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<br />Facility Audit Report 3 <br />San Leandro WWTF <br />1. INTRODUCTION <br />One Energy Efficiency Measure (EEM), a high efficiency aeration blower upgrade (Aeration <br />Blower EEM), was evaluated at the San Leandro Wastewater Treatment Facility (WWTF). This <br />measure was chosen following a walkthrough of the facility, and discussion with facility staff. <br />They have a cogeneration system using digester gas, which can supply approximately 60% of <br />plant load. The facility purchases all remaining electrical power from PG&E, which totaled 3.2 <br />million kWh from May 2010 through April 2011. <br />1.1 Project Process Overview and Objectives <br />A technical investigation and investment grade audit was performed for the EEM. The <br />objectives of the study were to establish the soundness of the EEM from both an operational <br />and financial standpoint, and estimate the electrical energy and demand savings that could be <br />expected. The facility maintains blower electrical current, airflow, and aeration system pressure <br />readings on the SCADA (Supervisory Control, Alarm, Data Acquisition) system’s historical <br />trending feature. Spot measurements of power and aeration system pressure were made to <br />verify the SCADA readings. The baseline energy demand for the blowers was established for <br />calendar year 2010 based upon hourly SCADA data samples. The process considerations for <br />the EEM involved estimating how much power demand will be reduced from baseline by <br />improving blower efficiency. Energy savings were translated into electrical cost savings. <br />1.2 General Facility Description <br />The San Leandro Wastewater Treatment Facility (WWTF) is owned and operated by the City of <br />San Leandro. The WWTF is called H2OWorks. It serves about 50,000 residents, numerous <br />businesses and 22 industrial facilities. It receives the highest concentration of treatable waste of <br />all the major Bay Area WWTF’s, as measured by Biochemical Oxygen Demand (BOD). The <br />average daily flow to the WWTF is 5 Million Gallons per Day (MGD), with a design dry weather <br />flow of 7.6 MGD, and wet weather spikes up to 23 MGD. The treatment train provides <br />secondary level treatment with primary clarifiers, a fixed film reactor (trickling filter), aeration <br />basins with fine bubble diffusers, hypochlorite disinfection, and dechlorination. 90% of the <br />treated effluent is discharged to the San Francisco Bay via the East Bay Discharge Authority <br />(EBDA), and the remaining 10% of the effluent is used for commercial irrigation. Secondary <br />biosolids are thickened with polymer and a rotary drum thickener, then combined with primary <br />biosolids and sent to an anaerobic digester. Methane from the anaerobic digester is fed to <br />cogeneration engines, supplying 60% of plant electricity, and 100% of the heat to operate the <br />digesters. The digested biosolids are then dewatered with belt filter presses, and taken to drying <br />beds to produce Class A biosolids. <br /> <br />Figure 1.2.1 provides and aerial view of the San Leandro WWTF and identifies the component <br />operations in the Facility’s treatment process. <br />