Hydrogen
sulfide (H2S) corrosion damage to wastewater treatment plant facilities often
means time consuming and costly rehabilitation. This was the situation the
Puerto Rico Aqueduct & Sewer Authority (PRASA) and the Puerto Rico
Infrastructure Finance Authority (AFI) faced when H2S corrosion damage was
discovered in both concrete piping and at two cast iron valve locations inside
the Puerto Nuevo Wastewater Treatment plant.
To
complicate matters further, the Puerto Nuevo plant is in the busy capital city of
San Juan and handles 75 million gallons per day (mgd) of sewage.
Paramount
to the successful completion of the $10 million rehab project to correct the
H2S problems in the plant was ensuring that the sewage entering the facility
could be safely diverted for a full four months while the repairs were being
made.
“A bypass
pumping system really was the only answer,” said Joe Abbott, national sales
manager of Godwin Pumps, headquartered in Bridgeport, New Jersey. “The problem
was that a bypass pumping system of this magnitude had never before been used
on the island of Puerto Rico.”
In 1998,
Godwin Pumps began working closely with AFI engineers to plan a pumping system
to meet requirements for the bypass. AFI contacted Godwin Pumps because of
Godwin’s reputation in the industry and its experience with this type and size
job.
Godwin
Pumps has supplied pumping equipment for bypasses as large as 150 mgd. However,
Abbott commented, “We’ve been very successful with small bypass jobs as well —
1 mgd to 20 mgd.”
Ultimately,
Godwin Pumps’ role was to devise a way to safely divert the 75 mgd of sewage
around the area where the repairs were to be made. Any leaking of the bypass
system was unacceptable.
Abbott said
part of the challenge was that there was a 25 foot suction lift from the inlet
channel to the grade. “This meant that the bypass pumping system had to draw
55,000 gpm at a critical suction lift of 25 feet,” said Abbott. “The Godwin
Dri-Prime® was ideal for this situation.”
A totally
automatic self-priming pump, the Dri-Prime will pump to 28 feet of suction
lift. In addition, it is capable of running dry without damage which is ideal
for intermittent flow conditions and peak periods. Specifically, the Godwin DPC
300 model Dri-Prime pump was selected for its ability to handle high volume
flows. Ease of installation and fuel efficiencies were also factors in pump
selection.
The bypass
solution devised by Godwin Pumps to divert the flow entering the plant included
20 Godwin Dri-Prime DPC300 12-inch, diesel-driven pumps; 22,000 feet of 18-inch
HDPE pipe; two fusion machines; and 10 specially designed discharge manifolds,
each channeling two pumps into one main discharge line.
This
20-pump system proved to have the capacity needed to handle the daily average
or peak flow and then some.
“The amount
of pumping power provided a safety zone in the event storm water entered the
system,” Abbott said. “Our pumping system provided the capacity to handle up to
100 mgd if necessary.”
Piping
design was another key to this successful pumping system. Godwin engineers knew
that thousands of feet of HDPE pipe would be required to divert the flow. Part
of the challenge of this project was the existence of a primary and secondary
discharge point. So the system had to accommodate higher discharge pressures. A
CAD drawing was supplied by Godwin Pumps to facilitate the pipe installation.
Because of the size and complexity of the piping system, two fusion crews were
required to fuse thousand of feet of HDPE pipe on site. Then, working with the contractor, the
installation began.
After weeks
of preparation, the contractor, the local Godwin distributor — Puerto Rico Wire
Products — and Godwin Pumps personnel put the bypass pumping system into
operation. Over the next four months, while work was under way to address the
maintenance problems in the plant, the Godwin team worked to oversee the
system’s operation.
“This
worked out really well,” said David Higgs, Godwin regional sales manager who
served as project manager on this job. “Puerto Rico Wire’s involvement allowed
Godwin Pumps’ U.S. crews to work with Bermudez & Longo’s project engineer
Manuel Pelayo to get the system up and running. At that point, Puerto Rico Wire
was able to take over and handle weekly routine maintenance.”
Higgs
added, “It was a perfect example of international teamwork between all three
organizations involved. The result was a successful design of a complex
system.”
