Miami-Dade Water and Sewer Department (MDWASD)
Miami, Florida
The Miami-Dade Water and Sewer Department (MDWASD) is implementing a major upgrade
program at the South District WWTP in response to capacity upgrade requirements, regulatory
mandates and commitments to optimize water resources. In the recent past, MDWASD initiated
implementation of one of the largest High Level Disinfection Programs in the country (285-mgd
peak hour). In general, wastewater treatment facilities deal with a large number of operating and
maintenance concerns, not the least of which is Figuring Out Good solutions to Fats, Oils and
Grease (FOG) problems. The MDWASD SDWWTP has unique FOG problems including typical
clogging and aesthetics concerns as well as the presence of very fine and dispersed FOG in its
secondary effluent. The chemical composition and characteristics of FOG result in an inherent
difficulty with its treatment and its impacts to WWTP’s, especially for effluent polishing (filtration
and chlorination) and advanced treatment with membranes. Based upon significant concerns
for impacts of Fats, Oils and Grease levels on the existing secondary WWTP and concerns for
clogging of 30 planned, large deep bed filters with a capacity rating of 285 mgd, an intensive
field sampling, testing and evaluation program for FOG sources and treatment options was completed.
Results of this evaluation were presented at WEFTEC 2005, and are hereinafter referred
to as “FOG Part 1”. Under FOG Part 1, FOG clogging of main WWTP pipelines, and existing
continuous backwash filters for effluent reuse onsite resulted in a detailed sampling and analytical
program that reviewed and characterized FOG sources. FOG characterization in the septage,
leachate and influent sources to the WWTP were addressed. Based upon this characterization,
influent sources and clarifier scum removal were identified as key areas of focus in the WWTP.
Related improvements to these key areas including the addition of a Septage Receiving and
Treatment System at the front end of the WWTP, improvements to FOG removal at the secondary
clarifiers, direct removal or vacuum removal of FOG from the wastewater flow stream, additional
separation and concentration of FOG that is removed from the wastewater flow, and the
addition of a select residuals management system for mixing, handling and disposal of FOG
along with other residuals (grit, screenings, etc) were recommended at this secondary plant in
preparation for the addition of an HLD system. These improvements are currently under construction
with a planned completion of around fall of 2011.
Concurrent with the HLD and FOG upgrades, MDWASD is implementing one of the country’s
largest water reclamation facilities – 21-mgd treatment, delivery of 18.6 mgd of finished product
water, used for augmentation of Miami-Dade County’s drinking water supply through groundwater
recharge. Thus, potential impacts of FOG on advanced treatment membrane processes- microfiltration
(MF) and reverse osmosis (RO) needed to be investigated due to potentially significant
impacts to capital costs, operation and maintenance and downtime that could limit capability
for reliably providing the necessary quantities of water to augment drinking water supplies in this
region.
An advanced treatment pilot system was constructed and tested using secondary effluent at the
SDWWTP. The pilot system consisted of deep bed filters and high level disinfection (HLD) with
chlorine solution, plus advanced wastewater treatment processes including MF, RO, ion exchange
(IX) and ultraviolet disinfection with advanced oxidation (UV-A). The pilot was utilized
to demonstrate treatment capability of the proposed process units, define design criteria, and better
understand operational and maintenance issues and potential concerns such as FOG.
At the time of the pilot testing, the majority of the upgrades for improved FOG removal from the
secondary process were still under construction, and therefore, the reclamation pilot was tested
under “worst-case” conditions from a FOG perspective. FOG influent and effluent data were collected
and analyzed. The pilot deep bed filter system removed FOG from the secondary process -
FOG levels of roughly 1 to 11 mg/l were reduced to roughly 1 to 3 mg/l. Also, visual observations
indicate that this removal of FOG at the filters did not impact the filter media. However,
due to the nature of the fine FOG particles at SDWWTP, FOG downstream of the filters still
needed to be addressed from the perspective of potential accumulation on the membranes. Regarding
potential impacts of FOG on the membranes, specific flux plotted versus run time for the
RO membranes shows relatively stable specific flux values, with gradual decline over a duration
of about 3 months. A cleaning cycle then was implemented for collection of “cleanability” data.
Subsequent to cleaning, the data generally show an increase in specific flux to roughly the initial
specific flux rate of the membranes which supports that FOG did not accumulate on the membranes.
