The South Bay Wastewater Treatment Plant is located in Ysidro, CA, just across the border from Tijuana, Mexico. New secondary treatment facilities have improved the quality of the discharged water.The IBWC selected a new generator package from MTU Onsite Energy to pair with an existing generator at the facility.
“The treatment plant wanted the new power system installation to physically match that of an existing 2,000 kW generator (from a different manufacturer) that was installed during the original construction in the late ’90s,” said Tim Oergel of W.W.Williams, the local distributor for MTU Onsite Energy. “Getting the two generators to fit into identical packages was a challenge.”
One design issue was the changes in technology over the past 16 years. The new unit is a 2,000 kW Tier 2 generator set operating at 12.47 kV housed in a specially designed ISO container. This newer generator set is EPA certified to meet Tier 2 emissions regulations, whereas the existing generator set was manufactured at the beginning of Tier requirements and was compliant with, but not EPA certified to, the less stringent Tier 1 standards.
In addition to not having modern emissions control hardware, the existing generator drive engine set did not have an electronic governor or other electronic controls to help it synchronize with the new, more advanced MTU generator drive engine. To get the two generators to communicate with each other, the existing generator’s governor was replaced, along with many other controls. The overhaul also included new paralleling switchgear, automatic transfer switches and various communications interfaces.
Unique considerations
“While the MTU Onsite Energy EPA-certified Tier 2 generator set is more fuel efficient and has significantly cleaner exhaust, it also has higher heat rejection that requires a specialized radiator,” Oergel said. “Because we had to match the size of the original 40-foot ISO container, we had to be creative in designing a radiator with higher heat rejection to fit in the same-sized package as the original generator set. The solution was a specially designed radiator from R.F. Partridge & IEA Radiator that was direct-driven through a planetary gear off the engine’s crank shaft. With a larger surface area and greater airflow, the special radiator was able to fit inside the container and still provide the necessary cooling.”
The physical installation of the containers is unique as well. Each containerized generator set is mounted on a concrete pad outside of the plant’s main building. Because the plant is located in earthquake country, both generator set containers are supported by a seismically reinforced mezzanine structure consisting of I-beams connected in crisscross patterns. These structures support the weight of the containers and are bolted to the concrete pad to prevent damage to the generators in the event of an earthquake.