Sustainability Archive » Sanitary Sewer

Improving Utility O&M and Capital Decisions by Incorporating the Concepts of Asset Condition, Criticality and Risk

justin — Fri, 20 May 2011 16:47:36 +0000

Toho Water Authority (TWA) provides water, wastewater and reclaimed water service to
approximately 85,000 customers in Kissimmee Florida. For the past three years the Utility has
been implementing an asset management program for their over $700 million dollars worth of
water, wastewater, and reclaimed water assets. During this program TWA has made significant
investments in asset management information systems including INFOR EAM Computer
Maintenance Management System (CMMS) and an ESRI Geographic Information System (GIS)
database. These two systems now contain the comprehensive asset inventory for the utility. A
built-in interface between the programs allows the CMMS and GIS to integrate and share
information.
Once the software implementation and inventory was complete, TWA wanted to obtain
additional physical, financial, and asset management attributes for their assets to support the
overall asset management program, which includes evaluating asset risk, measuring utility
performance and effectively planning for future renewal and replacement needs. The CMMS
software was configured to store the attribute data in January of 2008 after conducting interactive
workshops with staff to define the attributes. In August of 2008 a pilot project was implemented
to define the process to consistently collect and calculate the asset data including condition,
consequence of failure, risk, and replacement cost for all vertical assets in the utility. The pilot
area contained one water plant, one wastewater plant and 47 lift stations that fed the wastewater
plant. This paper will describe the methodology that was established to obtain and calculate the
data, the results of the data analysis, and uses for the data to further their asset management
program and overall decision making.

Converting Residuals To Reuse: Taking Aeration Out Of Oxidation

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

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.

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.

EPA’s Response to the Current Status of CSO Control Efforts Development of New Tools and Guidance

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

EPA’s combined sewer overflow (CSO) program has reached a mature stage. Some communities
have completed their CSO controls, while others are in the process of constructing controls or
evaluating potential alternatives. With the recent emphasis on green infrastructure, some
communities are evaluating the role of natural systems and ecological processes in Long Term
Control Plans (LTCPs) for controlling CSOs. The convergence of these critical milestones and
issues for the national CSO program highlights the need for updated tools and guidance to
facilitate future CSO control efforts. In response, EPA is developing guidance on post
construction compliance monitoring for CSOs, as well as the Green LTCP-EZ, a tool that allows
small CSO communities to incorporate green infrastructure as part of their LTCP efforts. This
paper discusses these initiatives serves as outreach to CSO communities on these efforts.

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.

“Say it Loud, Say it Clear”: Effective Communication Under Duress

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

Difficult times require an extra effort when it comes to communication. With all of the talk
about layoffs, budget cuts and salary reductions, utilities face an uphill battle against the internal
“rumor mill”, declining morale during the current economic downturn, and external pressures to
do more with less. A well-developed communication strategy is one key to sustaining
performance in the face of these challenges.
The Water Distribution and Transmission Division of the Miami-Dade Water and Sewer
Department is meeting these challenges “head-on” with an aggressive communication program
that has been developed and refined over a number of years. This presentation will highlight that
program from the perspectives of the Division Chief, managers and supervisors, and employees.
Extensive interviews at various levels of the organization identified key communication
strategies and tactics that are helping this agency maintain a high level of performance through
the most significant economic crisis the US has faced since the Great Depression. These
strategies and tactics will be discussed in detail and results will be presented as a “business case”
for optimizing communication during challenging times.
Focus of Study and Results:
This presentation will include discussion in communication topic areas including:
1. General overview of communication strategies and tactics
2. Types, frequencies, and styles for effective communication
3. Directional communication – up, down, and across the organization
4. Formal and informal communication methods and tools
5. Strengths and weaknesses of various communication approaches
6. Value and results from effective communication programs

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.

Anaerobic Co-Digestion for Increased Renewable Energy

justin — Fri, 20 May 2011 16:24:37 +0000

Significant opportunities exist to increase renewable energy production using existing municipal
anaerobic digesters. Many wastes can be added to co-digest more carbon and produce more
methane. The objectives of this study were to identify and compare potential co-digestates,
determine synergistic, antagonistic and neutral co-digestion outcomes, quantify performance of
co-digestion for selected wastes and estimate economic benefits. Over 80 wastes were identified
from 54 facilities within 160 km of an existing municipal digester. The most promising wastes
(26 wastes) were characterized by biochemical methane potential (BMP) and other testing. A
simple economic comparison identified the greatest benefits for seven co-digestates.
Performance was investigated using bench-scale digesters receiving synthetic primary sludge
with and without co-digestates. Methane production rates in co-digesters were as much as 180%
greater than anticipated from the additional chemical oxygen demand (COD). Therefore,
significant synergism was observed. The VS destruction efficiencies were 49 and 33% higher
when co-digestates were present. Co-digestion is one method to increase renewable energy
production via anaerobic digestion.

Lessons Learned While Implementing a New SCADA System

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

The Sacramento Area Sewer District (District) is in the final stages of implementing a new
Supervisory Control and Data Acquisition (SCADA) system for their 103 pump stations. While
implementing this new SCADA system, the District faced many challenges and obstacles, such
as developing the SCADA system requirements, designing the networking system, testing station
communication, and cutover to the new SCADA system. Implementing a new SCADA system
has provided the District with valuable experience that can be shared with other sewer agencies
that may also be in the process of replacing their SCADA system.

DAFT Optimization: How Much Air Is Enough?

justin — Fri, 20 May 2011 16:02:51 +0000

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.