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CYBER-PHYSICAL SYSTEM FOR A WATER RECLAMATION PLANT: BALANCING AERATION, ENERGY, AND WATER QUALITY TO MAINTAIN PROCESS RESILIENCE
Title
CYBER-PHYSICAL SYSTEM FOR A WATER RECLAMATION PLANT: BALANCING AERATION, ENERGY, AND WATER QUALITY TO MAINTAIN PROCESS RESILIENCE
Creator
Zhu, Junjie
Date
2015, 2015-07
Description
Aeration accounts for a large fraction of energy consumption in conventional water reclamation plants (WRPs). Although process operations at...
Show moreAeration accounts for a large fraction of energy consumption in conventional water reclamation plants (WRPs). Although process operations at older WRPs can satisfy effluent permit requirements, they typically operate with excess aeration. More effective process controls at older WRPs can be challenging as operators work to balance higher energy costs and more stringent effluent limitations while managing fluctuating loads. Therefore, understandings of process resilience or ability to quickly return to original operation conditions at a WRP are important. A state-of-art WRP should maintain process resilience to deal with different kinds of perturbations even after optimization of energy demands. This work was to evaluate the applicability and feasibility of cyber-physical system (CPS) for improving operation at Metropolitan Water Reclamation District of Greater Chicago (MWRDGC) Calumet WRP. In this work, a process model was developed and used to better understand the conditions of current Calumet WRP, with additional valuable information from two dissolved oxygen field measurements. Meanwhile, a classification system was developed to reveal the pattern of historical influent scenario based on cluster analysis and cross-tabulation analysis. Based on the results from the classification, typical process control options were investigated. To ensure the feasibility of information acquisition, the reliability and flexibility of soft sensors were assessed to typical influent conditions. Finally, the process resilience was investigated to better balance influent perturbations, energy demands, and effluent quality for long-term operations. These investigations and evaluations show that although the energy demands change as the influent conditions and process controls, in general, aeration savings could be up to 50% from the level of current consumption; with a more xix complex process controls, the saving could be up to 70% in relatively steady-state conditions and at least 40% in relatively challenging transient conditions. The soft sensors can provide reliable and flexible performance on target predictions. The plant can still maintain at a similar level of process resilience after 50% aeration saving, even during long-term perturbations. Overall, this work shows that it is well feasible to provide more cost-effective operations at the Calumet WRP, and meanwhile influent perturbations, effluent quality, and process resilience are well in balance. Keywords: Energy, aeration, effluent quality, perturbation, resilience, water reclamation plant.
Ph.D. in Environmental Engineering, July 2015
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INVESTIGATION ON THE INTERACTION BETWEEN NATURAL ORGANIC MATTER AND CALCITE
Title
INVESTIGATION ON THE INTERACTION BETWEEN NATURAL ORGANIC MATTER AND CALCITE
Creator
Zhu, Junjie
Date
2012-07-12, 2012-07
Description
Fox River water was supersaturated with respect to calcite; natural organic matter (NOM) might play a key role in this phenomenon. Fox River...
Show moreFox River water was supersaturated with respect to calcite; natural organic matter (NOM) might play a key role in this phenomenon. Fox River NOM (FRNOM) adsorption on the calcite surface is probably an important mechanism to explain this condition. Fox River water contained moderate ultraviolet absorbance (UVA) of NOM (0.19 1/cm), high concentration of calcium (70 mg/L), suspended solids with relatively high specific surface area (SSA) (6.9 m2/g), and moderate pH value (8.4) based on historical data. To test whether the phenomenon was caused by NOM adsorption, a series of experiments was conducted to explore the interaction between NOM and calcite in conditions similar to those of the Fox River. Suwannee River NOM (SRNOM) and Nordic Reservoir NOM (NRNOM) were used as surrogate NOM. The results show that SRNOM inhibited calcite dissolution significantly after 10 min based on measuring of the decrease in the free calcium concentration. The decrease in the free calcium was not solely due to formation of NOM-calcium complexes, because these complexes made up only about 3% of the total free calcium concentration. Therefore, NOM adsorption onto calcite was probably largely responsible for the inhibited calcite activity. Experimental results also showed that NOM adsorption increased with increasing NOM concentration in the range from 2 to 14 mg NOM/L, which is a common range for river water. Higher charge density also seems to promote sorption onto calcite; relative to NRNOM, SRNOM has a higher charge density and SRNOM has a higher affinity for calcite. Other factors that promoted NOM adsorption onto calcite included higher concentration of calcium and larger SSA of calcite seed. Based on water quality characteristics, the Fox River provides a suitable environment for NOM adsorption on calcite, and it seems likely that Fox River NOM (FRNOM) adsorption on calcite can inhibit calcite precipitation. This understanding of interaction between NOM and calcite could be used by WTPs along the Fox River for better optimization and improvement in treatment and operation.
M.S. in Environmental Engineering, July 2012
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