Nitrogen Reduction: Process & Application

Presentation Outline Environmental effects of Nitrogen Health Effects of Nitrogen The Nitrogen Cycle What interrupts the cycle? Applications Environmental effects of Nitrogen Health Effects of Nitrogen The Nitrogen Cycle What interrupts the cycle? Applications

Environmental Effects: Excess Nitrogen Increased Nitrogen in Rivers and Oceans Causes eutrophication of coastal waters Causes algal blooms Causes a decrease in oxygen in waters Killed significant numbers of fin fish and shellfish Increased Nitrogen in Rivers and Oceans Causes eutrophication of coastal waters Causes algal blooms Causes a decrease in oxygen in waters Killed significant numbers of fin fish and shellfish

Health Effects of Nitrates Methemoglobinemia (Blue Baby Syndrome) Hyperthyroidism CNS malformations in newborns Diabetes Methemoglobinemia (Blue Baby Syndrome) Hyperthyroidism CNS malformations in newborns Diabetes

The Nitrogen Cycle Forms of Nitrogen NITROGEN GAS (N 2 ) ORGANIC NITROGEN AMMONIA (NH 3 ) NITRITE (NO 2 ) NITRATE (NO 3 ) NITROGEN GAS (N 2 ) ORGANIC NITROGEN AMMONIA (NH 3 ) NITRITE (NO 2 ) NITRATE (NO 3 )

The Nitrogen Cycle N 2 – 78% of earth’s atmosphere Lightning – High-energy fixation Nitrates NO 3 - BiologicalFixation Ammonia NH 3

How does nitrogen get into our bodies? Plants produce organic molecules - Amino Acids - Proteins - Nucleic Acids Animals eat plants or other animals Plants produce organic molecules - Amino Acids - Proteins - Nucleic Acids Animals eat plants or other animals

The Nitrogen Cycle N 2 – 78% of earth’s atmosphere BiologicalFixation Lightning – High-energy fixation Nitrates NO 3 - Ammonia NH 3 Plants and microorganisms create proteins Food Chain

How does Nitrogen leave our bodies? Breakdown of proteins, etc. into organic forms of Nitrogen Returned to the environment as excretions Breakdown of proteins, etc. into organic forms of Nitrogen Returned to the environment as excretions

The Nitrogen Cycle N 2 – 78% of earth’s atmosphere BiologicalFixation Lightning – High-energy fixation Nitrates NO 3 - Ammonia NH 3 Plants and microorganisms create proteins Food Chain Decay

The Nitrogen Cycle In a denitrification wastewater treatment system N 2 – 78% of earth’s atmosphere Nitrates NO 3 - Ammonia NH 3 Nitrites NO 2 - Nitrifying bacteria Denitrifying Bacteria

Concentration Limits and Water Conservation Example: The Jar of Marbles 1 Liter of Water, 40 marbles1 Liter of Water, 40 marbles Concentration = 40 Mb/LiterConcentration = 40 Mb/Liter What happens if you take out half of the water? Concentration = 80 mb/literConcentration = 80 mb/liter

What does that mean? When it comes to treatment…. –A percent reduction removes the same number of marbles. –The receiving environment is accepting the same number of marbles. When it comes to treatment…. –A percent reduction removes the same number of marbles. –The receiving environment is accepting the same number of marbles.

Septic Tank Effluent – Nitrogen Breakdown Example (2004) Total N - 80 mg/L Org. Nitrogen10 mg/L NH 3 (Ammonia)70 mg/L NO 3 (Nitrate)0 mg/L NO 2 (Nitrite)0 mg/L

After Treatment – Total N - 24 mg/L Org. Nitrogen5 mg/L NH 3 (Ammonia)9 mg/L NO 3 (Nitrate)10 mg/L NO 2 (Nitrite)0 mg/L

Basic Steps in Nitrogen Removal Systems Anoxic Zone  Conversion of nitrate to nitrogen gas (denitrification)  BOD removal Aerobic Zone  BOD removal and nitrification Anoxic Zone  Conversion of nitrate to nitrogen gas (denitrification)  BOD removal Aerobic Zone  BOD removal and nitrification

NITRIFICATION Conversion of Ammonia–Nitrogen to Nitrate–Nitrogen Conversion of Ammonia–Nitrogen to Nitrate–Nitrogen

Nitrification Process Step 1: NH O 2 Nitrosomonas NO 2 + 2H + + H 2 O Step 2: NO O 2 Nirtrobacter NO 3 Overall Reaction: NH O 2 NO 3 + 2H + + H 2 O  4.6 lbs O2/lb NH3-N  7.14 lbs alkalinity destroyed/lb NH3-N

