v°/EPA
United States
Environmental Protection
Agency
Municipal Environmental Research
Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/PS2-80-182 Nov. 1980
Project Summary
EXEC/OP Reference Manual:
Version 1.2
Lewis A. Rossman
The original version of EXEC/OP, a
FORTRAN computer program that
synthesizes municipal wastewater
treatment system designs from a
specified list of unit treatment
processes, has been updated.
Revisions have been made in several
of the unit process performance sub-
models to produce results that
conform more closely to accepted
design practices. Modified sets of
program input instructions and unit
process sub-model descriptions have
been prepared. This publication is a
summary of the revised program
reference manual, which can be pur-
chased from the National Technical
Information Service. A computer tape
of the FORTRAN source code is also
available from NTIS.
EXEC/OP is a FORTRAN computer
program that synthesizes municipal
wastewater treatment system designs
from a specified list of unit treatment
processes. It selects the combination of
wastewater and sludge treatment
processes that approximately best
meets a stipulated set of design criteria.
The criteria may refer to system cost,
energy consumption, land utilization, a
subjective index of system desirability,
and effluent quality. The program can
also identify up to the next 40 best
designs relative to the stipulated
criteria.
Since the original description of the
EXEC/OP computer program
(Computer-Aided Synthesis of Waste-
water Treatment and Sludge Disposal
Systems, EPA-600/2-79-158, Decem-
ber 1979), several changes have been
made to the program. Most of these
changes have modified several of the
subroutines that model the perform-
ance of individual unit processes so that
the results conform more closely to
accepted design practice. The input
encoding and output reports for the
program have also undergone some
minor changes. Here is a brief example
of how EXEC/OP can be applied to a
waste treatment design problem.
In using EXEC/OP, a multi-option
flow diagram of the system being
analyzed is first prepared (Figure 1).
Each box in the diagram represents an
individual unit process option (or design
variation of a unit process) for treating
wastewater (stages 1 to 5) and sludge
(stages 6 to 12). For each unit-process
option, the program user supplies
values for design parameters related to
level of treatment, sludge production,
kinetic rate constants, loading rates!
etc. As showrvin Figure 1, the program
pays particular attention to the influ-
ence that return sidestreams from
sludge processing have on system per-
formance and design.
Additional input data to EXEC/OP
consists of influent flow, influent con-
centration values for 17 wastewater
parameters, required effluent discharge
standards for 5 parameters, and values
for 9 economic parameters (e.g., cost
indices, wage rates, energy costs, etc.).
The EXEC/OP program can then
identify those system designs that best
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meet a stipulated set of criteria. (A
system design consists of a choice of
one of the available process options for
each treatment stage of the system.)
The individual design criteria included
in EXEC/OP are listed in Table 1. These
are combined into a weighted, additive
objective function whose value is to be
minimized. The program user supplies a
weighting on the importance of each
criterion. The user can also specify
upper limits (or a lower limit for energy
production) on the individual criteria
that cannot be violated by any feasible
design
Figure 2 illustrates an abridged
output report for an EXEC/OP optimiza-
tion run. The run analyzes the multi-
option flow diagram of Figure 1 for a
typical domestic wastewater required to
meet effluent standards of 30 mg/I on
BOO and suspended solids. For this 10-
2
MGD system, EXEC/OP was instructed
to identify the first five least-total
annual cost designs whose net energy
consumption did not exceed 800
kwh/mu gal. Recovery of usable energy
was valued at 0.04 $/kwh. The first
table in the Figure 1 printout summar-
izes the available process optionswith a
subsequent listing of the five best
designs. Each design listing contains
the following information
1. The objective function value (exact
system value).
2. TheoptionlD number (refer totable
of process alternatives) to the pro-
cess used at each stage of the
System.
3. The quantity of sludge either
produced or handled by each
process.
4. Values for each of the eight design
criteria for each unit process an
for the total system
The final line of the printout indicates
that the amount of computational
resources used by EXEC’OP on this
problem was only 5.3% of that required
to evaluate each of the 2592 possible
system configurations one at a time.
The processing time for this example
was 55.86 seconds on a DEC PDP- 11 /70
computer.
