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A Cost Effective Operation and a Low Carbon Footprint for Solids Reduction Using Thermal Drying

justin — Fri, 20 May 2011 16:47:35 +0000

Many communities are faced with considering a change in how their boisolids processing and disposal
programs will operate in the future. This discussion is coming about due to many biosolids processes that
were installed in the 1970s and 1980s under a different era of reuse and regulation and reaching the end of
their useful life.
To move forward there needs to be the establishment of objectives and goals that an evaluation is to be
built around for the future needs of biosolids processing for the owner/authority. The evaluation should
indentify the process that will be the most cost effective in capital and operation and maintenance costs. In
addition, with today’s concerns regarding climate change every evaluation should evaluate the carbon
footprint created by the various processes.
This is a case study of one evaluation done by the author that turned into a thermal dryer project that has
now been in operation for over six years.

Decentralized Membrane Bioreactors for Water Reuse in Paulding County, Georgia

justin — Fri, 20 May 2011 16:47:35 +0000

Before the recession, Metro Atlanta and its surrounding counties were one of the fastest growing
regions in the United States. In order to reduce the impact of treatment plant discharges on its
limited water supply and to offset water demands on potable water systems, they were
increasingly looking at water conservation and water reuse. Paulding County was one of those
fast-growing counties, consistently ranked between the 12th and 15th fastest growing counties in
the United States. Wastewater treatment facilities are among the most critical to support the
County’s rapid population increase. With tighter effluent limits on the way and a halt on surface
water discharge permits, the County had to look at alternative uses for the treated wastewater.
Several technologies were evaluated, and based on this evaluation, MBR technology became the
apparent leader. This paper provides an overview of the selection process, the procurement
process, and the performance of four MBR systems currently operating in Paulding County.

Evaluation of Onsite Sodium Hypochlorite Generation at the Blue Plains Advanced Wastewater Treatment Plant

justin — Fri, 20 May 2011 16:47:35 +0000

Due to potential risks associated with transportation and handling of liquid chlorine, the District
of Columbia Water and Sewer Authority (DC Water), switched to the use of liquid sodium
hypochlorite as the disinfecting agent at the Blue Plains Advanced Wastewater Treatment Plant
(AWTP). The escalating cost of bulk purchased sodium hypochlorite prompted DC Water to
commission a study to evaluate disinfection alternatives that: 1) are compatible with existing
treatment processes; 2) meet all plant effluent disinfection requirements; and 3) reduce life cycle
costs of disinfection.
The study involved a detailed technical, economic and non-economic evaluation of the feasibility
of constructing and operating an onsite sodium hypochlorite generation facility in lieu of bulk
purchase. Economic analyses included capital and O&M costs, life cycle costs over a 30-year
time horizon, and sensitivity of price of bulk sodium hypochlorite and salt, electric power cost,
debt service on life cycle costs.

Selection of a Solids Management Plan to Meet a Sewerage District’s Vision of Becoming a Leader in Sustainability

justin — Fri, 20 May 2011 16:47:34 +0000

The Green Bay Metropolitan Sewerage District (GBMSD) is a public utility, established in 1931,
that reclaims 38 million gallons of wastewater per day at two treatment facilities in Green Bay
and De Pere, WI. Its service area covers 285 square miles and serves more than 219,000 people.
GBMSD’s mission is to promote public health and welfare through the collection, treatment, and
reclamation of wastewater, while assessing stable, competitive rates. In conjunction with others,
the organization will encourage pollution prevention and support programs to help ensure that
water contaminated by human activity is returned clean to the environment. GBMSD conducts
its business using a sustainable approach within the social, environmental, and economical
values of our customers and stakeholders.
GBMSD initiated the development of a Solids Management Plan in 2008 to address aging solids
handling facilities and the solids loadings from recently acquired De Pere Facility. The existing
solids processing system consists of belt press dewatering followed by multiple hearth
incineration. The solids system is located at the Green Bay Facility. Solids from the De Pere
Facility are transferred by pipeline to the Green Bay Facility for processing. The solids system
was constructed in the 1970s and is reaching the end of its useful life. The multiple hearth
incineration process is now considered an outdated technology. Current incineration technology
uses fluidized beds, which consume less fuel and lower air emissions.
The solids management planning effort was undertaken to develop a long-term plan for handling,
processing, and disposing of solids. The plan included a comprehensive evaluation of numerous
solids management technologies and approaches. This paper describes the process used to
develop the plan, the alternatives that were considered, the alternatives evaluation process, and
the preferred solids management alternative.

