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MODUL 6PENGOLAHAN BIOLOGIS ANAEROBIK DAN ANOKSIK SISTEM TERSUSPENSI DAN TERLEKAT

Joni HermanaJurusan Teknik Lingkungan FTSP – ITSKampus Sukolilo, Surabaya – 60111Email: [email protected]

PERENCANAAN PENGOLAHANAIR LIMBAH DOMESTIK (RE091322)Semester Ganjil 2010-2011

PENDAHULUAN

“OLD” SMALL SCALE ANAEROBIC TREATMENT ( ON SITE ) =

SEPTIC TANK

IPAL KOMUNAL PERKOTAAN = IMHOFF TANK DAN UASB

IMHOFF TANK = LOW RATE SYSTEM KURANG DIMINATI

HIGH RATE SYSTEM = PREFERABLE !

ANOXIC SYSTEM DENITRIFIKASI : ( NO3) N2

Gambar Upflow Anaerobic Sludge Blanket(a) Skema , (b) Reaktor

(a) (b)

DESKRIPSI PROSES

PROSES ANAEROBIK

1. TAHAP PEMBENTUKAN ASAM

susbtrat organik kompleks ( karbohidrat, protein, lemak) asam lemak

CONTOH : PENGURAIAN GLUKOSA

TAHAP PEMBENTUKAN ASAM

TAHAP PEMBENTUKAN GAS METHAN

HIDROLISIS

DIURAIKAN O/ BAKTERI FAKULTATIFH2, , CO2 dan CH3COOH

C6H12O6 + 4H2O 2CH3COO- + 2HCO3- + 4H+ + 4H ………………………. (1)

asetat

C6H12O6 + H2O CH3COO- + CH3CH2COO- + HCO3- + 2H+ + H2………. (2)

propionat

CONTOH : PENGURAIAN GLUKOSA ( LANJUTAN )

C6H12O6 + H2O CH3CH2COO- + 2HCO3- + 3H+ + 2H2……………………….(3)

butirat

CH3CH2COO- + 2H+ + H2O CH3COO- + HCO3- + 2H+ + 3H2…………………...(4)

propionat asetat

CH3CH2CH2COO- + H+ + 2H2O 2CH3COO- + 2H+ + 2H2……………………………..(5)butirat asetat

FATTY ACIDS, ALCOHOLSAMINO ACIDS, SUGARS

METHANE CARBON DIOXIDE

HYDROGEN CORBON DIOXIDE

ACETATE

INTERMEDIATE PRODUCTS (Propionate, Butyrate, etc)

PROTEIN LIPIDSCARBOHYDRATES

COMPLEX POLYMERS

1 1

11

2

3

5 4

1HYDROLYSIS

HOMOACETOGENESISACETOLASTICMETHANOGENESIS

ANAEROBICOXIDATION

Skema proses anaerobic (Pavlostathis dan Giraldo-Gomez, 1991)

KETERANGAN :]

1. Bakteri fermentatif2. Bakteri Asetogenik

Penghasil Hidrogen3. Bakteri Asetogenik

Pemakan Hidrogen4. Methanogenesis

Reduktif5. Asetoklastik

Methanogenesis

2. TAHAP PEMBENTUKAN GAS METHAN

BAKTERI METHANOGENESISHYDROGENOTROPHIC

( H2 ; CO2 Methan )

ACETOCLASTIC

( Dekarbolaksilasi Asam Asetat

Methan )

CH3COOH CH4 + CO2……………………….……………………………………………(6)methane

H2 + CO2 CH4 + 2H2…………………………………………………………………….(7)

Tabel 1. Proses Tahapan Degradasi Senyawa Organik Secara Anaerobik

Tahap Jenis Senyawa Asal

Bakteri Pengurai

Jenis Senyawa Produk

Keterangan

Tahap I : AcidogenesisHidrolysis Protein

KarbohidratLipid

Hydrolysing and fermentation bacteria

Asam amino,GulaAsam LemakAlkohol

Fermentasi Asam amino,GulaAsam LemakAlkohol

-Fermentationbacteria-Hydrogen-producingacetogenicbacteria-Hydrogen-consumingacetogenicbacteria

