Summary
This experiment investigates wastewater treatment optimization. Plackett-Burman screening of 7 factors (5 continuous, 2 ordinal) for BOD removal and sludge volume in wastewater treatment.
The design varies 7 factors: ph level (pH), ranging from 6 to 9, retention time (hours), ranging from 4 to 12, aeration rate (L/min), ranging from 2 to 6, flocculant dose (mg/L), ranging from 10 to 50, temperature (C), ranging from 15 to 30, mixing intensity, ranging from low to high, and filter grade, ranging from coarse to fine. The goal is to optimize 2 responses: bod removal (%) (maximize) and sludge volume (mL/L) (minimize). Fixed conditions held constant across all runs include plant capacity = 10000 m3/day.
A Plackett-Burman screening design was used to efficiently test 7 factors in only 8 runs. This design assumes interactions are negligible and focuses on identifying the most influential main effects.
Key Findings
For bod removal, the most influential factors were ph level (30.0%), flocculant dose (16.0%), mixing intensity (15.6%). The best observed value was 96.0 (at ph level = 9, retention time = 4, aeration rate = 2).
For sludge volume, the most influential factors were aeration rate (40.0%), mixing intensity (36.8%), retention time (9.8%). The best observed value was 86.0 (at ph level = 9, retention time = 12, aeration rate = 6).
Recommended Next Steps
- Follow up with a response surface design (CCD or Box-Behnken) on the top 3–4 factors to model curvature and find the true optimum.
- Consider whether any fixed factors should be varied in a future study.
- The screening results can guide factor reduction — drop factors contributing less than 5% and re-run with a smaller, more focused design.
Experimental Setup
Factors
| Factor | Low | High | Unit |
ph_level | 6 | 9 | pH |
retention_time | 4 | 12 | hours |
aeration_rate | 2 | 6 | L/min |
flocculant_dose | 10 | 50 | mg/L |
temperature | 15 | 30 | C |
mixing_intensity | low | high | |
filter_grade | coarse | fine | |
Fixed: plant_capacity = 10000 m3/day
Responses
| Response | Direction | Unit |
bod_removal | ↑ maximize | % |
sludge_volume | ↓ minimize | mL/L |
Configuration
{
"metadata": {
"name": "Wastewater Treatment Optimization",
"description": "Plackett-Burman screening of 7 factors (5 continuous, 2 ordinal) for BOD removal and sludge volume in wastewater treatment"
},
"factors": [
{
"name": "ph_level",
"levels": [
"6",
"9"
],
"type": "continuous",
"unit": "pH"
},
{
"name": "retention_time",
"levels": [
"4",
"12"
],
"type": "continuous",
"unit": "hours"
},
{
"name": "aeration_rate",
"levels": [
"2",
"6"
],
"type": "continuous",
"unit": "L/min"
},
{
"name": "flocculant_dose",
"levels": [
"10",
"50"
],
"type": "continuous",
"unit": "mg/L"
},
{
"name": "temperature",
"levels": [
"15",
"30"
],
"type": "continuous",
"unit": "C"
},
{
"name": "mixing_intensity",
"levels": [
"low",
"high"
],
"type": "ordinal",
"unit": ""
},
{
"name": "filter_grade",
"levels": [
"coarse",
"fine"
],
"type": "ordinal",
"unit": ""
}
],
"fixed_factors": {
"plant_capacity": "10000 m3/day"
},
"responses": [
{
"name": "bod_removal",
"optimize": "maximize",
"unit": "%"
},
{
"name": "sludge_volume",
"optimize": "minimize",
"unit": "mL/L"
}
],
"settings": {
"operation": "plackett_burman",
"test_script": "use_cases/309_wastewater_treatment/sim.sh"
}
}
Experimental Matrix
The Plackett-Burman Design produces 8 runs. Each row is one experiment with specific factor settings.
