems
4 Design of onsite sanitation systems in compliance to SLS 745 Part II:2009
5 Further Treatment Options
Presentation Outline
2
1 WHY WASTEWATER TREATMENT ?
Protect the environment from;high loads of suspended solids & organic mattereutrophication & groundwater pollutionSubstantial load of hazadous and non biodegradable compoundsSerious contamination with microorganisms
…in order to establish/maintain healthy environment for flora & faunaallow mankind to use water resources for different purposesprevent transmission of waterborne diseases/improve public health 3
4
Definition of Safe Sanitation
Ref: water supply and sanitation collaborative council
Collection, Transport, Treatment &
Disposal or reuse of human excreta,
domestic wastewater and solid waste,
and associated hygiene promotion
5
6
7
8
9
Pollution from human beings
45-60 g BOD/person/day
8- 14 g N/person/day
0.6-2.5 g P/person/day
Virus
Medical residues
10
Eutrophication & it’s impactsIncrease in rate of supply of organic matter
to an ecosystem resulting nutrient built up (N, P)
Massive algae growth, anaerobic conditions, oxygen depletion
Changers in the structure and functioning of the lake and marine ecosystem
Reduction in biodiversity, fish and shellfish harvesting
Increase risk of poisoning by algal toxins11
DO Sag CurveWastewater
DOsat
Distance (Km)
7.83mg/lat 280C
12
Health Problems
In some areas in the developing world, 75 -80% of human illness is related to water and water pollution
Discharge of wastewater represents the greatest risk for pollution of potable water
13
Ref: A.J. Arcivala
14
Ref: A.J. Arcivala
15
Ref: Metcalf & Eddy
2. Wastewater Separation
RainwaterRainwater Harvesting/Surface Drainage System
Hazardous WW
Separate them in concentrated formin separate plumbing system
Treat/Dispose as Hazardous WW
Restaurants Grease Interceptor Onsite/Sewerage
Reticulation SystemWW of Domestic Nature
X-Ray Processing AgCl+NaOH AgO
Dental Wastewater (Amalgam) Ag, Pb, Sn
Radioactive Iodine Treatment Mutagenic
Full Blood Count Test (Cn) Blood Urea Test Total Protein Test Albumin Test Liver Functional Test Cholesterol Test Sugar Test Skin Preparation (Salicylic, Benzoic Acid, yellow parafin) Bottle Washing (Antibiotics) Molecular Biology Research
(Ethidium Bromide Mutagenic) Formalin (preservative for biological specimens)
CONCEPT FOR HOSPITAL To the Existing Surface
Drainage System Storm Water/ Rain Water
Rat/ Mora WWTP
Retention(As per CEA/AEA Recommendation)
Grease Trap Kitchen WW Sewerage System
Other WW of Domestic Nature
Effluent from Radiation Treatment(Iodine)
Pumping Station
• X- Ray Processing (Dark Room)• Dental WW• Laboratory WW
Collection to Containers in concentrated form with separate plumbing system
Disposal as Hazadous Wastewater (GeoCycle)
Existing Oxidation Ditch & Settling tank will be converted to a Floting wetland
Hazardous WW Disposal-Preconditioning
22
23
24
Ref: National Institute of Minamata Disease
25
Ref: National Institute of Minamata Disease
26
Ref: National Institute of Minamata Disease
3. Types of Sanitation Systems
• On site sanitation systems (>90%)– Septic tank associated effluent disposal systems
• Off Site Sanitation Systems (>2.5%)– Wastewater collection, treatment & Disposal
• Decentralized System
27
PRODUCTION PRE TREATMENT DISPOSAL
EVAPOTRANSPIRATION
WATER TABLE
PURIFICATION
GROUND WATER
SOIL ABSORBTIONSEPTIC TANK
GREASE TRAP Drainage field
Unsaturated Zone
Saturated Zone
Schematic cross-section through a conventional septic tank soil disposal system for on-site
