The name Niagara Falls conjures images of enormous torrents of water
cascading over the precipice and crashing down on the rocks below. But just
upstream, at the Niagara Falls Water Board Wastewater Treatment Plant,
diminishing flows are the main concern.
When the treatment plant
was built in the 1970s, the plan was to centralize the city’s various types of
industrial wastewaters at one location to take advantage of the economy of
scale. Nearby industries included electro-metallurgical, electro-chemical, organic
chemical, paper, and abrasives businesses. In fact, in preparation for the
heavy industrial flows, it was decided to avoid biological process and instead
rely on physical–chemical processes that would be more resilient to industries’
Since the 1970s, federal
pretreatment regulations, global economic pressures, and the local business
climate have combined to greatly reduce the pollutant loadings that were
intended for the plant. The residential population also declined. When the
facility was planned in 1971, 84,000 people lived in the service area. That
number was expected to grow to 114,000 by 2000. But according to the 2010
census, the population now hovers around 50,000.
users account for about 40% of metered flow; the remaining 60% comes from
residents, businesses, and small industrial users. Unaccounted for flow from
infiltration and inflow and stormwater is high at more than 50% of total plant
The significant losses in
customers have severely eroded the economy of scale envisioned for the plant.
Although operational savings come from diminished use, a high overhead burden
must be distributed among fewer users, increasing unit costs and encouraging
those with a choice to discharge even less.
What was once an expensive
plant for many users has become a very expensive plant for fewer. Now the
plant’s managers and operators find ways to streamline treatment to curb the
costs of operating an oversized plant.
The treatment process
Two influent streams
reach the plant. About two-thirds of the flows arrive by gravity from the
southern, central, and eastern parts of the service area. The other one-third
comes from the 75,700-m3/d (20-mgd) Gorge Pumping Station and Force
Main that serves the western and northern service areas.
The two streams combine
in the main influent channel and pass through three traveling bar screens.
Concentrated sulfuric acid may be added here to counteract high pH events that
can cause problems later in the process. Ferric chloride and polymer are added
for phosphorus removal and clarification.
Next, the flow is
distributed among four 91-m × 18-m (300-ft × 60-ft) rectangular sedimentation
basins. Chain and flights collect settled solids from the flocculation cells at
the head end while traveling bridges collect it from the settling zone.
The primary effluent
passes to a pumping station with four 186-kW (250-hp) pumps that feed the
plant’s carbon adsorption system. Here, 28 carbon filters containing 2 million
kg (4.5 million lb) of granular activated carbon operate in a gravity downward
flow mode to achieve secondary treatment by filtering solids and adsorbing
pollutants. The system is built in two halves, with each having its own pair of
backwash pumps and an air blower.
Carbon filter effluent is
then chemically oxidized using hydrogen peroxide and sodium hypochlorite, which
also accomplishes disinfection. After final sampling, the effluent flows
through the ice shaft and tailrace tunnel of the former E.D. Adams Generating
Station to the outfall on the lower Niagara River, downstream from the American
Solids captured in the
primary sedimentation basins are pumped to one of two gravity thickeners and
thickened to 8% solids or greater. Thickened sludge pumps then pump the
underflow to one of three belt filter presses. Dewatered cake, which averages
30% solids, is mixed with lime to elevate pH and control pathogens. The
stabilized cake averages 33% solids. The high percentage of solids with an
industrial origin diminishes the stabilized cake’s fuel value and nutrient
content, so it is disposed of in a local sanitary landfill.
The pros and cons of chemical treatment
physical–chemical process remains insensitive to many influent character
changes — which would upset a biological treatment process — but is still a
more complicated and costly process to operate and maintain. A combined
collection system prohibits downsizing of the facility, while the discharge
permit prohibits deviation from the approved process train.
Multiple studies over the
years have examined the efficacy of converting to a less-expensive, traditional
treatment process, but have concluded that the anticipated lower operating cost
would not justify the expense of a conversion project, even assuming an
equivalent treatment performance could be attained. This presents the utility
with the ever-evolving task of optimizing the 35-year-old facility.
Immense needs on a tight budget
A 2005 strategic
wastewater treatment master plan established a 20-year treatment plant
rehabilitation program. The projected $143 million cost would require an
average $7 million expenditure in every year of the program.
Without outside financial
assistance, the program would place an unsustainable burden on the residential
population that has a higher average age, a lower average income, and a higher
unemployment rate than other western New York communities. Despite many
efforts, outside funding never materialized.
A “no action” option was
not a choice. The facility saw hard use in its early years and continued to
deteriorate as plants do. Concurrently, the complex plant discharge permit
continued to incorporate toughening performance requirements.
In 2005, plant management
and operators set in place a plan to attack the problems one piece at a time.
This approach continues to work well for the now 35-year-old plant whose
financial needs are growing as its economy of scale diminishes.
The planning effort
focused on the prioritization of plant repair needs, so that the funds
available were used for the greatest benefit. Multiple repair and replacement
tasks were bundled into biddable projects, allowing progress to commence.
Smaller tasks are tackled by plant maintenance staff.
Upgrades and repairs since
2005 have included the following:
rebuilding each of the three 1992 belt filter presses;
upgrading the sodium hypochlorite system;
replacing valves, gates, and flowmeters in the entire carbon system;
installing new odor scrubbing units;
repairing the main wet well;
replacing all three influent traveling bar screens;
rehabilitating the electrical substation and related electrical work;
replacing the drive, solids collection plows, and access bridge of one sludge thickener (work on the other thickener goes to construction this coming spring);
rebuilding main pumps and sedimentation basin mechanical equipment; and
replacing thickened sludge pumps.
The third phase of
rehabilitation work now is in construction, with reprioritization and planning
on the next phase continuing. This third phase will replace two carbon backwash
pumping systems, incorporate energy-saving measures, and enable the
second-phase automated control system. Repairs and partial replacements of all
facility roofs are planned for next spring.
Additionally, Niagara also
employs various strategies to attempt to control escalating costs. These
include chemical-use procedure improvements, energy conservation measures,
selective equipment replacement, carbon management improvements, development of
a hauled-waste customer segment — which in 2011 grew to a revenue of $378,000 —
and workforce reduction through attrition, job consolidation, and automation.