Sustainability Archive » Biosolids Management

Integrated Approach to Biosolids Management for a Utility with Multiple Small Facilities

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

To assure that Polk County Utilities (PCU) is ready for coming changes in regulations and ever
increasing solids production from ten treatment facilities geographically dispersed throughout the
County, the County wanted to develop a proactive long term biosolids management plan that
integrated residuals management approaches among the various treatment plants. Geographical
dispersion and capacity diversity combined with a desire for an integrated long-term
management plan gave rise to a number of possible alternatives to be included in the evaluation.
The landfill disposal alternative investigated met PCU’s objectives which were to identify a cost
effective method for managing current and future biosolids generated at PCU’s facilities that
would represent a viable plan for the next twenty years. An agreement developed between PCU
and Polk County’s Solid Waste Division to mutually address disposal of leachate and biosolids
resulted in significant cost savings for both these County agencies.

DIGESTER GAS POWERS ENERGY CONSERVATION AT BALTIMORE’S BACK RIVER WWTP

justin — Tue, 03 May 2011 20:12:57 +0000

Performance contracting provided the City of Baltimore and the Back River Wastewater
Treatment Plant with the expertise and guaranteed savings to warrant implementation of a
significant digester gas utilization system as well as other energy saving facility improvements.
The Back River process for wastewater treatment results in digested solids and methane gas, a
good portion of which was burned off with flares up to 20 feet in the air visible from the
surrounding area. The new cogeneration process will clean and utilize essentially all of the
methane gas burned on-site and use it, thus reducing the need for flares. Some gas will be used
in existing boilers and heaters, and the rest will run the generators that produce electricity. This
process will reduce the city’s purchase of electrical power by $1.4 million annually and
effectively utilize the methane gas produced at Back River.
The savings resulting from reducing the amount of electricity purchased was sufficient to pay for
the capital cost of the new facilities and other benefits including:
• Annual reduction of 19.4 million kWh of purchased electricity for plant operations.
• $14 million over ten years in energy savings and plant improvement projects.
• Annual reduction of 12.9 million pounds of carbon monoxide and 7.7 grams of nitrogen
oxide from electric power plants
The following is a description of a unique process used to develop, implement, and finance the
project.

LESSONS LEARNED (AND LESSONS SHARED) FROM THE TOWN OF CARY’S DEWATERING AND THERMAL DRYING FACILITY

justin — Tue, 03 May 2011 20:12:32 +0000

The Town of Cary completed construction and commissioning of a large biosolids dewatering
and thermal drying facility located at the South Cary Water Reclamation Facility in 2005. This
facility was designed to accommodate the dewatering and thermal drying of residuals generated
at both the North Cary and South Cary Water Reclamation Facilities with an average daily
operating throughput of approximately 24 dry tons per day.
This paper describes the key design, permitting, start-up and initial operational issues associated
with the dewatering and thermal drying facility. The following topics are covered in detail:
• Discussion of system sizing and design issues associated with the development of an
integrated dewatering and thermal drying facility capable of serving residuals generated from
both facilities
• Air permitting for the thermal drying facility with a specific emphasis on utilizing North
Carolina’s “Notice of Intent to Construct” provisions which allowed construction activities
on the thermal drying facility (emissions source) to proceed while the final air permitting
issues were resolved with the regulatory agency.
• Process performance and performance testing requirements for the high solids centrifuge
dewatering and rotary drum thermal drying equipment. Additionally, full-scale results from
the centrifuge and thermal dryer performance testing (including air emissions performance
testing and site specific emissions factors) will be presented.
• Discussion of operational performance and costs during the initial 1-1/2 year operations
period of the dewatering and thermal drying equipment.