EXEC/OP can also be run in another
computational mode that will produce a
detailed performance report for a parti-
cular system design specified by the
user, In addition to the information cited
above, the detaIled output report would
include values for those unit process
design specifications computed by the
program (e.g. equipment size and
operating capacity) and the composition
of all waste streams in the system.
Table 1. EXEC/OP Design Criteria
1. Total initial construction cost
(including equipment, materials,
piping, and instrumentation),
million dollars.
2. Total annual operation and main-
(enance cost (including labor
materials, supplies, chemicals, and
energy), S/million gallons ol
system in fluent.
3. Total equivalent annual life cycle
cost (amortized life cycle construc-
tion costs plus annual operaion
and maintenance costs) S/mi//ion
gallons of system in fluent.
4. Total gross energy consumption
(direct energy consumed by a/l
equipment and operations) kwh/
million gallons of system in fluent.
5. Total gross energy production
(usable energy extracted from
treatment by-products such as
digester gas and incinerator waste
heat), kwh/million gallons of
system in fluent.
6. Total net energy consumption (dif-
ference between criteria 4 and 5),
kwh/mi/lion gallons of system
in fluent.
7. Total land area utilization (only
considers those processes with
significant land requirements such
as drying beds, trickling filters, and
land disposal of sludges), acres.
8. System undesirability index.
3
4 5
Land Spreadin9j .
12
Landfil/ing J J Vacuum
Filtration
Null
Process
Incineration
Figure 1. Mu/ti-option flow diagram for sample design problem.
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** * ** * * * * ** *
* *
* EXEC/OF’ *
* *
* VERSION 1.2 *
* *
EXECUTIVE PROGRAM
(OPTIMIZATION VERSION)
FOR
PRELIMINARY SYNTHESIS OF WASTE TREATMENT SYSTEMS
U.S. ENVIRONMENTAL PROTECTION AGENCY
MUNICIPAL ENVIRONMENTAL RESEARCH LAE4ORATORY
SYSTEMS ANt’ ECONOMIC ANALYSIS SECTION
CINCINNATI, OHIO 45268
* *
* SAMPLE 10 MGI’ SYSTEM -- 30/30 SIt’S., JUNE 79 PRICES *
* *
PROCESS ALTERNATIVES
EXACT SYSTEM VALUE
236. 916
OF’TION
PROCESS
STAGE SIIIESTREAM
ND.
NO.
NO, t ’ESTINAlION REMARKS
1
15
1 8 RAW WASTEWATER PUMPING (30 FT. HEAD>
2
1
2 8 PRELIMINARY TREATMENT
3
2
3 8 PRIMARY SEFIIMENTATION (50% TSS REMOVAL)
4
2
3 8 PRIMARY SEDIMENTATION (60% 153 REMOVAL)
5
3
4 6 ACTIVATED SLUDGE ( )ILVSS = 2500. 30% RECYCLEPOIFFUSED AERATION)
6
3
4 6 ACTIVATED SLUDGE ( MLVSS 2500 30% RECYCLEPMECHANICAL AERATION)
7
11
4 4 TRICKLING FILTER (20 MGtI/AC LOADING RECIRC. RATIO 3)
8
12
5 6 CHLORINATION (10 MG/L FOR 30 NIH.)
9
13
6 3 FLOTATION THICKENING (TO 5% SOLIDS)
20
0
6 3 NULL PROCESS
24
0
7 3 NULL F’ROCESS
10
18
7 3 AEROBIC DIGESTION ( FOR 18 DAYS
11
8
8 3 GRAVITY THICKENING (TO 8 3, OR 6% SOLIDS DEFENDING ON SLUDGE TYPE)
20
0
8 3 NULL FROCESSS
12
6
9 3 ANAEROBIC [ ‘IGESTION (FOR 15 DAYS WITH GAS RECOVERY BY IC ENGINE)
13
23
9 3 LIME STABILIZATION (400 LB/TON LIME DOSAGE)
20
0
9 3 NULL PROCESS
11
8
10 3 GRAVITY THICKENING (TO 8, 3, OR 6 % DEFENDING ON SLUDGE TYPE)
20
0
10 3 NULL PROCESS
14
9
10 3 ELUTRIATION (3U UASHWATER RATIO>
15
7
11 3 VACUUM FILTRATION (LIEWATERING RATE = 10 - 17.5 GPH/SO FT)
20
0
11 3 NULL PROCESS
16
22
12 3 LANOFILLING (S MILE HAUL)
17
22
12 3 LANDSPREADING (10 MILE HAUL, 600 LB/AC/YR N LIMIT)
18
14
12 3 INCINERATION (2 UNITS, 2 LB/HR/SQ FT LOADING)
DESIGN 1
STAGE
PROCESS
SLUDGE CONSTR ANN 05)1 TOTAL ANN ENER USE ENER PROD NET ENER LAND REQO
UNDESIRE—
NO.