Basic Design Considerations for Nitrogen Removal Systems Aerobic Zone  Optimum Oxygen and Mixing  Aerobic SRT for Nitrification  Alkalinity & pH  HRT  Liquid Temperature  Toxicity

Toxic Chemicals (for wastewater treatment) Homes: liquid fabric softeners, pine oil, and drain cleaners Commercial Facilities: Strong sanitizers or Quats, floor stripping waste (Zinc) Pesticides Acid and Caustic Materials Homes: liquid fabric softeners, pine oil, and drain cleaners Commercial Facilities: Strong sanitizers or Quats, floor stripping waste (Zinc) Pesticides Acid and Caustic Materials

QUATERNARY AMMONIUM COMPOUNDS QUATs OR QAC BENZALKONIUM CHLORIDE CH 3 | Cl-Benz Ring-CH 2 -N-C 18 H 37 | CH 3 QUATs OR QAC BENZALKONIUM CHLORIDE CH 3 | Cl-Benz Ring-CH 2 -N-C 18 H 37 | CH 3

Problems with QUATs in Wastewater Treatment Toxic/Inhibitory to Nitrifying Bacteria - in concentrations <2 mg/l Non-biodegradable Organic Nitrogen Exponential Increase in Use Toxic/Inhibitory to Nitrifying Bacteria - in concentrations <2 mg/l Non-biodegradable Organic Nitrogen Exponential Increase in Use

Quaternary Ammonium Compounds - Disinfectant Ammonium Ion with 4 Radicals Attached Not oxidizers - Surface-active agents Breakdown bacterial cell walls Internal contents of bacteria leak out Commonly used at 200 ppm Effective at High Temperatures Ammonium Ion with 4 Radicals Attached Not oxidizers - Surface-active agents Breakdown bacterial cell walls Internal contents of bacteria leak out Commonly used at 200 ppm Effective at High Temperatures

DENITIRIFICATION Denitrification is the conversion of Nitrate–Nitrogen to Nitrogen gas through a biological process.

Denitrification Process NO 3 + organic carbon carb. bacteria N 2 + CO 2 + OH + H 2 0 CO 2 + OH HCO 3 NO 3 NO 2 NO N 2 O N 2  2.86 lbs oxygen recovered / lb NO3-N  3.57 lbs alkalinity recovered / lb NO3-N

Basic Design Considerations for Nitrogen Removal Systems Anoxic Zone  D.O. <0.5 mg/L  BOD:NO3-N Ratio  HRT  Mixing  pH ( ideally) Anoxic Zone  D.O. <0.5 mg/L  BOD:NO3-N Ratio  HRT  Mixing  pH ( ideally)

Carbon Source for Denitrification Influent BOD Endogenous Respiration External Source  Methanol  Ethanol  Acetic Acid  Sugar, etc.  External carbon source should be: Easy to use Low cost Available Favorable Microbial Growth Influent BOD Endogenous Respiration External Source  Methanol  Ethanol  Acetic Acid  Sugar, etc.  External carbon source should be: Easy to use Low cost Available Favorable Microbial Growth

Denitrification Rate It varies with the source of carbon  Methanol provides the highest rate  Endogenous respiration provides the lowest rate  It varies with temperature It varies with the source of carbon  Methanol provides the highest rate  Endogenous respiration provides the lowest rate  It varies with temperature

How Does One Size a System? How Does One Size a System? Influent Laboratory Analysis Experience Common Sense Influent Laboratory Analysis Experience Common Sense

Why Should I Worry About It? “Thou Shalt Not Live By Flow Alone” Biological Vs. Hydraulic Loading “Thou Shalt Not Live By Flow Alone” Biological Vs. Hydraulic Loading

Design Source of the waste Facility Practices Flow Patterns (e.g. churches) Effluent Requirements Operational/Management Resources Source of the waste Facility Practices Flow Patterns (e.g. churches) Effluent Requirements Operational/Management Resources

System Loading w/ N Reduce treatment expectations by 20% Why? Nitrifying bacteria are easily crowded out when high levels of BOD 5 are present.Nitrifying bacteria are easily crowded out when high levels of BOD 5 are present. The bugs that reduce BOD 5 are stronger than those that nitrify.The bugs that reduce BOD 5 are stronger than those that nitrify. Therefore physical space must be made available for nitrifiers.Therefore physical space must be made available for nitrifiers.

