Process Loading Calculations

GRCA:
Summarizing & Reporting Performance
Measures
29 Nov. 2012
Purpose:
To initiate voluntary annual reporting of
WWTP data.

GRCA:
2012 Plant Reporting:
Workshop Approach:
• Describe suggested approach (What?,
How?) for voluntary 2012 plant reporting;
• Practise associated skills (graph review &
calculations);
• Explain why we wish to initiate voluntary
watershed-wide reporting;
• Seek your advice on how to make the
process effective (afternoon workshops).

GRCA:
Reporting Spreadsheet Review

What’s wrong with this picture?

What’s wrong with this picture?
Don’t trend together

What’s wrong with this picture?
Missing data

Raw Sewage CBOD 5 ?
• The BOD 5 test measures the amount of oxygen
removed in a sample bottle at the end of 5-day
for:
– Carbon removal;
– Ammonia removal.
• In the cBOD 5 test, an inhibitor (a chemical) is
added to prevent nitrification (ammonia removal);
• The cBOD5 test is intended only for treated
effluents, not for raw sewage or primary effluent;
• cBOD5 results for raw sewage underestimates
BOD 5 by:
– ~ 20% for purely domestic wastewaters;
– > 20% for significant industrial wastewaters.

Raw Sewage CBOD5? (con’t)
• However: Many current CofAs
specify cBOD 5 for measuring raw
sewage;
• In such cases, BOD 5 should also be
measured to quantify true plant
loading;
• For GRCA annual reporting, raw
BOD 5 values will be estimated as
120% of cBOD5 (in the absence of
other data).

Process Loading
“Process loading” Rate at which a substance is
added (to plant or receiver):
– Loading = Flow x Concentration (Units in kg/d)
– Loading Plant Capacity & Sludge production
– Grand River Impact on health of river
Steps:
1. Convert concentrations from mg/L to kg/m 3
BOD 5 = 200 mg/L
= 200 mg/L* 1000 L/m 3 /(1000 mg/g* 1000 g/kg)
= 200/1000 kg/m 3
= 0.200 kg/m 3
Tip:
To go from concentration in mg/L to kg/m 3 , move the decimal
three places to the left:
200. 200. 0.200

Practice Session
Concentration
(mg/L)
157.
Concentration
(kg/m 3 )
3,200.
91.
7.

Process Loading
Steps (con’t):
2. Multiply Flow in m 3 /d by Concentration in kg/m 3
BOD 5 = 200 mg/L = 0.200 kg/m 3
Flow = 2,000 m 3 /d
BOD 5 Loading
= Flow x Concentration
= 2000 m 3 /d * 0.200 kg/m 3
= 400 kg/d

Practice Session
Flow Concentration Loading
(kg/d)
1,000 m 3 /d 2 kg/m 3
500 m 3 /d 4 kg/m 3
2,000 m 3 /d 3,000. mg/L
100 m 3 /d 12. mg/L

Questions?
• If the brewery in the town closes, what will
happens to BOD 5 loading to the plant?
• If the plant installs a centrifuge and the centrate
is returned to the head of the plant, what happens
to:
> BOD 5 loading?
> Oxygen requirements?
• During a storm at a town with a leaky sewer
system, what happens to:
‣ Flow to the plant?
‣ BOD 5 concentration?
‣ BOD 5 loading?
• What is the likely impact of a sewer use bylaw on
plant BOD 5 loading?

PROCESS LOADING EVALUATION
(12-months of Data)
Calculate/Compare per Capita flows and Load:
‣ 370 L/d per person (GRCA 2010);
‣ 80 g/d BOD 5 per person;
‣ 90 g/d TSS per person;
‣ 13 g/d TKN per person.
Calculate ratios:
‣ Peak Day/Annual Avg Flow: 2.5-3.5
‣ TSS/BOD 5 : 0.8 – 1.2
‣ TKN/BOD 5 : 0.1-0.2

Exercise
Background:
• Plant is a 700 m 3 /d extended aeration package plant
• Typically staffed less than 4 hours per day
Data (for 12-month period):
• Population served = 1065
• Annual average plant flow = 573 m 3 /d
• Peak day flow = 2,979 m 3 /d
• Average raw BOD 5 = 98 mg/L = _____ kg/m 3
• Average raw TSS = 142 mg/L
Reference Information:
• Per Capita Flows = 370 L/person.d
• Ratio: Peak Day Flow: Annual Average Flow = 2.5 – 3.5
• Per Capita BOD5 Loading = 80 g BOD 5 /person.d
• Ratio: TSS:BOD5 = 0.8-1.2
• 1 m 3 = 1000 L
• 1 kg = 1000 g