disposal and treatment of domestic liquid waste
How it Works
28
29
Onsite Sanitation Systems
SIMPLE PIT LATRINE
Manual 1:Latrine Construction
Technical Manual Series on Rural Water Supply & Sanitation
NORAD-Helvetas Sri Lanka
29
30
VENTILATED IMPROVED PIT LATRINE
Manual 1:Latrine Construction
Technical Manual Series on Rural Water Supply & Sanitation
NORAD-Helvetas Sri Lanka
30
31
On Site Sanitation
WATER SEAL POUR – FLUSH LATRINE (Off-set Pit Type)
NWSDB through ADB 3rd Project
Puttalam 10,112
Kegalle 11,634
Kalutara 8,745
Hambantota 12,675
Monaragala 23,128
Total 81,333
Total 164,000
Manual 1:Latrine Construction
Technical Manual Series on Rural Water Supply & Sanitation
NORAD-Helvetas Sri Lanka
31
32
DRY COMPOST LATRINES Environmentally friendly Designed to keep the faeces separate from the urine and water used for anal cleansing Is usually an elevated construction Urine/water drained into an evaporative plant bed or a cultivation plot To eliminate bad odour and nuisance from flies a handful of ash, lime or soil has to be sprayed into the pit
Manual 1:Latrine Construction
Technical Manual Series on Rural Water Supply & Sanitation
NORAD-Helvetas Sri Lanka
NWSDB About 100
NGO’s About 100
32
33
ECOSAN-BANGALIDESH/TAMIL NADU
33
34
Onsite Sanitation SystemsSEPTIC TANK / SOKAGE PITS/SOKAGE TRENCES
Manual 1:Latrine Construction
Technical Manual Series on Rural Water Supply & Sanitation
NORAD-Helvetas Sri Lanka34
GREAZE INTERCEPTOR
35
Service StationsPrimary treatment by Grease InterceptorsSubsequent Pre treatment by
CoagulationFlocculationSedimentation
Muthugala Service Station- Kurunegala
36
Disposal of OilAs furnace oil
37
Nippon Steel Cor.
38Frazer Thomas-NZ
38
39
Frazer Thomas-NZ
39
40
BIO TOILET-JAPAN
40
41
Problems in on site systems?• Faulty design & construction of septic
tanksInadequate water depth for solid separationFailure in construction/water tightness
• Faulty design of soakage arrangementsSeasonal high ground water tablePresence of non favorable soilsPresence of shallow rockProne for floodingOverloading
41
42
4. Treatment Options
SLS 745:Part I: 2004 • Part I- Small systems disposing to ground
SLS 745:Part II: 2009 • Part II- Systems Disposing To Surface, Systems For
On-site Effluent Reuse And Larger Systems Disposing To Ground
42
43
PLAN
SECTION
Inspection port150mm
Partition
Access openings500mm min.
Vent pipedia. 25mm min.
Free board200mm min.
Dia.100mmmin.
Min. 20% of liquid depth
50mm min.
Opening100mm min.
Liquid level 300mm min.
INLET
INLET
To further treatment
First compartment approx. 2/3 length Second compartmentapprox. 1/3 length
Total length between 2 – 4 times width
Inspection port150mm
Inspection port150mm
Access openings500mm min.
75
0mm
min
imu
m(i
nte
rna
l d
ime
nsi
on)
Opening25mm min.
Dia.100mmmin.
To further treatment
SEPTIC TANK
Ref: SLS745 Part II
43
44
SEPTIC TANKS
Design Requirements
SLS 745:Part I: 2004 SLS 745:Part II: 2009
• Main functions • Free board• Vent pipe & cowl • Access• Commissioning• Desludging
44
45
2 to 4=Length to Width Ratio
0.75m=Minimum width of Septic Tank
1m=Minimum depth of septic tank
55%=Assume reduction in BOD
mg/l200=Assume initial BOD
Septic Tank
m3/day0.56=Q
112 * 5 =Q Average daily WW flow
112=
liters/person/day 140 * 0.8=Per Capita Wastewater Flow
liters/person/day 140=Per capita Water Consumption
5=No of members in a family
Design for All Wastewater
The Design and Construction of Septic Tank and Associated Effluent Disposal Systems (SLS 745 Part I : 2004)
DESIGN CRITERIA
45
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SEPTIC TANK DESIGN FOR 5 PERSONS (DE-SLUDG PERIOD 5 YEARS)
