Sustainability Archive » 500K-1M

Process Recovery at the Humber Treatment Plant: “…by the people, for the people…” (Lincoln, 1863)

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

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.

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%.

Considerations for Alternative Supplemental Carbon Sources in Deep Bed Denitrification Filters to Achieve Low Effluent Nutrient Concentrations

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

The City of Baltimore has investigated various alternatives to meet the future effluent total
nitrogen goal of 3 mg/L and current stringent total phosphorous limit of 0.2 mg/L at its Back
River Wastewater Treatment Plant. The selected technology, deep-bed downflow denitrification
filter, allows for both nitrogen reduction and partial solids removal. In an effort to confirm the
design criteria, a small-scale filter pilot study was undertaken between January and July, 2009.
As a result of comprehensive nutrient reduction initiatives for the Chesapeake Bay watershed,
the demand for supplemental carbon sources such as methanol is growing and there has been a
great deal of interest in the practicability of utilizing alternative carbon sources. Hence, it was
also important to evaluate use of alternative carbon sources in order to (1) establish the carbon
requirements specific to each substrate (for design considerations) and (2) evaluate operational
conditions. This pilot study was segmented into three phases: methanol (as control), ethanol and
MicroC™-glycerin. The results of this study suggest that, under warm temperature periods
(~20C), the effluent nitrate (NOx-N) concentration of approximately 0.5 mg/L was achieved
with all the carbon sources at or below the average nitrate loading rate of 38 lb/1000 ft3/day (0.6
kg/m3/d). Even with higher loading rates, effluent quality did not degrade significantly and
remained < 1 mg/L most of the time. Observed COD/NOx-N ratios were ~5.5 (ethanol) and ~7.0
(glycerin). Some operational differences were noted between methanol, ethanol and glycerin.
Glycerin appeared to promote the growth of an unusual biofilm on all of the piping surfaces with
which it came in contact, and had noticeably higher yield that led to an increase in backwash
frequency when compared to ethanol. In summary, denitrification performance with both of the
tested alternative carbon sources met removal requirements. This testing also confirmed that
excess available carbon was needed in the filter effluent to maintain performance.

Cold Weather Design and Operational Considerations for Deep-bed Denitrification Filters to Achieve Limit-of-Technology Nutrient Removal

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

For several decades deep bed downflow denitrification filters have proven reliable as tertiary
treatment for achieving low effluent nitrogen levels. The majority of these facilities are operating
in the southeastern region where wastewater temperatures are generally warmer. In recent years,
a number of facilities have also been installed in the mid-Atlantic region to meet nutrient
reduction requirements. While wastewater temperatures are comparably colder in this region
most of these facilities are either operating in seasonal denitrification mode (low flow, warm
period), or operating in filtration mode only (no external carbon addition) where the plant’s
upstream process is capable of meeting current total nitrogen requirements. Also, it is found that
many of these facilities are operating at lower loading conditions and therefore reported
performance data may not be representative of design conditions. In an effort to confirm the
design criteria for typical mid-Atlantic cold weather operation and year-round performance to
meet limit-of-technology (LOT) levels (TN < 3 mg/L, TP < 0.3 mg/L) required for treatment
plants in Maryland, as well as other jurisdictions within the Chesapeake Bay watershed, the
Maryland Department of the Environment (MDE) and the City of Baltimore collaborated on a
denitrification filter pilot testing program. Testing was conducted at the Back River WWTP
from January through July of 2009 and the results are presented in this paper, and compared with
performance observed at full-scale facilities.
In summary, the cold weather testing demonstrated the system’s ability to achieve effluent
objectives (for nitrate removal) at loading rates from 40-50 lbs nitrate/1,000 ft3/day. The average
hydraulic loading rates were up to 3.0 gpm/ft2, with 80-90% removal efficiency at average
wastewater temperatures of about 13 oC. During warmer weather testing the nitrate mass removal
capacity increased and the system was able to achieve lower effluent concentrations at loadings
similar to or higher than those for cold weather testing. The filter system was also hydraulically
tested during warmer weather at peak-day loading rates up to 9 gpm/ft2 (at a loading near 100 lbs
nitrate/1,000 ft3/day) while still achieving about 80% nitrate removal, demonstrating the system’s
ability to handle peak flows and loads without significant reduction in effluent quality.