Development Criteria in the Age of Sustainability – DC Water’s New Paradigm for Biosolids and Energy Management

justin — Fri, 20 May 2011 16:47:34 +0000

The DC Water and Sewer Authority (DC Water) is implementing new sludge and biosolids
processing facilites at the 1.4 million cubic meters/day (370 million gallons per day [mgd]) Blue
Plains Advanced Wastewater Treatment Plant (AWTP) in Washington D.C. The program
involves thermal hydrolysis (TH) followed by anaerobic digsetion and includes a major
cogeneration facility to provide electric power for the treatment plant and steam for the TH
process.
Decision and development criteria for DC Water’s biosolids program have evolved over recent
years and now include a broad range of factors with strong emphasis on sustainability criteria. A
major link between high-performance digestion and renewable energy production has been
forged. Key criteria for decision-making now include renewable power and energy production,
climate change issues, biosolids product quality, digestion performance, and site efficiency, as
well as capital constraints and economics.

Primary Sludge Fermenters in BNR Plants: Are they Cost-Effective for Meeting Effluent Phosphorus Limits?

justin — Fri, 20 May 2011 16:47:06 +0000

The 100 ML/d Pine Creek WWTP is a state-of-the-art BNR facility that serves the City of
Calgary, Alberta. A delay in the construction of the primary sludge fermenters allowed a
comparison of the performance of the BNR process with and without fermentation for
extended periods of time, and facilitated a life-cycle cost analysis in which the cost of
primary sludge fermentation was compared with alternative forms of primary sludge
thickening and meeting the effluent total P limit by chemical addition. Data from the first 20
months of plant operation indicated that, with primary sludge fermentation, the plant is
capable of reliably meeting its stringent effluent total P target of <0.3 mg/L. Without
fermentation, the plant required the in-plant addition for approximately 50 mg/L of alum to
meet this same effluent quality standard. The life-cycle cost comparison between primary
sludge fermentation and enhanced biological phosphorus removal (EBPR), and two
alternative forms of primary sludge thickening and chemical P removal, indicated that
primary sludge fermentation is a cost-effective method of reliably meeting a stringent
effluent total P standard. Using a 20-year net present value (NPV) analysis, primary sludge
fermentation was found to be approximately 8 percent cheaper than mechanical primary
sludge thickening and chemical P removal, and 22 percent cheaper than gravity thickening of
primary sludge and chemical P removal.

An Economic Approach to Off-Line Storage: A Means of Mitigating SSOs

justin — Fri, 20 May 2011 16:47:05 +0000

This paper reports on the use of a two cell 30-million-gallon (MG) equalization basin and diesel
engine-driven pump station as a means of mitigating sanitary sewer overflows (SSOs). The
ultimate capacity of the pump station, which utilizes vertical turbine solids handling pumps
(VTSH) arranged in a self-cleaning trench-style wet well, is 68 million gallons per day (MGD).
Configuring the pump station with diesel engine-driven pumps provided a 20-year, $1 million
present worth savings in comparison to a conventional electrical motor driven pump station
arrangement. The use of diesel engine-driven pumps eliminated the peak electrical usage of 450-
horsepower (HP) electrical motors, as well as the need for variable frequency drives and
redundant power generation needs during electrical outage time periods. A supplemental 150-
kilowatt (kW) generator was installed to provide emergency power needs for SCADA, seal water
systems, influent screen, and a 50-HP maintenance pump for wetwell cleaning.