HANDLING RESIDUALS MANAGEMENT IN A CHANGING WORLD: LEE COUNTY UTILITIES REGIONAL BIOSOLIDS MANAGEMENT PLAN

justin — Tue, 03 May 2011 20:12:09 +0000

Many Florida public utilities continue to dispose of Class B sludge through various land
application methods permitted under current Florida Department of Environmental Protection
(FDEP) and the Federal 40 CFR 503 regulations. However, in rapidly urbanizing areas, such as
Lee County (FL), loss of agricultural land is placing increased pressure on biosolids generators
to pursue innovative management practices to dispose of wastewater treatment residuals.
Furthermore, an increase in local and regional regulatory constraints on land application is
further complicating residuals management activities.
To address the loss of agricultural land application sites and local/regional constraints, Lee
County Utilities (LCU) initiated an investigation into the feasibility of constructing and operating
an alternate biosolids management facility capable of producing a Class A quality end-product to
offer a wider variety of options for disposal. The final feasibility report included considerations
for regulatory issues, end-product market potential, a variety of possible technologies, alternate
site locations, and comparative costs to present operations. The report concluded that a Class A
facility was feasible but that present worth costs would be slightly higher than continuing present
practice of disposal of Class B biosolids at a land fill if the County were to self-perform all
hauling. However, in the interest of promoting beneficial re-use of biosolids, the Lee County
Board of Commissioners unanimously approved that the proposed biosolids facility, utilizing a
thermal dryer, be designed and constructed. The facility will be located on Lee County’s Solid
Waste Waste-to-Energy (WTE) Facility and will utilize excess steam produced at the WTE
facility as the heating medium. The RFP document development to procure a design-buildoperate
firm is ongoing. This paper high-lights the main aspects of the report and the common
issues that typical municipalities are facing in the ever declining world of Class B disposal
options.

Is Geotube® Technology a Good Fit for Residuals Management at your Facility?

justin — Tue, 03 May 2011 20:09:52 +0000

Municipalities across the Midwest typically operate at greater than 80% capacity and run out of
biosolids and back-filter (lime and alum) residual storage capacity when land application
contractors (if applicable), drying beds, and storage lagoons are unable to keep up with volume
demands. Land application may not be economically or operationally available, an operations
timeline for solids removal prompts onsite dewatering, and residuals may be contaminated with
metals (e.g., Cu, Fe, Hg, Mo, Ni, Pb, Zn, etc.), oil and grease (O&G), nutrients, pathogens, or
pesticides. Several mechanical dewatering options (e.g., belt filter press, centrifuge, etc.) are
available as short-term or long-term remedies for onsite dewatering but are capital intensive for
municipalities and contractors that already operate on competitive budgets. The objective of this
study was to evaluate Geotube® containers as a residuals dewatering option for a municipal
wastewater treatment facility (WWTP) and a water filtration plant (WTP) including cost
effectiveness, ease of operation, solids retention, handling time, flow and volume rates, and
seasonality.
A southern Alabama WWTP treats approximately four million gallons of influent per day (8 to
10 million gallons of biosolids annually at 3 to 5 percent dry weight solids). It was calculated
that 1,400 linear feet (lf) of 30-ft circumference Geotube® container would be needed to
supplement onsite sand drying beds to dewater and contain this annual volume to 20 percent
solids, sufficiently dry to pass a paint filter test and haul off site to an appropriate landfill. The
resulting volume and mass of residuals at 20 percent solids would be 3,931 yd3 and 3,343 tons,
respectively.
A southeast Ohio WTP produces approximately 1.19 million gallons (5,874 yd3) of back-filter
residual per year at 1.0 percent dry weight solids. It was calculated that 96 lf of 45-ft
circumference Geotube® container would be needed to complement onsite equalization basins to
dewater and contain this annual volume to 20 percent solids, sufficiently dry to pass a paint filter
test and haul off site to an appropriate landfill. The resulting volume and mass of residuals at 20
percent solids would be 345 yd3 and 248 tons, respectively.
WaterSolve performed bench-top dewatering trials for biosolids and back-filter residual samples
collected from the WWTP’s liquids storage tank and WTP’s equalization basin, respectively.
Dewatering polymers were evaluated based on water release rate, water clarity, settling rate, and
flocculent appearance. In addition, dosing rate(s) were determined during these bench-top
dewatering experiments and recommendations provided to the facilities during this phase of the program. We recommended using Solve 9244 at a dose rate of 200 ppm (7.4 lb/dry ton) for
dewatering this WWTP’s biosolids and Solve 152 at a dose rate of 100 ppm (15.0 lb/dry ton) for
dewatering the WTP’s back-filter residuals. Water release rate and volume during pumping to a
Geotube® container were evaluated by adding 150-mL flocculated residual samples to a filter
apparatus with a GT500 Geotube® filter. Water release rate and volume were measured with a
250-mL graduated cylinder over 12 hours. Remaining solids were collected and measured for
percent dry solids by U.S. EPA Method 160.3.
Geotube® containers, with the aid of dewatering polymers, were recommended to and
implemented by the WWTP and WTP into which solids were pumped directly from an above
ground storage tank and equalization basin, respectively. After inline flocculation, the permeable
textile that forms the Geotube® container allows efficient dewatering while containing the fine
grain solids and the filtrate water returns to the head-works of the WWTP and is discharged via
sand filters from the WTP. Overall, this dewatering methodology greatly reduced the volume and
mass of residual solids and costs associated with hauling and disposal while allowing continual
operation of the facilities. For containment and dewatering of biosolids and back-filter residual,
Geotube® dewatering (including polymer and feed equipment) cost less than $0.02/gallon,
required minimal technical assistance to install and operate, retained greater than 99 percent
solids, solids dried sufficiently for hauling and disposal (18 to 40 percent cake solids), and did
not interfere with plant operations. Compared to the previous management techniques (i.e., belt
filter press, sand drying beds, or hauling to a landfill), these Geotube® projects saved both
facilities nearly $25,000 after the first year of operations.

