Using Washington State’s Local Limits Spreadsheet

David J. Knight P.E. Environmental Engineer Water Quality Program

June 22, 2016

Find your Happy Place

AGENDA: • Exciting Powerpoint Slides on Workbook • Quick review of spreadsheets in Workbook • Loading spreadsheet on laptops with Excel™ • Break (hopefully with cookies) • Challenging small team exercise • Celebrate getting the right answers • Note: Instructor carries <$20 in cash

Why Develop Local Limits Tool: • Use EPA Spreadsheet (based on PRELIM) • Hand calculations using formulas in EPA

Manual on Development of LL’s and supp. Manual. - Arduous to do and to check

• Use POTW developed spreadsheet. – Difficult for Ecology to check & critique

• Use a consulting firm or outside expertise – POTW staff may not understand, maintain.

Benefits of Providing Spreadsheet: • Attempt to:

– Provide standardized format using common program. – Reduce burden of task (easy to do and update) – Use POTW’s site specific data (technically based) – Facilitates calculating local limits several different ways. – Yield limits that protect POTW processes, receiving waters,

and sludge uses – Generate limits to prevent sewer toxicity, explosion, HW – Provides tools for allocating organic loading capacity

Where to Find the Spreadsheet • http://www.ecy.wa.gov/programs/wq/permits/guid

ance.html • Guidance Manual: Using NEWLLqq • Local Limits Excel Spreadsheet -NEWLL11 (pub) • Today using NEWLL12 (improved HW function) • “Guidance Manual for Developing Local Discharge

Limits” • My Email: David.J.Knight@ecy.wa.gov

Local Limits Excel Spreadsheet: • Features to Facilitate Limits:

– Works (if necessary) with minimal POTW information such as no sampling data.

– Uses sampling data when available. – Evaluates the quality of the sampling data. – Accounts for the sludge disposal method. – Produces defensible local limits – Easily used by permit writer or POTW – Incorporates current WQ standards

Audience for the Spreadsheet

• Ecology staff that develop & review limits • POTWs that must or wish to revisit Local Limits and

ensure they are “technically based”. • People finding the data difficult to manage &

formulas to calculate LL’s complex & arduous. • Prior users of EPA spreadsheets who want a

contemporary and more flexible option.

Technically Based Local Limits

• Required of Approvable Programs • Requires staff time to do hand calculations • Depending on the allocation scheme, requires

maintenance as variables change. • Certain allocation schemes require close

maintenance and regular • Hiring outside contractor can yield product not be

understood by POTW staff.

Spreadsheet Care & Maintenance • Spreadsheet – Improvement requires feedback • What’s missing or frustrating? • How is it for entering sampling data? • Would locking cells that contain formulas prevent

accidents or just limit usefulness? • How useful is the spreadsheet manual? • Policy on use and revision of spreadsheet:

– Human Health Standards – Organic Pollutant limits

Ecology’s NEWLL11.xls

• PRO’s – Has a manual explaining program – Can see formulas used, infinitely customizable – Enter Mixing Zones directly – Several cross checks to improve accuracy – Uses most popular spreadsheet program – Estimates/projects the NPDES limits for a POTW

• CON’s – Specific to Washington MZ rules, criteria

Practical Exercise (NEWLL12.xls)

• Example with one metal intended to show: • What data is needed for analysis, • How the spreadsheet processes the data, • The options available in the analysis, • How to double check & refine the analysis, • How to implement new standards, AKART.

