Need of tertiary treatment for anaerobic wastewater treatment
Lecture onLecture on
CHEMICAL ENGINEERING DEPARTMENTSARDAR VALLABHBHAI NATIONAL INSTITUTE OF TECHNOLOGY,
SURAT 395 007
byDr. Arvind Kumar Mungray
B. Tech., M. Tech., Ph.D.
Municipal wastewater Components.
Sewage
Point sources
Wastes that are collected in pipes or Wastes that are collected in pipes or channels and discharged to a surface water channels and discharged to a surface water with or without treatmentwith or without treatment
Distinguished by sourceDistinguished by source municipal sewage or wastewatermunicipal sewage or wastewater industrial waste watersindustrial waste waters combined sewers and combined sewer combined sewers and combined sewer
overflowsoverflows
Nonpoint sources Storm water runoff discharged at multiple Storm water runoff discharged at multiple
pointspoints Varies substantially with use of the land runoff Varies substantially with use of the land runoff
originates fromoriginates from agriculturalagricultural urbanurban commercialcommercial special (e.g. golf courses)special (e.g. golf courses)
Municipal Wastewater
IMPORTANT WASTEWATER CONSTITUENTS
Dissolved solids (TDS/Salts) : less ImportanceDissolved solids (TDS/Salts) : less Importance Suspended solids: (SS) Suspended solids: (SS) Biodegradable organics: Organic matter (BOD)Biodegradable organics: Organic matter (BOD) Nutrients – Nitrogen & Phosphorus. Nutrients – Nitrogen & Phosphorus. (Important (Important
if treated wastewater is discharged into lakes)if treated wastewater is discharged into lakes) Heavy metals – Cr, Cd, Hg, Pb : less importanceHeavy metals – Cr, Cd, Hg, Pb : less importance Refractory organics: CFC, Benzene etc.: less Refractory organics: CFC, Benzene etc.: less
importance,importance, Pathogens – Transmit disease Pathogens – Transmit disease
T O W NT O W N
R I V E R
CREMATORIACREMATORIA
RFDRFD
LCSLCS
FORIRRIGATION
FORIRRIGATION
TREATED EFFLUENTTREATED EFFLUENT
SEWERSEWER
RFDRFD
NA
LL
AS
INDUSTRY
ETPETP
STPSTP
PUMPINGSTATIONPUMPINGSTATION
Significance of Wastewater Contaminants Dissolved solids – interfere with reuseDissolved solids – interfere with reuse Suspended solids – can cause sludge deposits Suspended solids – can cause sludge deposits
and anaerobic conditions in the environmentand anaerobic conditions in the environment Biodegradable organics – can cause anaerobic Biodegradable organics – can cause anaerobic
conditions in the environmentconditions in the environment Pathogens – transmit diseasePathogens – transmit disease Nutrients – can cause eutrophicationNutrients – can cause eutrophication Heavy metals – toxicity to biota and humansHeavy metals – toxicity to biota and humans
What we can Do ?
Any Solution Any Solution
- Wastewater Treatment -
Objectives of Wastewater Treatment
Removal of Suspended Solids by Clarification ( In Removal of Suspended Solids by Clarification ( In Sedimentation Tank)& Decomposition (By providing Sedimentation Tank)& Decomposition (By providing Suitable conditions for bacteria)Suitable conditions for bacteria)
Removal of Organics by Decomposition (By Removal of Organics by Decomposition (By providing Suitable conditions for bacteria) & Provide providing Suitable conditions for bacteria) & Provide conditions for separation of the wastewater from the conditions for separation of the wastewater from the Bacteria.Bacteria.
Removal of Residual bacteria present in separated Removal of Residual bacteria present in separated wastewater by adding powerful oxidants such as wastewater by adding powerful oxidants such as Chlorine.Chlorine.
