Ringlace Biomedia Used in Solving High Flow Wash-Out Problem.

PORTLAND, Ore.--(BUSINESS WIRE)--Oct. 24, 1997--Ringlace biomedia was a prominent factor in the elimination of a long-standing problem at the Blacklick WWTP at Columbus, Ohio.

The Blacklick facility is a 1.2 mgd conventional activated sludge plant, receiving primarily domestic wastewater. It occupies a site (1.3 acres) immediately adjacent to the homes which it serves.

The plant is one of more than 25 wastewater treatment facilities owned and operated by Citizens Utilities Co. The collection system is subject to infiltration inflow during heavy rains. This was a problem, especially during the spring months. Frequent rains and a high ground water table produce flow rates to the plant which are as much as four times the average daily flow. The high flow rates shortened the aeration tank detention time and interfered with normal operation of the secondary clarifiers. The resultant loss of mixed liquor biomass caused sudden and significant deterioration in the normally high quality of the plant effluent. When the wastewater flow returned to normal, it required as long as 2 - 3 weeks to build up the mixed liquor solids inventory and resume operation at the F/M ratio (0.4) required to produce high quality effluent.

Citizens Utilities Co. decided to upgrade the plant, to ensure high quality effluent at all times. The major changes (completed in early 1996) were the installation of grit removal facilities, conversion to fine bubble aeration, installation of Ringlace biomedia in the existing aeration tanks and increased final settling tank capacity. 186,000 linear feet (56,707 meters) of Ringlace media was installed in the existing 0.365 MGD aeration basins. Together, these improvements have resulted in the development and retention of a significant amount of attached biomass, which supplements the non-attached MLSS. The attached growth biomass is not subject to "wash-out," nor is it subject to the type and degree of anaerobiosis that is characteristic of "fixed film" biomass. The attached growth biomass also ensures rapid re-growth of mixed liquor suspended solids to replace MLSS solids which are lost in the plant effluent during high flow rate periods. The overall result is that the upgraded plant is now able to produce high quality effluent even under very high flow conditions.

Ringlace is a looped strand type of flexible biomedia developed in the late 1970s in Japan specifically to support aerobic attached growth, while well established as a major wastewater treatment and with nearly 400 operating installations overseas, it was virtually unknown in the United States until 1992.

Adding submerged biomedia in a conventional aeration tank has been previously tried as a means of increasing the amount of total system biomass. Various types of media have been proposed: rigid sheet biomedia, "dump" biomedia and sponge media.

The practical difficulty encountered with each of these media types has been that a significant portion of the resultant attached growth becomes partially (or wholly) anaerobic. This condition causes irregular "sloughing" which leads to unpredictable performance. Until the development of Ringlace media, no biomedia existed to prevent this condition. Ringlace media has been shown to be capable of supporting active aerobic attached growth when submerged in aeration tanks, without the "sloughing" problems associated with other types of biomedia.

Beyond solving "wash out" problems, Ringlace is also used to increase nitrification capabilities and organic (BOD) removal particularly in existing tankage. Since 1992 Ringlace biomedia has been used to increase the nitrification capability of the secondary treatment system at the 10 MGD Annapolis, MD, WWTP. The Annapolis plant is one of the seven WWTPs operated by Anne Arundel County and discharges effluent into the Chesapeake Bay Estuary. Initial results indicated increased and consistent nitrification resulted from the use of Ringlace. As a result the county purchased the additional Ringlace to retrofit the entire treatment plant. Ringlace also offers a solution for WWTPs with limited space which are organically (BOD) overloaded. Placement of a proper amount of Ringlace media in the existing aeration tanks will provide additional biomass (hence treatment). This will allow up to 50 percent additional BOD loading to the basin without any need for new construction.

For more information please contact Ringlace Products Inc., 9902 NE Glisan, Portland, OR 97220. Phone: [phone], FAX: [phone].

CONTACT: Ringlace Products

503/251-1295