POTW Data Needed for Analysis

• The receiving Water Hardness • If discharge is to Marine of Fresh Water • The biosolids quality chosen (EQ or C) • Whether activated sludge processes used • Total POTW, Domestic, & Industrial flows • The Acute and Chronic Dilution Factors • Digestor Flow (in MGD) at POTW flow • The dry sludge production (US Tons/day)

Remember: Not Everything Translates Well

Entering Data: “Basic Data” Rows 14-17

Name of Facility:Point of Contact:Person Entering Data:Reviewer:

Entering Data: “Basic Data” Rows 19-22

Receiving Water Hardness (if fresh)(M)arine, (F)resh, or (B)oth DischargesSludge: Class A (A) or (C)eiling levelPlant: (A)ctivated sludge or (O)ther

35FAA

Entering Data: “Basic Data” Rows 24-27

Total Plant Flow (in MGD) 5. MGDDomestic Flow (in MGD) 4.5 MGDIndustrial Flow (in MGD) 0.5 MGDInfiltration/Inflow (by subtraction)

Entering Data: “Basic Data” Rows 28-32

Acute Dilution Factor 6. : 1Chronic Dilution Factor 19. : 1Dilution Factor for Human Health Based WQ 19. : 1Digester Flow (in MGD) 0.075 MGDDry Sludge Production Rate (US Tons/day) 6.2 T/D

Entering Data: “Basic Data” Rows 35-39

Sampling Data Available (inf, eff, sludge) (Y/N YCredit present loading of existing sources (Y/ YAdjust for receiving water pollution (Y/N) YUse Observed Overall Removal Rate (Y/N) YUse Observed Primary Removal Rate (Y/N) Y

Options in Calculating Limits

• Sampling Data Available (Y/N) (a “N” uses pollutant concentrations from EPA Manual (typical of POTWs then)

• Credit present loading of existing sources (Y/N) (Enter a “Y” only if you have entered flow weighted average concentrations of industrial wastewater to the POTW.

• Adjust for receiving water pollution (Y/N) (Always enter a “Y” if you have receiving water pollutant concentrations)

• Use observed overall removal rate (Y/N) (Enter “Y” if you have influent and effluent sampling data, “N” uses EPA’s old RemRt data)

• Use observed primary removal rate (Y/N) (Enter “Y” If you entered primary clarifier data in “Sample Data”)

Reserving Capacity MAHL v.s. MAIL

Two Methods – Reserving a Portion of either The MAIL “Fraction of Industrial Loading Capacity in

reserve” (a slice of the MAIL)

The Headworks Loading, (a slice of the entire pie)

GENERALLY One or the Other

Domestic 42%

Industrial 43%

10% of MAHL 10%

10% of MAIL 5%

Sales

Entering Data: “Basic Data” Rows 40-41

Fraction of Industrial Loading Capacity in reserve 10.00%Fraction of Headworks Loading held in reserve 5.00%

Choosing Pollutants of Concern (rows 44 through 65)

• Pre-selected: Antimony, Arsenic, Arsenic+5, Beryllium, Cadmium, Chromium(Hex), Chromium(T), Copper, Cyanide, Lead, Mercury, Molybdenum, Nickel, Selenium, Silver, Thallium, Tributyl Tin, Zinc.

• ADD or remove pollutants from the local limits analysis by “unchecking” the box to the right of the analyte (column C) on the “Basic Data” spreadsheet.

• Four rows at end (62-65) will be normally blank. These are for additional analytes, but using these rows will require finding out the WQ and HH criteria (if exist) for them and entering that in the “POTW Limits” spreadsheet.

• NOTE: Rows 68-72 Provide a recap of the options chosen for each analyte, but the program anticipates you would adjust the analysis method for a particular analyte on the “Local Limits” tab (which then is pulled here).

