Aimee Mckane

Alex Lekov

Ernest Orlando Lawrence

Katherine Song

Lisa Thompson

CiteSeerX

 1 
 
 
Automated Demand Response 
Opportunities in Wastewater 
Treatment Facilities  
Lisa Thompson, 
Katherine Song, 
Alex Lekov, and  
Aimee McKane 
 
Environmental Energy Technologies 
Division 
November 2008 
 
This work was sponsored by the Demand Response Research Center 
(http://drrc.lbl.gov) which is funded by the California Energy 
Commission (Energy Commission), Public Interest Energy Research 
(PIER) Program, under Work for Others Contract No.150-99-003, Am 
#1 and by the U.S. Department of Energy under Contract No. DE-
AC02-05CH11231. 
ERNEST ORLANDO LAWRENCE 
BERKELEY NATIONAL LABORATORY 
 2 
 
 
Disclaimer 
 
This document was prepared as an account of work sponsored by the United States 
Government. While this document is believed to contain correct information, neither the 
United States Government nor any agency thereof, nor The Regents of the University of 
California, nor any of their employees, makes any warranty, express or implied, or 
assumes any legal responsibility for the accuracy, completeness, or usefulne s of any 
information, apparatus, product, or process disclosed, or represents that its use would not 
infringe privately owned rights. Reference herein to any specific commercial product, 
process, or service by its trade name, trademark, manufacturer, or otherwise, does not 
necessarily constitute or imply its endorsement, recommendation, or favoring by the 
United States Government or any agency thereof, or The Regents of the University of 
California. The views and opinions of authors expressed herein do not necessarily state or 
reflect those of the United States Government or any agency thereof or The Regents of 
the University of California. 
 
Ernest Orlando Lawrence Berkeley National Laboratory is an equal opportunity 
employer. 
 3 
Automated Demand Response Opportunities in Wastewater Treatment 
Facilities 
 
Lisa Thompson, Katherine Song, Alex Lekov, and Aimee McKane 
Lawrence Berkeley National Laboratory, Berkeley, California 
 
Wastewater treatment is an energy intensive process which, together wit  water 
treatment, comprises about three percent of U.S. annual energy use.1 Yet, since 
wastewater treatment facilities are often peripheral to major electricity-using industries, 
they are frequently an overlooked area for automated demand response opportunities.  
 
Demand response is a set of actions taken to reduce electric loads when 
contingencies, such as emergencies or congestion, occur that threaten supply-demand 
balance, and/or market conditions occur that raise electric supply costs. Demand response 
programs are designed to improve the reliability of the electric grid and to lower the use 
of electricity during peak times to reduce the total system costs. Open automated demand 
response is a set of continuous, open communication signals and systems provided over 
the Internet to allow facilities to automate their demand response activities w hout the 
need for manual actions. Automated demand response strategies can be implemented as 
an enhanced use of upgraded equipment and facility control strategies installed as energy 
efficiency measures. Conversely, installation of controls to support automated demand 
response may result in improved energy efficiency through real-time access to 
operational data.2,3  
  
This paper argues that the implementation of energy efficiency opportunities i  
wastewater treatment facilities creates a base for achieving successful demand reductions. 
This paper characterizes energy use and the state of demand response readiess in 
wastewater treatment facilities and outlines automated demand response opportunities.    
 
Energy Use in the Wastewater Treatment Process 
 
 In order to assess the potential for demand response in wastewater treatment 
facilities, it is important to understand the magnitude of energy use and demand in these 
facilities, the daily and seasonal load patterns, and the role of energy-intensive equipment 
in the wastewater treatment process.  
 
Load variation in wastewater treatment facilities depends on many factors 
including seasonal and daily load patterns, the type of industry, location, and population 
size.4  For example, many manufacturing facilities have fairly constant waste ter flow 
rates during daily production, but these can change dramatically during cleanup and 
shutdown.4  Industrial wastewater flow rates vary in this manner depending on the time 
of day, day of the week, season of the year, or sometimes the nature of the discharge.4  
Particularly for municipal treatment facilities, wastewater flows often follow a diurnal 
pattern where the peak flows generally occur twice a day: once in the late morning when 
wastewater from the peak morning water use reaches the treatment facility and a second 
 4 
peak flow during the early evening between 7 and 9 p.m.4 Figure 1 shows a sample 
summer load pattern for a municipal wastewater treatment facility.  
 
