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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