Similarly, Permeate Conductivity Versus Run Time and showing Differential Pressure
Versus Run Time indicate relatively stable data over roughly 3 months. In general, pilot testing
supports that FOG, which has been a concern for the South District Secondary WWTP, is not
anticipated to impact the advanced treatment processes for production of reclaimed water that
will supplement the Miami-Dade County drinking water supply through groundwater recharging.
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Posted: May 20th, 2011 | Filed under: >1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Advanced Wastewater, Cost Effective Alternative, Fats, Oils and Grease (FOG) Control, Optimize Water Resources, Reduced O&M Problems, Reduced Pipe Clogging | 1 Comment »
Donald C. Tillman (DCT) and Los Angeles-Glendale (LAG) Water Reclamation Plants
Los Angeles, California
The principal source of nitrogen compounds in the Los Angeles River is from the City of Los
Angeles upstream plants, Donald C. Tillman (DCT) and the Los Angeles-Glendale (LAG) Water
Reclamation Plants (WRP’s). These WRP’s were major contributors, with up to 75% of the total
dry weather nitrogen load during dry weather periods. In 2007, the City has completed a nitrogen
removal program to reduce the nitrogen mass discharge from its WRP’s. As part of the process, a
comprehensive research effort was undertaken involving bench, pilot and full scale testing to
identify the most effective way to upgrade and optimize the existing WRP’s. The combined
findings were then used to upgrade WRP’s to “full” BNR plants without derating, carbon and
alkalinity addition utilizing the MLE (Modified Ludzack Ettinger) process. This paper will focus
on the MLE process design and treatment practices successfully implemented at the City’s
WRP’s.
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Posted: May 20th, 2011 | Filed under: 100K-500K, 500K-1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Environmental Impact, Improved Nitrogen Removal, Improved Nutrient Removal, Plant Optimization, Plant Sustainability | No Comments »
Metro Wastewater Reclamation District
Denver, Colorado
Ongoing construction at the Robert W. Hite Treatment Facility in Denver, CO, requires taking up to 25
percent of the secondary treatment capacity off-line for extended periods of time. Weekly average effluent
limits for nitrate require diligent management of day-to-day performance to prevent excursions and
maintain consistent denitrification. Process modeling indicated intermittent carbon limitations for
denitrification during the construction period, leading to design and installation of a temporary carbon
addition system. Acetic acid was selected as a supplemental carbon source due to intermittent demands.
Performance testing of the acetic acid addition system at the RWHTF gave treatment personnel
confidence in its operation and performance. The carbon addition system assisted in maintaining
compliance with weekly nitrate effluent limits during construction and remains in occasional use. This
paper reviews the potential limiting factors for denitrification, solutions for compliance during
construction, and general criteria for supplemental carbon addition chemical selection.
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Posted: May 20th, 2011 | Filed under: >1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Construction Compliance, Decreased Effluent Nitrate Concentrations, Enhanced Denitrification Process, Improved Plant Confidence, Permit Compliance, Plant Optimization, Reduced Effluent Contaminants | 1 Comment »
Bureau of Sanitation, City of Los Angeles
Los Angeles, California
The goal of this research study is to enhance the efficiency and economy of carbon scrubbers in
controlling odors and VOCs at the wastewater collection and treatment facilities of Bureau of
Sanitation, City of Los Angeles. The objectives are: 1) to use carbon life expectancy and
breakthrough methods for monitoring carbon towers; 2) to reduce harmful impacts of pollutants
on public health and the environment; 3) and to recommend efficient active carbon application.
The butane activity and hydrogen sulfide breakthrough capacity of activated carbon were
assessed. Air streams were measured for odorous gases and VOCs. Single-stage wet scrubbers at
some wastewater treatment processes, while removing moderate levels of reduced sulfur
compounds, showed low to negative removal of VOCs when compared to carbon towers alone or
in series. Regular monitoring of activated carbon has resulted in useful information on carbon
change-out frequency and packing recommendations to enhance odor- and VOC-removal
capacity.