| Run | ph_level | retention_time | aeration_rate | flocculant_dose | temperature | mixing_intensity | filter_grade |
| 1 | 9 | 12 | 6 | 10 | 15 | low | coarse |
| 2 | 6 | 4 | 6 | 50 | 15 | low | fine |
| 3 | 6 | 12 | 2 | 50 | 15 | high | coarse |
| 4 | 9 | 12 | 6 | 50 | 30 | high | fine |
| 5 | 6 | 12 | 2 | 10 | 30 | low | fine |
| 6 | 9 | 4 | 2 | 50 | 30 | low | coarse |
| 7 | 6 | 4 | 6 | 10 | 30 | high | coarse |
| 8 | 9 | 4 | 2 | 10 | 15 | high | fine |
Step-by-Step Workflow
1
Preview the design
$ doe info --config use_cases/309_wastewater_treatment/config.json
2
Generate the runner script
$ doe generate --config use_cases/309_wastewater_treatment/config.json \
--output use_cases/309_wastewater_treatment/results/run.sh --seed 42
3
Execute the experiments
$ bash use_cases/309_wastewater_treatment/results/run.sh
4
Analyze results
$ doe analyze --config use_cases/309_wastewater_treatment/config.json
5
Get optimization recommendations
$ doe optimize --config use_cases/309_wastewater_treatment/config.json
6
Multi-objective optimization
With 2 competing responses, use --multi to find the best compromise via Derringer–Suich desirability.
$ doe optimize --config use_cases/309_wastewater_treatment/config.json --multi
7
Generate the HTML report
$ doe report --config use_cases/309_wastewater_treatment/config.json \
--output use_cases/309_wastewater_treatment/results/report.html
Features Exercised
| Feature | Value |
| Design type | plackett_burman |
| Factor types | continuous (all 5) |
| Arg style | double-dash |
| Responses | 2 (bod_removal ↑, sludge_volume ↓) |
| Total runs | 8 |
Analysis Results
Generated from actual experiment runs using the DOE Helper Tool.
Response: bod_removal
Top factors: ph_level (30.0%), flocculant_dose (16.0%), mixing_intensity (15.6%).
ANOVA
| Source | DF | SS | MS | F | p-value |
| Source | DF | SS | MS | F | p-value |
| ph_level | 1 | 110.2612 | 110.2612 | 2.993 | 0.1177 |
| retention_time | 1 | 8.2013 | 8.2013 | 0.223 | 0.6483 |
| aeration_rate | 1 | 22.1113 | 22.1113 | 0.600 | 0.4584 |
| flocculant_dose | 1 | 31.6012 | 31.6012 | 0.858 | 0.3785 |
| temperature | 1 | 27.0112 | 27.0112 | 0.733 | 0.4141 |
| mixing_intensity | 1 | 30.0312 | 30.0312 | 0.815 | 0.3901 |
| filter_grade | 1 | 0.4512 | 0.4512 | 0.012 | 0.9143 |
| ph_level*retention_time | 1 | 22.1113 | 22.1113 | 0.600 | 0.4584 |
| ph_level*aeration_rate | 1 | 8.2013 | 8.2013 | 0.223 | 0.6483 |
| ph_level*flocculant_dose | 1 | 27.0113 | 27.0113 | 0.733 | 0.4141 |
| ph_level*temperature | 1 | 31.6013 | 31.6013 | 0.858 | 0.3785 |
| ph_level*mixing_intensity | 1 | 0.4513 | 0.4513 | 0.012 | 0.9143 |
| ph_level*filter_grade | 1 | 30.0313 | 30.0313 | 0.815 | 0.3901 |
| retention_time*aeration_rate | 1 | 110.2612 | 110.2612 | 2.993 | 0.1177 |
| retention_time*flocculant_dose | 1 | 30.0312 | 30.0312 | 0.815 | 0.3901 |
| retention_time*temperature | 1 | 0.4513 | 0.4513 | 0.012 | 0.9143 |
| retention_time*mixing_intensity | 1 | 31.6012 | 31.6012 | 0.858 | 0.3785 |
| retention_time*filter_grade | 1 | 27.0112 | 27.0112 | 0.733 | 0.4141 |
| aeration_rate*flocculant_dose | 1 | 0.4513 | 0.4513 | 0.012 | 0.9143 |
| aeration_rate*temperature | 1 | 30.0313 | 30.0313 | 0.815 | 0.3901 |
| aeration_rate*mixing_intensity | 1 | 27.0112 | 27.0112 | 0.733 | 0.4141 |
| aeration_rate*filter_grade | 1 | 31.6012 | 31.6012 | 0.858 | 0.3785 |
| flocculant_dose*temperature | 1 | 110.2613 | 110.2613 | 2.993 | 0.1177 |
| flocculant_dose*mixing_intensity | 1 | 8.2013 | 8.2013 | 0.223 | 0.6483 |
| flocculant_dose*filter_grade | 1 | 22.1113 | 22.1113 | 0.600 | 0.4584 |
| temperature*mixing_intensity | 1 | 22.1113 | 22.1113 | 0.600 | 0.4584 |
| temperature*filter_grade | 1 | 8.2013 | 8.2013 | 0.223 | 0.6483 |
| mixing_intensity*filter_grade | 1 | 110.2613 | 110.2613 | 2.993 | 0.1177 |
| Error | (Lenth | PSE) | 9 | 331.5769 | 36.8419 |
| Total | 7 | 229.6687 | 32.8098 | | |
Response: sludge_volume
Top factors: aeration_rate (40.0%), mixing_intensity (36.8%), retention_time (9.8%).