Wastewater to Energy: The Integration of Biosolids Drying Technology and Energy Recovery

justin — Tue, 03 May 2011 20:09:25 +0000

Designed in the 1960’s and constructed in the mid-1970’s, the Milton Regional Sewer
Authority’s (MRSA’s) 3.420 MGD wastewater treatment plant (WWTP) is in need of a
complete facility upgrade. The upgrade will need to not only account for strict nitrogen
and phosphorus effluent requirements, but also seek out opportunities to minimize energy
dependence and operational costs through biogas production, electrical generation,
biosolids drying and sale of electricity to the Grid.
The end goal for this project is to create an energy independent, green wastewater
treatment facility. The objectives are to maximize energy recovery by exploiting all
reasonable sources; to minimize energy use throughout the facility; and to identify the
most feasible methods of energy recovery. Anaerobic treatment will be used were
applicable to meet these objectives through lower connected horsepower and biogas
production.

GREENFIELD WATER RECLAMATION PLANT SOLIDS FACILITY; FORM MEETS FUNCTION FOR A TECHNOLOGICAL SUCCESS

justin — Tue, 03 May 2011 20:08:28 +0000

A unique partnership of Owners, Engineers and Architects, and Contractors worked together for
the successful implementation of the Greenfield Water Reclamation Plant (GWRP) to meet
increased wastewater treatment capacity and reuse water supply requirements. The project team
faced several challenges ranging from local community integration, dramatic and on-going cost
escalations, and the need for a regional biosolids management solution. The project created an
architectural design that flawlessly blended the solids treatment facility with the surrounding
upscale residential community. Balancing the capital cost constraints with the functional needs
of the facility helped to keep the project within the Owner’s budgetary constraints. An
innovative project delivery method – Construction Manager at Risk (CMAR) – allowed the three
owners, the joint venture CMAR contractor, and the multiple architectural and engineering firms
to achieve a successful balance. The project achieved a regional biosolids management solution
by linking together the Mesa Southeast Water Reclamation Plant (SEWRP), a remote treatment
facility, and the GWRP using a solids pumping facility and a solids pipeline.

PLANT DESIGN FOR SYSTEM FLEXIBILITY – MINIMIZING PROCESS MODIFICATION REQUIREMENTS IN A CHANGING BIOSOLIDS ENVIRONMENT

justin — Tue, 03 May 2011 20:08:13 +0000

Wastewater and biosolids treatment processes are designed to support regulatory requirements
for effluent quality and solids final use. However, it is common that future changes in the
regulatory environment or solids management area can require subsequent modifications to the
plant’s processes. While the objective of the original design is to provide for anticipated future
requirements, it can be difficult to predict when, or if, more stringent requirements will be
imposed. Since higher levels of treatment correspond to greater capital and operating costs,
treatment that exceeds anticipated needs is typically not desirable. Consequently, the goal is to
design flexible systems that meet current needs but minimize future facility obsolescence or
abandonment.
The design for the Wakarusa WRF in Lawrence, KS incorporates features that support initial
liquid stream and biosolids treatment requirements, but allows relatively easy conversions and
upgrades to meet potential tightening of effluent treatment criteria as well as changes in biosolids
final use within the lifespan of the plant. These design features avoid abandoning or replacing
equipment or facilities. This paper discusses design approaches incorporated in the Wakarusa
treatment processes that can maximize system flexibility, which, in turn, will minimize costs
associated with removal or abandonment of existing treatment processes.