Recycled Water Corrosivity Control: The Additional Advantage of Disinfection with Sodium Hypochlorite

justin — Fri, 20 May 2011 16:47:05 +0000

Recycled water corrosivity control is an important consideration in the design and operation of
wastewater treatment plants and recycled water distribution systems. Even mild corrosivity can
have significant long-term impacts on equipment and pipelines. Corrosivity control involves
adjustments to water chemistry (pH, alkalinity, hardness, etc.), but how adjustments are
implemented can vary based on existing treatment processes. For the Michelson Water
Recycling Plant, corrosivity control was achieved by modifying an existing process rather than
adding a new one. This paper discusses the investigation and evaluation of several treatment
alternatives for corrosivity control. The study resulted in replacing chlorine gas disinfection with
sodium hypochlorite disinfection, which offered the additional advantage of addressing
operational, regulatory, and safety concerns associated with the use and storage of gaseous
chlorine. The study highlights the connection between disinfection and corrosivity, an important
consideration for other agencies starting water recycling programs to meet increasing water
demand.

Improving Nutrient Removal While Reducing Carbon Footprint at Three Swiss WWTPs Thanks to Advanced Control

justin — Fri, 20 May 2011 16:47:05 +0000

Aeration consumes about 60% of the total energy of a WWTP and therefore makes up for a
major part of its carbon footprint. Introducing advanced process control can help plants to reduce
their carbon footprint and at the same time improve effluent quality through making available
unused capacity for denitrification, if the ammonia concentration is below a certain set-point.
Measuring and control concepts are a cost-saving alternative to the extension of reactor volume.
However, they also involve the risk of violation of the effluent limits due to measuring errors,
unsuitable control concepts or inadequate implementation of the measuring and control system.
Dynamic simulation is a suitable tool to analyze the plant and to design tailored measuring and
control systems.
During this work, extensive data collection, modeling and full-scale implementation of aeration
control algorithms were carried out at three conventional activated sludge plants with fixed predenitrification
and nitrification reactor zones. Full-scale energy savings in the range of 16-20 %
could be achieved together with an increase of total nitrogen removal of 40%.

Using Whey as a Supplemental Carbon Source under Real Time Control Conditions

justin — Fri, 20 May 2011 16:47:04 +0000

The COD:TKN ratio in the influent wastewater to the J.D Phillips Water Reclamation Facility
(WRF) in Colorado Springs is too low to allow sufficient denitrification to meet the discharge
limit for pH. To reduce the reliance on adding caustic to the effluent to raise the effluent pH,
Colorado Springs Utility (CSU), began a search of local industries to find a source of local
supplemental carbon to increase denitrification, and hence alkalinity recovery. Simultaneously, a
local dairy approached CSU requesting relief from significant monthly excess BOD and TSS
surcharges. The dairy manufactures cottage cheese, producing acid whey as a waste. A full scale
pilot test was initiated at the WRF to investigate the opportunity to use whey as a supplemental
carbon source to enhance denitrification. During this test, it was discovered that fermented whey
provided superior results to unfermented whey.
The costs of implementing and operating advanced aeration control systems have to be justified
by the reduction in energy consumption and/or improvements of the effluent quality. Control
measures should also not introduce operational problems like foaming or bulking or higher green
house gas emissions (mainly N2O). In addition to the effluent pH issues, as with all utilities, CSU
is faced with reducing operating costs as much as possible. The effluent ammonia limit for the
WRF varies on a monthly basis, which raised the question – “With the use of on-line analyzers,
could the activated sludge process be operated to produce an effluent just below the permit limit
to save aeration power?” A desktop analysis using BioWin™ and the BioWin™ Controller was
performed to predict which of feed-forward or feed-back control would provide the best control.
On-line ammonia and nitrate probes were installed at various locations and programmed into the
aeration blower and mixed liquor recycle pump control systems to determine if aeration blower
airflow and whey feed rates could be optimized. This paper will summarize the results achieved
through the full scale pilot test, list future activities at the WRF and briefly discuss the outcome
of the pretreatment permit negotiations with the dairy.