Produk Perantara (Volatile Fatty Acids, VFA), Asam Asetat, Hidrogen dan CO2

ProsesAcetogenesis

Tabel 1. Proses Tahapan Degradasi Senyawa Organik Secara Anaerobik( Lanjutan )

Tahap II :MethanogenesisTAHAP JENIS

SENYAWAASAL

BAKTERI PENGURAI

SENYAWAPRODUK

KETERANGAN

AceticlasticMethanogenesis

Asetat Aceticlastic methanogens

Methane danCO2

ReductiveMethanogenesis

Hidrogen CO2 CO2-Reducingmethanogenes(Hydrogenotrophicmethanogens)

Methane danCO2

PROSES DENITRIFIKASI ( ANOKSIK )

NO3- NO3

- NO N2O N2……………………………………(8)

JIKA KESELURUHAN N BERADA DALAM BENTUK NITRAT, MAKA :

NO3- + 1.08 CH3OH + H+ 0.065 C5H7O2N + 0.47N2 + 0.76COY + 2.44 H2O (9)

JIKA N BERADA DALAM BENTUK NITRIT & MENGANDUNG SEDIKIT OKSIGEN

MAKA :

Cm = 2.47 N0 + 1.53 N1 +0.87 D0

Dimana:Cm = konsentrasi methanol yang diperlukan, mg/lN0 = konsentrasi nitrat awal, mg/lN1 = konsentrasi nitrit awal, mg/lD0 = konsentrasi oksigen awal, mg/l

PRINSIP RANCANG BANGUN

Jenis Nama Unit Pengolah PenggunaanProses Anoksik:Suspended growthAttached growth

Suspended growth DenitrificationFixed-Film Denitrification

Removal N (Denitrification)Removal N (Denitrification)

Proses Anaerobik:Suspended growthAttached growth

Anaerobik DigestionAnaerobik Cantact Process, ACPUpflow Anaerobic Sludge Bed, UASBAnaerobic Baffled Reactor, ABRAnaerobic Filter Process, AFExpanded Bed, EBR

Stabilisasi (lumpur)Removal BODRemoval BODRemoval BODRemoval BODRemoval BOD

Tabel 2. Jenis proses biologis anaerobik dan anoksik yang umum digunakan

Proses Influen COD

HRT(jam)

Beban Organik(kgCOD/m3.hari)

Removal COD(%)

ACPUASB

AFEBR

1500 – 50005000 –15000

10000 –20000

5000 - 10000

2 – 104 – 1224 – 485 – 10

0.03 – 0.150.25 – 0.750.06 – 0.300.30 – 0.60

75 – 9075 – 8575 – 8280 – 85

Tabel 3. Kriteria desain dan kinerja prosesanaerobik yang mengolah limbah cair industri.

MODEL PERSAMAAN KINETIKA : UNTUK REAKTOR TERADUK SEMPURNA (COMPLETE MIXED, STEADY STATE )

( )( )c

c

bSSY

Xθθ

θ+

−=

10

dimana :X = Konsentrasi pertumbuhan mikroorganismaθ = Waktu detensi hidrolis (HRT)θc = Umur lumpur (SRT) atau mean cell residance timeY = Koefisien pertumbuhan mikroorganismeS0, S = Konsentrasi influen dan effluen substrat pembatas pertumbuhanb = Koefisien kematian mikroorganisma

LAJU PERTUMBUHAN MIKROORGANISME ANALOGIS

XdtdX µ=

Dimana :µ = Laju pertumbuhan mikroorganisme spesifik

Maka :

bSKsS

−+

= maxµµ

Di mana :S = konsentrasi substrat dalam reaktor (massa/volume)µmax = kY = Laju penggunaan substrat spesifik (waktu –1)

k = Laju maksimum penggunaan substrat per unit berat mikroorganisma (waktu –1)

