Solar Drying of Biosolids – Recent Experiences in Large Installations

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.

Project Prequalification Process The Do’s, The Don’ts, and The How To’s

In 2004, Massachusetts passed another law regulating Public Construction in the
Commonwealth. Being mostly engineers and owners, the first thing that comes to mind when
you hear “law regulating public construction” is “how is this going to affect my project?” And
the next thing you see is dollar signs floating through the air. This paper will show you how this
is one regulation and one process that will cost a little money and legwork upfront but will save
you significant dollars, reduce stress, and benefit your project in the long term. Case studies will
include the Westborough Wastewater Treatment Plant Upgrade Project, Nantucket Surfside
Wastewater Treatment Plant Upgrade Project, Nantucket Public Safety Facility Project, and the
Hopkinton Fruit Street Wastewater Treatment Plant Project. Topics will include the
Massachusetts Chapter 193 of the Acts of 2004 and Division of Capital Asset Management and
their influence on the Prequalification Process.

Project Management – Overcoming Resistance to Change

The purpose of this paper is to help project managers in public agencies understand the reasons
for resistance to change and provide steps to overcome or minimize the resistance. These are
challenging times for all public agencies so there is a need to be wise stewards of public
resources. An increase in efficiency may require reorganizing departments, reallocating
resources and realigning staff roles and responsibilities and managing projects differently. These
all require change and growth from all levels of employees in an organization. Reducing the
resistance to change requires strong leadership qualities combined with proper project
management skills. If these combined skills are incorporated into projects that implement
change, they will be successful and can result in significant cost savings. The Orange County
Sanitation District (OCSD) has undergone many of the aforementioned changes in the past
couple of years and continues its austerity through efficiency while completing all tasks.

Converting Residuals To Reuse: Taking Aeration Out Of Oxidation

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.

Cost Savings and Performance Improvement of Large System Iron Salt Use for Integrated Sulfide Control and Chemically Enhanced Primary Treatment by Using Peroxide Regenerated Iron Technology

San Diego’s Point Loma WWTP is a 160 MGD (240 MGD permitted), 100% advanced primary
treatment plant that has historically used iron salts for collection system sulfide control and
chemically enhanced primary treatment. Beginning in 2006, a PRI-SC® (Peroxide Regenerated
Iron – Sulfide Control) program was implemented by adding H2O2 at the intermediate pump
station PS2 (in place of the FeCl3), and again to the plant influent (ahead of FeCl3 addition for
CEPT). The application of PRI-SC® in the Point Loma system was designed to provide at least
$685/day in cost savings, to be achieved through reduced ferric chloride use at PS2 and Point
Loma, while improving sulfide control and CEPT performance. Since integrating the PRI-SC®
program full-time in 2008, SDMWD is realizing savings of approximately $4,700 per day
(~$1.72 million/yr) compared to the 2007 baseline iron salts program. At the same time, both
sulfide control and CEPT performance has improved. The cost savings were helped by the
hedging aspect of the PRI-SC® program – iron salt price volatility in 2008 and 2009 was
upwards of 45%. The PRI program has reduced the total iron salt use from the 2007 baseline rate
of 32.5 dry tons per day to approximately 19.3 dry tons per day in 2009, with the core savings
coming from an overall reduction in ferric chloride use at PS2 and the treatment plant (Table 1).
Significantly, ferric chloride use at PS2 was eliminated and, for CEPT, reduced from 24 mg/L to
10 mg/L (16.6 to 6.8 dry tons per day) with no loss in performance. In addition, total sulfide
removal has improved over baseline levels, and average CEPT performance exceeds the permit
levels at 89% for TSS and 65% for BOD, and effluent water quality has improved (with 60% less
spent iron (as FeS) present in the ocean discharge). For the most part, digester biogas H2S levels
were maintained below the permit requirement of < 40 ppm, but required approximately twice
the baseline FeCl2 feed rate. Even so, the overall program has maintained the stated savings
benefit.

CSO Control, Treatment and Disinfection at Saco Wastewater Treatment Plant using Advanced Vortex Technologies

The use of novel CSO control, treatment and disinfection systems based on advanced vortex technologies
including Vortex Flow Controls (VFC) and Hydrodynamic Vortex Separator (HDVS) that enable,
Screening, Grit Removal, Sedimentation and Disinfection to be accomplished in one vessel is described.
The application of the technologies at the Saco Wastewater Treatment Plant involves a new generation of
HDVS and vortex flow controls that regulate wet-weather flows to control maximum flows to the existing
wastewater treatment plant to avoid hydraulic overloading and the diversion of excess combined sewage
flows to the new CSO treatment facility.
The wet-weather treatment facility utilizes an advanced HDVS that incorporates a non-powered, selfactivating
and self-cleansing CSO floatables screening system; with the captured pollutants comprising
sewer debris and solids including sediments, settleable organic solids and floatables, being returned to the
headworks at the treatment plant and the clarified, screened and disinfected overflow being discharged to
the receiving environment (Saco River), after de-chlorination.
The ability to perform several essential unit processes (i.e. Screening, Grit Removal, Sedimentation and
Disinfection) all in one vessel resulted in significant savings in the overall project scheme costs on
account of the more compact design of the advanced HDVS system coupled with the elimination of
additional tanks and vessels that would have been required with the conventional approach. Analytical
results from post-construction compliance monitoring have confirmed the efficacy of the advanced vortex
technologies.

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

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.

SPOTSYLVANIA COUNTY’S EXPANDED COMPOSTING FACILITY APPLIES AERATED STATIC PILE TECHNOLOGY ADVANCES

Spotsylvania County embarked up an aerated static pile composting program in 2002 to manage
undigested dewatered wastewater treatment plant (WWTP) residuals cake from their
Massaponax WWTP in conjunction with brush collected through a convenience center and at the
Livingston Landfill. The initial compost facility included a covered aerated static pile process
that provided intermittent positive aeration only. The quantity of dewatered residuals being
composted has increased from approximately 8,800 tons per year in 2003 to in excess of 12,600
tons per year in 2009. Even with this rapid increase in quantities, all regulatory process criteria
have been met and offsite odor impacts have been non-existent. Howeverer, residuals cake
continued to be landfilled from a second WWTP, the FMC plant, in the amount of 5,000 – 6,000
tons per year. The County embarked upon a compost facility expansion program in 2006 with
three main goals.
1. To manage the ever increasing quantities of residuals cake generated from both County
WWTP’s over the next 20 years.
2. To enhance and automate the compost process performance.
3. To accomplish this expansion with no offsite odor impacts.

Construction of the new facilities was completed in March, 2010. This paper presents data on the
process flow, process controls, and the odor management system of this successfully expanded
aerated static pile composting operation.

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

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

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.