Real World Examples Restaurant Subdivision School Restaurant Subdivision School

BOD 5 & TKN Calculations Must convert BOD5 and TKN influent from mg/L to lbs. /day. = flow (gpd) x 8.34 x BOD (mg/L) = BOD5 (lbs/day) 1,000,000 = flow (gpd) x 8.34 x TKN (mg/L) = TKN (lbs/day) 1,000,000

Restaurant Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD FOG150 TKN60

BOD 5 Calculation Restaurant. Flow 1500 gpd, BOD = 1000 mg/L. Calculation: = flow (gpd) x 8.34 x BOD5 (mg/L) = BOD5 (lbs/day) 1,000,000 = 1500 gpd x 8.34 x 1000 mg/L = ~12.5 (lbs/day) 1,000,000

TKN Calculation Restaurant. Flow 1500 gpd, TKN = 50 mg/L. Calculation: = flow (gpd) x 8.34 x TKN (mg/L) = TKN (lbs/day) 1,000,000 = 1500 gpd x 8.34 x 60 mg/L = 0.75 (lbs/day) 1,000,000

Restaurant Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~12.5 FOG150 TKN

Restaurant Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~12.5 FOG150  TKN 

Subdivision Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD FOG30 TKN70

BOD 5 & TKN Calculations Subdivision: Flow 1500 gpd, BOD = 220 mg/L, TKN = 70 Calculation: BOD= 1500 gpd x 8.34 x 220 mg/L = ~2.7 (lbs/day) 1,000,000 TKN= 1500 gpd x 8.34 x 70 mg/L = ~0.9 (lbs/day) 1,000,000

Subdivision Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~2.7 FOG30 TKN70 ~0.9

Subdivision Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~2.7 FOG30  TKN70 ~0.9

School Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD FOG50 TKN200

BOD 5 & TKN Calculations School: Flow 1500 gpd, BOD = 220 mg/L, TKN = 200 Calculation: BOD= 1500 gpd x 8.34 x 450 mg/L = ~5.6 (lbs/day) 1,000,000 TKN= 1500 gpd x 8.34 x 200 mg/L = ~2.5 (lbs/day) 1,000,000

School Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~5.6 FOG50 TKN200 ~2.5

School Lbs/day<200mg/L<30 mg/L NH3 Reduction Total Nitrogen Reduction Flow1500 BOD ~5.6 FOG50  TKN200 ~2.5

Effluent Influent (Q) Final Clarifier Nitrified Recycle ( % Q) RAS (10-100% Q) WAS Alternative Denitrification Systems: Single-Stage Anoxic Zone (MLE) Anoxic Basin Aeration Basin BODr & Nitrification

Alternative Denitrification Systems: Single-Stage Anoxic Zone Effluent nitrate of 8-12 mg/L without external carbon source Alkalinity and oxygen recovery Influent WW should have adequate BOD to satisfy the denitrification needs Sensitive to the aeration tank DO and the nitrate recirculation flow rate Suitable for large plants Effluent nitrate of 8-12 mg/L without external carbon source Alkalinity and oxygen recovery Influent WW should have adequate BOD to satisfy the denitrification needs Sensitive to the aeration tank DO and the nitrate recirculation flow rate Suitable for large plants

Alternative Denitrification Systems: Post Anoxic Influent Aeration Basin BODr & Nitrification Anoxic Basin Aeration Basin Final Clarifier Carbon Feed

Alternative Denitrification Systems: Post Anoxic Simple to Operate  Can tolerate variations in the influent nitrate  Monitoring of carbon addition is not very critical  No internal recirculation flows Can be designed to remove high influent nitrate Requires external carbon source (cost & complexity) Alkalinity and oxygen recoveries benefits from denitrification process are not used within the system Simple to Operate  Can tolerate variations in the influent nitrate  Monitoring of carbon addition is not very critical  No internal recirculation flows Can be designed to remove high influent nitrate Requires external carbon source (cost & complexity) Alkalinity and oxygen recoveries benefits from denitrification process are not used within the system

Challenges of Nitrogen Removal for On-Site Applications Periodic and Non-uniform Influent Flow Adverse Impact of High and Low Loading Rates on Nitrogen Removal Typically Non-Optimum Influent BOD:TKN for Denitrification Process Potential for unexpected toxicity in the Influent Periodic and Non-uniform Influent Flow Adverse Impact of High and Low Loading Rates on Nitrogen Removal Typically Non-Optimum Influent BOD:TKN for Denitrification Process Potential for unexpected toxicity in the Influent

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