Monod-type kinetic models, used in simulating microbial growth in biological treatment systems, suggest significant decreases of substrate utilization at lower temperatures. However, it is documented that performance of fixed film treatment systems are not hindered with declining temperatures. Studies at the Moorhead, MN, Wastewater Treatment Facility (WWTF) showed significant impacts of temperature on biofilm growth in its moving bed biofilm reactor (MBBR) and noted that more biomass was present at low temperatures. A series of kinetic bench-scale batch tests was performed to measure ammonium removal in the full-scale system. As part of this research, a diffusion based kinetic model was developed to simulate the bench-scale trials and determine if Monod kinetics and temperature corrections properly model fixed film systems. It was found that Monod kinetics and temperature corrections do apply to fixed film system as long as proper consideration is given to the change in biofilm characteristics.
To address the increasing water demand and changing source water quality, the City of Fargo, North Dakota is undergoing a 56,871 m 3 /day (15 mgd) membrane water treatment plant (WTP) expansion. The Membrane WTP will generate 9,464 m 3 /day (2.5 mgd) of RO concentrate at the design capacity and requires a North Dakota Pollutant Discharge Elimination System (NDPDES) permit for concentrate discharge to the Red River, which is the most appropriate means identified in facility plan. The permit application is unique because the Red River is a shared water body by both North Dakota and Minnesota. Extensive model simulations were performed to evaluate receiving water body quality, heavy metals, total dissolved solids, mixing zone, and multi-states regulations. An Antidegradation review showed that all required steps outlined in the ND Antidegradation Procedure have been previously addressed throughout the planning process. A unique approach for RO discharge permit was outlined in the paper.
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