 
 
Figure 1: Municipal Wastewater Treatment Facility Load Pattern  
 
Wastewater treatment facility electricity demand is high during the summer 
months, particularly in areas with hot summers like Southern California.5 The facility 
demand required to treat and transport wastewater is significant during the peak 
electricity demand periods experienced by the electrical utilities.5  This, combined with 
the characteristic energy-intensity of the wastewater treatment process, makes wastewater 
treatment facilities prime candidates for automated demand response.  
 
 In 2001, wastewater treatment facilities in California consumed 2,012 GWh of 
electricity.6  Within these facilities, the energy intensity for water collection and 
treatment ranged from 1,100 kWh/million gallons to 4,600 kWh/million gallons.6  One of 
the reasons for this wide range is the variability in transporting and pumping wastewater.  
The average amount of electricity used for transporting and pumping wastewater from a 
residential or commercial area to a municipal wastewater treatment facility is 150 
kWh/million gallons, but this value can vary greatly depending on wastewater treatment 
facility topography, as well as system size and age.6 Some wastewater collection systems 
rely on gravity to transport wastewater to a treatment facility, while oth rs use energy 
intensive pumps to lift or transfer the wastewater.6 Another reason for the variability in 
wastewater treatment energy intensity is the dependence of energy use on the quali y of 
the waste stream, the level of treatment required to meet regulations, and the treatm nt 
technologies used.6  
 
A New York State Energy Research and Development Authority (NYSERDA)  
study found that the national average energy intensity for wastewater treament was 1,200 
kWh/million gallons.7 New York State’s average energy use for treating wastewater was 
 5 
1,067 kWh/million gallons for large facilities (> 75 million gallons per day) and 3,749 
kWh/million gallons for small facilities (< one million gallons per day), with a statewide 
average of 1,353 kWh/million gallons. This shows that the energy use in large facilities is 
much lower than in small facilities, and that large facilities process a significantly higher 
portion of wastewater, bringing the average to the lower end of the range.  
 
The potential for implementation of automated demand response and energy 
saving measures depends on the technologies involved in the wastewater treatmen  
process. Wastewater is generally treated by removing coarse and suspended solids and 
organic matter from the waste stream through screens and sedimentation in the primary 
treatment process. It is then aerated in secondary treatment, which raises the dissolved 
oxygen levels, helping promote the growth of microorganisms which remove the 
remaining soluble and organic material. Finally, nutrients and toxic compounds are 
removed and the water is chemically disinfected.  Figure 2 shows the average distribution 
of energy end-uses in the municipal wastewater treatment process based on eight 
municipalities in New York State.  
 
Secondary 
Treatment
53%
Advanced 
Treatment
0%
Preliminary 
Treatment
3%
Wastewater 
Pumping
8%
Non-Potable 
Process Water 
Pumping
6%
Primary 
Treatment
0%
Solids Handling
11%
Disinfection
0%
Lighting & HVAC
4%
Other
15%
 
Figure 2. Wastewater Treatment Equipment Energy Use8 
 
The energy use by individual equipment in the wastewater treatment process 
plays an important role in formulating automated demand response strategies since 
energy-intensive equipment should be the primary target for demand response. The most 
energy-intensive equipment in a wastewater treatment facility are pumps and aerators 
fans. The energy required for influent wastewater pumping can range from 15 to 70 
percent of the total electrical energy depending on the wastewater treament facility site 
elevation and influent sewer elevation.9 In many cases, wastewater treatment facilities 
with  diffused aeration systems can use 50 to 90 percent of electric power demand to run 
aerator blower motors.10 Developing demand response strategies focusing on this key 
equipment may result in the most significant load reductions. 
 
Wastewater Treatment Facility Controls 
 
 6 
 Control systems are essential for automating demand response strategies in 
wastewater treatment facilities. The use of centralized computer controls, such as 
Supervisory Control and Data Acquisition (SCADA) systems in wastewater treatment 
facilities is increasing by about five percent annually.11 The introduction of centralized 
controls integrates existing standalone controls or distributed control system , improving 
operational efficiency and facilitating the automation of demand response strategies. 
 
