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NRP 3: Let’s get started

NRP 3: Let’s get started. Agenda. Project expectations Startup Checklist Organic Feed Lines Suspended solids targets, measurements SOP Research Ideas. Project Expectations. 6 weeks of plant operation For 3 weeks NRP is your only task 4 hours per week outside of class

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NRP 3: Let’s get started

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  1. NRP 3: Let’s get started

  2. Agenda • Project expectations • Startup Checklist • Organic Feed Lines • Suspended solids targets, measurements • SOP • Research Ideas

  3. Project Expectations • 6 weeks of plant operation • For 3 weeks NRP is your only task • 4 hours per week outside of class • Data collection and data analysis used for plant control (evidence of good engineering) • Maintain good records of what you did and what you learned • Collaboration between teams is encouraged • What is success? Cite source!

  4. Startup Checklist • Verify that all sensors are working • Replace DO membrane • Calibrate dissolved oxygen probe in saturated water • Fill reactor with mixed liquor from IWWTP activated sludge tank • Fill organic waste bottle with organic waste • Make sure that airflow calibration is complete before you leave! • Measure MLVSS (mixed liquor volatile suspended solids) • Begin in settle phase (make sure time is long enough)

  5. Organic Feed Lines • What will happen if the organic feed line holds a high concentration of organics at room temperature for several weeks? • Why might this be a problem? _______________________ • How can you solve this problem? _____________________________ Clog the screen in the valves Purge organic feed line with tap water

  6. Suspended Solids Targets and Measurements • Biggest problem last year was keeping adequate MLVSS in the reactor • Solids retention time is approximately 10 days • Target MLVSS of approximately 3 g/L • If reactor volume is 4 L then waste ___ g/day • Effluent concentration of solids needs to be very low 1.2

  7. Standard Operating Procedure (SOP) • How frequently do you check your plant? • What do you need to check and/or record? • Organic waste volume • MLVSS (by turbidity or by drying and ashing) • BOD of effluent? • Phosphorus concentrations? • How often must you add organic waste in the refrigerator? • Scrape sides of reactor to keep solids in suspension • Verify that fill and drain times are reasonable (no clogged valves)

  8. Research Ideas (due next Wednesday in lab) • Automate air flow calibration+ • Automate the measurement of the oxygen uptake rate • Develop a better algorithm to control the DO+ • Optimize biological phosphorus removal+ • Automate measurement and wasting of MLVSS+ • Measure BOD of reactor contents (or effluent) as function of time (use to optimize aeration time) + more on these topics coming up

  9. Automate Airflow Calibration • Identify what can cause the calibration to fail • Change the code so the calibration always works • Test the code under varied flow rates, valve settings, and pressure ranges • Eliminate the dialog box • Save calibration equation to a file and retrieve it when software begins running

  10. Develop a Better Algorithm to Control the DO • Compare different algorithms (perhaps two teams) • Simulation Model Based Control • PID • Log the relevant parameters to file (you will want this data for your final report) • Document problems getting either method to work

  11. Empirical Aeration Model (based on aeration data)

  12. Simulation Model Based Control input consumption change in storage + = Assume consumption is the same in next time step New transfer coefficient based on current and previous values

  13. Eliminate Derivates(Alternative is Linear Regression) Calculate the new airflow given the new transfer coefficient

  14. Oxygen Transfer Coefficient Range • Oxygen transfer coefficient should always be greater than the minimum transfer coefficient. • If the target transfer coefficient is less than the minimum then set air flow rate to _____ • It may also be wise to code a maximum air flow rate (___________________________________) zero Based on the air flow calibration range Figure out how to initialize parameters

  15. How might you choose Dt? • How fast do significant DO changes happen? milliseconds, seconds, minutes, hours, days • How could you get a parameter with units of time? ___________ • What would happen if you used a time interval based on the data acquisition rate? ________________________________ • What other response time is important? __________________ Inverse of kv,l Noisy data  rapidly changing air flow rate Air accumulator cycle time

  16. Code Suggestions • Place the code inside the Set Airflow.VI • Design the code so although it is called as frequently as the Plant Control SubVI that it only calculates a new airflow rate at a time interval that you set (____) • The code will need to remember previous oxygen transfer coefficients and previous oxygen deficits (____________) • Oxygen deficits might be based on an average measurement over a time period that is small relative to Dt. Dt Shift Registers

  17. Improve the Simulation Model Based Control • Measure oxygen transfer coefficient with your wastewater • Plot (and log to file) the transfer coefficient and the deficit • Note that is the rate of oxygen transfer (per liter) into the reactor • Integrate starting from the addition of waste to determine the total amount of BOD consumed

  18. Proportional Integral Derivative Control I D P Kc is controller gain (tuning parameter) TI is the integral time (tuning parameter) TD is the derivative time (tuning parameter) De/Dt is the error rate of change (Note that this is the same as the dissolved oxygen concentration rate of change) is the area under the curve of the error as a function of time. u(t) is the airflow rate that the controller sets The Error (e) is the difference between the Process Variable and the desired Setpoint. The controller uses the proportional gain, Kc, the integral time constant, Ti, and the derivative time constant, Td, to determine an Output which drives the Error to zero.

  19. Optimize Biological Phosphorus Removal • 1 hour of anaerobic operation after the addition of organic waste • Stored energy (Poly P) is used to sequester organic carbon • Cellular phosphorus is released in this phase • Main reactor (aerated) • Inorganic phosphorus is sequestered in a phosphorus rich energy storage (Poly P)

  20. Automate Measurement and Wasting of MLVSS • Use the Honeywell turbidity sensors to measure the turbidity of the mixed liquor • Develop a calibration between sensor voltage and MLVSS • Investigate the possibility of mounting the sensor in the side of the tank (at what elevation and orientation for dual purpose?) • Or use a pump to circulate mixed liquor through the turbidity sensor Where C is approximately 2.3 (mg/L)/NTU

  21. Class Activity • Go to the boards in your double teams • Split board in half • Write your research project titles • List what is required to make the project successful • List the most likely reasons for failure

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