Temperature effects on biodegradation kinetic parameters and settling characteristics of activated sludge treating pulp and paper wastewater

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The proposed process modifications of the pulp and paper mill made it necessary to evaluate the effect of alteration in local wastewater treatment facility owing to increased temperature, increased flow, and higher organic loading. The settleability of the MLSS was evaluated as a function of the elevated operating temperatures. The SVI values at 25- 40 °C were between 115-173 mL/g which is higher than the normal range (50-150 mL/g). Extant respirometry techniques were used to determine kinetic coefficients at multiple temperatures. The first order, maximum specific substrate removal rates at 25-40 °C ranged from 0.007-0.023 L/mg/hr. Temperature coefficients for sample A and B were 1.029 and 1.064 respectively. Temperature correction factors and kinetic values were used as part of a BioWin™ calibration to improve the model simulation. This study demonstrated the applicability of respirometric techniques and model simulation to evaluate pulp and paper wastewater treatment plant performance.

INTRODUCTION
The wastewater from pulp and paper mills is a constantly changing and complex mixture of lignin-derived dissolved organic compounds (Thompson et al., 2001). The activated sludge process is the most common biological treatment method for pulp and paper wastewater and many of these biological systems operate at high temperatures, e.g., 20-35°C, (Morgan-Sagastume and Allen, 2004). In addition, fluctuations in the operating temperature often causes system instability (Kriebitzsch et al., 1998; Tripathi and Allen, 1999). Consequently, the goal of this study was to evaluate the effect of temperature on pulp and paper wastewater treatment, including biodegradation kinetics and mixed liquor
settleability. 

Background.

The Grand Rapids Wastewater Treatment Facility (WWTF) is owned and operated by the Grand Rapids Public Utilities Commission and treats approximately 6.6 million gallons per day (MGD); nearly 90 percent of that flow is from a pulp and paper 103 mill. The Mill has proposed process modifications to increase paper output capacity, which will affect wastewater flow and quality. After mill upgrades, flow will increase to 13 MGD, solids will increase by 85%, and BOD will increase by almost 250%.

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