Sustainability Archive » 50k-100k

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.

A New Approach to Evaluating the Performance of a High-Rate IFAS Treatment System

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

The Council Bluffs Water Pollution Control Plant (WPCP) added a high-rate, integrated, fixedfilm,
activated sludge (IFAS) process in 2007 to increase the organic removal capacity of their
conventional trickling filter plant. Plant staff uses an innovative approach to estimate the fixed
biomass on the IFAS media through strategically placed miniature textile-media coupons. These
coupons were used to evaluate the performance of the high-rate IFAS system at design
conditions during cold-weather operation in 2009. Results showed that the system could operate
within permit limits at design conditions; however, the effluent quality was less than predicted
target values. Results also showed that the average IFAS media biomass loading was only 40%
of the manufacturer’s design value. Additional testing is needed to evaluate options for
improving effluent quality at design conditions such as increased mixed liquor, increased solids
retention time (SRT) or even increased hydraulic retention time (HRT).
KEYWORDS: Trickling Filter; Integrated, Fixed-Film, Activated Sludge; IFAS

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.

A Roadmap to Energy Self-Sufficiency for U.S. Wastewater Treatment Plants

justin — Fri, 20 May 2011 16:24:34 +0000

With increasing operating costs and concerns regarding climate change, most wastewater
treatment facilities are under pressure to reduce the net energy used to treat a gallon of
wastewater. The ultimate goal would be to reduce the net energy use to the point that the
wastewater plant actually “breaks even” on energy use, by a combination of more efficient
operations and production of energy via digestion and power generation. This paper presents a
“roadmap” showing how a wastewater treatment plant can pursue the goal of energy self-sufficiency
via a combination of alternative philosophical approaches and innovations .

Taking Green Steps Forward: The Study and Implementation of Renewable Projects for the City of Fayetteville, NC’s Public Works Commission

justin — Fri, 20 May 2011 16:24:06 +0000

Fayetteville Public Works Commission (PWC) is implementing a number of renewable energy
projects. These projects include digester gas cogeneration at their Cross Creek Wastewater
Treatment Plant, solar panels to be installed as part of an innovative, sustainable design for a new
elementary school, and smart grid technology for their power distribution. These technologies
will allow PWC to reduce their power demands, reduce their carbon consumption and emissions,
and take advantage of renewable energy sources to meet the requirement for renewable energy
portfolio standards required by North Carolina Statutes. This paper will provide a description of
the smart grid and solar panel projects, and a more detailed discussion of the digester gas
cogeneration project. Cogeneration technologies that were evaluated include engine generators,
microturbines, and fuel cells. A comparison of technologies, capacities, implementation plans,
alternatives analyses, and cost evaluations will be discussed.

A Small Community’s Goal of Improving Effluent Quality, Reducing Energy Costs and Managing Their Water Resources

justin — Fri, 20 May 2011 16:24:04 +0000

Recent societal pressures to reduce the costs associated with energy consumption and the related
greenhouse gas emissions have created a driver that is an inconsistent with the traditional goals
of water quality and environmental protection. The conflict between these goals is particularly
compelling for wastewater treatment facilities (WWTFs), as more stringent effluent requirements
are being promulgated. By and large, it can be said that the greater the required level of treatment
– the greater the energy demand. In addition, both influent concentrations and the type of
biological treatment processes used to meet the regulatory requirements play a considerable role
of the factors that must be considered. In most cases, many facilities over aerate, with no regard
to how much air is required for the process in order to obtain adequate margin of safety against
permit exceedances. The result is that the actual discharge concentrations of these constituents
are well below the permitted discharge concentration, while a significant amount of energy is
wasted in accomplishing this.
Another concern facing utilities are diminishing freshwater supplies, impacts from climate
change, population growth, and more stringent effluent disposal and water quality limitations, all
of which have all placed greater demands on the development of reclaimed water facilities to
supplement the use of this resource in lieu of potable water. Not only can the use of reclaimed
water help conserve potable water by replacing potable water for certain non-potable water uses,
it can also help recharge groundwater supplies. As a result, utilities are finding synergistic
solutions to water supply, wastewater treatment and water resources management issues.
Therefore, the adequacy and protection of our water supplies will be one of the more challenging
issues that utilities will face in the 21st century.

