The conversion of raw sewage sludge into valuable biosolids for beneficial reuse requires a
suitable pre-treatment process. However, traditional technologies are causing high investment
costs, operation costs, and energy demand; or are not fully meeting the demands of the market.
As recent experiences from the world’s largest solar drying and solar-assisted drying plants in
Palma de Mallorca, Spain and Oldenburg, Germany show, solar drying is an effective alternative
for large facilities. Drying costs and energy consumption are less than half, maintenance is low,
and operation is simple and safe at these facilities when compared to traditional thermal dryers.
Also, carbon dioxide (CO2) emissions are reduced by a factor of seven when compared to
conventional dryers. By using waste heat from other processes, the area requirement can be
reduced by a factor of three to five. The final product is suitable as fuel for Waste-to-Energy
(WTE) plants, coal power plants, or cement kilns. It can also be used as a Class-A fertilizer for
agricultural use, or land application.
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Posted: May 20th, 2011 | Filed under: Waste Water Treatment, Water Treatment | Tags: Cost Savings, Decreased Energy Consumption, Plant Sustainability, Smaller Carbon Footprint | No Comments »
Magna Water District
Magna, Utah
Aeration accounts for up to 60% of the total energy required for a typical activated sludge wastewater plant. A new process was developed that decreases aeration demand during secondary wastewater treatment. This process, called BIOBROx, blends oxidant-laden residuals with screened municipal wastewater followed by treatment in a fixed-bed (FXB) bioreactor. Pilot testing showed that the BIOBROx process was effective at removing perchlorate and nitrate from membrane residuals. Considerable biochemical oxygen demand (BOD) and suspended solids were also removed across the process. A 3.8-mgd BIOBROx demonstration facility is now operating at the Magna Water District. The BIOBROx train treats 1/3 to 1/2 of Magna’s total wastewater flow, uses no aeration, has an empty-bed contact time of 10 minutes, and has a footprint that is one-twentieth the size of the conventional secondary processes. Preliminary data show effluent that even under these conditions, BOD5 and TSS levels in the effluent from the BIOBROx process are similar to those in Magna’s conventional secondary treatment effluent.
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Posted: May 20th, 2011 | Filed under: <50K, Sanitary Sewer, Stormwater, Water Treatment | Tags: Cost Savings, Decreased Aeration Demand, Decreased Energy Consumption, Plant Sustainability, Smaller Carbon Footprint | No Comments »
Humber Treatment Plant (HTP)
Toronto, Ontario (Canada)
The Humber Treatment Plant (HTP) was experiencing severe settling problems. An opportunity
to improve the performance of the HTP was seized by the plant’s Senior Engineer by developing
and implementing a program of repair, continuous assessment, analysis, and tuning to ensure
optimal operation of the aging infrastructure. Through the strategic utilization of existing inhouse
expertise and resources, a new benchmark of excellence, serving the community through
improved and consistent effluent quality with accompanying odour reductions, was established.
This achievement was accomplished paradoxically using less energy and chemicals, thus,
significantly reducing the Humber’s environmental footprint. The direct delivery of these
services by City staff, while further enhancing in-house knowledge, skill, and stewardship,
eliminated the delays associated with project delivery using external contractors and made it
possible to reap the immediate rewards. The monetary benefits to the City are savings in
operating costs of $550,000 per year and capital savings of $6,000,000.
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Posted: May 20th, 2011 | Filed under: 500K-1M, Waste Water Treatment | Tags: Capital Savings, Decreased Energy Consumption, Improved Plant Sustainability, Operating Cost Savings, Reduced Carbon Footprint, Reduced Odor Problems | No Comments »
Odor control equipment is important to the wastewater industry throughout the world. It allows
wastewater plants and collection systems to operate with minimal impact on the surrounding
regions. One very prominent technology is engineered dry-scrubbing media. This media
consists of various base materials formed into spherical media through the processes of
agglomeration and impregnation. The base materials include adsorbents such as activated
alumina, activated carbon, and sodium bicarbonate. The liquid impregnants include potassium
permanganate, sodium permanganate, and potassium hydroxide. These materials combine to
form an engineered media having physical and chemical properties that allow contact with and
removal of odorous gases.
This paper focuses on reducing capital cost by increasing the velocity of air through an odor
control system. In the past, odor control systems performed well at face velocities of 60-100 feet
per minute (fpm) across a media bed. Experience and performance tests on installed systems
confirm this. In the examples sited here, systems have achieved acceptable life times as well as
efficiencies greater than 99.5%.
The efficacy of an air velocity increase depends on the following parameters: gas mass transfer
zone, media pressure drop, capital cost reduction, and energy consumption. These factors point
toward 125 fpm as the optimum velocity-increase point. The scrubber is also capable of
operating at 150 fpm with higher energy consumption. Wastewater plants can use these results
to evaluate scrubber options and meet budgetary constraints.
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Posted: May 3rd, 2011 | Filed under: Uncategorized | Tags: Decreased Energy Consumption, Engineered Odor Control Media, Improved Odor Control, Improved Plant Efficiency, Increased Cost Savings | No Comments »
This paper addresses harnessing bioenergy at wastewater treatment plants by focusing on
supply-side management: biogas production and use. Successful case studies are compared
and contrasted in terms of economic, environmental, social, and operational objectives. Rules of
thumb for determining when a project is economically viable are discussed. Air emissions and
permitting considerations are covered for equipment and overall installations. These case
studies include biogas used for process and space heating using steam or hot water boilers, and
for combined heat and power projects using cogeneration equipment, such as internal
combustion engines, gas turbines (conventional and mini), several types of fuel cells, and
Stirling engines. Examples of where carbon dioxide is removed from the biogas and
“biomethane” is fed to a natural gas pipeline or further compressed and used as a vehicle fuel
are also included.
