Anaerobic wastewater treatmentAnaerobic wastewater wastewater treatmentAnaerobic wastewater treatment ... conventional UASB design needs ... L2-4 Anaerobic wastewater treatment

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  • Anaerobic wastewater treatmentAnaerobic wastewater treatment

    Nidal MahmoudInstitute of Environmental and Water Studies,Institute of Environmental and Water Studies,,,

    Birzeit UniversityBirzeit Universitynmahmoud@birzeit.edu

    Ecological Sanitation Training CourseSWITCH PROJECT

    IEWS, Birzeit University, 25-27 January 2011

  • Outline

    1. Effect of Low Temperature on the bio-chemical and physical properties of wastewater and its effect onphysical properties of wastewater and its effect on anaerobic treatment

    Anaerobic bio-chemical processesp Physical and chemical properties of wastewater

    2 A bi T h l i f L T t S2. Anaerobic Technologies for Low Temperature Sewage Treatment

    Difficulties of anaerobic (low temperature) sewage treatment Difficulties of anaerobic (low temperature) sewage treatment Technical perspectives for anaerobic sewage Treatment

  • Effect of Low Temperature on the bio-chemical and physical properties of wastewater and its effect on anaerobic treatmenton anaerobic treatment

  • Effect of Low Temperature on the bio-chemical and physical properties of wastewater and its effect on anaerobic treatment

    Anaerobic bio-chemical processes:Mic oo ganisms t pe and g o th ateMic oo ganisms t pe and g o th ate

    on anaerobic treatment

    Microorganisms type and growth rate Microorganisms type and growth rate Substrate utilization rateSubstrate utilization rate

    Physical and chemical properties of wastewater Solubility of gaseous compoundsSolubility of gaseous compounds Viscosity of liquidsViscosity of liquids

  • Anaerobic biological conversion

  • Microorganisms type and growth rate

    Relative growth rate of pshchrophilic, mesophilic and th hili ththermophilic methanogens

  • S b t t tili ti tS b t t tili ti tSubstrate utilization rateSubstrate utilization rate

    Anaerobic conversion of organic matterAnaerobic conversion of organic matterAnaerobic conversion of organic matterAnaerobic conversion of organic matter

    Hydrolysisy y

    A id iAcidogenesis

    Acetogenesis

    M th iMethanogenesis

  • Hydrolysis Step

    dF Arrhenius equation xFkdtdF

    h RTEAek /dt h Aek WithWith:

    F:concentration of biodegradable solid substrate (g/L)

    With:

    T: the absolute temperature (K);

    R: the ideal gas constant (J molesolid substrate (g/L)

    Kh: hydrolysis constant (d-1)

    t: time (d)

    R: the ideal gas constant (J.mole -1.K-1);

    A: the pre-exponential factor (d-1); t: time (d)E: activation energy (kJ.mole-1)

  • MethanogenesisMethanogenesis StepStep

    temp Activitperatur ties at

    re / act abscistivity a sa

    t 35 C

    Temperature dependency of the methane production rate ofTemperature dependency of the methane production rate of

    C

    Temperature (C)Temperature dependency of the methane production rate of Temperature dependency of the methane production rate of

    mesophilicmesophilic anaerobic processanaerobic process

  • Physical and chemical properties of wastewater

  • Solubility of gaseousSolubility of gaseousSolubility of gaseous Solubility of gaseous compoundscompounds

    Solubility of gases increases below 20 C

    P

    Henrys law

    At low temperatureg

    Tg PH

    Px At low temperature H

    With:

    High dissolved gases in the effluent, i.e

    Xg: mole fraction of gas in water;

    H: Henrys law constant; ,

    methane and hydrogen sulfide

    PT: total pressure;

    Pg : mole fraction of gas in air

  • Viscosity of liquidsViscosity of liquids

    Low waterLow water temperature

    Viscosity of water Low biogas increases production

    rate

    Poor mixing; higher energy is required

    f i ifor mixing

  • Degree of Water Mixing in the Reactor

    Relation between temperature andRelation between temperature and

    V*pG

    Temperature Viscosity %

    Relation between temperature and Relation between temperature and turbulence in the reactorturbulence in the reactor

    V

    G l it di t ( 1)

    () of water in the reactor

    Increase of G from 15 CG: velocity gradient (s-1)

    P: power input (W)

    V: volume of water in the reactor (m3)

    reactor 15 CC Pa.s % 15 1.14x10-03 -

    03V: volume of water in the reactor (m3)

    : dynamic viscosity (Pa.s)20 1.00x10-03 725 8.90x10-04 13 30 7.98x10-04 1940 6.53x10-04 32

  • Anaerobic Technologies for Low TemperatureAnaerobic Technologies for Low Temperature Sewage Treatment

  • Anaerobic Technologies for Low Temperature Sewage Anaerobic Technologies for Low Temperature Sewage TreatmentTreatmentTreatmentTreatment

    Difficulties of anaerobic (low temperature) sewage treatment

    Technical perspectives for anaerobic sewage Treatment Anaerobic High Rate Wastewater Treatment Systems Digestion Limiting Step Technology Innovation