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Posted: May 20th, 2011 | Filed under: >1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Effective Odor Monitoring, Cost Effective VOC Monitoring, Cost Savings, Efficient Active Carbon Application, Environmental Impact, Increased Public Health, Odor Control, VOC Reduction | No Comments »
Ames Water Pollution Control Facility
Ames, Iowa
Hydrogen sulfide (H2S) produced during the anaerobic digestion process at wastewater treatment
plants is corrosive, toxic, and noxious.. Tire derived rubber particles (TDRP™) and other rubber
material (ORM™) are recycled waste rubber products distributed by Envirotech Systems, Inc
(Lawton, IA). They were previously found to be effective at removing H2S from biogas. A
scrubber system utilizing TDRP™ and ORM™ was tested at the Ames Water Pollution Control
Facility (WPCF) to determine operational conditions that would maximize the amount of H2S
removed from biogas in order to allow for systematic sizing of biogas scrubbers. Results showed
that longer contact times, compaction, and higher inlet H2S concentrations improved the amount
of H2S that was adsorbed, with an average of 1-3 mg H2S per gram of media removed. The effect
of temperature was not found to be significant. Additionally, in excess of 90% siloxane reduction
was observed from the biogas.
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Posted: May 20th, 2011 | Filed under: 50k-100k, Stormwater, Waste Water Treatment, Water Treatment | Tags: Biogas Purification, Cost Effective Approach, Environmental Impact, Improved H2S Adsorption Capacity, Improved Siloxane Reduction, Optimal Operating Conditions | No Comments »
Fort Collins Utilities
Fort Collins, Colorado
In response to population growth adjacent to the Drake Water Reclamation Facility (DWRF), the City of Fort Collins initiated an odor study to determine the impacts from the plant and identify possible odor mitigation alternatives. Subsequently, numerous technologies were evaluated based on criteria which included sustainability, constructability, and a chemical-free operation. The City’s design-build team, consisting of the contractor, engineer, and DWRF staff representatives, collaborated and selected a compost/woodchip biofilter as the most suitable technology for use. Two sets of biofilters were installed in 2007 and 2008, respectively. Since the commissioning of the biofilters, the City has tracked its performance and found that operation parameters differed from the initial design projections. This report and presentation will describe the odor study and evaluation process, as well as the biofilter design and operation. A key focus, and of direct importance to other facilities located in dry climates, will be the operational challenges and knowledge gained by DWRF staff in maintaining and optimizing the biofilters’ performance.
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Posted: May 20th, 2011 | Filed under: 100K-500K, Stormwater, Waste Water Treatment, Water Treatment | Tags: Improved Customer Relations, Improved Worker Morale, Odor Control, Optimized Biofilter Performance, Plant Optimization, Plant Sustainability | No Comments »
In January 2010, the American Society of Civil Engineers conducted a series of
workshops to address problems with infrastructure deficiencies in the United States. The
outcomes associated with these workshops were discussed in Civil Engineering Magazine
(April 2010). Based upon these outcomes, a consensus was reached that the water and
wastewater infrastructure in the United States is in a state of crisis and that the following
recommendations may provide a roadmap to ease that crisis and a vision for
improvement:
• Increase Federal Leadership in Infrastructure;
• Promote Sustainability and Resilience;
• Develop Federal, Regional and State Infrastructure Plans;
• Address Life-Cycle Costs and Ongoing Maintenance; and
• Increase and Improve Investment from all Stakeholders.
The above information and the predicted infrastructure rehabilitation and replacement
needs expected in the next decade prompted the USEPA to commit to promoting
sustainable infrastructure practices. If successfully implemented, these practices would
help reduce the predicted gap between infrastructure needs and infrastructure spending
(USEPA, 2006). Disinfection is one of the key unit processes for the protection of public
health. In order to fully implement the four pillars of the USEPA sustainable
infrastructure model, approaches must be taken to incorporate sustainability into
engineering design and operation of disinfection unit processes for water and wastewater
infrastructure systems.
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Posted: May 20th, 2011 | Filed under: Stormwater, Waste Water Treatment, Water Treatment | Tags: Environmental Impact, Green Infrastructure, Improved Disinfection, Improved Infrastructure, Increased Federal Leadership, Plant Improvement, Plant Sustainability, Reduced Carbon Footprint, Reduced Greenhouse Gas Emissions | No Comments »
Philadelphia Water Department (PWD)
Philadelphia, Pennsylvania
Because of issues with plant efficiency and the inconsistency of year round performance, the
Philadelphia Water Department (PWD) identified areas where they would like to see the
performance of their DAFT systems improve. The objective was to investigate factors that
would improve the DAFT’s performance, particularly by increasing float solids concentrations
and reducing the suspended solids loads returned to the treatment plants via the underflow. An
evaluation of existing plant operational data showed that in most cases the parameter that most
influences float solids concentration was the SVI and the parameter that most influences the
underflow concentration was the air/solids ratio.
