Dynamics of Power Demand, Carbon-Footprint, and Process Performance of Primary and Secondary Separations in Water Resource Recovery Facilities

Recent changes to the diurnal trend of power demand curves for the electrical grid and its new duck looking shape (Duck-Curve), as a result of increase in photovoltaic electricity generation, has also changed the power tariff structures and, in many cases, resulted in significant hike in the cost of power during the peak of demand (16:00-21:00). The significant effect of primary treatment on reducing the overall power demand in water resource recovery facilities, whose peak coincides with the Duck-Curve and power tariff peaks, placed this process at the center of attention for many recent studies focusing on power demand and cost. In contrast with the previous studies that only reviewed overall power demand optimization, this research effort focuses on the dynamics of power demand optimization for treatment facilities. Our approach elucidates the role of time-dependent power demand on the overall ability to perform treatment and the actual treatment cost and specific carbon emissions. This approach not only amplifies the cost-saving of this optimization due to higher electricity prices during the power demand peak periods, but also relieves the unexpected impacts associated with the Duck-Curve.A series of dynamic models were developed here to study the effect of different primary treatment technologies on the electricity demand, operating cost, and carbon-footprint of a large water resource recovery facility in California. This comparison demonstrated primary filters or its combination with the conventional clarifiers as the best option in terms of power, carbon-footprint and cost savings. Despite the different extents of secondary treatment required for these scenarios, activated sludge aeration electricity demand were the dominating electricity consumer. As such, the last three configurations of this facility’s activated sludge processes were also compared using the dynamic models developed here to assure that the power, cost, and carbon-footprint reductions demonstrated by some of the primary treatment options here are maximized. This comparison demonstrated that the evolution of the activated sludge in this facility was performed with the goal of lowering its operating cost, electricity demand, and effluent load. However, the current configuration has additional room for energy optimization