John Bidwell, Program Manager, Quantum Energy Services and Technologies (QUEST): California Wastewater Process Optimization Program (CALPOP).

Meeting Date: October 01, 2013

Agenda Item #1. John Bidwell, Program Manager, Quantum Energy Services and Technologies (QUEST): California Wastewater Process Optimization Program (CALPOP).

 

BACKGROUND

This Technical Memorandum (TM) presents a preliminary assessment of energy efficiency opportunities at the City of Livingston’s Wastewater Treatment Plant (WWTP) as provided by PG&E’s California Wastewater Process Optimization Program (CalPOP) , a program administered by QuEST. The CalPOP program offers engineering audits ("Facility Audit") to identify energy efficiency (EE) opportunities at municipal wastewater treatment facilities that are PG&E customers. The program offers rebates for the installation of energy efficiency measures (EEMs) qualified by Facility Audits, and also qualifies the EEMs for loan financing through PG&E’s On-Bill Financing (OBF) Program.

The preliminary assessment of energy efficiency opportunities identified in this TM is intended to provide the City of Livingston with background information on an EE project that would be explored in greater detail in a Facility Audit to follow upon the City’s request. Starting late in 2012, a QuEST engineering team conducted an initial assessment of the City of Livingston Wastewater Treatment Plant (WWTP). This memo summarizes the findings form that assessment and provides a preliminary estimate of the savings that could be realized from the proposed project. Actual energy savings from an installed project may be greater or less than estimated herein, and a CalPOP Facility Audit would be instrumental in refining estimates of project costs, energy and bill savings.

PLANT SUMMARY

The WWTP process consists of an oxidation ditch with a design treatment capacity of 1.84 MGD. Flows and wastewater loads are lower than the WWIP design capacity. Table 1 lists the monthly average and maximum daily flows from November 2011 through March 2013.

According to Table 1, the WWTP received an average daily wastewater flow of 1.04 MGD during the reported period. Maximum daily flows reached 1.41 MGD during the month of April 2012. It appears that wastewater flows have remained relatively constant. Incoming BODs range from 150 mg/l to 280 mg/l and average 193 mg/l. There is a significant variation in BOD concentrations.

The oxidation ditch is equipped with two 200 HP vertical turbine mixers /aerators. One vertical turbine operates using a Variable Frequency Drive (VFD) while the second one operates at a constant speed unit. At the current loadings, the WWTP operates using only one of the turbine mixers while the second one is on standby. The speed of the vertical turbine is automatically adjusted to maintain a set dissolved oxygen concentration in the mixed liquor.

A review of the last three years of power consumption at the WWTP shows an average power consumption of approximately $1,075,000 kWh annually. That equals to a continuous load of approximately 122 kW (165 HP). Assuming that 90 percent of the WWTP’s load is aeration and mixing, the vertical turbine average energy demand should be approximately 110 kW (148 HP).

Table 1 Average Daily Flow and Maximum Daily Flow (November, 2011 to March, 2013)

Month

Average Daily Flow

(MGD)

Maximum Daily Flow

(MGD)

BOD (mg/I)

November 2011

1.05

1.27

250

December 2011

1.02

1.15

170

January 2012

1.04

1.23

160

February 2012

1.01

1.23

230

March 2012

1.02

1.25

210

April 2012

1.04

1.41

200

May 2012

1.03

1.2

130

June 2012

1.04

1.27

260

July 2012

1.04

1.28

155

Augusts 2012

1.05

1.18

150

September 2012

.

.

.

October 2012

.

.

.

November 2012

1.09

1.31

150

December 2012

1.06

1.31

280

January 2013

1.01

1.11

.

February 2013

1.01

1.22

170

March 2013

1.02

1.12

190

Average:e

1.04

1.24

193

PROPOSED PROJECT (EEM)

It appears from this preliminary assessment that the oxidation ditch vertical turbines are larger than are actually needed to treat current wastewater flows and the design wastewater flow. One, or both, of the vertical turbines can be replaced with smaller turbines realizing significant energy savings. In addition, new model turbines are also available that can achieve 10 to 15 percent higher oxygen transfer efficiencies.

Based on initial calculations, it appears that a 100 HP vertical turbine would provide enough capacity to handle the current wastewater flows. A smaller vertical turbine could also be controlled using a variable frequency drive (‘VFD) to further reduce consumption. The power consumption from one single 100 HP turbine at the current loads is expected to be approximately 50 kW.

Table 2 shows the estimated reduction in power consumption (kWh), annual savings ($) and CalPOP rebate ($) that can be realized from replacing one of the existing 200 HP turbines with a smaller 100 HP unit.

Table 2 – Estimated Energy Savings from Replacing Vertical Turbine.

EEM

Reduction in Power

Demand (kW)

Annual Reduction

(Kwh/yr)

Annual Bill

Savings1 ($)

CalPOP

Rebate ($)

Replace \Vertical Turbine

60

525,600

$70,000

$48,000

1 : Assumes a power cost of $0.135/Kwh

CalPOP provides a rebate based on installed project energy savings and can provide up to 50 percent of project costs associated with an energy efficiency project. Replacing the vertical turbine mixer will reduce the WWTP’s overall energy consumption and is considered an eligible energy efficiency project for a CalPOP rebate. In order to receive the maximum rebate amount ($48,000), the project cost would need to equal or exceed $96,000 for the implementation of this proposed project.

Table 3 shows the estimated costs of replacing a vertical turbine mixer with a smaller one:

Table 3 – Opinion of Probable Construction Costs

Item

Amount

Equipment (quote from Westech)

$100,000

Installation

$25,000

Electrical/Instrumentation

$35,000

Project management/Engineering

$20,00

Total

$180,000

according to this preliminary estimate, the net expense of this EEM, after the CalPOP rebate, would be reduced to $132,000. Loan financing for imple1nentation can be obtained through PG&E’s On­ Bill Financing (OBF) program that offers a zero interest loan to cover costs of implementing qualified EEMs. The maximum OBF loan amount for municipalities is $250,000, and an OBF loan could be utilized to finance the net expense of the project. CalPOP rebates and OBF loan funds arc disbursed upon completion of project installation and verification of actual energy savings. Working together with the City’s assigned PG&E .Account Services Representative, the CalPOP program administrator will coordinate and process all the required documentation to obtain OBF financing for the City.

RECOMMENDATION

Based on the findings of this preliminary assessment we recommend the City to participate in the CalPOP program by conducting a more detailed engineering audit that will closely define the project (EEM) proposed above.

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