Wastewater treatment in Surprise, USA

Population growth can push the limits of any city. As the population swells, the infrastructure must keep one step ahead to support the community’s expanding needs. In the desert, clean water is always the most critical necessity.

This is why the Water Services Department in Surprise, Arizona has been working so hard to meet the challenges of rapid growth in this once sleepy community.

A mid-decade census puts the 2005 population of the city of Surprise at 88,265 – almost triple the 2000 census of approximately 30,000 residents. City officials say the 2006 figure is roughly 96,000 people.

45 years old and growing

The city celebrated its 45th birthday last year. When it was incorporated in 1960, it was primarily an agricultural community.

However, thanks to the warm climate and dry air, the semiconductor and warehousing industries have found niches in cities near Surprise. The city has an ambitious economic development plan, targeting biotechnology and high-end hotels, along with large retail chains, many of whom are already on site in Surprise. The Texas Rangers and Kansas City Royals do their spring training in the new Surprise Stadium. New housing and safe neighbourhoods are drawing thousands of new residents every year.

"The city is attractive to new businesses as industry is able to come in and help develop the area rather than have to adjust to what is already developed," said Daniel Blackson, Operations Manager for the City of Surprise Wastewater Treatment Plant.

Quietly preparing for growth

With rapid growth an everyday fact of life, wastewater treatment operations in Surprise are in an extensive growth phase. A single plant originally served the city of Surprise and this is currently expanding to serve a portion of the adjacent city of Glendale planning area. Growth pressures mean the plant will quadruple operations in just a few years.

The city now has three plants that together treat 7.2 million US gallons of wastewater daily. Increased capacity for several of the existing plants, along with the construction of two new plants, will increase the facility’s capacity to 16.3 million US gallons daily by 2008.

"Growth is a major challenge. Keeping up with the growth and the construction has been an important issue for the plant," said Mary Jo Paris, Operations Supervisor at the plant.

All of this growth has been met with widespread community acceptance and support. "We operate without disturbing the surrounding area with offensive odours or unwanted noise," said Paris.

Wastewater treatment in the desert

Groundwater conservation is not only mandated by law, it is highly valued in Surprise. "We live in a desert. Every drop of water is critical," observed Dave Quinby, Lead Utilities Technician for the plant. "The more we can use highly-treated reclaimed wastewater instead of pumping freshwater from the ground, the better off we are."

The special requirements for treating wastewater in the desert have meant that the Surprise plant has had to stay on top of the latest research and trends in wastewater treatment.

At plants in cooler climates, digesters used for treatment are much warmer than the wastewater being treated. At the Surprise water treatment plant, the waste-water about to be treated approaches digester temperatures at other facilities. Quinby commented, "Our wastewater is warmer than it typically would be in any other place. In the summer, our oxidation ditches can be 32 to 33 degrees centigrade. Just to give you perspective, back east we ran digesters at 35 degrees."

"We digest using autothermal thermophilic aerobic digestion (ATAD). The resulting ATAD sludge is well-known for being very difficult to dewater, so we have high chemical polymer consumption," said Quinby. The Surprise plant’s polymer consumption is about 50 to 70 pounds per dry ton of solids – much higher than conventional anaerobic sludge that requires 10 to 20 pounds per dry ton.

He added that, in wastewater treatment, unexpected variables often come into play. "Some parts of the process may not function as expected, making dewatering more challenging. Over the years, we have worked through all the issues in order to remain consistent."

Biodenitro process 

The plant uses an oxidation ditch wet process for wastewater treatment. In order to decrease levels of nitrogen and ammonia, a "biodenitro" conversion is used. This process reduces nitrogen levels in the water without using chemicals.

Quinby continued, "From there, we thicken the sludge and put it into the ATAD digesters. The digested sludge is dewatered through the Alfa Laval decanters to produce sludge that is typically 24 to 25 percent dry "cake." Our standards require that the minimum cake must be at least 20 percent." The moist activated sludge is spread on agricultural land as a soil amendment as often as possible or deposited in a landfill.

The Alfa Laval Sharples and Alfa Laval ALDEC G2 decanters are two key pieces of plant equipment. While both can produce cake of similar dryness, the ALDEC G2 has the capacity to handle 15 percent more solids.The planned expansion will increase the number of decanters.

Alfa Laval decanters used for digested sludge dewatering.Our next upgrade includes five machines – three ALDEC G2 100s for thickening and two ALDEC G2 100s for dewatering. We will build a brand new facility designed specifically for these machines. This facility will house the thickening and dewatering operations under one roof. This will help us consolidate our solids handling staff – putting everyone in one place," Quinby noted.

Blackson added, "The decanters are a vital component of the whole picture. If they break down or fail, the process stops – so it is vital that we maintain them properly to avoid any emergencies."

Making a difference in Surprise

Blackson said, "We actually act as environmentalists too – we take the wastewater, we process and treat it, and it goes back out into the environment. The final effluent water is used for landscape irrigation, groundwater recharge, or goes back to farmfields and is reapplied to crops."

This preserves groundwater for other uses. He added, "Today the City of Surprise relies on groundwater for everything – especially for drinking water. Groundwater is truly precious."

"Efficient wastewater treatment is vital to the community. You can’t develop or grow without wastewater treatment," said Blackson.

Reliable workhorses

In order to help manage the demands of the explosive population growth in its area, the City of Surprise Wastewater Treatment Plant selected Alfa Laval as its partner for many of its decanters used for dewatering the digested sludge, and all associated service required.

Dave Quinby, Lead Utilities Technician for the City of Surprise wastewater treatment plant commented, "The decanters have been great. We put them through hell and back, and they just keep going. Because of their reliability, we just purchased five new Alfa Laval decanters for our expansion facilities."

The City of Surprise plant has also been impressed with the Alfa Laval service team. "Alfa Laval has been great in dealing with our facility. Their customer service has been absolutely spectacular," said Quinby.

Quinby added, "We like dealing directly with Alfa Laval rather than a local outside service provider. It is nice to be able to deal with the supplier directly – if there is anyone who knows how to service the equipment properly, it would be the equipment manufacturer themselves."

"We are able to call in 24 hours a day, seven days a week, 365 days a year with questions. They pull up the machine specs and offer options as to what Alfa Laval may do to help. I can call Jay Stover or John Gum (Alfa Laval technical support specialists) at any time and they take all of the time necessary to deal with the situation. They will not let go of a problem until it is solved."