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Last Updated: June 16, 2009 |
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By the late 1960s, America became
aware that the discharge of partially treated and untreated wastewaters
was choking waterways throughout the nation. This prompted
the passage of the Clean Water Act in 1972, which mandated the
upgrading of existing treatment plants to secondary treatment levels,
and empowered the Federal government to begin contributing a major
portion of the cost.
Hopewell, which until then had been serviced by a wastewater treatment
plant built in the 1950s faced the same Federal requirements as cities
across the country. At the same time, five industries in the
community, along with Fort Lee, were required to handle their own
wastewater discharges. Action was critical, since the water
quality of Baileys Creek and the James River was quickly deteriorating.
After a detailed study, it became clear that the most economical way to
meet the new requirements was to unite efforts and build a regional
secondary wastewater treatment facility that would serve the needs of
both residents and industries. The City of Hopewell, five area
industries and Fort Lee entered into an agreement whereby the City
would build a plant using grants from the U.S. Environmental Protection
Agency, and the state; the industries and the Corps of Engineers would
finance any remaining costs.
Construction of the Hopewell Regional Wastewater Treatment Facility
(HRWTF) began in 1975 and the plant was placed into operation in 1977
with the mission of reducing the oxygen consuming pollutants in the
area's domestic and industrial wastewaters. Three years of
additional study and modifications finally resulted in a treatment
plant with one of the highest compliance records in the Commonwealth of
Virginia.
Today the HRWTF handles about 35 million gallons of wastewater a day,
coming from the City of Hopewell, Fort Lee, the Federal Corrections
Institute, portions of Prince George County, the five major
industries--Honeywell/Hopewell Plant, Smurfit-Stone (formally Stone
Container), Honeywell/Churchill Plant, Hercules and the Virginia
American Water Company.
To handle solids removed from the waste stream, the original design of
the HRWTF included facilities for thermal conditioning (heat treatment)
of combined thickened primary and waste activated sludge followed by
vacuum filtration and multiple hearth incineration. This system,
which literally cooked the sludge, was complex and costly to operate,
and produced difficult-to-control odors.
By 1991, wear and corrosion from years of high-temperature and pressure
took their toll on the thermal conditioning system, and replacement or
rehabilitation was necessary. Before spending the substantial
sums that would be involved, however, the HRWTF Commission decided to
evaluate the cost-effectiveness of continuing with the existing system
or replacing it with better technology.
Malcolm Pirnie, Inc., Hopewell's consulting engineer, first performed a
comprehensive evaluation of solids handling and disposal alternatives,
then concluded that replacing the existing facilities with dry solids
centrifuges would be the most cost-effective approach. This
alternative presented many operational advantages such as reduced odor
generation, improved reliability and ease of operation; capital costs
were $10.66 million. In May 1992 the Commission approved the
initiation of design of the dry solids centrifuge installation.
The new centrifuges work like a giant spin cycle in a washing
machine--water travels around the inside of the centrifuge, pushing the
solids to the outside of the machine at an impact about 2,500 times the
force of gravity. After separation, the dry matter is burned in
the plant's multiple hearth furnace. The two giant centrifuges
are installed in a new two-story dewatering building, which has space
for a third unit, and also houses centrifuge feed pumps and centrate
and drain pumps along with the incineration feed pumps. The new
facility began operation in May 1997, and initial results have been
even better than expected, with increased efficiency resulting in lower
operation and maintenance costs.
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