What the Recap Section Looks Like

Sampling Data Needed

• Influent concentration • Final effluent concentration • Final sludge (mg/kg dry wt.) • Receiving water concentration (total) • Primary clarifier effluent conc. (optional) • Industrial Concentration (optional) • Domestic Concentration (optional) • (MUST confirm detection levels are adequate)

Data to be Entered for Each Sampling Event

SAMPLE 1 Enter only dates and sampling results (white boxes in default palDate: LOCATION Antimony Arsenic (T) Arsenic(+5) Beryllium

1/13/2016 Influent 3. ug/l 2. ug/l 2. ug/l 5. ug/lEffluent 2. ug/l 1. ug/l 1. ug/l 3. ug/lPrim._Clar. 2. ug/l 1. ug/l 1. ug/l 4. ug/lSludge 2.4 mg/kg 2.1 mg/kg 1.7 mg/kg 3.2 mg/kgDetection_Limit 2. ug/l 1. ug/l 1. ug/l 1. ug/l

Primary Removal Rate: 33.33% 50.00% 50.00% 20.00%Overall Removal Rate 33.33% 50.00% 50.00% 40.00%

Data passed from the “Sample Data” Spreadsheet to “Local Limits” Equations

ENTER DATA FROM PLANT SAMPLING IN SUMMARY DATA AntimonyAve. Influent Conc. 3.000 ug/LAve. Effluent Conc. 2.000 ug/LAve. Primary Removal 33.33%Ave. Overall Removal 33.33%Effluent Variation (COV) #DIV/0!Average Sludge Conc. 2.4 mg/kgAmbient Receiving Water Conc 2.100 ug/LAVE Industrial Conc. 8.0 ug/L

Making Adjustments to the “Local Limits” Spreadsheet Click on the tab titled “Local Limits” to bring sheet to foreground

Part 1 is a listing of some information from the “Basic Data” Sheet.

TO Minimize click on the box with the “-” at Left of Row 11.

Part I: GENERAL INFORMATIONReceiving Water Hardness (if fresh)

35(M)arine, (F)resh, or (B)oth Discharges

FSludge: Class A (A) or (C)eiling level

APlant: (A)ctivated sludge or (O)ther

A

Local Limits Part II Data in this section also comes from the “Basic Data” Sheet

“Industrial Flow” can be adjusted when using either the “Contributing Flows” or “Tiered Limits” MAIL allocation schemes.

Pollutant: CopperPart II: PLANT DATA - OPEN AND CHANGE "BASICD

Total Plant Flow (in MGD) 5. MGDDomestic Flow (in MGD) 4.5 MGDIndustrial Flow (in MGD) 0.5 MGDInfiltration/Inflow (by subtraction) 0. MGDAcute Dilution Factor 6. : 1Chronic Dilution Factor 19. : 1Dilution Factor for HH Limits 19. : 1Digester Flow (in MGD) 0.075 MGDDry Sludge Production Rate (US Tons/day) 6.2 T/D

Local Limits Part III Part III is a summary of WQ, Inhibition, and Sludge Usage Criteria

Part III: CONCENTRATIONS LIMITING THE POTW DU WQ Acute criteria, aquatic life (mg/L) 0.011 mg/lWQ Chronic criteria, aquatic life (mg/L) 0.0076 mg/lWQ Chronic criteria, human health (mg/L) NAActivated Sludge Inhibition Level 1. mg/lAnaerobic Digestor Inhibition Level 40. mg/lClass A Sludge standards (40 CFR 503) 1,500. mg/lSludge ceiling concentration for beneficial u 4,300. mg/l

How the Data is Processed

• Hardness is used to derive fresh water stds. • Copper Example:

Cua = .96*e^(0.9422[ln(hardness)]-1.464) Cuc = .96*e^(0.8545[ln(hardness)]-1.465)

• Standards are adjusted to mixing zone size and amount of assimilative capacity already taken.

• Sludge class dictates biosolids standards • Activated sludge inhibition evaluated if “A” • POTW & IU Flows dictate how MAHL is divided

Part IV – Pollutant Concentration Summary All this data except “Typical Domestic Concentrations” and “Adjusted Domestic

Concentration” comes from the “Sample Data” spreadsheet.

The “Typical Domestic Concentration” is from EPA’s 1988 Local Limits Manual.

