Saturday, August 12, 2006

Wastewater plant ready for east-side growth

Jane Moorman News-Bulletin Staff Writer; jmoorman@nedws-bulletin.com

Tomé New Mexico Water Service Company's wastewater treatment system is ready for the growth on the east mesa.

The company has completed retrofitting of its Rio Del Oro facility east of the Tomé Cemetery to quadruple the capacity of the system. The facility serves customers from Cypress Gardens on Meadow Lake Road south to Nancy Lopez Road in Rio Communities.

"We took a plant that was processing 160,000 gallons per day using the extended aeration activated sludge system and expanded the capacity with the state-of-the-art Membrane Bioreactor microfiltration system to 200,000 gallons per day, plus having a potential for 800,000 gallons per day," said Paul Risso, general manager of New Mexico Water Service, during a dedication ceremony recently.

"To our knowledge, nobody has ever retrofitted a wastewater plant with the new Membrane Bioreactor system while keeping the plant fully operational, and we're pleased to report that we did it while meeting all water quality standards for effluent," Risso said of the $1.4 million renovation.

The company had only to take the wastewater treatment plant off line three times during the six-month project. During these two or three day periods, the sewage was stored in a holding pond and then processed when the plant was operating.

Presently, the plant processes 160,000 gallons of wastewater a day from the company's 740 customers. The retrofitting will allow the same sized facility to process approximately 3,000 households.

Cost of this project was included in the company's May 2005 wastewater rate increase that was approved by the New Mexico Public Regulation Commission on April 29, 2005.

The Rio Del Oro plant is only the second Membrane Bioreactor system in New Mexico. Laguna Pueblo converted its lagoon system recently, according to Ron Hay, the company's operations manager.

This state-of-the-art technology is currently used in thousands of skyscraper buildings in Japan, where each building as a self-contained system that processes the sewage in the basement, then recycles the water through holding tanks on the roof back to the toilet system.

During the dedication ceremony, company staffers gave tours of the plant to representatives of municipalities, the Valencia County Commission, the Public Regulator Commission, the Valley Improvement Association and the Greater Belen Chamber of Commerce.

Hay says the retrofit employed the same infrastructure used in the traditional aeration-activated sludge system.

"In the past, we would mix bacteria into the raw sewage and aerate it to allow the bacteria to eat the bio-matter. Then we'd let the mixture sit, allowing the bacteria to settle to the bottom before we'd pipe the clear water off the top," Hay said.

"There are several issues involved with this system. First, you have to keep your bacteria healthy so they will settle to the bottom of the settling tank. Secondly, you have to remove a large quantity of sludge, which is the bacteria from the bottom of the tank."

The Rio Del Oro facility would generate 4,000 gallons — or two septic truckloads — of sludge each day, which had to be transported to the sludge disposal site five miles east in the Manzano foothills.

"The Membrane Bioreactor system extracts the water through a microfilter system from the wastewater-bacteria mixer during the aeration process," Hay said.

The bioreactors are located in the former mixing and settling tanks of the facility. Each chamber holds four units, each containing 200 microfiber filters. The units suck water out of the wastewater-bacteria mixers while the bacteria is actively eating the bio-matter. Each unit extracts 1,500 gallons of water each day.

Excess bacteria is removed from the bioreactor on a daily basis to keep a balanced environment for healthy bacteria.

"Once the active bacteria reaches the sludge holding tank, it becomes cannibalistic and devours its fellow bacteria. This decreases the amount of sludge that we have to transport to the disposal site," Hays said. "We are anticipating only having to transport two to three truckloads every two weeks."

The water that is extracted by the microfiltering system has very little bacteria left in it. Hay says that the company still disinfects the water before it is released to the Veteran's Park wetlands project even though it has non-detectable colonies of fecal coliform in it.

"The filters are so efficient that the water is one-third the turbidity, which is a measuring system of the clarity of the water," he said as he held up a container of tap water and a beaker of the effluent water. "As you can see, there is very little difference in the color of the water. The effluent is just slightly tanner."

"This new system has taken our effluent quality from Class 1B to Class 1A, which is the highest possible rating," said Risso.

The quality of the effluent is important to New Mexico Water Service because the water is being piped a mile east of the wastewater treatment plant and used in the Veteran's Park to create a wetlands environment.

"We are proud that, while we are participating in this environmental project with the Valley Improvement Association, we are providing water that is of near drinking-water quality," Risso said.

E-mail this story Printer-friendly version