Treated Quality Standards
INTO WATER BODYINTO WATER BODY ON LANDON LAND
BOD (mg/l)BOD (mg/l)
COD (mg/L)COD (mg/L)
T S S (mg/l)T S S (mg/l)
FAECAL (MPN/100 ml)FAECAL (MPN/100 ml)
COLIFORMSCOLIFORMS
3030
250250
100100
10001000
1000010000
100100
200200
(Desirable)(Desirable)
(Maximum)(Maximum)
To Bring the River Water to Bathing Quality ( River Bathing Standards)
BODBOD -- BIO-CHEMICAL OXYGEN DEMANDBIO-CHEMICAL OXYGEN DEMAND
DODO -- DISSOLVED OXYGENDISSOLVED OXYGEN
MPNMPN -- MOST PROBABLE NUMBERMOST PROBABLE NUMBER
BODBOD 3 mg/L (MAXIMUM)3 mg/L (MAXIMUM)
DO DO 5 mg/L (MINIMUM)5 mg/L (MINIMUM)
COLIFORM (FAECAL)COLIFORM (FAECAL) 500 (DESIRABLE)500 (DESIRABLE)
2500 (MAX. PERMISSIBLE)2500 (MAX. PERMISSIBLE)
PERMISSIBLE LIMITPERMISSIBLE LIMITPARAMETERSPARAMETERS
MPN 100 ml
S.V. National Institute of Technology, Surat
Treatment of wastewaters
• Aerobic• Anaerobic
Aerobic MethodsAerobic Methods
– Activated Sludge ProcessActivated Sludge Process
– Trickling FiltersTrickling Filters
– Extended Aeration SystemExtended Aeration System
– Stabilization PondsStabilization Ponds
– Oxidation DitchesOxidation Ditches
– LagoonsLagoons
Anaerobic MethodsAnaerobic Methods
– UASB ProcessUASB Process
– Anaerobic PondsAnaerobic Ponds
– Anaerobic FiltersAnaerobic Filters
AEROBIC PROCESS
Organic Pollution
Nutrients
Aerobic
Micro-organisms
O2
CO2+H2O+New Cells
ANAEROBIC PROCESS
AEROBIC METHOD
ANAEROBIC METHOD(UASB PROCESS)
Sewage Treatment Plant
Anaerobic degradation process
HydrolysisHydrolysis
Acid production
Acid production
Methane production
Methane production
Carbohydrates, lipids, proteins broken down to low molecular weight compounds by enzymes.
Acidogenesis – amino acids converted to volatile fatty acids (VFAs)
Acetogenesis – VFAs, lactic acid etc converted to acetic acid, H2, CO2
Acetotrophic methanogensis – Acetic acid converted to CO2 and CH4
Hydrogenotrophic methanogensis – H2 and CO2 converted to CO2 and CH4
Step General process Description Notes
1
2
3
Rate limiting. Temperature dependant
Not rate limiting
Rate limiting. Temperature dependant
Overview Anaerobic BiodegradationPolymers
(proteins, polysaccharides)
Monomers(sugars, amino acids, peptides)
butyratepropionate
H2 + CO2 acetate
CH4 + CO2
h
h
111
1
2 2
2
3
3
44
4Hydrolytic enzymesFermentative bacteriaSyntrophic acetogenic bacteria
Homoacetogenic bacteriaMethanogens
Methanogenic Consortium
Types of anaerobic reactors
Low rate anaerobic reactors High rate anaerobic reactors
Anaerobic pond
Septic tank
Standard rate anaerobic digester
Imhoff tank
Slurry type bioreactor, temperature, mixing, SRT or other environmental conditions are not regulated. Loading of 1-2 kg COD/m3-day.
.
Anaerobic Sequencing BatchReactor (ASBR)
Anaerobic contact process
Anaerobic filter (AF)
Upflow anaerobic slugde Blanket (UASB)
Fluidized bed Reactor
Hybrid reactor: UASB/AF
Able to retain very high concentration ofactive biomass in the reactor. Thus extremely high SRT could be maintainedirrespective of HRT. Load 5-20 kg COD/m3-dCOD removal efficiency : 80-90%
.