ANOVA
| Source | DF | SS | MS | F | p-value |
| Source | DF | SS | MS | F | p-value |
| ph_level | 1 | 0.5000 | 0.5000 | 0.007 | 0.9367 |
| retention_time | 1 | 392.0000 | 392.0000 | 5.227 | 0.0481 |
| aeration_rate | 1 | 6498.0000 | 6498.0000 | 86.640 | 0.0000 |
| flocculant_dose | 1 | 162.0000 | 162.0000 | 2.160 | 0.1757 |
| temperature | 1 | 50.0000 | 50.0000 | 0.667 | 0.4353 |
| mixing_intensity | 1 | 5512.5000 | 5512.5000 | 73.500 | 0.0000 |
| filter_grade | 1 | 40.5000 | 40.5000 | 0.540 | 0.4811 |
| ph_level*retention_time | 1 | 6498.0000 | 6498.0000 | 86.640 | 0.0000 |
| ph_level*aeration_rate | 1 | 392.0000 | 392.0000 | 5.227 | 0.0481 |
| ph_level*flocculant_dose | 1 | 50.0000 | 50.0000 | 0.667 | 0.4353 |
| ph_level*temperature | 1 | 162.0000 | 162.0000 | 2.160 | 0.1757 |
| ph_level*mixing_intensity | 1 | 40.5000 | 40.5000 | 0.540 | 0.4811 |
| ph_level*filter_grade | 1 | 5512.5000 | 5512.5000 | 73.500 | 0.0000 |
| retention_time*aeration_rate | 1 | 0.5000 | 0.5000 | 0.007 | 0.9367 |
| retention_time*flocculant_dose | 1 | 5512.5000 | 5512.5000 | 73.500 | 0.0000 |
| retention_time*temperature | 1 | 40.5000 | 40.5000 | 0.540 | 0.4811 |
| retention_time*mixing_intensity | 1 | 162.0000 | 162.0000 | 2.160 | 0.1757 |
| retention_time*filter_grade | 1 | 50.0000 | 50.0000 | 0.667 | 0.4353 |
| aeration_rate*flocculant_dose | 1 | 40.5000 | 40.5000 | 0.540 | 0.4811 |
| aeration_rate*temperature | 1 | 5512.5000 | 5512.5000 | 73.500 | 0.0000 |
| aeration_rate*mixing_intensity | 1 | 50.0000 | 50.0000 | 0.667 | 0.4353 |
| aeration_rate*filter_grade | 1 | 162.0000 | 162.0000 | 2.160 | 0.1757 |
| flocculant_dose*temperature | 1 | 0.5000 | 0.5000 | 0.007 | 0.9367 |
| flocculant_dose*mixing_intensity | 1 | 392.0000 | 392.0000 | 5.227 | 0.0481 |
| flocculant_dose*filter_grade | 1 | 6498.0000 | 6498.0000 | 86.640 | 0.0000 |
| temperature*mixing_intensity | 1 | 6498.0000 | 6498.0000 | 86.640 | 0.0000 |
| temperature*filter_grade | 1 | 392.0000 | 392.0000 | 5.227 | 0.0481 |
| mixing_intensity*filter_grade | 1 | 0.5000 | 0.5000 | 0.007 | 0.9367 |
| Error | (Lenth | PSE) | 9 | 675.0000 | 75.0000 |
| Total | 7 | 12655.5000 | 1807.9286 | | |
Multi-Objective Optimization
When responses compete, Derringer–Suich desirability finds the best compromise.
Each response is scaled to a 0–1 desirability, then combined via a weighted geometric mean.
