Viewpoint: Stop wasting energy while treating wastewater
By Justin Rundle
Wastewater treatment plants (WWTPs) account for 3 percent of all energy consumed in the United States and require significant budgetary resources to operate. An endless flow of wastewater requiring treatment means blower and pumping systems are in use and consuming energy 24 hours a day. To reduce energy expenses, achieve greater energy independence and lower operating costs for customers, WWTP managers should be seeking ways to increase efficiency.
Reducing energy costs at WWTPs can be daunting. However, there are simple steps WWTP managers can take to begin identifying efficiency opportunities that will cut utility bills and streamline operations.
First, managers should start by comparing energy use metrics of their facility to a similar facility. For instance, a plant may compare the number of kilowatt-hours it spends processing 1 million gallons of wastewater, or the amount of kilowatt-hours it uses to remove each pound of biochemical oxygen demand. Metrics higher than those of the average facility indicate the facility is operating inefficiently and could be saving energy and money.
Next, managers must identify areas where efficiency can be improved. Establishing an in-depth understanding of where energy waste is occurring and how to mitigate it begins with an energy audit.
A preliminary energy audit typically entails a full-day site visit with an energy engineer who walks through the WWTP to review the operations and processing equipment. He then creates an audit report detailing:
- Overall facility energy use and the blended electrical rate.
- The facility’s operating parameters (e.g., the amount of wastewater processed, sludge hauled to landfills, biogas produced, etc.).
- A comparison of the WWTP metrics to similar WWTPs.
- A list of suggested energy efficiency measures and how much the facility can save by installing them. Examples might include installing high-efficiency lights, variable frequency drives on blowers, or high-efficiency motors.
- The expected costs, savings and simple payback for the energy-efficiency program.
Blueprint for savings
With that information, WWTP managers can determine if they would like a more thorough investment-grade audit (IGA). The IGA takes the preliminary audit one step further by determining which upgrades to pursue. During an IGA, WWTP staff and the energy services contractor:
- Select energy-efficient upgrades to implement.
- Procure proposals from contractors and calculate specific energy savings for each upgrade.
- Determine measurement and verification requirements for each upgrade.
After agreeing on a detailed plan, the WWTP can implement an energy program and begin installing measures to reduce its energy costs. The savings from each energy-saving measure implemented would be verified against a baseline to determine its effectiveness. The energy savings can pay for the up-front cost of the upgrades through loans guaranteed by performance contracts.
Making the audit decision
High utility bills are a problem many WWTPs face. Taking steps to reduce them can be a simple process with proper planning. By measuring overall energy use and taking inventory of how a plant is performing, WWTP staff and city officials can determine if an energy audit is appropriate, and work to construct a program to reduce energy costs and increase efficiencies.
Justin Rundle, PE, CEM, CCM, LEED-AP, is an energy engineer for Minneapolis-based Honeywell Building Solutions, part of Fortune 100 diversified technology and manufacturing leader Honeywell. He is a licensed WWTP operator and construction contractor in Arizona. With 25 years of experience in the construction and engineering industry, Rundle specializes in evaluating and developing energy efficiency measures at water and wastewater treatment plants. He can be reached at firstname.lastname@example.org