FTN was hired by a sugar mill in southern Louisiana that discharges wastewater to a nearby lake. The sugar mill was expanding and needed its NPDES permit limits changed to reflect an increased amount of effluent flow and biochemical oxygen demand (BOD) loading. The allowable effluent loading was limited by a total maximum daily load (TMDL) for dissolved oxygen (DO) that had been developed for the receiving water 16 years earlier. The TMDL was based on results of a water quality model that simulates nutrients, algae, BOD, and DO.
FTN revised the water quality model to develop multiple simulations – one with the effluent flow and load anticipated next year and another with the effluent flow and load anticipated farther in the future. FTN documented the revisions to the model and provided the documentation to the sugar mill for submittal to the Louisiana Department of Environmental Quality. The modeling was approved.