Optimisation of W Astew a Ter Treatment Plants by Means of Computer Models

Abstract

The objective of the work presented is to demonstrate how computer based models can be used to improve the effluent quality from wastewater treatment plants by optimisation of the operation. The investigation was carried out in connection with pilot plant investigations at Damhusllen Wastewater Treatment Plant in order to establish the design basis for upgrading the treatment plants in the city of Copenhagen. Calibration of the model was done with thorough characterisation of the wastewater and the activated sludge as the primary calibration tool. Special attention was paid to the nitrification process, which by previous investigations was shown to be occasionally inhibited. Model constants for the nitrification process were detennined from experiments. Default constants were used for nearly all other constants. The pilot plant was optimized with the calibrated model. Different operational strategies for improvement of the denitrification process were tested. The denitrification process was operated relatively poorly at the time for the optimisation. The calibration showed that it was possible to calibrate the model using the characterization of the wastewater and the activated sludge as the primary calibration tool. Further it was shown that the calihrated model could be used as a tool for optimising the operation of the pilot plant. The suggested operation correlated well with the practical realisable operation.

Mathematical Modelling and Computer Simulation of Activated Sludge Systems

“…An adequate modelling process including model calibration is a key issue for successful application of these models in practice. Henze et al 1987;Lesouef et al 1992;Pedersen and Sinkjaer 1992;Siegrist and Tschui 1992;Stokes et al 1993;USEPA 1993;de la Sota et al 1994;Dupont and Sinkjaer 1994;Xu and Hultman 1996;Kristensen et al 1998). However, the calibration of a site-specific model does not always receive the same level of scrutiny as does model development (Melcer 1999).…”

“…Design (1) and operating (2) data are always needed for a model calibration. Pedersen and Sinkjaer 1992;Stokes et al 1993;Dupont and Sinkjaer 1994;Xu and Hultman 1996;Kristensen et al 1998;Makinia and Wells, 2000). The settling characteristics (4) can be characterized via online or laboratory scale settling tests.…”

“…Adjustment of the phase lengths in alternating aeration and flow processes • (Dupont and Sinkjaer 1994;Potter et al 1996;Irizar et al 2003;Fikar et al 2005); DO control in the aerated zones (Leeuw • et al 1996;Solley and Barr 1999); Addition of the readily biodegradable substrate, such as fermentation • products of the raw sludge from primary clarifiers (Funamizu et al 1997); Shutting down one treatment line and overloading the other lines (Carucci • et al 1999); Reduction of the total nitrogen emission during stormwater events • (Seggelke andRosenwinkel 2002, Rosenwinkel et al 2007b;Ahnert et al 2009); Adjustment of the cycle range and the ratio between the nitrification and • denitrification length in an intermittently aerated process (Andreottola et al 2003); Adjustment of the mixed liquor recirculation between the nitrification • and denitrification compartments (Moussa et al 2004); Dosing ammonia rich substrate to the regeneration zone of the R-D-N • process (Novak and Havrlikova 2004); Adjustment of production schedules in a chemical industry WWTP (van • Hulle and Vanrolleghem 2004); Analysis of possible modifications in the layout of an oil refinery WWTP • and reduction of operating costs (Pardo et al 2007); Strategy of dosing external source to enhance denitrification (Phillips • et al 2009). …”

“…Estimation of a desired capacity for treatment processes (Coen • et al 1996;Coen et al 1997;Cheng and Ribarova 1999;van Niekerk et al 2000;Hanhan et al 2002;Moussa et al 2004); Efficiency comparison of different technologies for improving nitrogen • removal (Hvala et al 2002); Testing various operating strategies (Dupont and Sinkjaer 1994;Jobbagy • et al 2004); Splitting the wastewater flow between WWTPs (Ladiges • et al 1999;Ladiges et al 2000;Ladiges et al 2004) -this is one of the best examples illustrating benefits of using computer simulation in the wastewater industry. The cost of an intensive measurement campaign for model calibration was 150.000 Euro, but at least 20 million Euro were subsequently saved in the design phase; Installing an additional volume for nitrification and denitrification in a • food industry WWTP (Vandekerckhove et al 2008).…”

Modelling, Simulation and Control of Urban Wastewater Systems

“…Control can be performed either in a proportional way or by on/off control. (Dupont and Sinkjaer, 1994). Dupont and Henze's (1992) secondary clarifier model serves as the base for the secondary clarifier module ofEFOR.…”