Development, Simulation and Full Scale Verification of Aquifas MBR Energy Optimization Tool for Application to Hollow Fiber and Flat Sheet MBRs
Abstract:Research was undertaken to develop the IWA ASM2d based Aquifas process model for all activated sludge and biofilm systems. The model operates for steady state and dynamic simulation on two platforms: Excel-Visual Basic and Microsoft.NET platforms. The latter provides a complete graphical user interface for operators to use within a plant. The model simulates the headworks, secondary treatment and sludge treatment facilities.
The model was evaluated against energy optimization routines implemented at two full scale MBR plants at Redlands, CA, and Traverse City, MI. During the study, the Redlands plant is operated in a MLE configuration with hollow fiber membranes for nitrogen removal at a flow of 15,150 m3/d. The Traverse City plant was operated in an adaptation of the UCT configuration for membranes for both biological excess phosphorus and nitrogen removal at a flow of 16,800 m3/d. The MBR model allows the user to simulate and optimize the process by evaluating parameters such as cyclic aeration of the membranes with different on and off time cycles; various DO set points in the aeration zone and MBR cell, while optimizing the overall aeration and air scour energy demand across the entire process; optimize the recycle rates and their locations; evaluate and optimize process control strategies. At Traverse City, by changing the on and off cycles from 50% on to 25% on time fraction, the plant observed 58 KW reduction in energy. The model predicted 59 KW, which is within 2%. At Redlands, the model was used to simulate the effect of reduction in aeration zone operating DO. The model predicted a reduction of 132 KW as compared to actual observed data of 140 KW - this was within 6%. At both plants, the model predicted the effluent BOD5, phosphorus, NH4N, NOxN and sludge production before and after the changes.
Aquifas has been used to simulate the design or operations of MBRs for plants with flows ranging from less than 100 m3/d to more than 200,000 m3/d (50 MGD). The configurations include hollow fiber, flat sheet and cross flow membranes. The configurations also include oxidation ditches with surface aeration and conventional activated sludge plants. The range of mixed liquor temperatures at which the model has been applied and verified are from 12 C to 32 C. The user is able to size the tanks, blowers for aeration and air scour, compute the membrane surface area for normal and peak flow, determine the membrane tank footprint and recirculation for various types of membranes, and determine the impact of various types and locations of aeration devices.
Document Type: Research Article
Publication date: January 1, 2009
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