The “Adjusted Domestic Concentration” backs out industrial loadings from the MAHL. It’s used instead of Influent for estimating current HW loading if “Credit Present Loading of Existing Sources” is “Y”

Part IV: POLLUTANT CONCENTRATION COPPER33 Estimated Average Industrial Conc. 0.115 mg/l34 Ambient Concentration (receiving water) 0.0026 mg/L35 Adjusted Domestic concentration 0.07056 mg/l36 Typical Domestic Concentrations 0.061 mg/l37 Average Sludge Level (mg/Kg - Dry) 144. mg/kg38 Average Influent Level (mg/l) 0.075 mg/l39 Average Effluent Level (mg/l) 0.006 mg/l

Source of Data for Section III of the Local Limits Spreadsheet

NOTE: Data in the “Sample Data” spreadsheet is in ug/L v.s. mg/L. Data labels are included to ensure the right units are used.

SUMMARY DATA CopperAve. Influent Conc. 75.000 ug/L <-LL Row 38Ave. Effluent Conc. 6.000 ug/L <-LL Row 39Ave. Primary Removal 84.00% <-LL Row 42Ave. Overall Removal 92.00% <-LL Row 43Effluent Variation (COV) #DIV/0! (not used)Average Sludge Conc. 144. mg/kg <-LL Row 37Ambient Receiving Water Conc 2.600 ug/L <-- LL Row 34AVE Industrial Conc. 115.0 ug/L <-- LL Row 33

Part V Removal Rates Section for Reference Only First Two Rows are from the “Sample Data” Spreadsheet Next four rows are from EPA’s 1988 Local Limits Manual

Part V: REMOVAL RATES COPPER42 Average Primary Removal Rate 84.00%43 Average Overall Removal Rate 92.00%44 Reference Primary Removal Rate 22.00%45 Reference 2d Decile Plant Removal 67.00%46 Reference Ave Plant Removal 86.00%47 Reference 8th Decile Removal 95.00%

Part VI” How to Calculate Limits: Allows Adjustment of Methodology selected in the Basic

Data section for a particular Pollutant. For example, if sample data or removal rates are only

available for certain pollutants.

Part VI: HOW TO CALCULATE LIMITS:50 Sampling Data Available (inf, eff, sludge) (Y/N) Y51 Credit present loading of existing sources (Y/N Y52 Adjust for receiving water pollution Y53 Use Observed Overall Removal Rate (Y/N) Y54 Use Observed Primary Removal Rate (Y/N) Y

Part VII: Local Limits for Protecting the POTW Headworks

Comparison of Limits Indicated by the various routes of Pass Through, Inhibition, or Sludge Quality.

Part VII: LOCAL LIMITS FOR COMPLIANCE WITH:57 Acute WQ Standards (in mg/l) 5.955 mg/l58 Chronic WQ Standards (in mg/l) 11.664 mg/l59 HH Limits (in mg/L) NA60 Sludge Application Limits (in mg/l) 7.168 mg/l61 Activated Sludge Inhibition (in mg/l) 61.865 mg/l62 Anaerobic Digestor Inhibition (in mg/l) 5.887 mg/l

Evaluate the Lowest Limit Limits correspond to each criteria. The lowest is limiting,

but confirm applicability. Limits based on inhibition, may be adjusted based upon

research and experience. When limits are high, AKART may dictate lowering to a

reasonable level of treatment Factor of safety included only at the end (rather than in

several assumptions)

Part VIII – Sample Quality Evaluation Tools Used to see if (for conservative pollutants) what is coming in

matches what is going out (effluent and biosolids). Ignores losses to grit/screenings.

Done on a mass basis and relative percentages Part VIII: SAMPLE QUALITY EVALUATION TOOLS:

65 Influent Pollutant Loading (per sampling) 3.128 lbs66 Pollutants in biosolids (per sampling) 3.199 lbs67 Pollutants in effluent (per sampling) 0.2464 lbs68 % Influent load accounted for: (eff/inf) 110.17%69 Current HW Load Implied by Sludge Data: 20.51%

Mass Based Analysis With concentration based limits, industries have

an inherent disincentive to conserve water that can override the cost of water.

