The North Clackamas County Water Commission (NCCWC) owns and operates a 10-mgd slow-sand filtration plant in Oregon City, Ore. The plant experienced periodic shutdowns when the Clackamas River, the plant’s feed source, would encounter turbidity spikes in excess of 10 NTU. During these shutdowns, NCCWC’s customers, the Sunrise Water Authority and Oak Lodge Water District, would obtain water from neigh- boring communities.
In addition, an increased demand was projected due to rapid population growth. As a result, the Sunrise Water Authority developed plans to build a new 10-mgd water treatment facility with expansion capability.
Reliable water quality
In addition to managing episodic turbidity spikes, the new filtration plant would need to manage taste and odor, and seasonal algae to ensure constant, reliable service during high-demand periods. Therefore, the new system required the capability to handle high solids, and the addition of aluminum chlorohydrate and powdered activated carbon.
Also, because no sewer was available on location, all wastes needed to be recycled back to the head of the plant or hauled off site.
In order to address the seasonal water fluctuations, capacity increase and low waste requirements, a Memcor membrane submerged system was selected by the Sunrise Water Authority. The submerged system enabled it to:
- Easily handle turbidity spikes from fluctuating river water without losing capacity;
- Employ PAC in the feed to address taste and odor;
- Utilize ACH for assistance in the reduction of TOC and algae; and
- Reduce haul-off costs due to the high water recovery.
Low cost
After carefully evaluating various options, Memcor membranes were chosen over alternative filtrationmethods and other membrane suppliers because of lower life-cycle cost per gallon.
According to Alan Schacht, treatment plant operator, “Field data was very comparable with the competitors, but Memcor membranes were chosen over the competition because the service and quality were very high, but the cost was much less.”
In comparison to the previous slow-sand filtration facility, plant operators found that Memcor membranes were able to effectively and efficiently provide exceptional water quality consistently, despite changing feedwater conditions. Constant chemical addition was replaced with seasonal chemical dosing during the summer and early fall months when algae in the river is prevalent, thus reducing annual operating costs.
Physical barrier
Unlike conventional filters, Memcor membranes provide a physical barrier that is capable of eliminating solids, viruses and bacteria down to 0.04 microns from the water, thereby reducing the quantity of chemicals that need to be used in the treatment process.
Of all the treatment processes currently available, Memcor membranes offer optimal protection against Giardia and Cryptosporidium, two parasites that are exceptionally unaffected by chemical disinfection (inactivation), and therefore must be reliably removed.
Exceeding exectations
The NCCWC facility now boasts a 10-mgd capacity microfiltration water treatment plant housed in a 9,000- plus-sq-ft building. Also included are drying beds for solids handling, as well as links to existing raw water and treated water pump stations. The filtration building will accommodate all of the ancillary facilities to the membrane operation, as well as a new control room, maintenance area and chemical feed facilities.
The new treatment process is simplified and makes more financial sense for the Sunrise Water Authority.
Because the facility is fully automated with SCADA technology, 24-hour monitoring is not necessary, and labor costs are cut significantly.
Working together with the Sunrise Water Authority, USFilter/Memcor successfully managed a highly aggressive schedule for completion of the project.
“The project was fast-tracked,” Schacht said. “We got the products we needed in a very timely manner. USFilter exceeded our expectations.”
