ENERGY EFFICIENT SYSTEM DESIGN FOR WASTEWATER TREATMENT PLANTS0 pages

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ENERGY EFFICIENT SYSTEM DESIGN FOR
WASTEWATER TREATMENT PLANTS:
A System Splitting Approach

Stephen Horne, Product Manager, Blowers—USA
Kaeser Compressors, Inc.

Abstract
Energy is the single highest operating cost in a
wastewater treatment plant. More specifically,
the energy to operate blowers for aeration is the
single highest energy consumer. Fortunately,
blowers and blower systems are becoming more
energy efficient as system engineers pay more
attention to this critical cost factor. It is no longer
enough to only consider the individual equipment’s
efficiency. With energy costs on the rise, it is now
more important than ever to carefully examine the
entire system’s efficiency and understand how
each piece of equipment works with one another
and how this interaction impacts the overall plant
energy efficiency. This paper will outline the traditional approach to wastewater treatment plant
design, the efficiency problems associated with
this approach, and explain system splitting, an
alternate design approach with key efficiency
gains. The paper will include guidance on how to
calculate specific power for an individual unit as
well as an entire system and provide calculation
examples for comparing system specific power
between traditional and system splitting design
approaches.

Nature of WWTP Planning
Unlike commercial systems, municipal wastewater treatment plants are often designed and built
based on projected populations and demand 10,
20, and even 30 years in the future. Because

June 2014

FIGURE 1: OF ALL THE ENERGY COSTS AT A WASTEWATER TREATMENT PLANT, ENERGY FOR AERATION IS BY
FAR THE HIGHEST.

project funding is available now and may not be
available later on, system engineers are tasked
with building a system that will continue to serve
the community’s growing needs, and in the most
cost-effective, energy-efficient way possible. This
is no simple task. Although the volume of air
needed changes seasonally, day to day, even
hour to hour, the general practice is to design the
plant’s capacity for the worst case/maximum load.
This results in oversizing the blowers. Because the
blowers are oversized, they do not operate at their
most efficient design point, spending as much as
90% of their operating time wasting costly energy.

Kaeser Compressors, Inc. 877-586-2691 www.kaeser.com

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