Mass based limits provide equal protection when done properly (MAHL is a management tool).

Mass limits ensure that increased flows do not cause the industry to exceed MAHL.

Limiting both Flow & Concentration essentially limits Mass already, main difference is perception.

Mass Based Analysis Tools

This section shows the MAHL and MAIL (absent any reserve).

If using a mass based allocation scheme, you may wish to have each IU and their allocation listed to you can confirm the total is below the MAIL. PART IX: MASS BASED ANALYSIS

70 Limiting MAHL (Dom Load + LL*IUflow) 18.14 lb/d71 Max. Allowable Industrial Loading 15.49 lb/d

Determine the Allocation Scheme “Uniform Allocation” Method (default) “Contributing Flows” can be used by: Estimating total flows for each pollutant Changing flow on a pollutant by pollutant basis

Tiered Limits – Multiply flow by factor to get equivalent flow for the Tier (at SIU level), then adjust limit.

“Mass based limits” require an allocation scheme (accounting) as would conventional pollutants.

“Targeted reduction” is not addressed in NEWLL12

Using Uniform Allocation Method

Part X provides a recap of the limits, and what they are with the proposed reserve included.

Part X: LOCAL LIMIT RECAP: Copper74 Lowest Limit 3.716 mg/l75 With 10.% of MAIL reserved for future IUs 3.38 mg/l76 With 5.% of MAHL reserved for growth 3.498 mg/l77 With both reservations (MAIL and MAHL) 3.148 mg/l78 WA Dangerous Waste Threshold:

How About All Those Other Spreadsheets?

So far, covered “Basic Data” “Sample Data” and “Local Limits” sheets POTW Limits – Table of criteria the POTW must meet (feeds “Local Limits”) Non-Conservative – General notes for developing local limits for pollutants

which are biodegraded or lost to air emissions during the treatment process. Also includes notes for developing limits for pollutants that have some amount of vapor toxicity or explosivity.

Conventional Poll Tool – Tools to manage conventional pollutant capacity. Toxic-Explosive Limits – Table of toxic & explosive chemicals & limits at STP HW_Thresholds – Limits for discharge to POTW under WA State HW laws. WA-OSHA-STDS – Exposure limits for workers in WA State (used in T-E Limit sheet). RREL Henry’s Law Constants – Partitioning coefficients for some substances (do.)

Loading The Program on Computers Insert USB Drive into USB Port Open Windows Explorer Open window for both source and destination Drag and Drop “WDOE_NEWLL” folder from the USB

Drive Open “Excel™” Navigate to & open “NEWLL12-Minnowville.xls” Take a break, Pair Up, begin practical exercise #1

Coconut Crab (Crawling out of Sewer)

PRACTICAL EXERCISE #1 - Minnowville Enter the data provided in the Minnowville Handout, in

the “Basic Data” tab of “NEWll12.Example1.xlsm”. Summary of sampling data has been entered into the

“Sample Data” Tab. Review the output in the POTW Limits Tab assess:

Part 1: Which limits will be reduced by using a technically based methodology? (Current Minnowville limits at row 81)

Part 2: Would any limits exceed the HW Criteria? Part 3: Which limits, are different when adjusting to receiving

water hardness of 32 rather than 60mg/l, and by how much?