Overall Desirability
D = 0.6791
Per-Response Desirability
| Response | Weight | Desirability | Predicted | Dir |
bod_removal |
2.0 |
|
91.31 0.7253 91.31 % |
↑ |
sludge_volume |
1.0 |
|
136.59 0.5952 136.59 mL/L |
↓ |
Recommended Settings
| Factor | Value |
ph_level | 6.236 pH |
retention_time | 4.875 hours |
aeration_rate | 5.735 L/min |
flocculant_dose | 16.37 mg/L |
temperature | 17.96 C |
mixing_intensity | low |
filter_grade | coarse |
Source: from RSM model prediction
Trade-off Summary
Sacrifice = how much worse than single-objective best.
| Response | Predicted | Best Observed | Sacrifice |
sludge_volume | 136.59 | 86.00 | +50.59 |
Top 3 Runs by Desirability
| Run | D | Factor Settings |
| #4 | 0.4636 | ph_level=6, retention_time=4, aeration_rate=6, flocculant_dose=10, temperature=30, mixing_intensity=high, filter_grade=coarse |
| #2 | 0.4207 | ph_level=6, retention_time=4, aeration_rate=6, flocculant_dose=50, temperature=15, mixing_intensity=low, filter_grade=fine |
Model Quality
| Response | R² | Type |
sludge_volume | 1.0000 | linear |
Full Multi-Objective Output
============================================================
MULTI-OBJECTIVE OPTIMIZATION
Method: Derringer-Suich Desirability Function
============================================================
Overall desirability: D = 0.6791
Response Weight Desirability Predicted Direction
---------------------------------------------------------------------
bod_removal 2.0 0.7253 91.31 % ↑
sludge_volume 1.0 0.5952 136.59 mL/L ↓
Recommended settings:
ph_level = 6.236 pH
retention_time = 4.875 hours
aeration_rate = 5.735 L/min
flocculant_dose = 16.37 mg/L
temperature = 17.96 C
mixing_intensity = low
filter_grade = coarse
(from RSM model prediction)
Trade-off summary:
bod_removal: 91.31 (best observed: 96.00, sacrifice: +4.69)
sludge_volume: 136.59 (best observed: 86.00, sacrifice: +50.59)
Model quality:
bod_removal: R² = 1.0000 (linear)
sludge_volume: R² = 1.0000 (linear)
Top 3 observed runs by overall desirability:
1. Run #5 (D=0.5587): ph_level=9, retention_time=12, aeration_rate=6, flocculant_dose=10, temperature=15, mixing_intensity=low, filter_grade=coarse
2. Run #4 (D=0.4636): ph_level=6, retention_time=4, aeration_rate=6, flocculant_dose=10, temperature=30, mixing_intensity=high, filter_grade=coarse
3. Run #2 (D=0.4207): ph_level=6, retention_time=4, aeration_rate=6, flocculant_dose=50, temperature=15, mixing_intensity=low, filter_grade=fine
Full Analysis Output
=== Main Effects: bod_removal ===
Factor Effect Std Error % Contribution
--------------------------------------------------------------
ph_level 7.4250 2.0251 30.0%
flocculant_dose 3.9750 2.0251 16.0%
mixing_intensity 3.8750 2.0251 15.6%
temperature 3.6750 2.0251 14.8%
aeration_rate -3.3250 2.0251 13.4%
retention_time 2.0250 2.0251 8.2%
filter_grade -0.4750 2.0251 1.9%
=== ANOVA Table: bod_removal ===
Source DF SS MS F p-value
-----------------------------------------------------------------------------
ph_level 1 110.2612 110.2612 2.993 0.1177
retention_time 1 8.2013 8.2013 0.223 0.6483
aeration_rate 1 22.1113 22.1113 0.600 0.4584
flocculant_dose 1 31.6012 31.6012 0.858 0.3785
temperature 1 27.0112 27.0112 0.733 0.4141
mixing_intensity 1 30.0312 30.0312 0.815 0.3901
filter_grade 1 0.4512 0.4512 0.012 0.9143
ph_level*retention_time 1 22.1113 22.1113 0.600 0.4584
ph_level*aeration_rate 1 8.2013 8.2013 0.223 0.6483
ph_level*flocculant_dose 1 27.0113 27.0113 0.733 0.4141
ph_level*temperature 1 31.6013 31.6013 0.858 0.3785
ph_level*mixing_intensity 1 0.4513 0.4513 0.012 0.9143