S.V. National Institute of Technology, Surat
Up-Flow Anaerobic Sludge Blanket Reactor (UASB)
Granules
Effluent
Influent
biogas
UASB Reactor
Physical:
Microbial:
dense compact biofilmshigh settleability
high mechanical strength
balanced microbial community
syntrophic partners closely associated
high methanogenic activity(0.5 to 2.0 g COD/g VSS.d)
protection from toxic shock
(30-80 m/h)
Anaerobic Sludge Granules
Anaerobic Sludge Granules (close up)
Anaerobic Sludge Granules (settling)
granular flocculent dispersed
Who Discovered the UASB?
Gatze Lettinga
raw wastewater
screens
grit trap
to grit disposal
splitter box
UASBreactor
gas holder
excessflared
facultative lagoon
effluent to reuse or disposal
sludge to agriculture
sludge drying beds
UASB reactor
struvite precipitation
reuse
discharge
black water
kitchen waste
gray water
UASB-septic
bio
gas
nutrient richproduct
Nirogen removal
Removal micro-pollutants (ozone)
sludge
hygienisation
treatment
Landbouw?
UASB Reactor
Side Views of UASB Reactor
Top View of UASB Reactor
Salient Features of UASB
Low Energy Consumption (Almost Nil)Low Energy Consumption (Almost Nil)
Comparatively Low Capital CostsComparatively Low Capital Costs
Good removal EfficienciesGood removal Efficiencies
Generation of Methane Gas (Energy Recovery)Generation of Methane Gas (Energy Recovery)
Small Land Area RequirementsSmall Land Area Requirements
Low Sludge ProductionLow Sludge Production
N,P,K Conc. are Retained in Treated EfficiencyN,P,K Conc. are Retained in Treated Efficiency
Simple Construction, Operation & MaintenanceSimple Construction, Operation & Maintenance
Removal Efficiencies
TSSTSS 70-85%70-85% BOD BOD 65-75%65-75% CODCOD 70-80%70-80% Feacal ColiformFeacal Coliform 99%99%
Bilateral cooperation between India and Netherlands in 1985 led to the design and construction of first successful full scale UASB reactor for domestic sewage at Kanpur. This demonstration plant was designed to treat 5 ML/d of raw sewage at 6 h HRT with influent BOD and COD of 200 and 500 mg/L respectively.
One more UASB based treatment plant (36 ML/d) built in Kanpur to treat the wastewater of approximately 180 tanneries after dilution with domestic wastewater in a ratio of 1:3 is in operation since April 1994.
Development of UASB Technology in India
UASB TREATMENT PLANTS under Ganga Action Plan
5 MLD UASB Demonstration Plant at 5 MLD UASB Demonstration Plant at KanpurKanpur
14 MLD UASB STP at Mirzapur14 MLD UASB STP at Mirzapur
36 MLD UASB CETP at Kanpur36 MLD UASB CETP at Kanpur
Up-Flow Anaerobic Sludge Blanket (UASB) Reactors
The UASB reactor is the most widely used The UASB reactor is the most widely used high rate anaerobic high rate anaerobic
systemsystem for treatment. for treatment.
World wide more than 500 already installed.World wide more than 500 already installed.
More than 35 UASB based in IndiaMore than 35 UASB based in India
16 full scale UASB based STP (598 ML/d)
More than 900 UASB units are currently operating all over the world.
Locations of STPs selected for the study with their treatment capacities.
