Odors Associated With Stabilized Biosolids. Christopher Wilson, Ph.D. Joe Gorgan, P.E. Dimitri Katehis, Ph.D., P.E.

Transcription

1 Odors Associated With Stabilized Biosolids Christopher Wilson, Ph.D. Joe Gorgan, P.E. Dimitri Katehis, Ph.D., P.E. WATERCON 2012

2 ACKNOLEDGEMENTS WERF Research Projects on Biosolids Odors Virginia Tech Bucknell University DCWATER

3 Presentation Outline Causes and Sources of Biosolids Odors Odor Compounds and their Precursors Process and Operational Impacts Relationships with Regulated Parameters Vector Attraction Reduction Pathogen Indicators Potential Strategies to Mitigate Biosolids Odor Using What We Know to: Reduce Odor Potential Reduce Odor Release In Some Cases Live With It, Better.

4 Presentation Outline Causes and Sources of Biosolids Odors Odor Compounds and their Precursors Process and Operational Impacts Relationships with Regulated Parameters Vector Attraction Reduction Pathogen Indicators Potential Strategies to Mitigate Biosolids Odor Using What We Know to: Reduce Odor Potential Reduce Odor Release In Some Cases Live With It, Better.

5 Protein serves as a precursor for many recognized biosolids odor compounds Odor Group Inorganic Sulfur Organic Sulfur (tvosc) Aromatics Nitrogenous Aromatics Amines H 2 S, CS 2, COS Examples Methanethiol (Methyl mercaptan) Dimethyl Sulfide (DMS) Dimethyl Disulfide (DMDS) Dimethyl Trisulfide (DMTS) p-cresol, Toluene Indole, Skatole Ammonia Trimethylamine (TMA) Source Sulfate, Protein Protein Protein Protein Protein, Polymer

6 Precursor Amino Acid Biosolids Odor Compound Glycine (Any) Ammonia Cysteine Hydrogen Sulfide Methionine Methanethiol Phenylalanine Tryptophan Toluene Ethylbenzene Styrene Indole Skatole Tyrosine p-cresol

7 Sulfur-based odor compounds are cycled by various chemical and biological reactions SULFATE Protein Degradation CYSTEINE Reduction H 2 S Methylation Methanogens Methylation MT Oxidation DMS DMDS Methanogens METHIONINE Protein Degradation Oxidation DMTS Methanogens

8 Many (not all) biosolids odors arise from an imbalance in anaerobic metabolisms Solids Reduction Fermentation Methanogenesis Solids destruction, Sludge minimization Biodegradable Particulates Hydrolysis Proteins & Carbohydrates Lipids Acid Formation Precursors to odor Amino Acids & Simple Sugars Volatile Fatty Acids Long Chain Fatty Acids Methane Formation Acetic Acid H 2 plus CO 2 ~ 70% ~ 30% Energy recovery Methane

9 Headspace Sulfur (ppmv Sulfur per gram VS) Lab data used to simulate biosolids odor generation from an anaerobic stockpile Balance Point Inhibited Methanogens (BESA added Odor Potential ) Fermentation Methanogenesis Days of Incubation

10 General approaches to control sulfur based biosolids odor compounds: Reduce Odor Potential Readily biodegradable protein within biosolids can be converted to odor compounds Biosolids shearing during dewatering can release these materials, leading to biosolids odors Provide a Good Methanogenic Environment Methanogens convert organic sulfur odors to hydrogen sulfide Metal Salt Addition to Control Hydrogen Sulfide Alum, Ferric/Ferrous, Magnesium are all potentially beneficial Can be added directly during upstream processes (e.g. digestion)

11 Presentation Outline Causes and Sources of Biosolids Odors Odor Compounds and their Precursors Process and Operational Impacts Relationships with Regulated Parameters Vector Attraction Reduction Pathogen Indicators Potential Strategies to Mitigate Biosolids Odor Using What We Know to: Reduce Odor Potential Reduce Odor Release In Some Cases Live With It, Better.

12 Criteria used to assess biosolids quality: CFR 40 Part 503 Regulations Stability based on vector attraction reduction (VAR) For anaerobic digestion, often related to volatile solids reduction 38% VSR during digestion Other similar methods (residual activity, oxygen uptake rate, etc.) Pathogen reduction based on indicators Class B Biosolids: Fecal Coliform MPN < 10 6 per gram solids Class A Biosolids: Fecal Coliform MPN < 10 3 per gram solids Other specific methods How do these quality parameters correlate with biosolids odor?

