OCTOBER 31, NAMI Environmental Conference BEST PRACTICES: IMPROVING WW SYSTEMS

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1 OCTOBER 31, 2012 NAMI Environmental Conference BEST PRACTICES: IMPROVING WW SYSTEMS

2 Best Practices System Profiling Oxygen Management Carbon Management Real Time monitoring and automation

3 System Profiling COD OrthoP DO NH3 TKN NO3 NO2

4 Examples

5 Examples Florida Water Resources Journal 2005

6 Examples

7 Oxygen Management We have, or should have, direct control over oxygen through the system. Based on results of a system profile, Oxygen is one of the levers we can pull to drive the system in the direction we want In many cases will be limited by capabilities of blowers

8 Nitrification Denitrification O 2 Blowers Distribution

9 Exploring aeration-associated energy savings at a conventional water reclamation plant Jun-Jie Zhu, Paul R. Anderson. Water Science and Technology Oct 2017, 76 (8) Oxygen Management AIR

10 Considerations Blowers - VFD s and high turndown Flexible distribution system swing zones NH3 based aeration Sensors SND Simultaneous nitrification/ denitrification

11 Example

12 Carbon Management Right amount (scod:n of 5 or 6) Right Place (directly to anoxic or anaerobic) Right Time (when anoxic scod:n < 5) Right Source (consistent, high scod:n, minimal FOG, TSS, etc)

13 Sources of Carbon Carbon Internal External Exogenous Endogenous Methanol MicroC Influent COD -Protein -Fat -Blood -Chemical Endogenous Respiration Lysis Process Natural Enhanced Co-Products Crude Glycerin Molasses Waste Stream Beverage Waste Cheese Whey 13

14 Carbon Redirection Redistribution of flow allowed internal BOD to be used for denitrification in first anoxic zone Before redistribution of flow BOD/N=18.2 DAF Anaerobic After partial bypass of flow BOD/N=18.2 DAF Anaerobic BOD/N=13.9 BOD/N=1.5 BOD/N=1.5 BNR BOD/N=13.9 BNR 14

15 Supplemental Carbon

16 Concerns Anaerobic bypass variability to BNR Plumbing can be expensive FOGs, TSS, other contaminants straight into BNR Most of the challenges are with secondary anoxics closer to the end of the process physically more difficult

17 Monitoring/Automation ISE VS UV Relatively Inexpensive NH3, NOx More labor intense Matrix adjustments Cleaning Trending vs Accuracy Can be $15-20K for NO3+NO2 COD is on the horizon Minimal labor, self cleaning Quarterly vs weekly Accuracy in addition to trending Range tops out at about 100 mg/l NO3+NO2-N

18 Automation Air DO, NH3 Dedicated blowers Carbon NO3, Flow, COD, NH3

19 Nitrack 19

20 Nitrack 20

21 Appendices Nitrification Temp/SRT ph/alk DO Denitrification BOD ORP - O2 MLR ChemP EBPR Process Configs Design Parameters

22 Nitrification Autotrophic Bacteria Nitrification is a two step biochemical process performed by specific bacteria known as nitrifiers that convert ammonia to nitrate use carbon dioxide as the carbon source use ammonia and oxygen as an energy source NH O 2 NO 3 + H + + H 2 O NH O 2 NO 2 +H + + H 2 O by Ammonia Oxidizing Bacteria (AOB) NO O 2 NO 3 by Nitrite Oxidizing Bacteria (NOB) To Oxidize 1 g NH 3 -N: 4.57 g O 2 is needed (3.43 g O 2 for Nitrite and 1.14 g O 2 for Nitrate) 7.14 g of Alkalinity as CaCO 3 is needed ( 2 50g CaCO 3/eq ) 14 g N NH HCO 3 + 2O 2 NO 3 + 2CO 2 + 3H 2 O Considering the whole biological process including the assimilation for nitrification of 1 g Ammonia: 4.25 g of O 2 are utilized 0.16 g of new cells are formed 7.07 g of alkalinity as CaCO 3 are removed 0.08 g of inorganic Carbon are utilized in the formation of new cell 22