UASBASP OP
UASB ASP OP
Roorkee
(a) COD
0
100
200
300
400
500
600
27 34 38 56 70
CO
D (
mg
/L)
Total Filterable
COD: Discharge standard = 250 mg/L
CODt = 100- 159 mg/L
CODs = 70 – 90 mg/L
(BOD/COD)eff = 0.29
(b) BOD
0
50
100
150
200
250
27 34 38 56 70
BO
D (
mg
/L)
Total Filterable
Mean unfiltered BOD (3d, 270 C) = 33 – 43 mg/L
Discharge limit = 30 mg/L
Marginal improvement required
Mean filterable BOD (3d, 270C) = 25.6 – 28.7 mg/L
(c) TSS, VSS
0
100
200
300
400
500
600
27 34 38 56 70
TS
S,
VS
S (
mg
/L)
TSS VSS
TSS = 124 – 155 mg/L
TSS > 100 mg/L
1 kg COD = 0.35 m3 CH4 1 kg COD = 0.35 m3 CH4
complete anaerobic degradation of 1 Kg complete anaerobic degradation of 1 Kg COD produces 0.35 m3 CH4 at STP COD produces 0.35 m3 CH4 at STP
Main advantage: Energy can be generated
Town Capacity(ML/d)
Town Capacity (ML/d)
Town Capacity(ML/d)
Kanpur 5 Panipat 35 Ghaziabad 70
Kanpur 36 Sonipat 30 Ghaziabad 56
Mirzapur 14 Faridabad 20 Noida 27
Yamuna Nagar
25 Faridabad 45 Noida 34
Yamuna Nagar
10 Faridabad 50 Agra 78
Karnal 40 Gurgaon 30 Hydrabad 50
Panipat 10 Saharanpur
38 Kabitkhadi 78
Kapurthala 25 Mohali 45 Jalandhar 25
Vadodara 43 Surat 100
Table: UASB Based Sewage Treatment Plants in India
Place V(m3)
T(ºC)
Influent concentration (mg/L)COD BOD TSS
HRT(h)
Removal efficiency (%)COD BOD TSS
Reference
India 1200 20-30
563 214 418 6 74 75 75 Draaijer et al.,1992
India 12000 18-32
1183 484 1000 8 5 1 63
53 69 46 64 Haskoning, 1996; Tare et al., 1997
India --- -- 387 195 360 -- 57 64 66 Hammad 1996
India 6000 18-32
404 205 362 8 62 72 65 71 70 78 Haskoning, 1996b; Tare et al., 1997
India 36000 -- 1180 480 1000 -- 56 61 55 Wiegant et al., 1999
India 36000 -- 838 398 846 --- 52 50 56 Tare et al., 2003
India -- -- 315 403
-- 162 836
4.49 5.49
45 78 -- 45 76 Ghangrekar and Kahalekar, 2003
India (15-UASBs)
(10-78) x 106
18.8-23.8
754 258 410 8.4 10.7
46.5 49.6 7.31 Sato et al., 2006
India (5
UASBs)
(27-70) x 106
--- 373 452
159 175
324 419
9.4 10.3
42 55 55 69 30 43 Mungray , 2007
Review of UASB process removal efficiency in India
STANDARDS FOR TREATED SEWAGE STANDARDS FOR TREATED SEWAGE INDIAN STANDARDS INDIAN STANDARDS
FOR DISCHARGEFOR DISCHARGE
INTO WATER BODYINTO WATER BODY PUBLIC SEWERSPUBLIC SEWERS
BOD (mg/L)BOD (mg/L)
COD (mg/L)COD (mg/L)
T S S (mg/L)T S S (mg/L)
FAECAL (MPN/100 ml)FAECAL (MPN/100 ml)
COLIFORMSCOLIFORMS
3030
250250
100100
10001000
1000010000
500500
600600
(Desirable)(Desirable)
(Maximum)(Maximum)
Oil & Grease 10 100
Temp 40 45
pH 5.5-9
Main limitations of anaerobic systems
(1) Limitations regarding organic matter Does not follow the discharge standards in terms of BOD, COD Requires post treatment step. UASB Effluent BOD: 60-120 mg/L BOD removal Efficiency: 55 - 75%
(2)Limitations regarding nitrogen and phosphorous Discharge of nutrients in to surface water may caused increased algal biomass = eutrophication
1.0 Kg of phosphorous can result in the reconstruction of 111 Kg of biomass = which corresponds to approx. 138 Kg of COD
1 Kg of Nitrogen can result in the reconstruction of Approx. 20 Kg COD under the form of dead algae
(3) Limitations regarding
microbiological indicators Pathogens = 10,000 MPN/100 ml
(Maximum) = 1000 MPN/100 ml
