Nestled in a valley between the Pukalani Country Club’s golf course and a surrounding residential community is the Pukalani MBR Water Reuse Facility. It is a state-of-the-art membrane bioreactor system (MBR) producing R-1 water that is reused to irrigate the award-winning golf course. Prior to its startup in October 2010, the Pukalani STP was in a state of serious disrepair. The concentric circular steel tank was in such poor condition that the design and construction of the MBR was fast-tracked to ensure treatment was not interrupted.
Hawaii Water Service Co. solicited bids from several engineering firms for design services in March 2009. Their selection committee chose Water Works Engineers (WWE) of California. At the end of April, the design team had a project kickoff meeting where WWE presented its 30% design. This design team included operators and management from Hawaii Water, Water Works, Ovivo (formerly Enviroquip) and a project manager to represent California Water. Weekly conference calls with the team kept the project moving along at lightning speed. Within five months, the project was out for construction bids.
A very limited site drove the design configuration and the sequence of construction for the plant. The 460,000-gal-per-day MBR had to fit into the area allotted to a future 66-ft-diameter concentric circular package plant. While a creative layout permitted the MBR to fit into the small space, Bodell Construction had to be just as creative in its sequence of construction. With little room to mobilize (or even move around), Bodell was still able to get the MBR constructed and started up in less than 10 months.
It is Hawaii Water’s philosophy to standardize on its MBR designs, so any one of its operators can operate any one of its MBRs. Equipment manufacturers, controls systems, layouts and process design will be standardized as much as possible to alleviate the need for multiple sets of critical spare parts. Standardizing these systems will also allow Hawaii Water to increase the learning curve of new operators who will be able to train and operate at another MBR plant before taking over a new plant.The pride and joy of the plant manager, Tom Johnson, the plant was designed to far exceed Hawaii’s R-1 water reuse limits. Although there are no nitrogen limits on the island, Tom’s MBR is designed to meet a total nitrogen effluent of less than 10 mg/L. Aside from the great quality effluent, Tom has seen other benefits from his new MBR. It has improved the efficiency of his belt filter press (producing 17% to 18% cake), dropped his polymer use by 50% and cut his solids hauling cost by half.
Startup, design, construction and training time will be reduced as the team gets experience from multiple projects. Hawaii Water will employ a central location for spare parts. Although each plant will house some critical spare parts, the central location at Waikaloa will house a more extensive inventory. These spare parts can be easily deployed to outlying islands with little to no downtime.