m30.092=Vd
2.8=
Q(m3/day) / 0.2(m3/p/day)=pPopulation equivalent for all wastewater
(for an ambient Temperature of 20 0C) days33=tdTime required for sludge digestion
(for all wastewater)m3/day0.001=qsVolume of fresh sludge per person
qs. Td. P=Vd
1.2) Volume required for sludge digestion Vd (All Waste)
m3 0.88 =Vs
OK
Should be > 0.2 d
days 1.58 =
days(1.5-0.3 log Q)=tsTime required for settling
ts.Q=Vs
1.1) Volume required for settling, Vs (All Waste)
46td =1853T-1.25
47mg/l90=BOD of effluent
55%=Assume rate of BOD removal in septic
tank
Hence ok
( 2<L/W<4 ) 3.23 =L/W
m 2.42 =Then Length L
m0.75=Assume width, W
m2 1.81 =Then, Surface Area A
( Minimum Depth 1m)m1=Take Depth, H
( 1m3 < V < 12m3 )m3 1.81 =V
m3
Vs+Vd+1.5*Vst
=1.5)Total Volume required for septic tank
Vst0.5= Volume required for scum storage
1.4) Volume required for scum storage
m30.56=Vst
year5=nDesludging interval>1
m3/year0.04=rVolume of digested sludge per person per year for all wastewater
r.p.n=Vst
1.3) Volume required for sludge storage Vst (All Waste)
47
48
De-sludging Interval (Years) 2 5
No of Occupants /House 5 7 10 5 7 10
ST Volume (m) 1.31 1.80 2.52 1.81 2.51 3.53
ST Height (m) 1.00 1.00 1.20 1.00 1.00 1.20
ST Width (m) 0.75 0.75 0.80 0.75 0.90 1.00
ST Length (m) 1.75 2.40 2.63 2.42 2.78 2.94
Length / Width 2.33 3.20 3.28 3.23 3.09 2.94
Surface Area (m2) 1.31 1.80 2.10 1.81 2.51 2.94
SIZING OF SEPTIC TANKS
48
49Sludge Judge
Sludge judge
49
SOKAGE PITS
Soakage pits• Soak septic tank effluent• Effluent get treated before reaching GW
Applicability– GWT below 2.5m (seasonal fluctuation)– Soil percolation rate between 25mm/h to
125mm/h
Location– At least 18m away from nearest well/drinking
water source– At least 5m away from the nearest building
50
dia. 100 mm min.
Minimum1.2 m
GWT (Seasonal high )
SECTION
Impermeableliner / wall
Between 900mm & 3000mmImpermeable
cover
Minimum 1000 mm
Inlet pipe
300 mm min.
Minimum2.5 mOpen jointed
brick / cementblock
Ground level
PLAN (CIRCULAR TYPE) PLAN (SQUARE TYPE)
PLAN (RECTANGULAR TYPE)
900mm <
Dia. < 3000mm
900mm < Length < 3000mm
Width > 900 mm
Length < 3000mm
Inlet pipe
Inlet pipe
Inlet pipe
SOKAGE PIT
Ref: SLS745 Part II
51
Minimum Distance Between Soakage PitsRef :table 2,SLS 745 part 2
Average daily flow(m3/d)
Minimum distance between soakage pits (m)
<2 10
2-5 15
5-10 20
10-30 36
52
Specific Effective Areas for Soakage Pits Ref :table 3,SLS 745 part 2
Percolation Rate mm/hr
Specific Effective Area (m2 / m3 per day)
25 34
50 17
75 11
100 8.4
125 6.653
Minimum depth to groundwater table from bottom of soakage pit
Ref :table 4,SLS 745 part 2
Percolation rate(mm/hr.)
Minimum depth to GWT (m)
25-50 1.2
50-75 1.8
75-100 2.4
100-125 3.054
Existing surface
Topsoil
Finished surface
Perforated distributor pipesdia.100mm min.Soil barrier
Settlementallowance
Level floorarea
Prepared aggregate(20 – 40mm)
100mm min.
300mm min.
1000mm max.From wall
2000mm max. spacing 1000mm max.From wall
Level site – slope less than 5 %
TYPICAL ARRANGEMENT OF SEEPAGE BED
Length < 20m
SECTION
PLAN
1m
< W
idth
< 6
m
75mm min.
Septic tank
Gro
und
slop
e <
5%
Distributor pipes
SEEPAGE BED
The maximum bed length
shall be 20 m.
SLS 745 Part II:200955
100mm min.
300mm min.
Topsoil
Ground surface
Perforated pipedia.100mm min.
Soil barrier
Settlement allowance
Finished surface
Prepared aggregate(20 – 40mm)
300mm min.
75mm min.
TYPICAL ARRANGEMENT OF SEEPAGE TRENCH
Gro
und
slop
e 25
% m
ax.Septic tank
Disposal field trenches
SECTION
PLAN
Ground slope 5% max.
20m max.