(Desirable)
Post-Treatment Options
Final Polishing PondsFinal Polishing Ponds Aerated LagoonsAerated Lagoons Overland flow systemOverland flow system Activated sludgeActivated sludge Trickling filterTrickling filter Construction wetlandsConstruction wetlands Combination of Aerated Lagoon & PondsCombination of Aerated Lagoon & Ponds Down Hanging Sponged Media SystemDown Hanging Sponged Media System
Post treatment of UASB effluents
The main role of the post-treatment is to complete the The main role of the post-treatment is to complete the
removal of organic matter, as well as to remove removal of organic matter, as well as to remove
constituents little affected by the anaerobic treatment, constituents little affected by the anaerobic treatment,
such as nutrients (N and P) and pathogenic organisms such as nutrients (N and P) and pathogenic organisms
(viruses, bacteria, protozoans and helminths). (viruses, bacteria, protozoans and helminths).
Limitations imposed by environmental agencies for Limitations imposed by environmental agencies for
effluent discharge standards. effluent discharge standards.
Treatment plant with UASB reactor & Overland flow system
Treatment plant with UASB reactor & Submerged ABF
Treatment plant with UASB reactor and Anaerobic filter
Treatment plant with UASB reactor and Trickling filter
Rawsewage
Screen chambers
Polishing Ponds (PP)
Grit channels UASB reactors
Sludge drying beds (SDB)
Screenings Grit
Wet UASB sludge
Dried sludge
Final effluent
1 2 3
4 5
SCHEMATIC FLOW-DIAGRAM OF UASB BASED STP
Treatment plant with UASB reactor and polishing ponds
Polishing pondsPolishing ponds
Down Hanging Sponged Media (DHS)
Top View of DHS
Raw sewage
Effl uent f rom UASB
Effl uent f rom DHS
Effl uent f rom PP
Post treatment process efficiency CountryCountry HRTHRT UASB effluent (mg/L)UASB effluent (mg/L)
COD BOD SS COD BOD SS
Post Post Treatment Treatment
HRTHRT Effluent concentration (mg/L)Effluent concentration (mg/L)
COD BOD SSCOD BOD SS
Brazil Brazil 7hr7hr 126126 4242 5151 OzonationOzonation 50min50min 53 53 20 20 13 13
India India ---- 170170 7070 124124 FPUFPU ------ 83 83 36 36 56 56
Brazil Brazil ------ 112112 ------ 1414 AFAF 2424 60 60 ------ 29 29
Brazil Brazil 4-6 hr4-6 hr 23.323.3 1010 3737 BFBF 4hr 4hr 36 36 9 9 10 10
Brazil Brazil 8hr8hr 112112 3636 3737 SubmergedSubmergedABFABF
1.5m1.5m33//mm22.h.h
38 38 36 36 10 10
Israel Israel 5 days5 days 126±81126±81 23±1323±13 35±3035±30 DWDW 4.7 days 4.7 days 49±20 49±20 8±15 8±15 11±4 11±4
Belgium Belgium 10 hr10 hr 53±28 53±28 25±625±6 35±435±4 ZeoliteZeolite ---- 45±6 45±6 ---- -- --
IndiaIndia 5days5days 600600 ---- 7070 SBRSBR 8 days8 days 100 100 ---- ----
Brazil Brazil 7.5hr7.5hr ------ 4646 6060 PPPP 4.2hr4.2hr ---- 4040 108108
Japan Japan 8hr8hr 178178 6767 4747 DHSDHS 2.72.7 4343 2.32.3 1212
Japan Japan 6hr6hr 226.8226.8 136136 40.940.9 DHSDHS 2.5hr2.5hr 62 62 16.5 16.5 17.5 17.5
India India 9.4-10.3h9.4-10.3h ------ 200200 4040 PPPP 1-1.6d1-1.6d ------ -------- ----------
DHS = Down Flow Hanging Sponge, RBC = Rotating Biological Contactor, FPU = Final Polishing unit, AF = Aerated Filter, BF = Biofilters, ABF = Aerated Biofilters, PP = Polishing ponds, DW = Duckweed.