OPTION
TONS/DAY COST MS COST S/MG COST S/MG KWH/MG KWH/MG KWH/MG ACRES
ABILITY
1
1
0.00 0.8878 9.09 32.05 141,37 0.00 141.37 0.00
0.00
2
2
0.00 0.2701 8.27 15.26 5.22 0.00 5.22 0.00
0,00
3
3
5.62 0.4740 10.35 22,61 6.80 0,00 6.80 0.00
0.00
4
7
2.73 1.7948 20.86 67.27 172.02 0.00 172.02 0.50
3.00
5
8
0.00 0,2797 19.06 26.29 22.80 0.00 22.80 0.00
0.00
8
11
8.35 0.1443 1.86 5.59 1.69 0.00 1,69 0.00
0.00
9
13
7.52 0.0892 11,50 13.81 3.13 0.00 3.13 0.00
2.00
12
17
9.03 0,6942 29.40 54.04 107.45 0.00 107.45 428.07
8.00
SYSTEM
VALUES
— — 8.35 4,63 110.39 236,92 460.47 0.00 460.4? 428.5?
13.00
PRIMARY AND SECONDARY SLUDGES MIXED AT STAGE 8
Figure 2. EXEC/OP output for sample design optimiza(ion.
3
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Figure 2. (conf’d)
PRIMARY AND SECONDARY SLUDGES MIXED AT STAGE 8
t’ESIGN 4
EXACT SYSTEM VALUE
240 • 028
PRIMARY AND SECONDARY SLUDGES MIXED AT STAGE 8
DESIGN 2
EXACT SYSTEM VALUE
247.375
CONSTR
COST MS
0, 8878
0, 2701
0 • 4724
I • 7986
0.2798
1 • 2358
0.1242
0.6193
5,69
ANN O M
COST S/MG
9 • 09
8 • 27
10.29
20,89
19,07
15.89
1 .63
21 .43
106,54
TOTAL ANN
COST S/MG
32.05
15.26
22.50
67.40
26.31
47.84
4.84
44.04
- 260.23
STAGE
PROCESS
SLUDGE
CONSTR ANN OEM TOTAL ANN ENER USE ENER PROD
NET ENER
LANtI PLOD
UNDESIRE—
NO.
OPTION
TONS/DAY
COST MS COST s/MG COST S/MG KWH/MG KWH/MG
KWH/MG
ACRES
ABILITY
1
1
0.00
0,8878 9.09 32.05 141.37 0.00
141.37
0.00
0.00
2
2
0.00
0,2701 8.27 15.26 5.22 0.00
5.22
0,00
0.00
3
4
6.70
0.6042 12.24 27.86 8.69 0.00
8.69
0.00
0.00
4
7
2.15
1.7086 20.21 64.40 156.11 0.00
156.11
0.50
3.00
5
8
0.00
0,2796 19,05 26.28 22,79 0.00
22.79
0,00
0.00
8
11
8.94
0,1494 1.92 5.79 1,7 0.00
1.75
0.00
0.00
9
13
8.04
0,0933 12.05 14.46 3,28 0.00
3.78
0.00
2,00
12
17
9.66
0.7109 31.18 56.28 114.38 0.00
114.38
446.03
8.00
SYSTEM
VALUES
8.94
4.70 114.02 242.38 453,60 0.00
453.60
446.53
13.00
PRIMARY ANt ’ SECONDARY SLUDGES MIXED AT STAGE 8
[ tESIGN 3
EXACT SYSTEM VALUE 237.942
STAGE
PROCESS
SLUDGE
NET ENER
LAND REOD
UN [ ’ESIRE—
NO.
