An ultraviolet disinfection system that makes use of triangular “wings” in the influent stream to improvement UV contact has been successfully tested in a full-scale prototype system at a municipal wastewater plant in Dundas, Ontario.
Introduced to the market in late 1997, Calgon Carbon Corporation’s medium-pressure Aurora UV® Disinfection System features higher power UV lamps than other medium pressure systems and improved treatment efficiency through mixing.
Prior to its market introduction, the Aurora UV design was subjected to two years of extensive testing - initially in laboratory settings and, later, in several pilot tests. Also, a full-scale prototype system has been on-line since March 1998 at Dundas.
The prototype system, designed with 60 kW of UV power provided by 12 five-kW lamps, is treating flows of up to 6 MGD. The lamps are configured in two banks of six, with each bank having three modules and two lamps per module. At a flow rate of 4 MGD, effluent fecal coliform (F.C.) is consistently <10 F.C./100 ml with lamps running at full power.
Because the permissible discharge limit is <200 F.C./100 ml, the system normally would be expected to operate at half power, which would be either with half of the lamps inactive or with all the lamps at 50 percent power. Operating the disinfection system at half power (30 kW) and at a flow rate of 4 MGD, the effluent is more typically 100 F.C./100 ml.
Objectives and Results
The objectives of the Dundas prototype testing were to confirm that the disinfection process scales up accurately from pilot-scale to full-scale and to validate the reliability of the mechanical components of the system.
Objectives and Results
A two-lamp pilot system was operated at the Dundas site for several days. Its treatment performance matched the performance of the full-scale system. Treatment efficiencies in terms of log kill versus electrical power input matched closely; therefore, it can be concluded that the pilot unit is hydraulically scaleable to a multi-lamp system. Also, the headloss across the full-scale prototype is approximately 3 to 4 inches at a flow rate of 4 MGD. This closely matched the headloss across the gravity flow pilot unit.
Objectives and Results
The system has been operating with no major problems. The basic components of the system, such as the ballasts, lamps and automatic quartz cleaning elements, are performing reliably.
Objectives and Results
One of the unique mechanical components of the Aurora UV system is the DeltaTM mixing technology, which increases the efficiency of the system by placing triangular wings in the flow of the water. The wings create powerful vortices which swirl the water as it flows past the UV lamps, helping distribute the UV dose evenly. By comparing operations both with and without Delta wings, an analysis of the data demonstrated that the wings improved the efficiency of the system by 20-30 percent, without significantly affecting pressure drop.
Objectives and Results
The 5 kW lamp used in the Aurora UV system is 75 percent more powerful than other medium-pressure lamp disinfection systems. This means the system can have lower maintenance costs, due to changing fewer lamps. Using fewer lamps also creates a smaller system, resulting in lower installation costs. The system also features automatic lamp cleaning, which can reduce maintenance costs.
Objectives and Results
Two additional Aurora UV systems, including an 18 MGD plant in Hinesville, Ga., are coming on-line in late summer 1998, based in part on the successful operation of the full-scale prototype.