Because of the importance of the air/solids ratio in maintaining low underflow solids
concentrations, an on site evaluation of the efficiency of the air saturation systems was
performed. Representative tanks were tested using a saturator monitoring unit which isolates a
small portion of the pressurized flow from the saturation tank and measures the mass of air
precipitated from the volume of flow. The mass of the precipitated air volume was compared to
the theoretical mass of air dissolved under the same ambient conditions to compute efficiency. A
well designed saturation system should provide an efficiency of approximately 88-percent. The
measured efficiencies ranged from approximately 48 to 78 percent. There are a number of
actions that could be taken to improve efficiencies including nitrogen purging from the saturator
headspace, verification that impingement plates are adequately designed and fully intact, and
adequately sized nozzles within the saturators. Improving the A/S ratios would reduce underflow
solids thereby reducing the return solids loads and overall operating costs at the plants.
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Posted: May 20th, 2011 | Filed under: >1M, Sanitary Sewer, Stormwater, Waste Water Treatment, Water Treatment | Tags: Improved Plant Efficiency, Improved Plant Performance, Increased Float Solids Concentration, Operating Savings, Optimized Air/Solids Ratio, Reduced Suspended Solids | No Comments »
Ithaca Area Wastewater Treatment Facility
Ithaca, New York
The results of the Fenton reagent treatment of biosolids at a bench scale and at a full scale
operation, as well as the cost-benefit analysis, are presented here. We compare the results of one
year of full-scale operation of Fenton reagent treatment during 2008 against the normal operation
parameters for the period 2005 – 2007. The treatment of biosolids with Fenton reagent was tested
in a full-scale reactor at the Ithaca Area Wastewater Treatment Facility, IAWTF. The Fenton
reagent treated biosolids were returned back to an anaerobic digester for additional digestion.
The most relevant results were the reduction in the amount of final residual biosolids for disposal
(11.5% reduction), the increase in the percent solids content of the final residual biosolids (7.5%
higher), and a higher energy cogeneration output (13.0% higher specific biogas production, &
13.0% higher heat output). The net economic benefit was $78,000.00 per year.
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Posted: May 20th, 2011 | Filed under: 100K-500K, 500K-1M, Stormwater, Waste Water Treatment, Water Treatment | Tags: Cost Savings, Energy Savings, Improved Anaerobic Digestion, Improved Biogas Production, Improved Plant Efficiency, Reduced Biosolids Disposal | No Comments »
Sacramento Area Sewer District
Sacramento, California
The Central Trunk Sewer is an eight mile pipeline that conveys both residential and industrial
sewage for Sacramento County. Constructed in the 1960’s of unlined reinforced concrete, the
pipeline ranges from 33-inches to 60-inches in diameter and is located deep under major roads,
residential backyards, creeks, protected wetlands, and a state highway. Nearly 50 years of
corrosion has severely deteriorated the pipeline and restoring the structural stability of the
pipeline in a cost effective manner with minimal decrease in capacity and distribution to the
community became the primary goals for the Sacramento Area Sewer District (SASD). To meet
these goals SASD and their design consultant West Yost Associates (West Yost) chose cured-inplace
pipe (CIPP) to rehabilitate the entire eight mile pipeline alignment.
Throughout construction several lessons have been learned from this large CIPP project. This
paper will discuss some of the lessons learned as well as considerations for owners and designers
regarding quality control and quality assurance of liner samples, bypass vs. plugging sewer
flows, environmental mitigation monitoring and reporting program, public outreach, air quality
regulations, construction noise mitigation, and debris estimating.
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Posted: May 20th, 2011 | Filed under: >1M, Sanitary Sewer, Stormwater, Waste Water Treatment, Water Treatment | Tags: CIPP Rehabilitation, Corrosion Prevention, Environmental Impact, Improved Customer Relations, Improved Sewer Rehabilitation, Increased Sewer Life, Minimized Community Disruption, Noise Mitigation, Pipe Construction Alternative, Reduced Inflow and Infiltration | No Comments »