Biolog ical treatment processes
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Biolog ical Treatment Processes. Outline. Overview 3.1 Criteria for Successful Biological Treatment 3.2 Principles of Biological Reactions 3. 3 Wastewater Treatment Ponds 3. 4 Anaerobic Treatment Processes. Wastewater Treatment. 2.1 Overview of Treatment Processes.

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Biolog ical treatment processes

Biological TreatmentProcesses


Outline

Outline

  • Overview

  • 3.1 Criteria for Successful Biological Treatment

  • 3.2 Principles of Biological Reactions

  • 3.3Wastewater Treatment Ponds

  • 3.4 Anaerobic Treatment Processes


Wastewater treatment

Wastewater Treatment


2 1 overview of treatment processes

2.1 Overview of Treatment Processes

  • Preliminary & Primary Treatment

  • Physical / chemical processes to prepare wastewater for biological treatment

  • Removal of solids mainly

  • Usually cheaper/ easier than secondary processes

  • Examples:

    a. equalisation (flow and load),

    b. neutralisation,

    c. settling of solids,

    d. flotation of oil and grease,

    e. filtration etc


2 1 overview of treatment processes1

2.1 Overview of Treatment Processes

  • Secondary Treatment

  • Biological removal of biodegradable, mostly soluble organic compounds (carbon removal)

  • Aerobically

    • activated sludge plants,

    • aerated ponds

    • trickling filters etc.

  • Anaerobically

    • non-aerated ponds,

    • high rate anaerobic (biogas) plants


Biolog ical treatment processes

  • Tertiary Treatment

  • Removal of specific pollutants with physical, chemical and/or biological methods

  • Examples:

    a. adsorption of organics by activated carbon

    b. precipitation or flocculation of phosphate etc.

    c. biological nitrogen removal

    d. disinfection

  • In general, costs increase with increasing degree of treatment


Wastewater treatment1

Wastewater Treatment


Outline1

Outline

  • Overview

  • 3.1 Criteria for Successful Biological Treatment

  • 3.2 Principles of Biological Reactions

  • 3.3Wastewater Treatment Ponds

  • 3.4 Anaerobic Treatment Processes


3 1 criteria for successful biological treatment

3.1 Criteria for Successful Biological Treatment

  • Produce biological catalyst (biomass)

    • source of energy

    • source of cellular components (C, H, N, O, P, S etc.)

  • Maintain biomass

    • adequate environment (T, pH, toxics)

    • adequate retention time (rate of treatment)

  • Separation of biomass

    • grow suitable types of organisms ie. floc forming bacteria


Outline2

Outline

  • Overview

  • 3.1 Criteria for Successful Biological Treatment

  • 3.2 Principles of Biological Reactions

  • 3.3 Wastewater Treatment Ponds

  • 3.4 Anaerobic Treatment Processes


3 2 principles of biological reactions

3.2 Principles of Biological Reactions

A. Three Important Biological Reactions

  • Aerobic

    CHO + O2biomass + CO2 + H2O

    ≈ 50 % ≈ 50 %

    respiratory metabolism

  • Anaerobic

    CHO biomass + CO2 + CH4 + H20

    10 - 20 % 80 - 90 %

    fermentative metabolism

  • Photosynthesis

    CO2 + H2O biomass + O2

    energy supplied externally (light)


B aerobic or anaerobic

100

Anaerobic digestion

Aerobic treatment

Low Rate Anaerobic

Treatment

10

Hydraulic Retention Time (days)

1

High Rate Anaerobic

Treatment

0.1

100

1000

10000

100000

Wastewater COD (mg/L)

B. Aerobic or Anaerobic ?


3 2 principles of biological reactions1

3.2 Principles of Biological Reactions

C. Nutrient Requirements

  • "Major" elements: C, H, O, N

  • "Minor" elements:

    • P  DNA/RNA, phospholipids, ATP

    • S  for proteins, amino acids

    • K  in RNA, coenzymes

    • Mg  in RNA, coenzymes, as cation

  • Trace elements

    • Often essential: Ca, Mn, Fe, Co, Cu, Zn

    • Rarely essential: B, Na, Al, Si, Cl, V, Cr, Ni, As, Se, Mo, Sn, I


Outline3

Outline

  • Overview

  • 3.1 Criteria for Successful Biological Treatment

  • 3.2 Principles of Biological Reactions

  • 3.3 Wastewater Treatment Ponds

  • 3.4 Anaerobic Treatment Processes


3 4 wastewater treatment ponds

3.4 Wastewater Treatment Ponds

  • Applied mostly in rural industries and small communities

  • Main benefits are low construction and operating cost

  • Classification based on biological activity, form of aeration and influent composition


1 anaerobic ponds

1. Anaerobic Ponds

Characteristics:

  • High organic load;

  • Deep (3-6m);

  • Biomass formation small (5-15% of C in feed)


Anaerobic pond design operation

Anaerobic Pond Design & Operation

Operational Considerations:

  • BOD removal 60-80%

  • Scum formation to contain odour emissions

  • Monitor pH (should be 6.4 - 7.8)


2 facultative ponds

2. Facultative Ponds

Characteristics:

  • “two zone” environment, depth 1.5 - 4 m; large

  • microbial diversity; medium organic load; odour free


Facultative pond design operation

Facultative Pond Design & Operation

  • Design: Area Loading Rate

    • 40 - 140 kg BOD5/ha/d T>15oC

    • 20 - 40 kg BOD5/ha/d T<15oC

    • HRT 5 - 30 days

  • Operational Considerations:

    • Maintain aerobic conditions. Beware of over-loading causing the pond to turn anaerobic - odour problems


3 aerated ponds

3. Aerated Ponds

  • Characteristics:

    • Mode is determined by the mixing intensity

    • Completely mixed: P/V = 2.3 - 4 W/m3

    • Facultative: P/V ≈ 0.8 W/m3


Aerated pond design operation

Aerated Pond Design & Operation

  • Design:

    • HRT 0.5 - 3 days

    • Aeration capacity ≈ 2*BOD load

    • Aerators: 1 - 1.5 kg O2/kWh

    • ΔBOD: 50 - 70%

  • Operational Considerations:

    • Can be very efficient for soluble BOD/ COD removal but solids concentrations too high for discharge (irrigation ok).


