Conference Agenda

Clean water agencies, regulatory agencies, and watershed stakeholders are searching for innovative approaches and best practices to address water quality challenges due to nutrient enrichment and a changing climate. A key component of such improvements is to take advantage of existing assets through optimization. While potentially attractive, optimization is a daunting task and a comprehensive guide on implementing optimization has been lacking.

This presentation is part of the Water Research Foundation project 4973 “Guidelines for Optimizing Nutrient Removal Plant Performance” that developed a comprehensive guide on implementing an optimization strategy for water resource recovery facilities (WRRFs) with an emphasis on nutrient management (based on full-scale examples). The presentation focuses on a key component of the guide, the nutrient optimization decision trees that can assist WRRFs with navigating nutrient optimization.

The nutrient decision trees developed will be available on the Water Research Foundation’s website this calendar year as part of a web-based interactive tool. The decision trees ask the user a series of questions, whereby the responses inform the generation of a list of potentially viable optimization strategies for their WRRF. Each potentially viable strategy has a corresponding Fact Sheet associated with it to further assist the user as to whether such a strategy might work for their WRRF.

While more extensive detailed analyses will likely be required to verify/validate each potential strategy for facility specific applications, the decision trees expedite the optimization effort and help initiate the process. For example, the decision tools have been applied to satisfy the optimization planning requirements of the Puget Sound Nutrient General Permit (PSNGP). The decision trees benefit wastewater utilities by providing a comprehensive screening of optimization opportunities that efficiently narrow considerations to the most promising options. In this way, resources can be focused on the facility specific details of optimization.

As part of the presentation, the Water Research Foundation web-based interactive tool will be used in real-time to highlight the ease of using the tool. The audience should leave the presentation with an understanding on how to use the decision tree tool.

The City of North Las Vegas Water Reclamation Facility (CNLV WRF) uses a traditional Johannesburg process and a membrane biological reactor (MBR) aimed at removing phosphorus and nitrogen. During a recent capital improvement project to re-coat the MBR basins, the CNLV consolidated the number of basins in-service from 12 to 9 MBR trains. The basin consolidation impacted the stability of the biological phosphorus removal performance.

A study was conducted to identify and evaluate potential optimization opportunities to improve the stability of the biological phosphorus removal process. The study targeted key process parameters, such as chemical addition, solids retention time, hydraulic retention time, and oxidation reduction potential, all of which can also impact MBR performance. Seven optimization scenarios were developed focusing on three themes: peak flow management, solids loading in the MBR (chemical and biological), and dissolved oxygen concentration in the MBR and recycle streams.

All optimization opportunities were evaluated using a wastewater process modeling software with the intent of shortlisting several optimization alternatives to test on the full-scale process. The simulation results were used to estimate process performance, such as MBR permeate phosphorus, ammonia, and nitrate concentrations, under varying operational conditions.

This presentation will highlight the impact of peak flow management with the use of an equalization basin and the importance of balancing solids loading by optimizing chemical addition and dissolved oxygen concentration in the return streams by optimizing recycle rates.