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
wastewater treatment.
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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 development of the Carbon Heat Energy Analysis Plant Evaluation Tool (CHEApet) by
the Water Environment Research Federation (WERF) was in response to the identified need
for a predictive modeling tool that unifies prior WERF research information regarding
quantifying and managing energy consumption. CHEApet was created under OWSO4R07C
of WERF’s Optimization Challenge to model performance and energy consumption of waste
water treatment plants (WWTPs). Energy consumption, along with treatment process
emissions, contributes to a facility’s carbon footprint. CHEApet can be used to create a
baseline scenario, or inventory, of a utility’s carbon footprint for informational purposes as
well as to compare with hypothetical treatment plants. This kind of comparison allows the
user to identify facilities in the utility for energy optimization and the potential for biogas
recovery which can save in costs and improve the footprint of the facility.
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Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Biological Phosphorus Removal, Chemical Phosphorus Removal, Cost Savings, Energy Optimization, Energy Savings, Environmental Impact, Heat Drying, High Efficiency Air Diffusers, Improved Biogas Production, Phosphorus recovery, Plant Sustainability, Process Modeling, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Strass Wastewater Treatment Plant
Innsbruck, Austria (Europe)
With increasing operating costs and concerns regarding climate change, most wastewater
treatment facilities are under pressure to reduce the net energy used to treat a gallon of
wastewater. The ultimate goal would be to reduce the net energy use to the point that the
wastewater plant actually “breaks even” on energy use, by a combination of more efficient
operations and production of energy via digestion and power generation. This paper presents a
“roadmap” showing how a wastewater treatment plant can pursue the goal of energy self-sufficiency
via a combination of alternative philosophical approaches and innovations .
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Posted: May 20th, 2011 | Filed under: 100K-500K, 50k-100k, Stormwater, Waste Water Treatment | Tags: Cost Savings, Energy Optimization, Energy Savings, Environmental Impact, Improved Plant Reliability, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Owls Head Water Pollution Control Plant
Brooklyn, New York
The Owls Head Water Pollution Control Plant (WPCP) is a 120 million gallon per day (MGD)
secondary level treatment facility serving Brooklyn, New York. As part of a city-wide
environmental sustainability program, extensive renovations are being made to minimize fugitive
greenhouse gas emissions, maximize the utilization of biogenic gas produced during the
anaerobic digestion of wastewater sludge, and conserve energy that is consumed during the
wastewater treatment process. Two projects are in progress. One project will provide supply
side improvements to collect digester gas (digas) and produce usable electrical energy and heat
while the second project provides demand side improvements by reducing the energy
requirement associated with process aeration of the activated sludge process.
These projects are being carried out by the New York City Department of Environmental
Protection (DEP) in cooperation with the New York Power Authority (NYPA). When completed,
the projects will have the net result of a 76% reduction in greenhouse gas (GHG) emissions, a
75% reduction in utility-provided electrical consumption, and operating cost savings of over $1
million per year.
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Posted: May 20th, 2011 | Filed under: 500K-1M, Stormwater, Waste Water Treatment | Tags: Cost Savings, Energy Savings, Environmental Impact, Improved Biogas Production, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Fayetteville Public Works Commission
Fayetteville, North Carolina
Fayetteville Public Works Commission (PWC) is implementing a number of renewable energy
projects. These projects include digester gas cogeneration at their Cross Creek Wastewater
Treatment Plant, solar panels to be installed as part of an innovative, sustainable design for a new
elementary school, and smart grid technology for their power distribution. These technologies
will allow PWC to reduce their power demands, reduce their carbon consumption and emissions,
and take advantage of renewable energy sources to meet the requirement for renewable energy
portfolio standards required by North Carolina Statutes. This paper will provide a description of
the smart grid and solar panel projects, and a more detailed discussion of the digester gas
cogeneration project. Cogeneration technologies that were evaluated include engine generators,
microturbines, and fuel cells. A comparison of technologies, capacities, implementation plans,
alternatives analyses, and cost evaluations will be discussed.
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Posted: May 20th, 2011 | Filed under: 50k-100k, Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Savings, Environmental Impact, Green Infra, Improved Biogas Production, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions, Solar Energy Utilization | No Comments »
Victoria, BC WWTP
Victoria, British Columbia (Canada)
A part of the planning effort for two green field secondary treatment plants that will service the
Core District of Victoria, British Columbia, a modified triple bottom line analysis was conducted
to identify technologies that meet the Province’s goals of cost effective, environmentally
sustainable socially responsible wastewater treatment. One element of this analysis was to
evaluate the impact of a combination of solids stabilization and end use alternatives on the net
greenhouse gas (GHG) emissions of the future utility. If managed appropriately, biosolids
production and utilization is a way to offset emissions from wastewater treatment operations and
accrue carbon credits. Long-term benefits to Capital Regional District (CRD) include compliance
with municipal carbon neutrality goals as well as potential revenue from the development of
carbon trading markets.