4 aerobic oxidation ponds

4. Aerobic (Oxidation) Ponds

Characteristics:

  • Natural oxygenation (wind, photosynthesis); large surface area; shallow (1 - 1.5m); low organic loading.

  • Suitable for treating effluent from anaerobic ponds


Aerobic pond design operation

Aerobic Pond Design & Operation

  • Design: 40 - 120 kg BOD5/ha/d

  • Operational Considerations:

    • Maintain aerobic conditions. Beware of over-loading causing the pond to turn anaerobic.


Outline4

Outline

  • Overview

  • 3.1 Criteria for Successful Biological Treatment

  • 3.2 Principles of Biological Reactions

  • 3.3Wastewater Treatment Ponds

  • 3.4 Anaerobic Treatment Processes


3 4 anaerobic treatment processes

3.4 Anaerobic Treatment Processes

  • Treatment under exclusion of oxygen

  • Carbon mainly converted to methane (CH4) and carbon dioxide (CO2)

  • Used for high organic loadings

  • Efficient and economic COD/BOD removal

  • Low rate systems use very long HRT eg. Anaerobic ponds

  • High rate systems use low HRT but need biomass retention mechanism eg. UASB

  • Increase rate of biological action by increasing temperature.


Anaerobic process principles

Slow growing, pH

sensitive archaea

Fast growing,

robust bacteria

Anaerobic Process Principles

Pathways of organics in anaerobic treatment


Process types

Process types

A. Single-stage processes

  • Long solids & hydraulic retention times (HRT)

  • Eg. Anaerobic digesters (20-30 d HRT)

    Anaerobic ponds (10-30 d HRT)

    B. Two-stage (high rate) processes

  • Short HRT in first stage, no biomass retention

  • Short HRT but with biomass retention in second stage, usually pH controlled

  • Eg. UASB, Hybrid, fluidised bed reactors etc.


A single stage process

Biogas

SLUDGE DIGESTER

Treated effluent

Wastewater

Mixing mechanically

or often by biogas

recirculation

A. Single Stage Process


1 upflow anaerobic sludge blanket uasb

Gas collection

below water

level to reduce

turbulence at

overflow

Biogas

Treated effluent

Gas collector

Uniform flow

distribution

essential

Sludge blanket

From

Pre-acidification

Tank

Granular biomass

1. Upflow Anaerobic Sludge Blanket (UASB)


2 hybrid reactor

Packed bed

(plastic material)

for biofilm growth

Biogas

Treated effluent

Uniform flow

distribution

essential

Sludge blanket

From

Pre-acidification

Tank

Granular biomass

2. Hybrid Reactor


B two stage reactor performance

B. Two-Stage Reactor Performance

  • COD removal 60 - 95%

  • BOD removal 80 - 95%

  • Gas production 0.3-0.6 m3/kg CODremoved

  • Methane production 0.2-0.35 m3/kg CODremoved

  • Methane conc. 55 - 75%

  • Sludge production 0.05-0.1 kg VSS/kgCODremoved


Biolog ical treatment processes

Two-stage high-rate hybrid reactor for abattoir & industrial wastewater


Anaerobic reactor design

Anaerobic Reactor Design

1. Pre-acidification tank

  • Often on the basis of an equalisation tank (also variable volume operation)

  • Typical HRT 12-24 h

  • pH 5-6 if controlled, 4-5 if uncontrolled

  • Mixing usually only by inflow 􀃎 importance to minimise solids in influent

  • Covered tank, gas vented and treated or incinerated (with biogas in boiler or flare)


Anaerobic reactor design1

Anaerobic Reactor Design

2. Methanogenic (2nd stage) reactor

  • Volume-based organic loading rate (OLR)

    Cin  biodegradable COD conc. in influent mg/L

    Q  wastewater flow rate m3/d

    VR methanogenic bioreactor volume m3

  • Typical HRT 12-24 h, Solids RT 10-150 days

  • Usually heated to operate at 30 - 40°C


  • High rate anaerobic treatment

    Recycle and mix tank reduce pH

    control dosing

    Biogas

    CSTR-type tank usually not heated

    Methanogenesis

    Sludge

    blanket

    Acidif. Tank

    Mix Tank

    Acidogenesis

    Biomass

    retention as

    granules

    High Rate Anaerobic Treatment

    • Typical process flowsheet using Upflow Anaerobic Sludge Blanket (UASB) reactor


    Anaerobic reactor design2

    Anaerobic Reactor Design

    • OLR designs for various reactor types:

      • UASB  6-12 kg COD/m3/d

      • Internal Circulation  15-25 kg COD/m3/d

      • Fluidised/expanded bed 12-20 kg COD/m3/d

      • Hybrid Reactor  6-12 kg COD/m3/d

    • OLR varies with degradability, temp., pH…

    • Hydraulic loading up to 24 m3/(m2reactor area d)

    • Gas loading 70 - 200 m3 gas /(m2reactor area d)


    Questions

    Questions?


    Documentation

    Documentation


    Terima kasih

    Terima Kasih


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