Ks = Koefisien setengah jenuh, sama dengan konsentrasi air buangan atau substrat ketika µ = 1,5 µmax

bSKs

akSUSRT

−+

==1

Biological Solids Retention Time ( SRT )

SRT > SRT m = 1 / µ

SRT=µ1

Tabel 4. Koefisien Kinetika Untuk Penggunaan Substrat danPertumbuhan Biologis

Substrat Suhu (0C)

k*(mg/mg-

hr)

Ks(mg/l)

Y**(mg/m

g)

B(hr-1)

SRTm(hr)

Asam AsetatLumpur buangan kotaAsam AsetatAsam PropionatLumpur buangan kotaBuangan susu sintetisAsam asetatAsam asetatAsam PropionatAsam butiratLumpur buangan kotaBuangan pengepakan

20

25

3035

3,6

5,07,8

0,385,18,77,78,3

0,32

2130

869613

24333254325

5,5

0,04

0,050,051

0,370,0540,04

0,0420,047

0,76

0,015

0,0110,04

0,070,0370,0190,010,027

0,017

7,810,0

4,22,87,5

4,74,23,13,22,7

2,8

PRINSIP REKAYASA PERENCANAAN

1. EFISIENSI PENGOLAHAN

Efisiensi pengolahan pada HRT 4 – 6 jam adalah :COD (total/ total): 50 - 70 %COD (total/ filtered): 70 - 95 %BOD (total/ total): 70 - 90 %COD (filtered/ filtered): diatas 60 %TSS : 60 – 85 %

2. PRODUKSI GAS METHAN0,19 N m3/kg CODremoved

0,33 CH4 COD/kg CODremoved

56 – 63 % gas methan akan keluar bersama efluen

3. KONVERSI TSS

40 % TSS berada dalam lumpur25 % TSS terkonversi menjadi methane30 % TSS keluar reaktor bersama efluen

4. PRODUKSI LUMPUR

Umumnya 0,1 kg COD/ kg COD in

Nilai maksimum yang diperoleh 0,25 kg COD / kg COD in

0,4 – 0,6 kgTSS/kg TSS in (= 0,06 – 0,1 kg TSS/m3)

5. KONSENTRASI LUMPUR DALAM REAKTOR

31 – 37,5 kg TSS/m3 9,4 – 12,5 kg VSS/m3

6. UMUR LUMPUR

35 – 100 hari (pada saat reaktor sudah penuh lumpur)7. KARAKTERISTIK LUMPUR

Kandungan abu : 55 – 56 %Specific methanogenic activity : > 0,1 kg/kgVSS.dayStabilitas : 20 – 50 L CH4/kg lumpurKarakteristik pengeringan : 20 kg/m2 dalam 7 hari dan menghasilkan 35 – 40 % DS.

8. KONSENTRASI LUMPUR DALAM SLUDGE BEDDapat mencapai 100 kg TSS/m3 pada bagian bawah reaktor, bergantung pada jenis air limbah domestik yang diolah. Karakteristik air limbah ini dapat mempengaruhi settleability lumpur dan kandungan ash (debu)

9. FAKTOR DESAIN LAIN

Minimum HRT rata-rata adalah 4 jamKetinggian 4 mTitik inlet limbah :1 per 4 m2 apabila reaktor penuh berisi lumpur1 per 1 m2 apabila reaktor terisi sedikit lumpur

9. FAKTOR DESAIN LAIN

Tekanan statis pada kotak inlet air limbah : sampai dengan 50 cmKecepatan keatas pada saat bukaan: rata-rata harian 4 m/jam, selama 2-4 jam 8 m/jam.Material untuk konstruksi: stainless steel atau plastik (untuk gutter), beton tahan asam dan gunakan bahan anti karat untuk pemisah gas dan pelapisan bagian tertentu.