ph_level*filter_grade 1 30.0313 30.0313 0.815 0.3901
retention_time*aeration_rate 1 110.2612 110.2612 2.993 0.1177
retention_time*flocculant_dose 1 30.0312 30.0312 0.815 0.3901
retention_time*temperature 1 0.4513 0.4513 0.012 0.9143
retention_time*mixing_intensity 1 31.6012 31.6012 0.858 0.3785
retention_time*filter_grade 1 27.0112 27.0112 0.733 0.4141
aeration_rate*flocculant_dose 1 0.4513 0.4513 0.012 0.9143
aeration_rate*temperature 1 30.0313 30.0313 0.815 0.3901
aeration_rate*mixing_intensity 1 27.0112 27.0112 0.733 0.4141
aeration_rate*filter_grade 1 31.6012 31.6012 0.858 0.3785
flocculant_dose*temperature 1 110.2613 110.2613 2.993 0.1177
flocculant_dose*mixing_intensity 1 8.2013 8.2013 0.223 0.6483
flocculant_dose*filter_grade 1 22.1113 22.1113 0.600 0.4584
temperature*mixing_intensity 1 22.1113 22.1113 0.600 0.4584
temperature*filter_grade 1 8.2013 8.2013 0.223 0.6483
mixing_intensity*filter_grade 1 110.2613 110.2613 2.993 0.1177
Error (Lenth PSE) 9 331.5769 36.8419
Total 7 229.6687 32.8098
Note: Error estimated using Lenth's pseudo-standard-error (unreplicated design)
=== Interaction Effects: bod_removal ===
Factor A Factor B Interaction % Contribution
------------------------------------------------------------------------
retention_time aeration_rate -7.4250 10.0%
flocculant_dose temperature 7.4250 10.0%
mixing_intensity filter_grade -7.4250 10.0%
ph_level temperature 3.9750 5.3%
retention_time mixing_intensity 3.9750 5.3%
aeration_rate filter_grade 3.9750 5.3%
ph_level filter_grade -3.8750 5.2%
retention_time flocculant_dose 3.8750 5.2%
aeration_rate temperature -3.8750 5.2%
ph_level flocculant_dose 3.6750 4.9%
retention_time filter_grade -3.6750 4.9%
aeration_rate mixing_intensity -3.6750 4.9%
ph_level retention_time 3.3250 4.5%
flocculant_dose filter_grade -3.3250 4.5%
temperature mixing_intensity 3.3250 4.5%
ph_level aeration_rate -2.0250 2.7%
flocculant_dose mixing_intensity 2.0250 2.7%
temperature filter_grade -2.0250 2.7%
ph_level mixing_intensity 0.4750 0.6%
retention_time temperature 0.4750 0.6%
aeration_rate flocculant_dose -0.4750 0.6%
=== Summary Statistics: bod_removal ===
ph_level:
Level N Mean Std Min Max
------------------------------------------------------------
6 4 79.9000 2.1087 77.4000 82.1000
9 4 87.3250 5.9461 83.0000 96.0000
retention_time:
Level N Mean Std Min Max
------------------------------------------------------------
12 4 82.6000 3.0033 79.0000 86.3000
4 4 84.6250 8.0500 77.4000 96.0000
aeration_rate:
Level N Mean Std Min Max
------------------------------------------------------------
2 4 85.2750 7.4410 79.0000 96.0000
6 4 81.9500 3.7171 77.4000 86.3000
flocculant_dose:
Level N Mean Std Min Max
------------------------------------------------------------
10 4 81.6250 2.9216 77.4000 84.0000
50 4 85.6000 7.5820 79.0000 96.0000
temperature:
Level N Mean Std Min Max
------------------------------------------------------------
15 4 81.7750 2.2066 79.0000 84.0000
30 4 85.4500 7.9173 77.4000 96.0000
mixing_intensity:
Level N Mean Std Min Max
------------------------------------------------------------
high 4 81.6750 4.1724 77.4000 86.3000
low 4 85.5500 7.0098 81.1000 96.0000
filter_grade:
Level N Mean Std Min Max
------------------------------------------------------------
coarse 4 83.8500 8.4354 77.4000 96.0000
fine 4 83.3750 2.2911 81.1000 86.3000
=== Main Effects: sludge_volume ===
Factor Effect Std Error % Contribution
--------------------------------------------------------------
aeration_rate -57.0000 15.0330 40.0%
