The physics of moving vast amounts of water from deep wells, rivers and reservoirs to customers through a network of pipes requires large amounts of energy. In fact, according to the EPA, water and wastewater systems account for approximately 3-4 percent of all energy used in the United Sates, which results in emissions of more than 45 million tons of greenhouse gases (GHGs) annually.
At Aqua, 84 percent of our total energy consumption is from drinking water operations and 16 percent is related to wastewater services. Each year, Aqua filters and distributes enough drinking water to cover the entire State of Delaware with two inches of water – and that filtering and distribution requires a lot of energy!
As a large consumer of energy, Aqua aims to be as efficient and responsible in our energy usage as possible. A vast majority of our energy consumption – 83 percent – is electricity. In the course of our operations, we also utilize:
- natural gas for heating our facilities;
- gasoline and diesel fuel for our fleet of vehicles and construction equipment, as well as backup generators at our treatment facilities; and
- compressed natural gas (CNG) as a diesel alternative in our heavy-duty utility and truck fleet.
Committed to renewable energy sources
Because our operations are dependent on electricity, Aqua is committed to investing in and utilizing renewable energy sources. Across our footprint, we maintain nearly 2.5 megawatts of solar production capacity, which generated 3,771 megawatt-hours of electricity in 2017. This is approximately 1 percent of our electrical power needs, or enough electricity to power 350 homes for a year. Unfortunately, it is not feasible to install solar panels at every Aqua location, which is why we also purchase Green-e Energy certified wind power. In 2017, wind power represented 6 percent of Aqua’s total purchased electricity.
Tracking energy intensity, or measuring energy efficiency from an economical perspective, allows Aqua to benchmark operations across our regions and states. Aqua has a very diverse network of water systems across it states, maintaining nearly 1,500 water systems ranging in size from less than 25 to 275,000 connections. While our median water system is 64 connections and economy of scale favors larger systems for single efficiency opportunities, our large number of nearly identical smaller systems provides an opportunity to replicate energy efficient methods across a large number of similar systems.
The energy intensity for water production across all eight states is 3.18 kilowatt-hours per thousand gallons, ranging from 1.90 to 4.49 kWh/kgal. These energy intensity values are highly dependent on physical factors, which vary not only state to state, but by region and location. The depth and lift required to gather water, and the pressure required to pump water across distance and elevation are the most significant factors in energy intensity. And because of our large number of smaller systems, heating pump stations during the winter can often cause the intensity factor to double during the colder months. Also, our increasing use of ultraviolet light and the on-site generation of chlorine from salt brine for disinfection purposes raises our electrical consumption.
Aqua also tracks the energy intensity of our wastewater systems. More than 50 percent of the energy consumed at a wastewater treatment plant is often from aeration, the process of adding air into wastewater to allow aerobic bio-degradation of pollutants. Aeration is an essential part of wastewater treatment systems and Aqua is actively evaluating this process at all of our wastewater treatment plant facilities. We are investigating the implementation of variable speed drive blower motors, in which sensors control dissolved oxygen to the optimal level. This approach has been shown to reduce energy consumption by up to 50 percent.
Aqua is actively engaged in reducing our energy consumption through energy efficiency projects, including variable-frequency drive motors, eliminating throttle valves and ensuring equipment is right-sized to reduce energy consumption, while meeting our customers’ future needs as water demands decrease.
Maintaining the level of oxygen in the wastewater is critical to the biological growth to remove nutrients and organics. At the Candlelight wastewater treatment plant located in Spring, Texas, we installed a dissolved oxygen (DO) set point controller with a new variable-frequency drive (VFD) blower for wastewater aeration. This technology using DO set point controls and variable-frequency blowers is the most efficient and effective method to maintain the wastewater oxygen levels at an effective level. Using this variable-frequency blower resulted in a reduction of energy consumption by 46 percent and more than $12,000 in annual energy savings, compared with a fixed speed blower. Additional benefits include a reduction in the risk of wastewater discharge compliance limit excursions, lower background ambient noise and a $15,690 energy efficiency rebate from CenterPoint Energy. The investment was such a success that we have planned additional wastewater treatment VFD blower projects in the state in 2018 and 2019 to further lower our energy benchmark.