23 Process Parameter - Nitrification Oxygen: DO is normally maintained at 2 mg O 2 /L to have the optimal nitrification rate. Temperature: ph: Higher temperature increases the growth rate. Every 10 C increase in Temp doubles the growth rate of Nitrifiers and cuts the required MLSS in half Nitrification is ph sensitive and rates decline significantly below ph 6.8 At ph 6 and below the rates may be 10% of the rate at ph 7 Optimal Nitrification rate occurs at ph values in the range A ph 7.2 is normally used to maintain the reasonable nitrification rate Toxicity: Nitrifying organisms are sensitive to a wide range of organic and inorganic compounds (organic solvents, amines, proteins, phenolic compounds, alcohols, benzene and etc.) Metals: complete inhibition of growth occurs at 0.1 mg/l copper and 0.25 mg/l nickel. Un-Ionized Ammonia: at 20 C and ph 7, NH 4 -N concentration at 100 mgn/l and 20 mgn/l may initiate inhibition of AOB and NOB respectively. Alkalinity: SRT: Added depending the initial alkalinity and ammonia in the influent (7.15 Ib alkalinity as CaCO 3 per Ib of Ammonia) Typical design SRT values may range from days at 50 F to 4-7 days at 68 F 23

24 C. Hellinga, M.C.M.van Loosdrecht 1998, The Sharon Process W. Gujer 2010, Nitrification and me- A subjective Temp and SRT Effect on Nitrification Temperature has direct correlation with the growth rate. In the cold weather, increasing the SRT may help to improve the Nitrification At temperature below 50 F, plant may not nitrify more than 50% of the influent Depending on the temperature, the best SRT for Nitrifiers in between 8 and 14 days 24

25 Anthonisen et al. 1976, Inhibition of Nitrification by Ammonia and Nitrous Acid ph and Alkalinity Importance of Alkalinity Carbon source for Nitrifiers Nitrifiers are ph sensitive. Insufficient alkalinity decreases the ph and depress the Nitrifiers Source of Alkalinity consumption 0.08 g of Inorganic Carbon will be consumed per Ib NH3-N oxidized NH 4 HCO 3 + O 2 HNO 3 + H 2 O +CO 2 Adding chemicals for phosphorus removal destroys alkalinity 7.15 Ib of Alkalinity as CaCO3 is needed per Ib NH 3 -N Oxidized FN and FNA inhibition: NH 4 + NH 3 + H + NO 2 + H + HNO 2 Optimum ph for Nitrification: 7.2 Zone1: Nitritation and Nitratation inhibition by FA Zone2: Nitratation Inhibition by FA Zone3: Complete Nitrification Zone4:Nitratation inhibition by FNA 25

26 Gustaf Olsson, Lund University, Sweden. Dissolved Oxygen Due to competition between heterotrophic and autotropic bacteria, all of the existing BOD must be exhausted first to achieve full nitrification. F:M ratio should be less than 0.25 Optimum DO for Nitrification is 2 mg O 2 /L 26

27 Denitrification Heterotrophic Bacteria Denitrification is a biochemical process performed by specific bacteria known as heterotrophs that convert nitrate to nitrogen gas use organic carbon as the carbon source NO 3 + BOD N 2 + OH + H 2 O + CO 2 Anoxic Condition Mixing and Nitrogen Recycle Important Process parameter : Carbon: Denitrification rate depends upon the availability of carbon. Theoretically 2.86 g BOD is needed to reduce Nitrate to Nitrogen gas (Practically 4-6 g BOD) BOD = 2.86 ; NO3 N Y n where Y n is net biomass yield g VSS g BOD 3.57 g of Alkalinity as CaCO3 is formed (~Recovering the 50% of consumed alkalinity in nitrification) 0.45 g of New Cells will be formed O 2 : Anoxic condition, DO should be less than 0.2 mg O 2 /L ph: Denitrifiers are less sensitive to ph than Nitrifiers. ph recommended range is 7.2 SRT: 3-6 days 27