Quantifying the Environmental Benefits of Real-Time Control in a Sewer Collection System

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

The City of Indianapolis Department of Public Works (DPW) constructed eleven real-time
controls (RTC) in the operation of the collection system between 1995 and 2004 to reduce
combined sewer overflows (CSO). These eleven RTC facilities are part of the Early Action
Projects (EAP) to reduce CSO frequency and volume. In 2009, DPW completed a hydraulic
performance evaluation of each RTC facility using a computer hydraulic model simulation of
RTC operations, and successfully quantified their environmental benefits in CSO volume
reduction. This evaluation helped DPW to demonstrate the feasibility of utilizing RTC in the
collection system to reduce CSOs. This evaluation of the RTC facilities provided a basis for
DPW to further investigate additional CSO control projects that can utilize RTC. This technical
paper provides a case study on quantifying the environmental benefits of RTC in a large sewer
collection system.

A Case for Low Return Sludge Flow Rates

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

A common problem encountered by traditional activated sludge systems involves failure
to develop biomass that separates efficiently from the liquid, leaving behind a clear
effluent that is low in BOD5 and suspended solids. Another problem is the bleed-through
of ammonia due to low detention time in the aeration tank. Oftentimes, failure may be
attributed to high return sludge flow rates (RSF) that affect not only clarifier hydraulics,
but also the growth of bacteria in the system. In order to promote efficient separation and
nitrification, system conditions should be maintained that favor the growth of flocforming
bacteria and nitrifiers over nuisance microorganisms that may include filaments.
Favorable conditions are encouraged by a regime of higher detention time and feast and
famine experienced by the bacteria in the system. By viewing system operation through
this lens, the following paper proposes that many activated sludge treatment systems can
achieve significant operational improvement through reduction in RSF. This paper
further provides a method for minimizing RSF and presents examples of successful
application of this method.

Co-digestion at Annacis Island WWTP: Metro Vancouver’s Path to Renewable Energy and Greenhouse Gas Emissions Reductions

justin — Fri, 20 May 2011 16:47:03 +0000

Annacis Island Wastewater Treatment Plant which is operated by Metro Vancouver, is leading
the way in working within a carbon based regulatory environment. British Columbia has
instituted carbon reduction legislation province wide, a leader in North America. As a result
public entities, such as Metro Vancouver, must be carbon neutral by 2012. In response the utility
is holistically investigating different approaches to achieve the required GHG reductions. One
approach now being actively pursued is the implementation of co-digestion at Annacis Island.
Having developed a the scope for a full co-digestion program at the plant, a pilot facility was
constructed to provide further process controls as well as a start at reducing emissions by codigesting
material at the plant. This project also provided Metro Vancouver a basis of handling
its own sludges from other wastewater treatment plants on an emergency or planned basis by
dual tasking the receiving facility to receive both sludges and co-digestion substrates.

Utility Operations under Financially and Politically Constrained Conditions

justin — Fri, 20 May 2011 16:24:36 +0000

With the world economy struggling under a severe recession water utilities are
experiencing difficulties in continuing their business operations. They also face political
challenge since they are directly responsible to the communities they serve and at the
same time their customers are also their constituency. During such politically and
financially constrained times, utility operators have been forced to look into new ways to
cut costs and improve efficiency. Our experience shows that water utilities can become
more efficient via implementation of various strategies such as business process redesign
and implementation of lean six sigma techniques. Utilizing the above mentioned
strategies enabled Gwinnett County, GA’s Department of Water Resources (DWR) to
improve its process flow and eliminate waste, decrease personnel required for process
execution, reduce on-hand inventory and ordering costs, and to completely eliminate
Total Potential Stock-out Situations.