JENIS REAKTOR ANAEROBIK Suspended Growth

Complete mixed suspended growth Anaerobic contact process Anaerobic sequencing batch reactor (ASBR)

Anaerobic Sludge Blanket Upflow anaerobic sludge blanket (UASB) Anaerobic baffle reactor (ABR) Anaerobic migrating blanket reactor (AMBR)

Attached Growth Upflow packed-bed reactor Anaerobic expanded-bed reactor Anaerobic fluidized-bed reactor

Covered Anaerobic Lagoon

UPFLOW ANAEROBIC SLUDGE BLANKET

UASB

PRINSIP UMUM

•Aliran dalam reaktor = aliran vertikal ke atas ( up flow )•Sludge untuk mendegradasi bahan organik dalam air buangan berada di dasar reaktor

• influen dasar reaktor mengalir ke atas (upflow)

Gas Solid Liquid Separator Gas ditampung GLSS, sludge kembalike zona sludge blanket, air limbahdipompake ke outlet

KEUNTUNGAN•Beban Loading tinggi•Waktu detensi lebih rendah u/ skala anaerobik•Tidak perlu suplai Oksigen / hemat biaya•Dapat mereoval PO4 ( fosfat ) & NH3 ( Nitrat ) menjadi gas N2 melaluiproses denitrifikasi

SKEMA REAKTOR UASB

BEBAN VOLUMETRIK

COD air limbah( mg / L )

Fraksi COD partikulat

Volumetric Loading ( Kg COD / m3.hari)

Sludge Flocculant

Granular Sludge Removal TSS tinggi

Granular Sludge Removal TSS rendah

1000 - 2000 0.1 – 0.30.3 – 0.60.6 – 1.0

2 – 42 – 4n.a

2 – 42 – 4n.a

8 – 128 – 14n.a.

2000 - 6000 0.1 – 0.30.3 – 0.60.6 – 1.0

3 – 54 – 84 - 8

3 – 52 – 62 - 6

12 – 1812 – 24

n.a.

6000 - 9000 0.1 – 0.30.3 – 0.60.6 – 1.0

4 – 65 – 76 – 8

4 – 63 – 73 - 8

15 – 2015 – 24

n.a

9000-18000 0.1 – 0.30.3 – 0.60.6 – 1.0

5 – 8n.a.n.a.

4 – 63 – 73 – 7

15 – 24n.a.n.a.

Beban volumetrik COD yg diijinkan untuk removal COD UASB 85 - 95%

Sumber : Lettinga & Hulshoff Pol, 1991

BEBAN VOLUMETRIKBeban Organik volumetrik yg dianjurkan berdasarkan suhu substrat COD soluble

Untuk removal COD 85 – 95%, konsnetrasi rata-rata sludge = 25 mg / L

SUHU ( C)

VOLUMETRIC LOADING ( Kg s COD / m3.hari )

VFA WASTEWATER NON – VFA WASTEWATER

TIPIKAL RANGE TIPIKAL RANGE

15 3 2 – 4 2 2 – 3

20 5 4 – 6 3 2 – 4

25 6 6 – 12 4 4 – 8

30 12 10 – 18 10 8 – 12

35 18 15 – 24 14 12 – 18

40 25 20 – 32 18 15 – 24


BEBAN VOLUMETRIK

Hidraulic Retention Time ( HRT ) τ yang dipakai untuk pengolahan air buangan domestik

Pada kedalaman reaktor UASB = 4 m

SUHU ( C) τ RATA-RATA (jam)

Τ MAKSIMUM, 4 – 6 peak (jam)

16 – 19 10 – 14 7 – 922 – 26 7 – 9 5 – 7

> 26 6 - 8 4 - 5


UPFLOW VELOCITY ( v )Upflow Velocity & Reactor Heights Recommended for UASB Reactor