SEEPAGE TRENCH
SLS 745 Part II:200956
Specific effective areas for seepage beds and seepage trenches
Ref :table 5, SLS 745 part 2
Percolation rate(mm/hr)
Specific effective area(m2 / m3 per day)
25 50
50 25
75 17
100 12.5
125 10
150 8.3
175 7.1
200 6.25
225 5.6
250 5.057
Minimum, maximum and typical dimensions of seepage beds
Ref :table 6, SLS 745 part 2Bed dimension Typical
Range(mm)
Maximum(mm)
Minimum(mm)
Width 1000-6000 6000 1000
Depth of aggregate
300-600 600 300
Depth of topsoil 100-150 N/A 100
Spacing between beds (sidewall to sidewall)
- N/A 1000
58
Typical dimensions of seepage trenches Ref :table 7, SLS 745 part 2
Trench dimension Typical Range(mm)
Maximum(mm)
Minimum(mm)
Width 300-600 600 300
Depth of aggregate
300-600 600 300
Depth of topsoil 100-150 N/A 100
Spacing between beds (sidewall to sidewall)
1000-2000 N/A 1000
59
MOUND SYSTEMS
Cross-section of a mound system for slowly permeable soil on a sloping site (US EPA, 1980)
ROCK STRATA OR IMPERMEABLE SOIL LAYER
SLOPE
PLOUGHED LAYER OF TOP SOIL
ABSORBTION BED
DISTRIBUTION LATERAL
CAP
3
1
STRAW, HAY OR FABRIC
FILL
60
MOUND SYSTEMS
Cross-section of a mound system for a permeable soil with hight ground water or shallow creviced bed rock (US EPA, 1980)
ROCK STRATA OR IMPERMEABLE SOIL LAYER
PLOUGHED LAYER OF TOP SOIL
ABSORBTION BED
DISTRIBUTION LATERAL
CAP
3
1
STRAW, HAY OR FABRIC
FILL
61
Frazer Thomas-NZ62
Frazer Thomas-NZ
63
In compliance to Disposal StandardsInland Water BodySea OutfallRe Use For Non Potable Uses
BOD
COD
SS
N,P
Faecal Coliform
Further Treatment
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OUTLET
Dia.100mmmin.
OUTLET
PLAN
Dia.100mmmin.
INLET
Access openings500mm min.
Inspection port150mm
SECTION
Inspection port150mm
Access opening500mm min.
Vent pipe dia. 25mmmin.
Liquid level
Dia. 50mmmin.
INLET
TYPICAL ARRANGEMENT OF ANAEROBIC FILTER
Washed & graded filterMedia (min. size 2mm).
200mm min. Perforated filter floor
Perforations dia.10mm min.
Inletchamber
Access opening500mm min.
ANAEROBIC FILTERS
SLS 745 Part II:2009
65
The minimum design HRT shall be 0.6 days and the maximum shall be 1.5 days.
Surface loading rate (m/d) = Average daily flow (m3/d) Plan area of filter (m2)
SLR ≤ 2.8
Total volume of void space in the bed > 35 per cent
Volume of the bed
0.6m < h > 1.8m
invert of the outlet shall be at least 50 mm below the invert of the inlet
66
WETLANDS
• FREE WATER SURFACE WETLANDS
67
WETLANDS
• SUBSURFACE WETLANDS
68
Typical Wetland Plants
69
Cattails
70
Kok mota
SUBSURFACE WETLANDRATMALANA TSUNAMI RESETTLEMENT HOUSING
SCHEME AT FOOD STORES LAND
71
Free Floating Aquatic Plants
Floating Treatment Wetlands72
Floating Wetlands
Biofilm covered roots
Variable water depth
Floating mat
Leaf litter
73
3. Floating Wetlands
1. Duckweed
2.Salvinia74
Natural Floating Wetlands cont...
3. Water lettuce
Common Features
Self buoyant root structureUncontrolled rapid growthCutoff sunlight 75
Natural Floating Wetlands cont..4. Eichhornia crassipes
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77
Floating Wetlands
77
Removal glycol from de-icing water at Heathrow Airport
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JHOKASOU(private sewage treatment system)
80
Jhokasou
Anaerobic contact aeration type
Anaerobic contact aeration type
Sludge Return Pipe
Sludge Return Pipe
Blue valve for aeration
Blue valve for aeration Yellow valve for air-
release
Yellow valve for air-release
White or Grey valve for air-Lift
White or Grey valve for air-Lift
Red valve for Back-washing
Red valve for Back-washing
Sludge Return Equipment ( Air-Lift )
Sludge Return Equipment ( Air-Lift )
Disinfection Tank ( Disinfectant )
Disinfection Tank ( Disinfectant )
Sedimentation TankSedimentation Tank
Anaerobic contact aeration type
contact aeration type
(3) Separate aeration type
(4) Total aeration type
aeration
chambersettling
chamber
disinfection
chamber
inflow
effluent
air pump
sludge
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GL
↓↑
Sprinkling filter bed type
sludge
scum
Filtermedia Filter
media
Exhaust pipe
Sprinkling weir
inflow
effluent← anaerobic tank → ← aerobic part →