Balancing Analysis and Optimization Model

Inland Empire Utilities Agency Facilities, 
California

Balancing Analysis and Optimization Model

Project Highlights: 
  • Development of an Agency-wide model that integrates engineering, science, and business decision principles.
  • The system-wide model incorporates real cause and effect relationships, so that the feasibility and cost associated with any one alternative can be evaluated on a system-wide basis.
IEUA Model Schematic
Carollo developed a system-wide facilities model for IEUA that integrates engineering, science, and business decision principles to analyze capital improvement program and operating decisions.

Carollo, together with the Inland Empire Utilities Agency (IEUA), has created an innovative planning tool, OPTIMO®, that uses optimization algorithms to minimize operational costs for a complex and interconnected collection, wastewater treatment, and recycle water system. OPTIMO® is a mass and energy balance model that simulates wastewater flow routing, treatment, recycle water distribution, and energy demand/supply. The model accounts for multiple physical and water quality constraints, while maximizing the use of recycled water and minimizing total system operations and maintenance (O&M) costs, including power, chemical, and labor demands. OPTIMO® provides IEUA with a tool that simplifies the complex interactions of its extensive wastewater system to maximize capacity, minimize costs, and balance risks, while meeting regulatory constraints.

IEUA owns and operates a network of wastewater treatment plants with different treatment capacities, process efficiencies, and discharge/reuse alternatives. IEUA’s system consists of four tertiary wastewater treatment plants including Carbon Canyon Water Reclamation Facility (CCWRF), Regional Plant No. 1 (RP-1), Regional Plant No. 4 (RP-4), and Regional Plant No. 5 (RP-5). Solids treatment and cogeneration facilities are located at RP-1 and Regional Plant No. 2 (RP-2). Natural gas powered generation is provided at CCWRF and RP-4. Several of the plants are interconnected with the ability to divert wastewater (raw and primary effluent) and/or solids to other plants. For example, CCWRF can divert wastewater to RP-5 and discharges solids to RP-2 for treatment. RP-1 can also divert wastewater to RP-5. RP-4 can divert wastewater (including solids) to RP-1 for liquid and solids treatment.

In addition, water reuse is a major component of IEUA’s system. The ultimate goal is to maximize reuse for “zero” discharges. This requires evaluating supply and demand on an hour-to-hour basis.

Given the complexity and interdependent nature of IEUA’s facilities and the available options for power generation, the optimum set of operating conditions for the IEUA facilities is not necessarily intuitive. Carollo developed OPTIMO® to assist IEUA staff in addressing questions such as:

  • What new capital facilities are required and when are they needed, because growth rates and future regulatory requirements are uncertain?
  • How do we optimize capacity, minimize operations costs, and reduce energy and chemical usage by effectively using storage and diversion to utilize hidden capacity and delay future expansions?
  • What new technologies are required, and where in the system are they needed, to minimize capital improvements, save on operations costs, and complete “just in time” replacement and repair to minimize maintenance costs?

Carollo custom programmed OPTIMO® using an object-oriented software platform. The engineering inputs to OPTIMO® are projected influent flows and loadings, reuse market demands, plant performance, and anticipated regulatory requirements. Financial input data include existing and projected labor and supply costs and power costs (cogeneration, natural gas power generation, and power purchased from the “grid”). Model outputs include total O&M expenditures, exceedences of peak hourly and average daily capacities, total power consumption, and whether reuse demands are met.

Model run options include scenario generation and optimization. For a single run or scenario, the user can compare a new scenario to a base-case scenario. An optimization run employs a genetic algorithm optimization engine that automatically runs the model numerous times, varying key parameters to determine the optimal solution (e.g., lowest total cost of operation). For IEUA, the key parameters are the diversions and bypasses between treatment plants and the operation of storage basins within and outside of the wastewater treatment plants.

The greatest strengths of OPTIMO® are its rapid generation of “what if” scenarios and its ability to incorporate capacity, reuse/disposal, and regulatory constraints to determine ideal operating conditions at a minimum cost. The scenario and optimization run modes can be used to answer the aforementioned strategic decision-making questions. For example, if the existing system cannot convey projected flows, the bottlenecks and additional required capacities for each scenario are identified by the model, raising a red flag to the user that capital improvements are required. This integration of engineering and business principles is achieved with the use of a “business model” (risk versus return) analysis, creating a better understanding of the effect of management actions involving CIP and operating decisions. This allows for the minimization of the overall cost of service and risk of failure to meet strategic agency objectives.

Carollo trained IEUA staff on the use of the model and developed extensive user manuals to further assist in applying the model. IEUA will use the model for planning and decision support and to help plan for monthly and yearly capital improvement and operations and maintenance budgets.