Centralized control systems allow for integrated data collection and analysis, nd 
provides opportunities to improve overall facility performance.12 Within wastewater 
treatment facilities, SCADA systems direct when to operate remote equipment and make 
complex decisions based on input from the system.11  These systems provide continuous 
and precise control of process variables11 and can start, slow down, or stop equipment 
when monitored process information such as flow rates and dissolved oxygen levels 
deviate from pre-established parameters.13  SCADA systems can be programmed to 
monitor and automatically adjust equipment in response to deviations from preset levels 
for biological oxygen demand, air density, blower efficiency, and facility flow on a real-
time basis, and meet discharge regulations with better control at the treatment level.13,14 
Centralized control systems allow for more efficient overall operation of allfacility 
systems, and provide an entry point to the facility to implement automated deman  
response strategies.  
 
Automated Demand Response Strategies 
 
 The technologies that enhance efficiency and control within wastewater treatment 
facilities could also enable these facilities to become successful deman  response 
participants. Comprehensive and real-time demand control from centralized computer 
control systems can allow facility managers to coordinate and schedule load shedding and 
shifting through equipment-level controls to reduce energy demand during utility peak 
hours. This section outlines several load shedding and load shifting opportunities that 
could be successful in wastewater treatment facilities.   
  
 Opportunities for load shedding during demand response events include turning 
non-essential equipment off and transitioning essential equipment to onsite power 
generators. Facilities can turn off aerator blowers, pumps, facility HVAC systems, and 
other non-essential equipment to shed electrical load during peak hours. Alternatively, 
facilities can use variable frequency drives to operate this equipment at lower capacity 
which reduces demand and better matches the requirements for operation within 
regulatory limits. Centralized control systems can provide wastewater treatment facilities 
with an automatic transfer switch to running onsite power generators during peak dem nd 
periods.13  Onsite power generators running on anaerobic digester gas, a byproduct of the 
treatment process, can also provide off-grid power during demand response events. This 
strategy has been proven successful in municipal wastewater treatment facilities; the East 
Bay Municipal Utilities District has implemented a load management strategy which 
includes a digester cover that stores anaerobic digester gas until it can be used during 
peak-demand periods.15  
 
 7 
Implementing load shifting strategies in wastewater treatment facili ies allows the 
main energy-intensive treatment processes to be rescheduled to off-peak hours.16  A 
major opportunity for shifting wastewater treatment loads from peak demand hours to 
off-peak hours is over-oxygenating stored wastewater prior to a demand response event. 
This allows aerators to be turned off during the peak period. However, facilities must be 
careful to monitor and maintain the correct range of aeration since over-oxygenation due 
to prolonged detention time can also adversely affect effluent quality. Further, if site 
conditions allow, wastewater treatment facilities can also utilize exc ss storage capacity 
to store untreated wastewater during demand response events and process it during off-
peak hours.15 Additionally, facility processes such as backwash pumps, biosolids 
thickening, dewatering and anaerobic digestion can be rescheduled for operation during 
off-peak periods, providing peak demand reductions in wastewater treatment facilities.13, 
17  
 
Conclusions and Future Directions 
 
Wastewater treatment is an energy intensive process with high electrical load 
during the utility peak demand periods. Integrated centralized control systems ar  
becoming more commonplace in wastewater treatment facilities. These control systems 
improve efficiency and allow for greater control of facility process, and can also be used 
in the integration of automated demand response strategies. These controls can be used to 
shed or shift loads through lowering the capacity of aerator blowers, pumps and other 
equipment, temporarily transitioning to onsite power generators, over-oxygenating or 
storing and processing wastewater during off-peak periods.  
 
While only a few of the demand response opportunities outlined in this paper 
have been tested and proven as successful load management strategies, similar activit es 
have long been incorporated as energy efficiency measures in wastewater treatment 
facilities. The success of energy efficiency opportunities in these facilities, combined 
with the increased use of centralized control systems, demonstrates the potential f r 
automated demand response. Furthermore, the magnitude of the load in these facilities
alone suggests the extent of demand response reduction potential, and indicates the need 
for further study of automated demand response in wastewater treatment facilities.  
Further research is underway to better understand opportunities for demand response 
control strategies in wastewater treatment facilities and evaluate how such strategies 
perform in actual facilities. 
 
Acknowledgements 
 
This work was sponsored by the Demand Response Research Center 
(http://drrc.lbl.gov) which is funded by the California Energy Commission (Energy 
Commission), Public Interest Energy Research (PIER) Program, under Work for Others 
Contract No.150-99-003, Am #1 and by the U.S. Department of Energy under Contract 
No. DE-AC02-05CH11231.  
 8 
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Automated Demand Response Opportunities in Wastewater Treatment Facilities

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Automated Demand Response Opportunities in Wastewater Treatment Facilities

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