M.N. Pons, S. Le Bonté , O. Potier

1. Adaptive Principal Component Analysis for toxic event detection M.N. Pons, S. Le Bonté, O. Potier Laboratoire des Sciences du Génie Chimique, CNRS-ENSIC-INPL, Nancy

2. Introduction • New regulations: • treatment in adequate facilities of all incoming waters • stricter limits on effluent quality, on sludge • Crisis: • rainstorm • accidental release of toxic components • some may be forecast (fire water) • other not

3. A short selection of potential toxics • Heavy metals: Hg, Cr, Pb, Cd, Zn, Cu ... • Solvents: white spirit, ... • Pesticides • Herbicides • Motor fuels: diesel oil, ... • Detergents • Dyes

4. Introduction • New regulations: • treatment in adequate facilities of all incoming waters • stricter limits on effluent quality • Crisis: • rainstorm • accidental release of toxic components • some may be forecast (fire water) • other not • Improvement of plant control strategy • New scenarios

5. Introduction • Characterisation of wastewater composition • COD, BOD5, SS • NT, NH4+, NO3- • PT, PO4- • K, Ca, Mg, ... • Heavy metals (Cu, Zn, Cd, Hg, Cr, …) • Micropolluants • Some are time-consuming • Some are very specific

6. Introduction • Global (and faster) measurements • temperature, conductivity, pH, redox • turbidity • light absorbance • fixed wavelength • spectra • respirometry • buffer capacity • ... On-line In-line (sampling)

7. Introduction • Three methods under test • Respirometry • Absorbance spectra • Buffer capacity • Multivariate data analysis method • Validation on simulation • Experimental validation • Conclusions

8. Respirometry test: experimental set-up

9. Respirometry test Typical response curves DO probe sludge + substrate

10. Characteristic parameters OUR curve • 4 parameters • Maximal value of Oxygen Uptake Rate • Oxygen volume (VO2) (5 or 15min) • Peak width • Initial slope

11. Experimental results + CuSO4

12. Experimental results + dye

13. Experimental results 2 respirometers in parallel toxics added in one respirometer White Spirit Gasoil javel HCl CuSO4 NaOH

14. Experimental results

15. UV-visible spectrometry

16. UV-visible spectrometry Anthropogenic substances 270 nm 254 nm 220 nm 210 nm

17. UV-visible spectrometry Detergents 220 nm 210 nm 254 nm 270 nm

18. UV-visible spectrometry Dyes

19. UV-visible spectrometry Norm. Abs Abs. Abs

20. Buffer capacity • Normally measured • Wastewater pH • Alkalinity • Here • Acidification (pH  3) • Titration to pH  11 • Buffer capacity versus pH

21. Buffer capacity Buffer capacity

22. Buffer capacity

23. Fault detection background Overload of data Univariate SPC MultivariateSPC PLS Partial Least Squares Projection to Latent Structures PCA Principal Component Analysis • Continuous process (steady state) • Kresta et al. (1991): fluidized bed and extractive distillation column • Batch and Fedbatch • Lennox et al. (1999): Fermentation processes ?Wastewater treatment plant = continuous process but not at steady state

24. Adaptive PCA • Diurnal cycle • 1 sample / 30 min (48 samples / day) or / 1hr (24 samples / day) • 4 Principal Variables (PVi) : Ourex max, Ourex T, Slope, Width ( 15 min) • In the case of 1 sample / 1 hr, the samples j to j+23 are used and 2 PCs are considered: • PC1 = a1PV1 + b1PV2 + g1PV3 + h1PV4 • PC2 = a2PV1 + b2PV2 + g2PV3 + h2PV4 • At sample j+24: prediction • PC1 (j+24) = a1PV1 (j) + b1PV2 (j) + g1PV3 (j) + h1PV4 (j) • PC2 (j+24) = a2PV1 (j) + b2PV2 (j) + g2PV3 (j) + h2PV4 (j) • At sample j+24: actual • PC ’1 (j+24) = a1PV1 (j+24) + b1PV2 (j+24) + g1PV3 (j+24) + h1PV4 (j+24) • PC ’2 (j+24) = a2PV1 (j+24) + b2PV2 (j+24) + g2PV3 (j+24) + h2PV4 (j+24)

25. Adaptive PCA • Prediction error = Detection (Q statistic) • SPE = [PC1(j+24) - PC ’1(j+24)]2 + [PC2(j+24) - PC ’2(j+24)]2 • Update of ai, bi, gi, and hi using samples j+1 to j+24

26. CP1 CP2 h h+1 h+2 h+3 h+4 . . . h+23 σ1, μ1 σ2, μ2 σ3, μ3 …etc h+24 h+25 . . . Adaptive PCA

27. Effect of slow change in plant state PCA on 24 previous samples (1 sample/hr), estimation of actual sample

28. Why simulating ? • Unsteady state • Many factors to examine: • Location of sludge sampling • Ratio sludge / raw water • Quality of detection in function of the toxic conc. and nature, release time and type • …. • Experiments on the real plant should be carefully selected • « Experiments » on a simulated plant

29. Plant layout Incoming water to be tested Biomass sample Aeration tank Primary settler Biomass sample River Biomass sample Wastage flow External recycle Secondary settler

30. Concentration of toxic Release profile Detection Concentration

31. Toxic release time Release profile Detection Release time

32. Toxic release time Detection = 1.49 (0.07) Detection = 2.77 (0.17)

33. Normal situation • Normal 24hr cycle: • dry weather • normal activity

34. Normal situation 5 initial variables : OURend, OURmax/A254, VO2/A254, width et A254

35. Critical situation: heavy metals HgSO4 6 mg/l 30 mg/l K2Cr2O7 6 mg/l

36. Critical situation: diesel oil Addition of various amounts of diesel oil

37. Critical situation: white spirit Addition of various amounts of white spirit very strong inhibition

38. Buffer capacity 4 initial variables : pH, β(pH=4,75),β(pH=7,21), β(pH=9,25) SPE = [PC1(h) - PC’1(h+24)]2 + [PC2(h) - PC’2(h+24)]2

39. Buffer capacity 5-6 Nov.2001, 14h : Wastewater + citrate

40. UV-visible spectrophotometry

41. Conclusions • Global (and rapid) characterization of the composition of wastewaters • Absorbance spectra - Buffer capacity - Respirometry • + Classical measurements (T, pH, rH, …) • + flowrate + rainfall • Combined with statistical methods • Community activity (design, control, critical situation) • We wish to thank • the Grand Nancy Council for its help • GEMCEA, LCPC, NANCIE • the students and colleagues

43. Plant model • 2D models for the primary settler (Stokes) and the final clarifier (Takacs et al.) • Reactors in series with backmixing = f(flowrate, aeration rate) • Basic control on sludge wastage • IAWQ ASM 1 + inhibition : • growth rate of heterotrophs and autotrophs • death rate • degradation of toxic • Influent description • COST 624 Benchmark • Functions describing the Nancy WWTP effluent • Respirometer model • FORTRAN code on PC