Questions?
1.) Calculate per capita flow to plant (in
L/person.d) and compare to typical:
Per capita flow (L/person.d)
= flow (m 3 /d)x 1000 L/m 3 / population
= 573 m 3 /d x 1000 L/m 3 / 1065 persons
= 538 L/person.d
Typical = 370 L/person.d
Therefore, reported plant flows are greater
than typical

Questions?
2.) What percentage is the annual average
flow of the plant’s nominal design flow:
Percent of nominal design flow
= annual average flow/ nominal design flow
*100%
= 573 m 3 /d / 700 m 3 /d * 100%
= 82%

Questions?
3.) Calculate the ratio of peak day flow to
annual average flow & compare to typical:
Peak day flow: annual average flow
= peak day flow/ annual average flow
= 2,979 m 3 /d / 573 m 3 /d
= 5.2
Typical = 3.5-4.5
Therefore, reported ratio is greater than
typical

Questions?
4.) Calculate average per capita BOD 5 loading (in
g/person.d) to the plant and compare to typical
Per capita BOD 5 loading (kg/person.d)
= flow (m 3 /d) x concentration (kg/m 3 )/population
= 573 m 3 /d x 0.098 kg/m 3 / 1065 persons
= 0.053 kg BOD 5 /person.d
Per capita BOD 5 loading (g/person.d)
= 0.053 kg BOD 5 /person.d x 1000 g/kg
= 53 g BOD 5 /person.d
Typical = 70 – 90 g BOD 5 /d
Therefore, plant’s per capita BOD 5 loading is less
than typical

Questions?
5.) Based on the population and the typical per capita
BOD 5 loading, estimate the raw BOD 5 ( in mg/L).
Estimated BOD 5 loading (kg/d) =
= Population x Per Capita BOD 5 loading (g/person.d) /1000 (g/kg)
= 1065 persons x 80 g/person day /1000 g/kg
= 85.2 kg/d BOD 5
Flow = 574 m 3 /d
Estimated Concentration (kg/m 3 )
= Estimated load (kg/d) / flow (m 3 /d)
= 85.2 kg/d / 573 m 3 /d = 0.149 kg/m 3
Estimated Concentration (mg/L)
= Estimated concentration (kg/m 3 ) x 1000 (mg/L/kg/m 3 )
= 0.149 (kg/m 3 ) x 1000 (mg/L/kg/m 3)
= 149 mg/L BOD 5

Questions?
6.) Calculate the ratio of raw TSS
concentration to the raw BOD5
concentration:
TSS: BOD5
= TSS/ BOD5
= 142 / 98 m 3 /d
= 1.4
Typical = 0.8-1.2
Therefore, reported ratio is greater than
typical

SUMMARY
Parameter Value Typical
Per capita flow
(L/person.d)
% Nominal Design
Peak: Avg Flow
Per Capital BOD5
(g/d per person)
TSS: BOD5

SUMMARY
Parameter Value Typical
Per capita flow
(L/person.d)
538 370
% Nominal Design 82% --
Peak: Avg Flow 5.2 3.5-4.5
Per Capital BOD5
(g/d per person)
53 80
TSS: BOD5 1.4 0.8-1.2
At Your Table:
• What are your preliminary conclusions about this plant?
• What additional information would you seek to help verify your
preliminary conclusions?

Suggested Response
Preliminary Conclusions:
• The plant is subject to I/I as per capita flows and ratio
of peak: average flows are high.
• The raw BOD5 concentrations appear to be low as
the per capita BOD5 loading is low & the TSS:BOD5
ratio is high.
Follow-up information:
I/I:
• Review graph of monthly average and peak flows
• Water production per capita.
• Does the town have an I/I program?
• Does the town experience basement flooding?
• How old is the sewer system?

Low raw BOD5:
Suggested Response (con’t)
• What are the raw TKN concentrations and hence the
TKN/BOD 5 ratio?
• How many samples are collected per month?
• How are the raw samples collected (grab vs
composite vs. flow proportioned composite), how
often, and when?
• Who analyzes the samples and how are the samples
preserved?

Approach Summary
For each facility for the 12-month period (Jan. –
Dec. 2012):
• Input data into spreadsheet provided
(background, flows, concentrations);
• Review the graphs (missing data, trends,
compliance status, etc.)
• Prepare “process loading evaluation” calculations
& input in spreadsheet;
• Compare to typical values;
• Review with staff internally;
• E-mail Mark Anderson the completed spreadsheet
for compilation into a watershed roll-up

Why do this?
• To develop & practise skills in summarizing,
displaying & interpreting data;
• To demonstrate how to upgrade reporting practices;
• To quantify year-to-year changes loading to Grand
River;
• To identify issues for discussion with MOE (i.e. raw
cBOD 5 ) ;
• To develop approaches which could serve a model
for other areas;
• To help prioritize plants for follow-up optimization
activities.

Along the way:
Something really wild about these
calculations. Should we give Mark a call?

Comments or Questions?