Treatment efficiencies of a pilot scale constructed wetland treating greywater from a staff canteen of the University of Moratuwa was studied to estimate the temperature dependent reaction rate constants of specific pollutant removal mechanisms.

1. PARAMETER ESTIMATION OF THE POLLUTANT REMOVAL MECHANISMS OF SUBSURFACE HORIZONTAL FLOW CONSTRUCTED WETLANDS TREATING GREYWATER Dr. Shiromi Karunarathne MKBS Wijesiri VM Jayasooriya

2. Think Ecologically……. Reduce Reuse Recycle

11. DESIGN OF SHF CW SAMPLING POINT 01 SAMPLING POINT 04 SAMPLING POINT 03 SAMPLING POINT 02

14. Assuming first order kinetics prevail, ( C e / C i ) = e -K T t C a = C e {(1- e -K T t ) / e -K T t } .………....….. (2) Where; K T – temperature dependent reaction rate constant t – retention time Then differentiate the equation (2) w.r.t. K T and simplify the equation; d(C e )/ d(K T ) = - tC e …...………...….... (3)

15. Effective sizing of the constructed wetland Then differentiate the equation (2) w.r.t. t and simplify the equation; d(C e )/d(t) = -K T C e ………………….... (4) Maximum retention time is taken that would yield satisfactory levels of treatment, Q = V/t max …………….......................... (5) A = Q.t max /d …………......................... (6) Then, resized surface area can be calculated using above equations.

16. RESULTS Variation of weekly COD Variation of weekly BOD

17. Variation of weekly nitrate nitrogen Variation of weekly nitrite nitrogen

18. Variation of weekly total kjeldhal nitrogen Variation of weekly total phosphorous

19. Variation of weekly total coliforms Variation of weekly total suspended solids

20. Estimation of reaction rate constants (K T ) using dessolver 1.7 Graphical representation of the variation of effluent BOD 5 against K T (BOD )

21. Estimated reaction rate constants Parameter Temperature dependant reaction rate constant – K T (day -1 )±SD BOD 5 0.80799 ± 0.070 COD 0.61166 ± 0.062 Nitrate Nitrogen 0.80131 ± 0.024 Nitrite Nitrogen 0.85634 ± 0.010 Total Kjeldhal Nitrogen 0.28327 ± 0.050 Total Phosphorous 0.34343 ± 0.078 Total Suspended Solids 0.38157 ± 0.095

22. Estimation of optimum retention time (t opt ) Estimation of optimum retention time (t) for BOD

23. Estimated retention time for each parameter Parameter (Reference) Retention time – t (day) BOD 5 (50 mg/l) 3.150 COD (250 mg/l) 2.100 Nitrate Nitrogen (1 mg/l) 3.125 Nitrite Nitrogen (0.005 mg/l) 3.375 Total Kjeldhal Nitrogen (1.2 mg/l) 2.850 Total Phosphorous (3.5 mg/l) 2.525 Total Suspended Solids (30 mg/l) 3.067

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