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Biological Treatment Processes. Outline Overview 3.1 Criteria for Successful Biological Treatment 3.2 Principles of Biological Reactions 3.3Wastewater.

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Presentation on theme: "Biological Treatment Processes. Outline Overview 3.1 Criteria for Successful Biological Treatment 3.2 Principles of Biological Reactions 3.3Wastewater."— Presentation transcript:

1 Biological Treatment Processes

2 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 Wastewater Treatment Physical process Primary Biological Secondary Combination Tertiary

4 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

5 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

6 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

7 Wastewater Treatment Physical process Primary Biological Secondary Combination Tertiary

8 Outline Overview 3.1 Criteria for Successful Biological Treatment 3.2 Principles of Biological Reactions 3.3Wastewater Treatment Ponds 3.4 Anaerobic Treatment Processes

9 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

10 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

11 3.2 Principles of Biological Reactions A. Three Important Biological Reactions Aerobic CHO + O 2  biomass + CO 2 + H 2 O ≈ 50 % ≈ 50 % respiratory metabolism Anaerobic CHO  biomass + CO 2 + CH 4 + H % % fermentative metabolism Photosynthesis CO 2 + H 2 O  biomass + O 2 energy supplied externally (light)

12 B. Aerobic or Anaerobic ? Wastewater COD (mg/L) Hydraulic Retention Time (days) Aerobic treatment Anaerobic digestion High Rate Anaerobic Treatment Low Rate Anaerobic Treatment

13 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

14 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

15 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 POND TYPEBIOLOGICAL ACTIVITY TYPE OF AERATION Anaerobic Avoided Facultative (Stabilisation) Anaerobic/ AerobicNatural AeratedAerobicMechanical Aerobic (Maturation, Oxidation) AerobicNatural

16 1. Anaerobic Ponds Characteristics: High organic load; Deep (3-6m); Biomass formation small (5-15% of C in feed)

17 Anaerobic Pond Design & Operation Operational Considerations: BOD removal 60-80% Scum formation to contain odour emissions Monitor pH (should be ) ParameterUnitTypical values Loading (volumetric)kg BOD5/m3/d Temperature°C25-35 Mean HRTdays6-25 Influent CODmg/L Effluent CODmg/L

18 2. Facultative Ponds Characteristics: “two zone” environment, depth m; large microbial diversity; medium organic load; odour free

19 Facultative Pond Design & Operation Design: Area Loading Rate kg BOD5/ha/d T>15oC kg BOD5/ha/d T<15oC HRT days Operational Considerations: Maintain aerobic conditions. Beware of over- loading causing the pond to turn anaerobic - odour problems

20 3. Aerated Ponds Characteristics: Mode is determined by the mixing intensity Completely mixed: P/V = W/m3 Facultative: P/V ≈ 0.8 W/m3

21 Aerated Pond Design & Operation Design: HRT days Aeration capacity ≈ 2*BOD load Aerators: kg O2/kWh ΔBOD: % Operational Considerations: Can be very efficient for soluble BOD/ COD removal but solids concentrations too high for discharge (irrigation ok).

22 4. Aerobic (Oxidation) Ponds Characteristics: Natural oxygenation (wind, photosynthesis); large surface area; shallow ( m); low organic loading. Suitable for treating effluent from anaerobic ponds

23 Aerobic Pond Design & Operation Design: kg BOD5/ha/d Operational Considerations: Maintain aerobic conditions. Beware of over- loading causing the pond to turn anaerobic.

24 Outline Overview 3.1 Criteria for Successful Biological Treatment 3.2 Principles of Biological Reactions 3.3Wastewater Treatment Ponds 3.4 Anaerobic Treatment Processes

25 Treatment under exclusion of oxygen Carbon mainly converted to methane (CH 4 ) and carbon dioxide (CO 2 ) 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.

26 Anaerobic Process Principles Pathways of organics in anaerobic treatment Fast growing, robust bacteria Slow growing, pH sensitive archaea

27 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.

28 A. Single Stage Process Biogas Treated effluent Wastewater SLUDGE DIGESTER Mixing mechanically or often by biogas recirculation

29 1. Upflow Anaerobic Sludge Blanket (UASB) Treated effluent Biogas From Pre-acidification Tank Gas collector Granular biomass Gas collection below water level to reduce turbulence at overflow Uniform flow distribution essential Sludge blanket

30 2. Hybrid Reactor Treated effluent Biogas From Pre-acidification Tank Granular biomass Uniform flow distribution essential Packed bed (plastic material) for biofilm growth Sludge blanket

31 B. Two-Stage Reactor Performance COD removal % BOD removal % Gas production m3/kg COD removed Methane production m3/kg COD removed Methane conc % Sludge production kg VSS/kgCOD removed

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

33 Anaerobic Reactor Design 1. Pre-acidification tank Often on the basis of an equalisation tank (also variable volume operation) Typical HRT 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)

34 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 V R  methanogenic bioreactor volume m3 Typical HRT h, Solids RT days Usually heated to operate at °C

35 High Rate Anaerobic Treatment Typical process flowsheet using Upflow Anaerobic Sludge Blanket (UASB) reactor Acidif. Tank Mix Tank Sludge blanket Methanogenesis Acidogenesis Biogas Biomass retention as granules Recycle and mix tank reduce pH control dosing CSTR-type tank usually not heated

36 Anaerobic Reactor Design OLR designs for various reactor types: UASB  6-12 kg COD/m3/d Internal Circulation  kg COD/m3/d Fluidised/expanded bed  kg COD/m3/d Hybrid Reactor  6-12 kg COD/m3/d OLR varies with degradability, temp., pH… Hydraulic loading up to 24 m 3 /(m 2 reactor area d) Gas loading m 3 gas /(m 2 reactor area d)

37 Questions?

38 Documentation

39 Terima Kasih


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