mixing_intensity 52.5000 15.0330 36.8%
retention_time -14.0000 15.0330 9.8%
flocculant_dose 9.0000 15.0330 6.3%
temperature 5.0000 15.0330 3.5%
filter_grade 4.5000 15.0330 3.2%
ph_level 0.5000 15.0330 0.4%
=== ANOVA Table: sludge_volume ===
Source DF SS MS F p-value
-----------------------------------------------------------------------------
ph_level 1 0.5000 0.5000 0.007 0.9367
retention_time 1 392.0000 392.0000 5.227 0.0481
aeration_rate 1 6498.0000 6498.0000 86.640 0.0000
flocculant_dose 1 162.0000 162.0000 2.160 0.1757
temperature 1 50.0000 50.0000 0.667 0.4353
mixing_intensity 1 5512.5000 5512.5000 73.500 0.0000
filter_grade 1 40.5000 40.5000 0.540 0.4811
ph_level*retention_time 1 6498.0000 6498.0000 86.640 0.0000
ph_level*aeration_rate 1 392.0000 392.0000 5.227 0.0481
ph_level*flocculant_dose 1 50.0000 50.0000 0.667 0.4353
ph_level*temperature 1 162.0000 162.0000 2.160 0.1757
ph_level*mixing_intensity 1 40.5000 40.5000 0.540 0.4811
ph_level*filter_grade 1 5512.5000 5512.5000 73.500 0.0000
retention_time*aeration_rate 1 0.5000 0.5000 0.007 0.9367
retention_time*flocculant_dose 1 5512.5000 5512.5000 73.500 0.0000
retention_time*temperature 1 40.5000 40.5000 0.540 0.4811
retention_time*mixing_intensity 1 162.0000 162.0000 2.160 0.1757
retention_time*filter_grade 1 50.0000 50.0000 0.667 0.4353
aeration_rate*flocculant_dose 1 40.5000 40.5000 0.540 0.4811
aeration_rate*temperature 1 5512.5000 5512.5000 73.500 0.0000
aeration_rate*mixing_intensity 1 50.0000 50.0000 0.667 0.4353
aeration_rate*filter_grade 1 162.0000 162.0000 2.160 0.1757
flocculant_dose*temperature 1 0.5000 0.5000 0.007 0.9367
flocculant_dose*mixing_intensity 1 392.0000 392.0000 5.227 0.0481
flocculant_dose*filter_grade 1 6498.0000 6498.0000 86.640 0.0000
temperature*mixing_intensity 1 6498.0000 6498.0000 86.640 0.0000
temperature*filter_grade 1 392.0000 392.0000 5.227 0.0481
mixing_intensity*filter_grade 1 0.5000 0.5000 0.007 0.9367
Error (Lenth PSE) 9 675.0000 75.0000
Total 7 12655.5000 1807.9286
Note: Error estimated using Lenth's pseudo-standard-error (unreplicated design)
=== Interaction Effects: sludge_volume ===
Factor A Factor B Interaction % Contribution
------------------------------------------------------------------------
ph_level retention_time 57.0000 13.3%
flocculant_dose filter_grade -57.0000 13.3%
temperature mixing_intensity 57.0000 13.3%
ph_level filter_grade -52.5000 12.3%
retention_time flocculant_dose 52.5000 12.3%
aeration_rate temperature -52.5000 12.3%
ph_level aeration_rate 14.0000 3.3%
flocculant_dose mixing_intensity -14.0000 3.3%
temperature filter_grade 14.0000 3.3%
ph_level temperature 9.0000 2.1%
retention_time mixing_intensity 9.0000 2.1%
aeration_rate filter_grade 9.0000 2.1%
ph_level flocculant_dose 5.0000 1.2%
retention_time filter_grade -5.0000 1.2%
aeration_rate mixing_intensity -5.0000 1.2%
ph_level mixing_intensity -4.5000 1.1%
retention_time temperature -4.5000 1.1%
aeration_rate flocculant_dose 4.5000 1.1%
retention_time aeration_rate -0.5000 0.1%
flocculant_dose temperature 0.5000 0.1%
mixing_intensity filter_grade -0.5000 0.1%
=== Summary Statistics: sludge_volume ===
ph_level:
Level N Mean Std Min Max
------------------------------------------------------------
6 4 152.0000 52.6181 86.0000 214.0000
9 4 152.5000 38.0745 114.0000 205.0000
retention_time:
Level N Mean Std Min Max
------------------------------------------------------------
12 4 159.2500 41.5321 114.0000 214.0000
4 4 145.2500 48.6098 86.0000 205.0000
aeration_rate:
Level N Mean Std Min Max