Analysis revealed significant carbon credits could be achieved with sludge stabilization by
anaerobic digestion and biosolids utilization in mine reclamation. The greatest reduction in GHG
emissions was achieved when the biogas from digestion was cleaned to natural gas line quality
for introduction to the commercial grid. Co-generation proved to be less beneficial due to the low
GHG intensity of the commercial power source available in the region. Additional carbon credits
are obtained from mine reclamation due to improvement of soil productivity and carbon
sequestration potential. However, it was also found that all of the end uses which capitalized on
either the fertilizer value or energy content of biosolids can provide significant benefits to a
wastewater utility.
Results of this analysis enabled the CRD to make an informed decision about how to produce
and use biosolids to maximize benefits from a sustainability perspective. However, it should be
noted that the findings of this study are contrary to other studies in the published literature. This
is attributed to the low GHG intensity associated with the power utility in the region (0.000022
tonne-CO2e/kWh). This observation suggests that utilities and engineering practitioners should
be conducting site specific inventory analysis and use great care when evaluating literature
reported results to make process decisions.
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Posted: May 20th, 2011 | Filed under: 100K-500K, 500K-1M, Waste Water Treatment | Tags: Cost Savings, Energy Savings, Environmental Impact, Green Infrastructure, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Sugar Creek WWTP
Charlotte, North Carolina
When complete, the Sugar Creek WWTP Expansion Project increases the capacity of a 90-year old facility
from 20 mgd to 34 mgd in two sequential phases. Considering the uncertainty associated with rising
energy costs, regulatory requirements for greenhouse gas (GHG) emissions, and the desire to be a leader in
environmental stewardship, Charlotte-Mecklenburg Utilities (CMU) integrated carbon footprint analysis
into the Project. This analysis determined the base case carbon footprint – a 20 mgd facility, and measured
that against each of the incremental expansions – first to 28 mgd and subsequently to 34 mgd.
Completing the carbon footprint analysis for the Expansion Project:
- Provides a baseline for GHG for potential regulatory requirements.
- Drives energy optimization and energy efficiency into the design process.
- Considers GHGs in the alternatives evaluation.
- Quantifies a success story for CMU for this Expansion Project.
This analysis looked at the relative GHG emissions of process configuration alternatives considered and
discusses ideas for reducing the overall carbon footprint impact of the Sugar Creek WWTP expansion. In
addition, this paper quantifies the GHG emissions related to wastewater process components in general.
As a result of the Sugar Creek WWTP Expansion Project’s energy efficiency initiatives, CMU avoids an
estimated 1,595 metric tons of carbon dioxide equivalent emissions by 2014. Reduced emissions continue
to increase as influent flows increase over time, thus further reducing CMU GHG emissions on a unit flow
equivalent basis. Continued expansion to the Sugar Creek WWTP West Side process facilities can be
expected to reduce GHG emissions by nearly 30% (over alternative locations for treatment) by 2034. As
expected, indirect emissions associated with electricity purchases comprise over 80% of the overall
emissions for the Sugar Creek WWTP. Thus, the most significant impact that CMU can make is to
continue to focus on energy efficient design and operation.
