Whether large or small pumps, there comes a debate when multiple drive motors are used to
cover a broad range ofoutput flow requirements: use one Variable Frequency Drive (VFD) plus
a number of softstarts, some small and some large pumps with or without VFD’s, one or more
VFD’s on a group ofpumps, and all combinations in between. Equipment rotation and
maintenance, starts per hour, starts per day, minimum flows, maximum demands, etc., all are
considerations and decisions to be made. Many of these combinations invoke unintended
hydraulic consequences. The focus ofthis paper is the benefits of synchronous, closed transition
hand-off between VFD’s and utility powered devices in multi-motor applications. Using off-theshelf,
standard, available equipment that can synchronize drive output with across-the-line loads,
the best of numerous options can be had while reducing power costs, protecting personnel and
equipment, and achieving process control.
Posted: May 20th, 2011 | Filed under: Uncategorized | Tags: Energy Efficiency, Equipment Protection, Lower Capital Cost, Personnel Protection, Reduced Power Costs, Smaller Carbon Footprint | No Comments »
Pump stations are an integral part of wastewater collection and treatment systems. Their
applications can be quite varied: lift stations in the collection network pump raw sewage up to a
level where gravity can take over; pumping systems within the treatment plant move effluent
through various treatment stages or deliver it from the plant to agricultural users and others.
While wastewater pumps have a common function––moving fluid where gravity can’t––the
design of any individual pump station can depend on many factors.
Choosing the right pump station design for the application is a matter of balancing personal
preference with the requirements of the job, the necessity for energy efficiency and the need for
pump station reliability. This presentation examines three very different pumping system
designs, and weighs the advantages and disadvantages of each in the context of real-world
Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment | Tags: Efficient Lift Station Design, Energy Efficiency, Improved Plant Performance, Improved Plant Reliability, Improved Wastewater Pumping | No Comments »
Public agencies are increasingly pressured to become more sustainable. Wastewater plants are
significant consumers of energy and correspondingly produce significant quantities of
greenhouse gas (GHG). Reductions in energy and GHG are challenges for wastewater facilities
as flows and loads increase and discharge requirements become more restrictive. The results
highlight some methods to reduce energy and GHG, including the concept of becoming energy
neutral. Energy (as represented by electrical energy or fuels) equate directly to GHG production.
A significant portion of the fuel source for most utilities in the United States is from
anthropogenic sources such as coal, oil, or electric. To achieve energy neutral facilities, the
wastewater plant must implement energy conservation and shift to biogenically derived energy
sources, such as biogas, or alternative energy sources, such as wind. This paper and presentation
describe how wastewater treatment plants can significantly reduce energy to the point of
becoming energy neutral.
Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Best Practices, Cost Savings, Energy Efficiency, Energy Savings, Environmental Impact, Improved Biogas Production, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Energy consumption for municipal wastewater treatment accounts for 15% to 30% of the
operating cost at large treatment facilities and 30% to 40% at small facilities (WEF, 2009).
Energy costs are expected to continue escalating as a result of the rising price of fossil fuels used
for energy production while the energy demand for wastewater treatment is expected to grow as
the use of energy intensive treatment processes increases to meet water quality objectives that
may demand increasingly stringent wastewater discharge limits.
The United States Environmental Protection Agency (EPA) is committed to promoting energy
efficiency and implementation/use of energy conservation measures at municipal wastewater
treatment facilities. EPA, in partnership with The Cadmus Group and HDR, has undertaken a
project to identify and evaluate innovative energy conservation methods implemented at
wastewater utilities in the U.S. and report on their effectiveness in achieving reductions in energy
use and cost associated with wastewater treatment.
Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Saving, Energy Efficiency, Energy Savings, Environmental Impact, Operational Modification, Plant Sustainability, Process Control Enhancements, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
This paper outlines how energy management planning can accomplish dual goals of
energy self-sufficiency and optimum treatment processing, and how this provides robust
performance and acceptable payback on investment, leading to net zero energy
wastewater operations. The energy content of wastewater surpasses the energy required
by treatment, reportedly be a factor of up to 10 times. Nevertheless, conventional
activated sludge plants with advanced treatment consume typically 1,800 kWh/MG of
electricity, but facilities vary from 1,000 to 3,000 kWh/MG. Energy efficiency studies
conclude that the potential for energy use reductions through efficient pumps and aerators
are on the order of 30 to 50 percent, which is a range of about 400 to 700 kWh/MG. For
plants with anaerobic digestion, a rule-of-thumb for electrical production from biogasfueled
generators is 500 kWh/MG. Supplementation of anaerobic digesters with high
strength organic waste and fats, oils and grease is possible where utilities have excess
digester capacity. The experience with supplementation is that facilities have increased
biogas by a factor of two or three times pre-existing conditions, and are able to have a
corresponding increases in electricity production, where generators have been adequately
sized. When thermal heat can be returned for plant processes, overall plant efficiencies
rise even higher. Energy planning studies have also shown that innovative technologies
that build upon anaerobic processes reduce energy usage from typical values, and,
further, energy plans have demonstrated some unexpected results, such as the economic
and environmental justification of anaerobic digestion combined with thermal processing,
such as dryers and incinerators. While local conditions, particularly energy pricing and
government subsidies, likely shape the specific planning objectives and outcomes of any
individual plant, the variety of energy efficiency and production technologies that are
becoming proven can result in a similar endpoint, and specifically net zero energy
Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Efficiency, Energy Savings, Environmental Impact, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
The MBR technology is an attractive, flexible solution for plant expansion/enhancement
as well as for greenfield facilities. While capital costs of MBRs have become fairly
competitive with conventional treatment systems, the operating costs, specifically energy
requirements, require additional focus. In order to provide the most cost effective and
energy efficient system, enhancements with design, operations, and equipment selection
are required. There are several areas within the design of an MBR plant which provide the
opportunity for a cost effective design which balances capital and operating costs. These
include use of primary clarification, use of flow equalization, adjusting the balance of the
solids between biological treatment and the membrane basins, and pump configuration.
Key operational focus areas include membrane scour air operational strategies, use of flux
enhancers, optimization of the number membranes in service, and biological operating
conditions. Along with the operational strategies to reduce energy, energy efficient
equipment must be selected.
Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Saving, Energy Efficiency, Energy Savings, Plant Enhancements, Plant Sustainability, Reduced Operating Costs | No Comments »
Upper Occoquan Service Authority
The cost of energy has become an increasing concern to water and wastewater utilities.
Economic drivers, combined with general industry concerns about energy supply reliability,
climate change, and sustainability have encouraged many utilities to consider alternative project
delivery methods to finance desired energy efficiency and renewable energy projects. One such
alternative delivery method is the Energy Performance Contract.
Energy performance contracting has been applied most actively by Energy Service Companies
(ESCOs) to implement building efficiency improvements at institutional facilities: universities,
schools, hospitals, and government buildings. It has been only within the past five years that
municipal water and wastewater utilities began using this alternative delivery method to
implement energy efficiency improvements at their treatment plants.
This paper provides an overview of energy performance contracting and the ESCO market. It
also presents a case study from a municipal wastewater utility in Virginia that is utilizing energy
performance contracting to implement energy efficiency projects: the Upper Occoquan Service
Authority in Centreville, VA.
Posted: May 20th, 2011 | Filed under: >1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Efficiency, Energy Savings, Heat Drying, Plant Optimization, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions, Renewable Energy | No Comments »
Alexandria Sanitation Authority
The world’s focus on sustainability is increasing at a rapid rate. Over the last year on the World
Wide Web, searches for key words like “Sustainability” and “Green” have risen 165%. People
are beginning to question our civilization’s behavior over the last century and whether our quest
for advancing our species can be maintained. We as an industry of public servants are also
questioning some things that were previously held as fact:
• Clean water professionals are environmentalists by trade. We already practice sustainability… right?
• Our treatment plants were designed and constructed to protect the environment. That means their sustainable… right?
• We are primarily non-profit, focusing on providing service to our rate payers in the most cost effective manner. That’s sustainable… right?
Since focusing on sustainability causes you to look at the most core elements of your business, it is a pretty overwhelming task. This paper will attempt to tell a story about one clean water plant’s stepwise journey towards sustainability. Source: WEFTEC 2008 Proceedings
Posted: August 27th, 2010 | Filed under: 100K-500K, Sanitary Sewer, Waste Water Treatment, Water Treatment | Tags: Energy Efficiency, Increased Plant Efficiency, Plant Sustainability | No Comments »