  • Difficulties of anaerobic (low temperature) sewage treatmenttreatment

  • Sewage belongs to the complex wastewater category because:category because:

    It contains a higher fraction particulate COD

    The biodegradability of the various COD fractions is moderate

    It is a low strength wastewater with varying concentrations

    Its temperature is relatively low

  • COD fractions

    Raw sewageRaw sewage

    Suspended COD (CODss)

    4 4 m paper-filtered sewage

    Suspended COD (CODss)

    4.4 m paper-filtered sewage

    Colloidal COD (COD l)

    0.45 m membrane filtered

    Colloidal COD (CODcol)

    Dissolved COD (CODdi )sewage Dissolved COD (CODdis)

  • Wastewater Characteristics of Ramallah City,

    Parameters Ramallah Al-Bireh Al-Jalazoon

    Wastewater Characteristics of Ramallah City, Al - Bireh City and Al-Jalazoon refugee camp

    COD Total 2180 1586 1489

    Suspended 1096 919 725Suspended 1096 919 725Colloidal 323 274 327

    Dissolved 761 393 438 VFA as COD 187 160 123VFA as COD 187 160 123SO42- as SO42- 975 138 213 TSS 729 736 630 VSS 584 617 480pH 7.45 7.26 7.31 Tww Summer 30.9 25.8 23.4

    Winter 13 Tamb. Summer 27

    Winter 13.8 Winter 13.8Colour Reddish to black Medium brown Light brown

  • Technical Perspectives for Anaerobic Sewage TreatmentTreatment

  • Anaerobic High Rate Wastewater Treatment SystemsAnaerobic High Rate Wastewater Treatment Systems

    Advantages of High-rate anaerobic systemsAdvantages of High-rate anaerobic systemsLow construction, operation and maintenance costs,Small-land requirement,q ,Low excess-sludge production,Production of biogas (source of energy).

    Anaerobic biotechnology

    Anaerobic biotechnologyUASB for sewage treatment has been applied successfully in several countries of hot climates, e.g. India, Colombia, Brazil, and GhanaGhana

  • Digestion Limiting Step

    Under low temperature conditions (< 15C) and/or strong temperature fluctuations between summer (25C) and winter (15C), the

    g g p

    fluctuations between summer (25 C) and winter (15 C), the conventional UASB design needs reconsideration:

    Limited Hydrolysis High SS

    Accumulation of particulate organic matter

    High SS

    Deterioration of the reactor performance Limited hydrolysis p

    Low removal efficiency

    y y

    Long retention time

  • Technology InnovationTechnology Innovation

    Sewage treatment under low temperature conditions (<

    gygy

    g p (15C) and/or temperature fluctuations:

    One stage:One stage:1. UASB reactor

    Two Stage1. HUSB reactor followed by UASB2 HUSB t f ll d b EGSB2. HUSB reactor followed by EGSB3. AF followed by AH system4 Two-stage UASB system4. Two stage UASB system

    UASB-Digester1. UASB-Digester system

  • Wang (1994) treated domestic sewage in a two-step system: UASB/EGSB reactor at 12oC

    Removal (%)Parameter

    UASB+EGSBTotal COD* 51Suspended COD 67Colloidal COD 42Dissolved COD 41

    * measure for organic matter measure for organic matter

  • Elmitwalli (2000) improved the particulate matter removal during ( ) p p gthe anaerobic treatment of domestic sewage at low temperature using two stage AF-AH system

    5 5

    10

    9

    10

    46

    9

    1 282

    7AF reactor AH reactor

  • Packing material: AF and AH reactors

    The packing material consists of vertical sheet ofKnob thicknessBase thickness

    The packing material consists of vertical sheet of reticulated poly-urethane foam (RPF) with knobs .

    Why RPF?

    has a high specific surface area (500 m2/m3), K b

    g p ( / ),has a high porosity of 97%, RPF enables the retention of 15 gVS/l in attached

    Knob

    All biomass is attached, as the accumulated sludge

    form.

    , gon the bottom of the reactor is wasted weekly. Therefore clogging of the AF reactor is avoided.

  • COD removal efficiency (%) in the AF+AH at HRT of 4+8 h at y ( )13 oC

    Removal(%)

    Maximumremoval (%)*

    Total COD 71**Suspended COD 91Colloidal COD 60 72Colloidal COD 60 72Dissolved COD 55 55

    * from Last and Lettinga (1992) from Last and Lettinga (1992)** similar to that achieved in tropical countries

  • Two stage UASBFirst stage inlet

    Second stage inlet Maha Hallalsheh, 2002

    Results two-stage pilot trials Middle

    COD Removal: up to 80% BOD Removal: up to 85%SS Removal: up to 80%pilot trials Middle

    East (Jordan):SS Removal: up to 80%Pathogen Removal: insufficient Potential CH4 production in Amman(at 170 000 m3 sewage/day): 17 500 m3/day !(at 170.000 m3 sewage/day): 17,500 m3/day !

    2 2.5 MW

  • UASB - Digester system

    Effluent

    G