MAKING ENERGY FROM BIOSOLIDS, FATS, OILS AND GREASE

justin — Fri, 20 May 2011 16:24:36 +0000

The F. Wayne Hill Water Resources Center (FWHWRC), owned and operated by the Gwinnett
County, GA, Department of Water Resources (DWR), is an advanced wastewater treatment plant
which currently discharges into the Chattahoochee River and Lake Lanier. The FWHWRC
maximum month design flow is 60 million gallons per day (mgd) and currently about 30 mgd of
wastewater is received.
In light of rising energy costs and declining revenues reflective of the continuing, severe
economic downturn that began in 2007, the Gwinnett County DWR began an initiative to make
the best possible use of resources under DWR control, including renewable energy resources.
DWR retained CH2M HILL to identify and evaluate opportunities to improve resource
utilization and reduce energy costs at the FWHWRC. The results of the evaluations, procedures
for capturing stimulus funding, and technologies employed are discussed in this paper.
The energy types considered for the FWHWRC were biogas derived from anaerobic digestion,
solar, wind, and low-head hydropower. A screening analysis concluded that biogas combustion
to produce power and heat was the optimum alternative.
Next, a Business Case Evaluation (BCE) was conducted to determine if the construction and
operation of a gas-to-energy facility would be economically feasible. The BCE considered
several different scenarios for generating power from biogas, including biogas production with
and without addition of fats, oil & grease (FOG) and high strength waste (HSW) to the existing,
anaerobic sludge digesters.
The BCE concluded that a gas to energy facility based on an internal combustion engine (ICE)
was feasible. The proposed system, in addition to continuously generating electrical energy for
use at the FWHWRC, would be capable of producing sufficient heat to keep the anaerobic
digesters operating in the mesophilic temperature range of 95-100 degrees Fahrenheit (F). By
capturing the heat produced by the ICE, in addition to generating power, the system would have
a total energy-recovery efficiency approaching 80%.
The BCE recommended a gas to energy facility of approximately 2 megawatts (MW) in capacity
at the FWHWRC. The biogas requirement at a nominal 600 British Thermal Units (BTU) per
cubic foot (ft3) for an ICE of this capacity is approximately 520 standard cubic feet per minute
(scfm). However, as the FWHWRC is at only about 50% of its total design capacity, the
currently available biogas is considerably less than 520 scfm, and a purchased natural gas fuel
blend would be required to obtain full power generation and heat recovery benefits. To minimize purchase of natural gas, maximize biogas, and as a result improve the return on
investment in the cogeneration system, DWR next investigated addition of FOG and high
strength waste (HSW) to the anaerobic digesters to supplement the solids feed. The project was
made even more attractive by DWR’s successful pursuit of funding under the American
Recovery and Reinvestment Act (ARRA), as administered by the Georgia Environmental
Facility Administration (GEFA), and from the U.S. Department of Energy (DOE).
A schematic design of the system with specifications was prepared for competitive selection of a
design-build contractor. The design-build contract was awarded in October 2009. The contract
value is $5.19 million and includes the installation of a 2.1 MW engine generator along with
digester gas cleaning and drying equipment. The gas-to-energy facility is expected to reach
substantial completion by the end of 2010 with contractual completion in May 2011.
A second RFP for the design and construction of a FOG and HSW receiving facility was
advertised in February 2010. The design-build contract was awarded in June 2010 at a contract
value of $3.16 million. Its completion and startup will closely follow the completion and startup
of gas cogeneration facilities.
Once operational, the FOG/HSW handling and cogeneration facilities will have the potential to
save over one million dollars annually in power costs and generate more revenue in FOG and
HSW disposal fees. When operating at its rated capacity, the resulting power production will
offset the amount of fossil fuel used to generate over 17,000 MW-hours of electrical power
annually.

Force Mains: Not To Be Forgotten Assets

justin — Fri, 20 May 2011 16:24:35 +0000

During the development of the Johnson County Wastewater District (JCW) Asset Management
Plan it became apparent the available data in the current system did not include sufficient
information on the force mains. To evaluate the condition of the force mains and provide the
missing information the District is embarking on a comprehensive and proactive approach to
prioritization and inspect their force main assets. With the growing environmental awareness
and ever increasing stringent environmental regulations, JCW took a proactive approach to
develop force main asset management protocols and develop an inspection prioritization matrix.
With nearly 40 miles of force mains, JCW’s inventory is comprised of pipes varying in size,
material type, age and condition.
This paper documents the implementation of asset management principles to develop an
inspection prioritization matrix based on risk analysis, recommended inspection technologies
and procedures for collecting data through scheduled routine physical inspections.