Challenge

The desert community of Scottsdale, Arizona had no natural surface water sources and a decreasing groundwater supply. Scottsdale had historically treated and disposed of its wastewater. As the city has grown, disposal of wastewater presented several problems, such as:

• The city was paying money to give away reclaimed water – a commodity
• The sewerage system would need upgrading, at a similar cost to the Water Campus
• Water lost from the city would have to be replaced, at a further treatment cost

In 1980, the State of Arizona passed the Groundwater Management Act (GMA), whereby facilities are given withdrawal credits when recharging groundwater – an attractive alternative for Scottsdale, as groundwater requires only disinfection for potable use. The Scottsdale Water Campus was developed as a water resources management facility.

Solution

Siemens Water Technologies supplied a MEMCOR® CMF (Continuous Microfiltration) system as a pretreatment to RO. This system consists of 24 units containing 90 modules each, with a capacity of 18.5 MGD.   

The Water Campus contains a 50 MGD water treatment plant, a 12 MGD water reclamation plant, and an advanced water treatment facility, which consists of CMF, RO and recharge systems.

The CMF units are designed to achieve a minimum 14-day cleaning frequency. They were also designed to run at a flux of 17.9 GFD, treating Colorado River water, and a 24.3 GFD when treating effluent.

Results

Since commissioning, the CMF units have consistently exceeded their performance target of a 14-day cleaning frequency.

• CMF units on Colorado River water run at effluent flux, and when running on effluent, have been cleaning at least monthly.
• All CMF units are operating with a Pressure Decay Test of less than 0.2 psi/min.
• Operating costs are approximately half of the pilot trial estimated costs.
• The CMF plant does not require a full-time operator.

Black & Veatch won the 2001 Grand Prize Award for its design. 

The CMF has greatly enhanced Scottsdale’s ability to meet its growing demand for water and secure future supplies.