SMALL COMMUNITIES PARTNER TO DRY UP THEIR BIOSOLID REGULATORY ISSUE

justin — Tue, 03 May 2011 19:58:26 +0000

This paper provides an evaluation of the need and advantages of regionalization in a biosolids
dryer system that will operate with renewable energy sources and attain a beneficial use Class A
(referred to as Class AA in Florida) biosolid product to solve a looming regulatory issue. This
dryer system affords a unique and cost-effective solution for a region that has eight cities and a
county and solves the pending regulatory issue for all of these entities. This study will discuss
the measures that these nine entities, operating 16 wastewater treatment plants, have applied to
go forward in this regional system. The study will discuss how these entities are partnering
together with a private company to share the energy source to run the regional dryer. The
regional drying system will be operated based on the innovative use of landfill methane gas or
turbine generator waste heat from a private company as the energy source. In addition, the study
will provide the capital cost estimate and the results of the present worth analysis for these nine
entities in the regional system versus the current wastewater biosolids management practice of
each community providing their own separate solution for this regulatory issue. This paper is
prepared with local government utilities in mind that are currently attempting to work through
the cost dilemma of solving a regulatory issue and using an informal partnering process to unify
in a regional system versus attempting to provide a solution as a single entity.
This study indicates that the small community biosolid utility managers should strongly consider
partnering in the biosolids treatment and disposition practices through the regional facility. In
this study the regional drying facility, treating to Class A levels, is a good long term and costeffective
solution. The biosolid regulatory issue at federal, state, and county levels is a trend of
necessitating the higher level of treatment. For this regional facility, the costs for the Class A
biosolid product is comparable to the majority of the contributors current Class B practices. The
marketability of the Class A biosolid product opens many doors for the regional facility,
including use by the general public. In conclusion, the regional drying facility solution produces
a marketable beneficial use Class A product, solves the uncertainty of the current regulatory
issue for biosolids, and using renewable energy results in a more cost-effective option than each
entity attempting to provide their own biosolid management practice solution.

Carbon Footprinting for Biosolids Processing and Management Alternatives at DC WASA’s Blue Plains AWTP

justin — Tue, 24 Aug 2010 16:25:31 +0000

Carbon footprinting was used to evaluate several biosolids processing alternatives
considered for the Blue Plains Advanced Water Treatment Plant AWTP biosolids
management plan update. These alternatives include a combination of a thermal
hydrolysis process followed by anaerobic digestion; anaerobic digestion followed by
thermal drying; and lime stabilization of dewatered solids. Energy and mass balance was
conducted for the different alternatives where biogas was used for energy recovery in a
combined heat and power facility to produce electricity and necessary heat for the
thermal hydrolysis and thermal drying processes. CO2 emission factors for the different
processing were obtained from published literature and were used to estimate CO2
emission. The analysis showed that the Blue Plains facility has the potential of producing
about 11 MW of electricity, at an annual equivalent savings of $9.6 M, from biogas when
processing annualized solids production through anaerobic digestion.
Carbon footprinting benefits from land application of biosolids and dried pellets were
considered in this analysis. Results showed that of the various digestion options, thermal
hydrolysis offered the most benefit in terms of reduced CO2 emissions. This benefit was
further enhanced when the offsets associated with land application of the Class A
biosolids produced by this process were considered.
Beneficial reuse of class B, lime stabilized biosolids, also offsets CO2 emissions,
however the benefit is reduced somewhat by CO2 emissions associated with lime
production. When the dried pellets are used as a fuel source offsetting use of fossil fuel,
the carbon footprinting for processing combining thermal hydrolysis and thermal drying
are the most beneficial.