Several wastewater treatment plants are also taking advantage of the opportunity to
supplement wastewater solids fed to digesters with organic waste from food processing or
other sources (restaurant waste, etc.). This approach—known as codigestion—has several
advantages: it increases biogas production, decreases solid waste at landfills, and decreases
greenhouse gases by capturing and beneficially using methane that otherwise could be emitted
to the atmosphere at the landfill. Successful case studies of plants practicing codigestion are
described.
Harnessing bioenergy at wastewater treatment plants has the potential to produce enough
electricity for more than 4 million people, while also reducing greenhouse gases. Diverting the
organic fraction of municipal solid waste to anaerobic digesters would further reduce
greenhouse gas emissions and could generate enough electricity to serve more than 10 million
additional people. This potential is based on just the wastewater treatment plants and organic
fraction of municipal solid waste generated in the United States alone. With worldwide
application and using agricultural organic wastes, the potential is immense. This paper on
harnessing bioenergy at wastewater treatment plants brings together the collective experience
of numerous bioenergy projects in the United States and Canada. Those involved in the
planning of biosolids and biogas facilities will benefit from the lessons learned, rules of thumb,
and insights obtained from these case studies.
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Posted: May 3rd, 2011 | Filed under: Waste Water Treatment | Tags: Biogas Recovery, Cost Savings, Decreased Energy Consumption, Environmental Impact, Increased Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | 1 Comment »
The wastewater treatment systems account for 2-3% of the nation’s electric load. Novel
processes are critical to reduce energy consumption. The study aims at converting the organic
substrates in wastewater to new energy sources (hydrogen and electricity) through anaerobic
treatment. Hydrogen is produced in anaerobic acidogenic phase, which has a shorter retention
time and a higher shock tolerance than traditional methanogenic processes. The results showed
the biogas containing more than 60% H2 was achieved in anaerobic hydrogen production
reactors. Hydrogen production was closely related with the fermentation types in the reactors.
Microbial fuel cell (MFC) is another promising technology to convert the organic compounds to
clean energy (electricity). The effects of substrate concentration and bacterial concentration on
the voltage generation in MFCs were investigated. Finally, the effluent from anaerobic
hydrogen production reactors was connected with MFCs for further contaminant removal and
power generation. This study reveals that wastewater treatment plants could possibly be
operated as energy production sources through the removal of contaminants, which is significant
in progress towards environmental sustainability.
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Posted: July 30th, 2010 | Filed under: Waste Water Treatment | Tags: Decreased Energy Consumption, Environmental Impact, Plant Sustainability, Reduced Carbon Footprint | No Comments »
City of Columbus Utilities
Columbus, Indiana
In recent years there has been an exponential rise in concern and interest regarding global
warming trends, with the evidence becoming increasingly stronger that climate change is a
result of greenhouse gases (GHGs) emitted largely by human activity. The GHGs of most
concern are carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3),
chlorofluorocarbons (CFCs), hydrofluorocarbons (HFCs), perfluorinated carbons (PFCs), and
sulfur hexaflouride (SF6). By far the most common of the GHGs is CO2, but several of the
other GHGs have considerably stronger effects on global warming potential relative to their
total mass, and at least two of them (CH4 and N2O) are common to wastewater treatment.
Wastewater treatment facilities are not considered to be among the top producers of GHGs
from human activity; however, a more holistic view of wastewater management indicates that
its impacts on GHG emissions spread into other sectors of GHG production. Because of their
engineered nature, wastewater treatment facilities represent significant opportunities to reduce
GHG emissions. It follows that when a municipality is planning new wastewater treatment
facilities, the evaluation of treatment alternatives needs to consider the relative impacts of
those alternatives on GHG emissions. Sustainability principles also need to be incorporated
into the evaluation methodology.
This paper presents a case study evaluation of wastewater management alternatives including
GHG-emissions and overall “carbon-footprint.” This case study is for a future, greenfield-type
wastewater treatment facility in Columbus, Indiana. The evaluation demonstrates how
different wastewater management options present differing impacts on GHG emissions and
carbon sequestration. Consequently, the impacts of GHG emissions and carbon management
need to be part of the wastewater facility planning process.
Using a decision science approach, the evaluation compares potential impacts of wastewater
management alternatives for new wastewater treatment facilities (19-mgd design capacity).
Five different treatment alternatives were evaluated, with three of those alternatives involving
sub-options, for a total of eight treatment scenarios investigated:
This paper summarizes the results of the evaluation and demonstrates how traditional and
non-traditional wastewater management options are affected by their impacts on carbon
management and their potential for reductions in GHG emissions. It is concluded that the
evaluation of the GHG-emission impacts and “carbon footprints” of wastewater treatment can
and should be considered when evaluating alternatives for the design and implementation of
water reclamation facilities.
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Posted: July 29th, 2010 | Filed under: Sanitary Sewer, Stormwater, Waste Water Treatment | Tags: Biosolids Management, Decreased Energy Consumption, Environmental Impact, Plant Sustainability, Reduced Carbon Footprint | No Comments »