Answers to Exercise #1 Part 1: Which limits does the analysis find must be lower than presently in force:

Cadmium (.29 mg/L v. 1.0 mg/L), Copper (3.28 mg/L v. 3.38 mg/L) Cyanide (1.015 mg/L v. 1.2 mg/L) Nickel (2.12 mg/L v. 3.98 mg/L) Silver (0.22 mg/L v. 0.43 mg/L)

Part 2: Chromium limits must be 5.00 mg/L or less to meet 173-303-090(8)(c) WAC

Part 3: Reducing receiving water hardness from 60 mg/L to 32 mg/L changes the

following limits (all other factors remaining constant): Cadmium: 0.29 mg/L reduce to 0.10 mg/L Copper: 3.28 mg/L reduced to 1.25 mg/L Lead: 1.2 mg/L reduced to 0.28 mg/L Silver: 0.22 mg/L reduced to 0.02 mg/L

Exercise #2 – Managing The MAIL

Continuing the Minnowville situation, the mayor wants you to allow a new industry that wants to start discharging 30,000 gpd with copper levels of up to 1.0 mg/l. Existing industries (40,000 gpd) have average pollutant concentrations listed in “Sample Data” tab. Part 1: Find at least two options you might employ that would

allow taking this wastewater? Part 2: Which option would you prefer, and why? Part 3: How would you implement your preferred option? Part 4: Would growth in domestic wastewater flows help?

Exercise #2 Solutions: Evaluation Two existing SIUs have flows of 20,000 gpd each. The two existing SIU’s have average copper levels of 0.115

mg/L, and so discharge about 8.34*.04*0.115 = 0.04 lb/d. (see “AVE Industrial Conc.” at row 10 of “Sample Data” sheet)

Row 71: MAIL = 0.49 lb/d Row 70: MAHL = 0.70 lb/d Requested loading = 0.03MGD * 8.34 * 1.0ppm = .25 lb/d, Loading from all SIU’s (0.07 MGD) @ 1.0ppm = 0.58 lb/d

Exercise #2 Solutions: Part 1 OPTIONS 1. Limit Minnowville’s two existing industries (w / 0.4MGD) to twice their

“normal” concentration (0.23 mg/L), freeing up .41 lb/d of loading (49,000 gpd at 1.0 mg/L). DRAWBACK: Existing Users may protest.

2. Give all IU’s mass based limits, e.g. 0.05 lb/d for existing Users, 0.39 lb/d for the new one. DRAWBACK: Maintenance of the limits.

3. Limit SIU’s to 59,000 gpd from all SIU’s at 1.0 mg/l copper (= the MAIL = 0.49 lb/d total). DRAWBACK: Doesn’t provide the requested limits.

4. Explore NPDES permit options to get a larger mixing zone ratio or to calculate POTW limits using the hardness of effluent and ambient waters (i.e. “mixed hardness”). If effluent hardness is 120, mixed hardness at the acute MZ Boundary = 53.5 DRAWBACK: Slow, difficult

5. Revisit IU monitoring data to see if either is “dilute” for copper. If so, use “contributing flows” method to allocate MAIL only to SIU’s with above domestic concentrations. DRAWBACK: Need data for analysis

Exercise #2 Solutions Part 2: Which option would you prefer, and why? All solutions have their drawbacks, but how much time there is to make a decision may limit the available solutions. Part 3: How would you implement your preferred option? Changes which relax local limits require program modification, specific notice to existing SIU’s, ordinance changes, and AA approval. Part 4: Would growth in domestic wastewater flows help? Yes: In fact, if all other variables remain constant a 10% increase in domestic flow (combined with the .04 MGD new SIU flow) would allow all 0.07 MGD of SIU flows at 1.0 mg/L of copper (absent any safety factor). Adjust “POTW flow” in the “Basic Data” tab to evaluate different scenarios

Exercise #3 – Explosivity & Vapor Toxicity Limits Problem: One of the City of Minnowville’s existing

industries (Clown Shoes Inc.) is changing their processes & sent in a new permit renewal application with the following previously unaddressed pollutant characteristics: • Carbon Disulfide = 1.5 mg/L • Trichloroethylene = 2.1 mg/L • Chloroform = .53 mg/L

Part 1: Do these levels meet Explosivity screening levels? Part 2: Does these levels meet Vapor Toxicity screening

levels? Part 3: What limits would you propose for these pollutants?