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Posted: May 20th, 2011 | Filed under: 100K-500K, Stormwater, Waste Water Treatment | Tags: Cost Savings, Energy Savings, Environmental Impact, Green Infrastructure, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
City of Newton WWTP
Newton, Mississippi
The case study described in this paper demonstrates that the nitrifying trickling filter (NTF) is a
reliable and robust bioreactor. The studied NTF was designed to oxidize ammonia-nitrogen
(NH3-N) remaining in the effluent stream of an aerated lagoon that is located in Newton,
Mississippi, USA. NTF performance data was collected during a period beginning in June 2007
and ending in January 2010. An analysis of the data demonstrated that the NTF consistently met,
amongst other permitted criteria, a moderately stringent permit limit requiring an annual average
NH3-N concentration less than 2.0-mg/L remaining in the effluent stream. Comparison of
operating costs revealed that the NTF evaluated in this study required approximately one-third of
the power required to meet the same treatment objective with a moving bed biofilm reactor
(MBBR). However, the NTF required a slightly more foot print than the MBBR (e.g. 90 vs. 80
m2) to meet the treatment objective. The studied NTF was designed using generally accepted
criteria defined throughout this paper. The NTF used medium-density modular plastic trickling
filter media comprised of corrugated plastic sheets. The required biofilm surface area, and
therefore bioreactor volume, was defined based on a 0.65-g NH3-N/m2/d zero-order nitrification
rate and a 0.1-kg/m3/d five-day biochemical oxygen demand (BOD5) load at 12oC. The method
for calculating NTF ventilation is demonstrated. Implementation of the NTF design and
construction included some unique features: (1) the NTF influent pumps were located to provide
NTF effluent recirculation (which provides proper media wetting, controls biofilm thickness and
minimizes macro fauna accumulation), (2) use of influent pump(s) speed control to optimize the
NTF superficial hydraulic application rate (or Spülkraft), (3) the ventilating area was
conservatively designed to maximize airflow, and therefore process oxygen, for the nitrification
process (i.e., 0.1-m2 (1.0-ft2) open area per 2.4-m (8.0-ft) of NTF periphery), and (4) the
application of a column and pier support system to facilitate simple installation and increased air
flow.
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Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment | Tags: Cost Savings, Effective Tertiary Process, Energy Savings, Environmental Impact, Improved Plant Reliability, Nitrifying Trickling Filter, Plant Sustainability | No Comments »
City of North Port Wastewater Treatment Facility
North Port, Florida
Recent societal pressures to reduce the costs associated with energy consumption and the related
greenhouse gas emissions have created a driver that is an inconsistent with the traditional goals
of water quality and environmental protection. The conflict between these goals is particularly
compelling for wastewater treatment facilities (WWTFs), as more stringent effluent requirements
are being promulgated. By and large, it can be said that the greater the required level of treatment
– the greater the energy demand. In addition, both influent concentrations and the type of
biological treatment processes used to meet the regulatory requirements play a considerable role
of the factors that must be considered. In most cases, many facilities over aerate, with no regard
to how much air is required for the process in order to obtain adequate margin of safety against
permit exceedances. The result is that the actual discharge concentrations of these constituents
are well below the permitted discharge concentration, while a significant amount of energy is
wasted in accomplishing this.
Another concern facing utilities are diminishing freshwater supplies, impacts from climate
change, population growth, and more stringent effluent disposal and water quality limitations, all
of which have all placed greater demands on the development of reclaimed water facilities to
supplement the use of this resource in lieu of potable water. Not only can the use of reclaimed
water help conserve potable water by replacing potable water for certain non-potable water uses,
it can also help recharge groundwater supplies. As a result, utilities are finding synergistic
solutions to water supply, wastewater treatment and water resources management issues.
Therefore, the adequacy and protection of our water supplies will be one of the more challenging
issues that utilities will face in the 21st century.
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Posted: May 20th, 2011 | Filed under: 50k-100k, Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Savings, Environmental Impact, Improved Effluent, Plant Sustainability, Reclaimed Water, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Gloversville-Johnson Joint Wastewater Treatment Facility (GJJWWTF)
Johnstown, New York
The lack of effective large-scale designs and inexpensive electrode materials has limited
the real-world applications of MFCs. This paper aimed at addressing these problems by
developing a multi-anode/cathode MFC and MnO2 (OMS-2) cathodes. The results
demonstrated that the multi-anode/cathode MFC substantially increased the total power
production of MFC since the average power density per anode/cathode channel did not
significantly change when the MFC was operating with 12 and 4 channels (575 mW/m2
vs. 635 mW/m2) at an organic loading rate of 0.5 kg/m3/day. Meanwhile the power
density increased from 300 to 380 mW/m2 as the organic loading rate increased from
0.19 to 0.66 kg/m3/day. MFCs achieved 80% of COD removal at HRT of 20 hours while
the COD removal at HRT of 5 hours was 66% and fluctuated greatly with the shock in
influent COD. MnO2 cathodes produced power density as high as Pt cathodes. A decrease
in the power density (from 400 mW/m2 to 150 mW/m2) and an increase in Rin of MFCs
(175 Ω to 225Ω) was observed due to the cathode fouling. Analysis revealed that the
interior fouling was mainly caused by calcium precipitation (89%) and the exterior
fouling was mainly caused by diffusion of sodium (83%) through the cathodes.
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Posted: May 20th, 2011 | Filed under: 50k-100k, Waste Water Treatment | Tags: Cost Savings, Efficient Contaminant Removal, Energy Savings, Environmental Impact, Plant Sustainability | No Comments »