------------------------------------------------------------
2 4 180.7500 34.1992 143.0000 214.0000
6 4 123.7500 29.7139 86.0000 148.0000
flocculant_dose:
Level N Mean Std Min Max
------------------------------------------------------------
10 4 147.7500 52.3601 86.0000 214.0000
50 4 156.7500 37.7216 114.0000 205.0000
temperature:
Level N Mean Std Min Max
------------------------------------------------------------
15 4 149.7500 7.8049 143.0000 161.0000
30 4 154.7500 64.3500 86.0000 214.0000
mixing_intensity:
Level N Mean Std Min Max
------------------------------------------------------------
high 4 126.0000 32.9545 86.0000 161.0000
low 4 178.5000 35.9861 147.0000 214.0000
filter_grade:
Level N Mean Std Min Max
------------------------------------------------------------
coarse 4 150.0000 49.1460 86.0000 205.0000
fine 4 154.5000 42.3045 114.0000 214.0000
Optimization Recommendations
=== Optimization: bod_removal ===
Direction: maximize
Best observed run: #4
ph_level = 9
retention_time = 4
aeration_rate = 2
flocculant_dose = 50
temperature = 30
mixing_intensity = low
filter_grade = coarse
Value: 96.0
RSM Model (linear, R² = 1.0000, Adj R² = 1.0000):
Coefficients:
intercept +83.6125
ph_level +0.0125
retention_time -1.1625
aeration_rate -2.7125
flocculant_dose +2.6625
temperature +2.7625
mixing_intensity +2.0625
filter_grade -1.0125
Predicted optimum (from linear model, at observed points):
ph_level = 9
retention_time = 4
aeration_rate = 2
flocculant_dose = 50
temperature = 30
mixing_intensity = low
filter_grade = coarse
Predicted value: 96.0000
Surface optimum (via L-BFGS-B, linear model):
ph_level = 9
retention_time = 4
aeration_rate = 2
flocculant_dose = 50
temperature = 30
mixing_intensity = 1.0000
filter_grade = -1.0000
Predicted value: 96.0000
Model quality: Excellent fit — surface predictions are reliable.
Factor importance:
1. temperature (effect: 5.5, contribution: 22.3%)
2. aeration_rate (effect: -5.4, contribution: 21.9%)
3. flocculant_dose (effect: 5.3, contribution: 21.5%)
4. mixing_intensity (effect: 4.1, contribution: 16.6%)
5. retention_time (effect: 2.3, contribution: 9.4%)
6. filter_grade (effect: -2.0, contribution: 8.2%)
7. ph_level (effect: 0.0, contribution: 0.1%)
=== Optimization: sludge_volume ===
Direction: minimize
Best observed run: #8
ph_level = 9
retention_time = 12
aeration_rate = 6
flocculant_dose = 10
temperature = 15
mixing_intensity = low
filter_grade = coarse
Value: 86.0
RSM Model (linear, R² = 1.0000, Adj R² = 1.0000):
Coefficients:
intercept +152.2500
ph_level +14.2500
retention_time -13.0000
aeration_rate -3.5000
flocculant_dose +25.2500
temperature +17.7500
mixing_intensity -14.0000
filter_grade +7.0000
Predicted optimum (from linear model, at observed points):
ph_level = 9
retention_time = 12
aeration_rate = 6
flocculant_dose = 50
temperature = 30
mixing_intensity = high
filter_grade = fine
Predicted value: 214.0000
Surface optimum (via L-BFGS-B, linear model):
ph_level = 6
retention_time = 12
aeration_rate = 6
flocculant_dose = 10
temperature = 15
mixing_intensity = 1.0000
filter_grade = -1.0000
Predicted value: 57.5000
Model quality: Excellent fit — surface predictions are reliable.
Factor importance:
1. flocculant_dose (effect: 50.5, contribution: 26.6%)
2. temperature (effect: 35.5, contribution: 18.7%)
3. ph_level (effect: 28.5, contribution: 15.0%)
4. mixing_intensity (effect: -28.0, contribution: 14.8%)
5. retention_time (effect: 26.0, contribution: 13.7%)
6. filter_grade (effect: 14.0, contribution: 7.4%)
7. aeration_rate (effect: -7.0, contribution: 3.7%)