High Power Recovery with Large-scale Multi-anode/cathode Microbial Fuel Cells Treating Wastewater

justin — Fri, 20 May 2011 16:24:04 +0000

The lack of effective large-scale designs and inexpensive electrode materials has limited
the real-world applications of MFCs. This paper aimed at addressing these problems by
developing a multi-anode/cathode MFC and MnO2 (OMS-2) cathodes. The results
demonstrated that the multi-anode/cathode MFC substantially increased the total power
production of MFC since the average power density per anode/cathode channel did not
significantly change when the MFC was operating with 12 and 4 channels (575 mW/m2
vs. 635 mW/m2) at an organic loading rate of 0.5 kg/m3/day. Meanwhile the power
density increased from 300 to 380 mW/m2 as the organic loading rate increased from
0.19 to 0.66 kg/m3/day. MFCs achieved 80% of COD removal at HRT of 20 hours while
the COD removal at HRT of 5 hours was 66% and fluctuated greatly with the shock in
influent COD. MnO2 cathodes produced power density as high as Pt cathodes. A decrease
in the power density (from 400 mW/m2 to 150 mW/m2) and an increase in Rin of MFCs
(175 Ω to 225Ω) was observed due to the cathode fouling. Analysis revealed that the
interior fouling was mainly caused by calcium precipitation (89%) and the exterior
fouling was mainly caused by diffusion of sodium (83%) through the cathodes.

A novel and cost-effective hydrogen sulfide removal technology using tire derived rubber particles

justin — Fri, 20 May 2011 16:02:52 +0000

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.

Maximizing Economic and Environmental Returns On Digester Gas System Investments

justin — Fri, 20 May 2011 16:00:01 +0000

Combined Heat and Power (CHP) systems are superior to other digester gas utilization systems
in their ability to reduce utility costs and carbon emissions. Economic viability of digester gasfired
CHP is a function of many plant specific variables, foremost of which are electric and gas
utility rates, building and process heating (and cooling) loads, digester gas impurities, and
digester gas production. These and other utility, system, and plant specific data impacts on
digester gas energy recovery system economics are presented, discussed, and evaluated using
both simple and sophisticated energy modeling techniques.
Some noteworthy findings are the greatly superior return on investment, compared to CHP
alternatives, of heating-only systems in plants with significant facility heating loads, and the
general need for monetary incentives, both capital and operating, to lower economic hurdles to
cogeneration implementation.

Improving Wastewater Mixing and Oxygenation Efficiency with Solar Powered Circulation (SPC)

justin — Fri, 20 May 2011 15:59:35 +0000

Electrical-grid powered aeration is used to mix and oxygenate wastewater in most treatment
plants. However, much more mixing than oxygenation typically is needed. This imbalance
creates an operational inefficiency that increases costs and greenhouse gas emissions. The New
Hampshire Department of Environmental Services directed a 3-site study to assess the ability of
solar powered circulation (SPC) to reduce or eliminate the need for aeration. Water quality, odor
event, sludge buildup and power consumption data were collected 1-year pre-SPC and 1.25-years
during-SPC. The results generally indicated no differences between study periods in effluent
flow rates, total suspended solids, biochemical oxygen demand, dissolved oxygen, pH, ammonia
or nitrate levels. No discharge violations or odor events, and little or no sludge buildup, occurred
during SPC. Power consumption declined by 43-91%, and payback periods were 1.5-3.9 years.
These data and a 25-year, low maintenance, SPC-unit life expectancy indicated a long-term
improvement in operational efficiency.