Managaha boasts of new high-tech wastewater treatment

In January 2008, the U.S. EPA issued the NPDES permit for the operation of the Managaha Wastewater Treatment System. The issuance of the permit was the culmination of a three-year effort to upgrade the wastewater treatment system for one of Saipan’s most pristine environmental attractions. The newly installed wastewater treatment plant on Managaha Island employs the use of a submerged membrane separation activated sludge process, often referred to as a membrane bioreactor (MBR) system. This is a relatively new treatment process and one which is rapidly replacing older activated sludge treatment plant systems throughout the United States and other developed nations. It is believed that this is the first wastewater treatment system in Micronesia that employs the membrane bioreactor system.

It was not until the 1990s that filtering technology had improved to the point where they were determined to be practical for use in wastewater treatment plants. Stricter U.S. EPA discharge regulations have spawned a tremendous growth in the use of membrane filters.

The growing use of the filters has made the process more appealing, practical and more economical than the traditional wastewater practices. Membrane filters, such as the one on Managaha, have been proven to safeguard public health, occupy less space, and consume less energy while consistently producing a high quality water suitable for reuse or recycling.

The choice for this type of system for use on Managaha resulted from several meetings with DEQ, EPA and Tasi Tours for a reasonably priced and easily maintained system that met or exceeded expected effluent requirements. The treatment plant selected was manufactured in Japan and installed by Pacific Daiken under the direction of the manufacturer’s technical representatives. Start-up operations began in April 2007. Initial operational problems were resolved and the old treatment facility phased out and demolished. US EPA staff made a site visit in December 2007 and were impressed by the initial results, the low impact on the island, and relative ease of maintenance. The attached photos show that the outward appearance of the facility is both pleasing and unobtrusive. This is important for the tourist industry as objectionable odors, noise, or a large exposed plant would detract from the island’s natural appeal.
[B] MBR System[/B]

Membrane systems for wastewater treatment are an outgrowth from the use of reverse osmosis in the production of potable water from brackish or seawater. The mechanism by which the membrane filtration operates is simple in concept. The process uses a submerged hollow polyethylene fiber membrane with a 0.4F (micron) pore size. The membranes are a physical barrier that captures all suspended particles larger than the membrane pore size. The membrane separation unit is internally immersed in the bioreactor. As the wastewater passes through the membrane residual suspended solids, bacteria, viruses, degradable organic molecules and other impurities are separated from the wastewater. Air moving across the membrane keeps it free of solids build-up allowing a higher concentration of solids in the aeration basin.

Tasi Tours asked Azuma Limited of Saipan to design the treatment plant on Managaha and after EPA and DEQ reviews, was purchased by Tasi Tours from Daiki Johkasou of Japan.

The filtered wastewater is passed through a photooxidation system, which is a combination of ultraviolet light and oxidants (ozone, chlorine) to kill residual bacteria and viruses.

In the months the membrane filter has been in operation there has been a dramatic improvement in the effluent quality. Impurities in the effluent, measured by the BOD test, have been reduced by over 99 percent. As the plant operation was adjusted and the waste stream stabilized the treatment continued to improve. At present the treated wastewater is recycled through the toilets on Managaha saving potable water and power. All make-up water for the process is from a combination of rainwater catchment and reverse osmosis water. This assures a continual high quality effluent.

The good news for the Commonwealth is that this new wastewater treatment process will safeguard the pristine waters around Managaha Island. As of today, the treated effluent from the membrane filter is discharging wastewater that is cleaner than it has been for the past three decades. The Department of Public Lands in cooperation with Tasi Tours has used modern technology to ensure our visitors that the waters around Managaha will remain safe and pure.

For future consideration by CNMI government officials, membrane systems for wastewater treatment have replaced many older activated sludge plants in the US mainland. The membrane systems not only produce an exceptionally high quality effluent, they occupy less space, require less maintenance, and consume less power than the older activated sludge plants. The largest membrane systems constructed to date are in the 20 million gallon per day size, about 5 times larger than the Agingan or Sadog Tasi treatment plants.

As the membrane filtration technology continues to improve the plants will become smaller, more efficient, and continue to reduce overall maintenance costs.

Prepared by Stan Good for the Division of Environmental Quality.