Exercise #3 -- Solution Part #1 – NO, Carbon Disulfide Explosivity limit = .5 mg/L Part #2 – NO Part #3 – Limits proposed are as follows:

Carbon Disulfide = .08 mg/L vapor toxicity limit (< 1.5 mg/L) Trichloroethylene = 0.5 mg/L HW Limit (0.7 mg/l vapor Toxicity) Chloroform = .41 mg/L (Vapor toxicity limit) (< .53 mg/L)

NOTE: EPA Methodology promotes the % of exposure limit for several substances should be added to approximate the cumulative toxicity of the mixture. (e.g. if one substance is at 50% of its threshold vapor toxicity concentration, and another at 80%, the total would be at 130% of the permissible limit.)

Exercise #4 – Compatible Pollutants Minnowville’s POTW is required to meet low ammonia limits. The POTW is at 51% of their BOD capacity of 1,670 lb/day

and has blowers capable of satisfying an Actual Oxygen Requirement (AOR) of 3,000 lb/day.

The POTW receives maximum monthly average ammonia loadings of 180 lb/d and MMA flows of 0.4 MGD and needs to know if they can accommodate an IU (a Cold storage company using ammonia as refrigerant) which will need to discharge up to 75lb/day of ammonia.

Can they accommodate this additional ammonia loading and still meet permit limits? How does this change the date they run out of capacity if they are growing at 5% per year?

Given information at “Conventional” Tab Strategies for Managing Capacity:

CURRENT BOD Loading Breakout

Loading in reserve for

SIU's

in reserve for domestic use

Loading in reserve

Loading used by Significant

Industries Loading in use for

Commercial Sources

Loading of current

Domestic Sources

Typical Analysis Methods: Surcharge Rates (Generic backstop

useful for all POTWs) Purchasing Capacity (up to Max rate) Contracts (Useful for larger Users that

need to reduce risks) Permits (Terms & conditions used to set

upper limits, not typically for cost reimbursement)

First come first served (until it’s all gone - not recommended)

Solution to Compatible Pollutant Problem

Since flow capacity is not at issue, Check loading capacity: Oxygen Delivery Capacity of the POTW: = 3,000 lb/d (design value) Present MMA loading of BOD5: = 850 lb/d Conversion Factor lb O2/lb BOD: = 1.25 Total Oxygen used for BOD5 treatment = 1062.5 lb/d Present MMA Ammonia (NH3+4 as N) loading: = 180lb Desired MMA loading of Ammonia = 180+75 lb/d = 255 lb/d Conversion Factor lb O2/lb Ammonia (as N) = 4.6 Total Oxygen used for Ammonia = 4.6 * 255lb/d = 1,173 lb/d Total Oxygen for BOD and Ammonia = 2,235.5 lb/d Percentage of Oxygen Delivery Capacity Used: = 74.5%

ANSWER: Additional Loading can be treated without upgrading the POTW Time until capacity reached at 5% overall growth per year? = 6 years (with new ammonia loading) v.s. 10 years (without additional ammonia)

Years of Capacity Remaining Use iterative approach or Engineering Economic Analysis

Tables. (Iterative approach is simpler to explain): Future Loading = Current Loading (1+growth rate %) 2016 = 2,235.5 lb/d (Current loading with new User) 2017 = 2,235.5 * (1.05) = 2,346.75 lb/d (in 1 year) 2018 = 2,346.75 * (1.05) = 2,464.09 lb/d (in 2 years) 2019 = 2,464.09 * (1.05) = 2,587.29 lb/d (in 3 years) 2020 = 2,587.29 * (1.05) = 2,716.66 lb/d (in 4 years) 2021 = 2,716.66 * (1.05) = 2,852.49 lb/d (in 5 years) 2022 = 2,995.11 (~ 3,000 lb/d) AOR in 6 years Similarly, absent the new User capacity reached in 10 years

AT THIS TIME THERE SHOULD BE NO QUESTIONS