S.V. National Institute of Technology, Surat
UASB, Vadodara
UASB, Surat
INDIA
Locations of STPs selected for the study with their treatment capacities.
43 ML/d UASB, Vadodara100 ML/d UASB, Surat
Fig. Flow diagram in UASB + post treatment unit
Surface Aeration System
Fig. Photograph of Surface Aeration Tank at 43 ML/d UASB based STP at Vadodara
Diffusion Aeration System
Fig. Photograph of Diffusion Aeration Tank at 100 ML/d UASB based STP at Surat
Sampling Parameters
Sampling Points
UASBR + Surface Aeration ( Vadodara)
UASBR + Diffused Aeration ( Surat)
Raw Sewage
UASB Effluent
Final Effluent
Raw Sewage
UASB Effluent
Final Effluent
pH 7.33 7.18 7.58 7.12 6.78 7.18
Dissolved oxygen (mg/L)
0.11 0.12 2.66 0.12 0.08 4.31
Total COD (mg/L) 878.47 514.93 124.00 726.87 405.00 128.47
Filtered COD (mg/L) 336.47 186.53 55.07 330.73 160.60 52.60
Total BOD (mg/L) 229.67 115.33 15.87 256.60 153.27 16.40
Filtered BOD (mg/L) 88.47 58.80 7.07 78.40 52.67 9.40
Suspended solids (mg/ L)
214.6 113.07 84.267 261.4 167.267 93.8
Total Coliform ( MPN/100 ml )
8x1012 5x107 5.71 x105 2.7 x1012 1.9 x107 6.7 x105
Fecal Coliform ( MPN/100 ml )
3x1012 1.93x107
3.67 x105 1.0x1010 6.8 x106 2.2 x105
Parameters for 43 ML/d and 100 ML/d STP.
Feed Tank ( FT)
Gas Collection Chamber
Peristaltic Pump
UASB Reactor
Cascade Sponge Reactor (CSR)
Final Effluent
Schematic flow-diagram of Experiment.FIG.16
Prior to start up of CSR (Cascade Sponge Reactor)
After accumulation of biomass on CSR (Cascade Sponge Reactor)
FIG.17 FIG.18
SEM images of clean Sponge at 7 x.
SEM images of accumulation of biomass on Sponge at 7 x.
SEM images of measurement of pore size of Sponge at 50 x.
y = 0.9971x - 0.1533
R2 = 0.99260
0.51
1.52
2.53
0 1 2 3
OLR (KgCOD/m3.d)
CO
D R
emo
val
Rat
e(K
gC
OD
m3.
d)
Variation of COD removal rate according to OLR (Organic Loading Rate)
FIG.68
Appearance of (A) Raw sewage (B) UASB effluent (C) CSR effluent
(A) (B) (C)
Conclusions
Of all the anaerobic wastewater treatment process currently being used, the UASB process has excellent potential to become highly competitive for municipal wastewater treatment. However treated effluent from UASB contains significant amounts of organics, nutrients, sulphide and fecal coliform. When discharge to the environment creates risk to aquatic and terrestrial region. So there is a need of post treatment for the UASB effluent before discharging it to the surface water or terrestrial region. It can be concluded that all these technologies are feasible for the post treatment of UASB effluents for satisfying the discharge standards in surface waters.
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