Plant Strives for Zero Discharge
November 16, 2011
For many people, the image of Puerto Rico brings to mind sunny beaches, glamorous hotels and wet mountainous rain forests. Lesser known is that the island also sports a large pharmaceutical manufacturing infrastructure. With favorable tax incentives and a sophisticated communications and transportation system, Puerto Rico has facilities that make many of the most-prescribed medicines in the United States.
Like most islands with modern infrastructure and manufacturing, Puerto Rico faces a finite supply of resources - especially water. Pharmaceutical manufacturer Pfizer has a leading manufacturing presence in Puerto Rico, with five plants employing more than 5,500 people who produce some of the company’s top-selling medications, including Celebrex, Lipitor, Neurontin, Norvasc, Zoloft and Zithromax. At its facility in Fajardo, Puerto Rico, Pfizer initiated a water conservation and waste minimization program with a goal of reusing 100 percent of its wastewater.
In its drive toward making the plant a zero-discharge facility, Pfizer originally installed a reverse osmosis system to treat process water before returning it to non-potable water uses. The RO system was installed to reduce the volume of discharge water - 50,000 gal/day - that previously had to be loaded into tankers around the clock and trucked to a municipal waste treatment facility about two hours away. The water supply to the Fajardo plant comes from surface water originating from the nearby Yunque rain forest. Before entering the plant, the water undergoes conventional treatment from the municipality.
In 2002, Pfizer contacted ITT Industries' Aquious Water Equipment Technologies unit in Dallas to discuss its wastewater treatment. According to ITT Aquious, Pfizer was extremely displeased with the operation of its existing RO system. Installed without a thorough engineering analysis, the RO system had never operated correctly.
“When we visited the plant for the first time, they had a waste bin filled with old membranes," says Mainor Vega, the Aquious products manager for Latin America and the Caribbean. "The customer was buying membranes on a monthly basis due to the inefficiency of the existing RO system, which resulted in astronomical operational costs.” The customer wanted to replace and improve its existing RO system.
After analyzing the complete process, ITT’s engineers proposed an ultrafiltration system followed by a dual reverse osmosis system, which would provide a quality of feedwater for the RO system to allow for ease of operation and the best lifecycle cost of the equipment.
At the Pfizer plant, the wastewater originates from the sanitary processes, the cafeteria and the cooling towers. There are many concerns when trying to recycle wastewater. For the RO system at the site, one of the biggest concerns was the level of silica in the waste stream, which is first sent through a 13,000 gal capacity clarification process. From that point, the wastewater moves into a secondary effluent tank. In many facilities, this is where the waste treatment process would stop and discharge would take place into local waterways or be sent for further processing at a municipal wastewater treatment plant, depending on local regulations. From the secondary effluent tank, the wastewater is processed through a multilayer sand filtration system.
Reducing Turbidity and SDIITT’s engineers analyzed the sand filtration system to make sure that the media loads inside the tank were correct and that all valves for the automatic operation of the system were functioning correctly. From the media filtration, the wastewater enters ITT’s ultrafiltration system. Pretreatment is important for the system to operate properly. The main purpose of having the ultrafiltration system is for reduction of turbidity and silt density index. The RO membranes would not operate for long without this layer of protection.
The system ITT installed at the plant included a 50,000 gal/day ultrafiltration system and a 30,000 gal/day RO system. The ultrafiltration portion takes care of suspended and colloidal matter and acts as a barrier to provide a quality of water in which the RO membrane system can operate properly. Hollow-fiber-style membranes go through a series of flush cycles during the day (up to 200 cycles/day) to keep the dirty water from sticking to the ultrafiltration membranes.
From the ultrafiltration system, the treated water goes to a 1,000 gal/day filtration tank where a set of re-pressure pumps feed it to the RO system with the addition of pretreatment chemicals. ITT designed and installed two 30,000 gal/day RO systems on a single chassis to provide the customer with redundancy. In this lead-lag approach, the RO system receives a signal from the permeate tank and a computer directs one or the other RO system to turn on so there is an even wear across the system. In addition, ITT also designed the RO system with low-fouling membranes. This not only provides an additional level of security for the customer, but allows the plant to process water without the use of the ultrafiltration system in case of an emergency.
In an RO system, pressure is applied to push water molecules across a membrane to overcome the osmonic pressure. As the purified water ions go across the membrane, any ions that have a high molecular weight (anything over 200) are rejected. There are, however, some specific ions that will be rejected at a higher rate and some at a lower rate.
Lower Operating CostsLeaving the RO system, the water returns to the cooling tower, where normally there are cycles of concentration. The number of cycles depend on the quality of the make-up and process stream. With the purified permeate water from the RO process blended with the normal cooling tower water supply; the customer was able to take the cycles of concentration up to new levels of efficiency.
From a previous total of 50,000 gal/day of wastewater, the reject from the RO, which now is only 8,000 gal/day, will go to a holding tank and from there into a tanker that takes it to a larger waste treatment facility. With a fraction of the wastewater now being disposed, the customer is realizing a tremendous reduction from the half a million dollars a year that it was spending on tanker truck collection. As it continues to drive towards zero discharge, the pharmaceutical plant is looking at new ways to reduce the 8,000 gal/day of discharge with evaporation or heat to just a few pounds of solids.
Because the old RO system operated so inefficiently, the customer had significant costs for membrane replacement. Chemical costs were also high because the customer was using anti-scalants at a high rate to keep the membranes from fouling. ITT's ultrafiltration/reverse osmosis system has been operating since 2002 and the RO membranes have not been changed once. Adding the ultrafiltration system in front of the RO process also greatly reduced fouling tendencies. The facility now uses much less power to run the system.
“The old system was designed to operate at 400 to 500 psi," Vega says. "Our RO system is operating at 105 to 107 psi. That huge reduction in pressure provides the customer with significant energy savings. There are some additional pumps that are run with the UF system, but because the UF typically runs at about 15 psi, the additional energy costs are small. With growing zero-discharge regulations, we provide solutions for treating effluent that provides excellent water quality for non-potable water uses.”