1. Study and Proposed Pilot of Biogas Water Wash and Struvite Recovery Process at MMSD’s Wastewater Facilities
Md Abul Bashar – Research Assistant, UWM (Presenter)
Prof. Jin Li, Ph.D. – Principal Investigator, UWM
Bryan Johnson, P.E. – Energy Tech Innovations, LLC

2. Study Outline
Biogas Purification
Phosphorus Recovery

3. Study Part 1: Biogas Purification

4. Methods of Biogas Purification
Amine-Based Chemical Absorption (CHEM)
Organic Solvent-Based Physical Absorption (PHY)
Pressure Swing Adsorption (PSA)
Water Wash (WW)

5. Why Water Wash? No additional chemical necessary
Can remove problematic impurities with single simple step system.
Both raw biogas and plentiful water is available at both of MMSD’s SSWWTP at JIWWTP.
No corrosion in system instruments.
Low energy consumption in treatment.

6. Objectives of Biogas Water Wash Study
The Problem: Raw biogas can (be)  dirty  corrosive  have low BTU content  have higher cost to utilize for energy recovery purposes and flared because of it. Objectives: 1. Clean and purify biogas to remove H2S and Siloxanes using a lower cost process approach. 2. Upgrade 65% CH4 content in raw biogas up to 98%.

7. Biogas Water Wash ASPEN Plus Flow Diagram

8. Biogas Water Wash ASPEN Plus Modeling Results
Absorber
Pressure
Water Flow (cfm)
Biogas (cfm)
Water Temp (F)
Methane in PDRTGAS(%)
Methane Loss (%)
45 psi
150 and 100
250 40
98.8
5.20 60 98
5.21 70
97.3
5.22 80
96.3
5.24
150 psi
38 and 25
98.7
2.94
97.6
2.98
96.6
3.01
95.3
3.10
Number of Absorbers: 2
Flash Pressure: 60 PSI

9. Biogas Water Wash ASPEN Plus Modeling Results
Initial Methane Content = 65%

10. Significance and Innovation
30% Cost Savings
Low operating Pressure (50 psi)
Gas contaminant removal
Less costly than natural gas
Significance
Non-metallic materials
Unique internal Features
Usable in both Parallel & Series
Modular Scalable System
Innovation

11. Study Part 2: Phosphorus Recovery

12. Phosphorus and Water Pollution
Phosphorus discharge levels are creating significant environmental issues, algal blooms and GW drinking supplies.
WWTPs and agricultural operations significantly contribute to this issue.
Phosphorus discharge levels are becoming highly regulated and treatment is being increased.
CO2 by-product may be integrated beneficially into phosphorus removal processes.
Photo Source: MPR News

13. Phosphorus Content (as P2O5 )
Why Struvite?
Chemical Formula of Struvite: (NH4)MgPO4•6(H2O)
Phosphorus Content (as P2O5 )
Milorganite: 2.88%
Struvite: 29%
DAP: 46%
Photo Source: The Home Depot and

14. Pilot Scale Struvite Recovery
Source: (AT Britton et al., 2007)

15. Struvite Solubility Product
> Phosphorus is highly soluble in lower pH using recovered CO2 from biogas water wash separation process.
> A pH of at least 8 for optimum phosphorus recovery can be integrated with CO2 removal, NaOH and MgCl2.
Source: (AT Britton et al., 2007)

16. Completed Study will Summarize
Correlate modeling to biogas water wash pilot performance demonstrating methane purification.
Preliminary assessment of struvite recovery process in phosphorus removal.
Study of both systems can be integrated to any waste water treatment plant with anaerobic digestion.

17. Thank you Questions?