13 Criteria used to assess biosolids quality: CFR 40 Part 503 Regulations Stability based on vector attraction reduction (VAR) For anaerobic digestion, often related to volatile solids reduction 38% VSR during digestion Other similar methods (residual activity, oxygen uptake rate, etc.) Pathogen reduction based on indicators Class B Biosolids: Fecal Coliform MPN < 10 6 per gram solids Class A Biosolids: Fecal Coliform MPN < 10 3 per gram solids Other specific methods How do these quality parameters correlate with biosolids odor?

14 TVOSC (ppmv Sulfur/g VS) Biosolids odor (as tvosc) from a series of bench scale digestion studies on DC Water s sludge

15 Volatile Solids Reduction In this series of studies, there was no discernable correlation between VSR and Biosolids Odor 80% 60% 40% 20% 0% tvosc (ppmv/g VS)

16 Criteria used to assess biosolids quality: CFR 40 Part 503 Regulations Stability based on vector attraction reduction (VAR) For anaerobic digestion, often related to volatile solids reduction 38% VSR during digestion Other similar methods (residual activity, oxygen uptake rate, etc.) Pathogen reduction based on indicators Class B Biosolids: Fecal Coliform MPN < 10 6 per gram solids Class A Biosolids: Fecal Coliform MPN < 10 3 per gram solids Other specific methods How do these quality parameters correlate with biosolids odor?

17 FC MPN/g TS WERF Research on Indicator Regrowth, Odors, and Sudden Increase (ROSI): REGROWTH DECAY FC Class B Class A tvosc, Soluble Protein tvosc Odor Precursors/Bacteria Food Time after Dewatering

18 Interesting conclusions regarding relationship between biosolids odor and CFR 40 Part 503 Parameters: Volatile Solids Destruction Not a great predictor of biosolids odor across the board Soluble organics after dewatering may be more important than VSR Ongoing question: Is there a better indicator of VAR? Pathogen Indicators Same factors that cause indicator regrowth in biosolids seem to impact control biosolids odors Soluble organics after dewatering are again an important factor TAKE HOME: Process that result in leftover soluble protein may produce odorous biosolids

19 Presentation Outline Causes and Sources of Biosolids Odors Odor Compounds and their Precursors Process and Operational Impacts Relationships with Regulated Parameters Vector Attraction Reduction Pathogen Indicators Potential Strategies to Mitigate Biosolids Odor

20 Recurring themes in biosolids odor control Soluble protein in biosolids is a precursor for biosolids odors Methanogens help to control biosolids odors Biosolids odors increase shortly after dewatering, then decrease over time

21 Recurring themes in biosolids odor control: Soluble Protein Shear during dewatering releases soluble protein Higher Shear Dewatering Higher Biosolids Odors Lower Shear Dewatering Lower Biosolids Odors Higgins et al. (WERF Odor Studies)

22 Recurring themes in biosolids odor control: Restoring methanogenesis Goal is to maintain balance between VOSC producers and degraders Shear and oxygenation during dewatering impairs methanogens (VOSC degraders) Biosolids odors are typically lower once methanogens recover from shock during dewatering Some success in blending stockpiled biosolids with fresh biosolids to bioaugment methanogens Actual methane release is minimal

23 Recurring themes in biosolids odor control: Biosolids Odor Trends Biosolids odors (particulalrly tvosc) follow a predictable production and decay pattern Biosolids can be land applied and incorporated very soon after dewatering Odors may not yet be present Biosolids can be land applied after some on-site storage Odors will subside, generally in several days to several weeks following digestion Same control measures are useful for managing pathogen indicator levels

24 In conclusion, biosolids odor is predictable based on soluble constituents and biosolids management Many biosolids odors are derived from the degradation of soluble protein Methanogens and Multivalent Metal Cations control sulfur-based odors Typical indicators of biosolids stability (VSR) may not provide a good prediction of biosolids odor

25 In conclusion, biosolids odor is predictable based on soluble constituents and biosolids management Trends in biosolids odors and pathogen indicators appear to be linked Both related to bioavailable soluble organics Known mechanisms provide clues towards controlling biosolids odors Minimize shear during dewatering and handling Encourage methanogens within biosolids stockpiles Use characteristic biosolids odor trend to manage biosolids storage and land application

26 Headspace Sulfur (ppmv Sulfur per gram VS) Discussion Balance Point Inhibited Methanogens Fermentation Methanogenesis Days of Incubation

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