28 Low BOD Theoretically 2.86 Ib of BOD is required to denitrify one Ib-N of NO 3. Practically this number is above 5 mg/l. If BOD is not soluble, extra retention time would be required in order to convert particulate BOD to the soluble form. Since solubilization is the slowest part of process, it s recommended either to use soluble supplemental carbon or increasing the size of anoxic tank and reducing the MLRcy Specific denitrification rate as function of F/M ratio and the ratio of readily biodegradable BOD to total BOD (Metcalf & Eddy, 2003) 28

29 Relation between ORP and metabolic processes (Goronsky, 992) High ORP and High Recycle O2 O 2 can be carried to the anoxic reactor from the aeriation basin ORP can be used as an indictor. Denitrification could occurring in an ORP of -100 to +100 mv. However to achieve better results, it s recommended to keep ORP below 50 mv On/Off Aeriation: Changing the Regime 29

30 Low Mixed Liquor Recycle Rate MLR recycles the nitrate produced in the aeration tank to the anoxic basin. To achieve denitrification a significant MLR is required Denitrification efficiency may be enhanced by increasing the MLR. However a higher MLR may return excess oxygen to the anoxic tank and the hinder the process. 30

31 Chemical Phosphorus Removal Most Commonly Used Chemicals:» Ferric Chloride:» Alum: FeCl 3 + H 3 PO 4 FePO 4 + 3HCl 5.2 Ib ferric per 1 Ib-P (Theoretically) 0.92 Ib Alkalinity per 1 Ib Ferric Ferric Chloride tend to be corrosive Al 2 (SO 4 ) 3. 14H 2 O + 2H 3 PO 4 2AlPO 4 + 3H 2 SO H 2 O 9.6 Ib alum per 1 Ib-P (Theoretically) 0.5 Ib Alkalinity per 1 Ib Alum Alum tend to result in significant additional sludge production 31

32 Practical ratios: 1.5 to 4 Molar ratio for 80-98% removal 5 to7 Molar ratio for higher efficiency and lower Soluble P Phosphorus removal is most efficient in the ph range of 5 to 7 for alum and 6.5 to 7.5 for ferric salt Pros: Reliable process and easy to control Cons: Safety issues, May inhibit the UV disinfection performance Decrease the ph, Additional Cost Overall feeding may cause system to become P limited 32

33 Stoichiometry of EBPR Existence of Significant amount of DO and NOx in the anaerobic tank may interrupt the EBPR. In the anaerobic zone, ortho-p can be measured as high as 40 mg P/L (5-8 mg P/L in the influent) 1.06 g acetate will be produced per g of bscod 0.3 g of cell will be produced per 1 g of acetate Up to 30% weight of the cell consists of phosphorus (normal cells is less than 2%) 10 g bscod is required to remove 1 g P (corresponds to 3.3g cell) 33

34 Biological Nutrient Removal, WEF 2007 Process Configuration 34

35 Design Parameter Process Nitrogen Removal Phosphorus Removal MLE 7 < TN < 9 None A 2 O 7 < TN < 9 TP < 1 4 Stage Bardenpho 3 < TN < 6 None 5 Stage Bardenpho 3 < TN < 6 TP < 1 UCT & VIP 7 < TN < 9 TP < 1 Metcalf & Eddy,

36 Troubleshooting Foaming White frothy and not stable Characterization: High F/M loading Start-up situation Principal causes BOD material is not degraded due to high F/M ratio Young sludge or Low MLSS concentration Start-up situation, time to reach steady state condition New plant, Over loaded plant Solution Reduce F/M Check the detergent in the PE Dark/chocolate foam, stable Characterization: Low F/M Long Sludge age Principal causes Long sludge age High MLSS concentration due to high nitrogen in the PE Produced Nitrogen gas from Denitrification phenomena in the final clarifiers Solution Improving the denitrification process: Extending Anoxic tank Increasing the internal recycle Adding supplemental carbon to the anoxic zone (Increasing the F/M ratio) 36