Jenis air buanganUpflow Velocity

( m / jam)Tinggi Reaktor

(m)Range Tipikal Range Tipikal

COD hampir 100% soluble 1 – 3 1.5 6 – 10 8

COD sebagian soluble 1 – 1.25 1 3 – 7 6

Air buangan domestik 0.8 - 1 0.7 3 – 5 5


ν = Q / A

DIMENSI REAKTORVOLUME

Vn = Q . S0

Lorg

Vn = volume reaktor nominal ( efektif ) liquid, m3

Q = debit influen , m3/ jamLorg = organic loading rate, Kg COD / m3.hariSo = influen COD, Kg

VL = Vn

E

VL = volume reaktor total liquid , m3

Vn = volume reaktor nominal ( efektif ) liquid, m3

E = faktor efektif, tanpa satuan

A = Q / v

HL = VL / A HT = HT + HG

Petunjuk Ukuran Luas / Area yang dilayani oleh Saluran Pipa Inlet

Sludge Type COD loading

(Kg/m3.hari)

Area per feed

inlet, m3

Dense flocculent sludge, > 40 kg TSS/m3

Medium Flocculent Sludge, 20 – 40 kg TSS / m3

Granular Sludge

<11 – 2> 2

>1 – 2 > 3

1 – 22 – 4> 4

0.5 – 11 – 2 2 – 31 – 2 2 – 5

0.5 – 1 0.5-2

>2


Contoh perhitungan UASB Treatment Process Design dapat dilihat pada Metcalf&Eddy,2003 Chapter 10:1012-1016

GENERAL DESCRIPTION High rate reactor firstly developed by Bahman & Mc Carty Consists of several compartments producing gaseous,

designed by using several vertical baffles couraging upflow by activated sludge which allowed contact between microorganism & wastewater

Bacterias tend to grow, move & settle horizontally within each compartment, low velocity, increase Solid Retention Time (SRT) equal to 100 days on Hydraulic Retention Time (HRT) equal to 20 hours

Less HRT ≈ minimizer reactor size ≈ less O&M cost Consists of 3 zone : Acidification Zone Methanation Zone Buffer Zone

ANAEROBIC BAFFLED REACTOR

ZONE CLASSIFICATION

1. Acidification ZoneOccurred mostly on intial compartmentVolatile fatty acid ( VFA) formation decrease pH valueBuffer capacity increased, pH value = increased

2. Methanation ZoneMethane gas produced

3. Buffer ZoneDetermined to stabilize the process

ADVANTAGES ( Barber & Stuckey, 1999 )

1. Constructiona. simply designb. no need mechanical mixingc. minimize cloggingd. minimize sludge bed expansione. low construction costf. low O & M cost

2. Biomassaa. no need biomass with special settlingb. low sludge growthc. high SRTd. no need fixed medium / solid settling chambere. no need gaseous / sludge separation

ADVANTAGES ( Barber & Stuckey, 1999 )

3. Operationala. Low HRTb. allowed intermittent operationalc. stabil hydraulic shock loadingd. long operational without sludge disposal

ATTACHED GROWTH ANAEROBIC PROCESSES

• Upflow Packed-Bed Attached

• Upflow Attached Growth Anaerobic Expanded-Bed Reactor

• Attached Growth Anaerobic Fluidized-Bed Reactor

• Downflow Attached Upflow Attached Growth Processes

Nitrogen removal

Nitrification and denitrification

Nitrogen CycleNO2

-

NH2 groupof protein

NON2O

NH3

N2

N2

NO3-

NH2 groupof protein

NO2-

AnoxicOxic

Nitrification

Nitrogenfixation

Denitrification

Nitrogenfixation

Nitrogen removal

Ammonia nitrogen(NH4

+)

zNitrite (NO2-)

zNitrite (NO3-) zNitrogen (N2)

Organic nitrogen

(bacteria cells)

Organic nitrogen(net growth)

Organic nitrogen(protein;urea)

Key Processes and Prokaryotes in the Nitrogen Cycle

Processes Example organisms

Nitrification (NH4+ NO3

-)NH4

+ NO2- Nitrosomonas, Nitrosospira

NO2- NO3

- Nitrobacter, Nitrospira

Denitrification (NO3- N2) Bacillus, Paracoccus, Pseudomonas

N2 Fixation (N2 + 8H NH3 + H2)Free-living

Aerobic Azotobacter, CyanobacteriaAnaerobic Clostridium, purple and green bacteria