OPTION
TONS/DAY
KWH/MG
ACRES
ABILITY
1
1
0.00
141,37
0.00
0.00
2
2
0.00
5.22
0.00
0.00
3
3
5.51
6.80
0.00
0.00
4
7
2.78
172.64
0.50
3,00
5
8
0.00
22.82
0.00
0.OC
9
12
8,29
—138.78
0,00
7.00
10
11
6.12
1.42
0.00
0.00
12
17
5.51
80.86
34 i, 8
8.00
SYSTEM
VALUES
8,29
—- 292,35
346.48
18,00
‘STAGE
PROCESS
SLUDGE
CONSTR ANN O*M TOTAL ANN ENER USE ENER PROD
NET ENER
LANE’ PEOn
UNDESIRE—
NO.
OPTION
TONS/DAY
COST MS COST S/MG COST S/MG KWH/MG KWH/MG
KWH/MG
ACRES
ABILITY
- 1
.00
0.8878 9.09 32.05 141,37 0,00
141.37
0.00
0,00
2
2
0.00
0.2701 8.27 15.26 5,22 0.00
5,22
0.00
0.00
3
3
5.95
0.4793 10.53 22.93 6,80 0.00
6,80
0.00
0 oo
4
7
2,97
1.8147 21,01 67.94 175,61 0.00
175.61
0.50
3.00
5
8
0.00
0.2798 19.07 26.31 22.82 0.00
22.82
0.00
0.00
8
11
8.92
0.1493 1.92 5.78 1.75 0.00
1.75
0.00
0.00
9
12
8,03
1.0752 14.56 42.37 291.21 533.89
—242.68
0.00
7.00
10
11
5,95
0.1226 1.61 4.78 1.40 0.00
1.40
0.00
0.00
12
17
5.35
0.6351 20.93 43.98 78.82 0.00
78.82
372.29
8.00
SYSTEM
VALUES
8.92
5.71 106,99 261.38 725.01 533.89
191.12
372.79
18.00
ENER USE
KWH/MG
141 .37
5,22
6,80
172.64
22.82
418.54
1.42
80,86
849,68
ENER PROL’
KWH/MG
0.00
0.00
0.00
0.00
0.00
557,33
0.00
0.00
557,33
4
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DESIGN 5
EXACT SYSTEM VALUE
140,935
PRIMARY AND SECONDARY SLUDGES MIXED AT STAGE 8
BEST DESIGN IS NUMBER 1
SEARCH EFFORT WAS
5,2653% OF TOTAL ENUMERATION
Figure 2. (cont’d)
5
STAGE
NO.
FROCESS
OPTION
SLUDGE
TONS/DAY
CONSTR
COST MS
ANN
COST
0th
s/MG
TOTAL ANN
COST S/MG
ENER USE
KWH/MG
ENER PROF
KWH/MG
NET ENER
KWH/MG
LAND REGE’
ACRES
UNDESIRE—
ABILITY
1
2
3
4
5
8
9
12
1
2
3
7
8
11
12
17
0.00
0.00
5,62
2.73
0.00
8.35
7.52
5.51
0.8878
0.2701
0,4740
1,7948
0.2797
0.1443
1,0618
0.6942
9,09
0,27
10,35
20.86
19.06
1.88
14,44
25.88
32.05
15.26
22.61
67.27
26.29
5.59
41.90
50.50
141.37
5.22
6.80
172.02
22.80
1.69
279.95
107.45
0.00
0.00
0.00
0.00
0.00
0.00
513.39
0.00
SYSTEM
VALUES
8,35
5.61
109.79
261.47
737.30
513.39
223,90
428.57
18.00
141,37
5.22
6.80
172.02
22.80
1.89
—233.44
107.45
0.00
0.00
0.00
0 • 50
0.00
0.00
0,00
428,07
0,00
0.00
0,00
3.00
0,00
0,00
7.00
8.00
The EPA author of this Project Summary was Lewis A. Rossman (see below).
The complete report and/or magnetic tape, entitled “EXEC/OP Reference
Manual: Version 1.2,” (Report Order No. PB 81 104176; Cost: $11.00;
Magnetic Tape Order No. PB 81-104168; Cost: $360.00, costs subject to
change) will be available from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
The EPA author can be contacted at:
Municipal Environmental Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, Ok 45268
US 0000RNMENT PRINTING OFFICE 980 .757—O64/O &j
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