Symbiotic (w/ plants) Rhizobium, Bradyrhizobium, Frankia

Ammonification (organic-N NH4+)Many organisms can do this

Biological Removal of Nitrogen and Phosphorus

Anaerobic-Anoxic-Aerobic Process (A2/O)

Influent

Sludge recycle

Settler Settler

Mixed-liquor NO3- recycle

Effluent

Aerobic Anoxic Anaerobic

Sludge waste

Step-Feed Biological Nitrogen Removal process

Low Energy Cost and High Removal Rate of Nitrogen

Influent

Sludge recycle

Settler

Settler

Mixed-liquor NO3– recycle

Effluent

Aerobic Anoxic Anoxic Aerobic

Sludge waste

One-Sludge Denitrification by Biomass Storage and Decay

Sludge recycle

Aerobic Anoxic

Sludge waste

BOD0

TKN0 Low BODLow NO3

–

High NH4+

BOD oxidation Nitrification Biomass synthesis

NO3–

Biomass

Denitrification with biomass as donor

One-Sludge Denitrification by Simultaneous nitrification with denitrification

Sludge recycle

Sludge waste

BOD0

TKN0 Low BODLow NO3

–

Low NH4+

Controlled Low D.O. Simultaneous nitrification, denitrification, and BOD oxidation θ X > 15 days

Biofilm predenitrification

Aerobic biofilm reactor Nitrification Aerobic BOD oxidation

Anoxic biofilm reactor Denitrification

High effluent recycle to return NO3–

Influent Effluent

Biological Nitrification

Conditions pH: 7.5 - 8.6DO: above 1 mg/L

Nitrosomonas

Nitrobactor

400NO2− + NH4

+ + 4HCO3 + HCO3− +195O2

→ C5H7O2N + 3H2O + 400NO3−

NH4+

NO2-

NO3-

3222275

324

1045754

1097655

COHOHNONOHC

HCOONH

+++→

++−

−+

Biological DenitrificationNO3

- NO2- NO N2O N2

Microorganisms:

Achromobacter, Aerobacter, Alcaligenes, Bacillus, Brevibacterium,Flavobacterium, Lactobaillus, Micrococcus, Proteus, Pseudomonas, Spirillum

Conditios:pH: 7 - 8DO: anoxic

Pond Treatment ProcessesAerobic Stabilization Ponds

Fig. symbiotic relationship between algae and bacteria

Factors: organic loading, degree of pond mixing,pH, nutrients, sunlight, temperature

Pond Treatment Processes

Fig. Facultative Ponds

Phosphorus Removal

C & N

C, N, &P

algae

EUTROPHICATION

(mg/L)

municipal wastewater 12

conventional wastewater treatment 6

effluent standard for a protected watershed 1

Additional phosphorus removal is necessary

Total P concentration

Phosphorus RemovalPhosphorus in wastewater

Orthophosphate (PH43-)

Polyphosphate (P2O7)Organically bound phosphorus 70% of influent

10 - 30 % removal by secondary biological treatment:Utilization for cell synthesis and energy transport

Additional phosphorus removal is necessary

Anaerobic zone

Aerobic zone(Oxic zone)

Enhanced Biological Phosphorus Removal

Release of stored phosphorus

Additional uptake of phosphorus

Phosphorus RemovalPhoStrip process

Biological Release of Phosphorus

Concentrated phosphorus

Precipitationof phosphorus

Fig. (a)

Activated Sludge Process

① ② ③

①, ③: Chemical precipitation

②: Biological treatment

Phosphorus removal from wastewater

Normal phosphorus uptake into biomass (11.1)

Precipitation by metal-salts addition to a biological process (11.2)

Enhanced biological phosphorus removal (11.3)

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