Controlling, Treating Runoff with Modular Filtration Technology

Huntington Beach, CA, is an oceanside community 20 miles south of Los Angeles. Well known for its 8 miles of beachfront, the city has trademarked itself “Surf City USA.

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by David Scott

Huntington Beach, CA, is an oceanside community 20 miles south of Los Angeles. Well known for its 8 miles of beachfront, the city has trademarked itself “Surf City USA.”

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The filter incorporates multiple elements of a treatment train — screening, sedimentation and high-rate filtration — in a compact, modular device.
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A couple of miles inland, however, the operators of the Good Shepherd Cemetery have been more concerned with containing and managing the stormwater that runs through their site. The owner, the Diocese of Orange, has embarked on an expansion of the century-old Catholic burial ground. Before the expansion could take place, however, the Diocese was required to come up with a stormwater management plan for the site.

The area has experienced flooding problems over the years, with nearby roads and yards flooding during heavy rains that overwhelmed local drains. The water management plan will eventually include a new public drainage system to control the runoff flowing through, as well as additional runoff emanating from, the cemetery site.

In addition to controlling the runoff from the site, the owners were required for the first time to create a system to treat the runoff. The state of California had tightened its rules regarding the installation of filtration systems in new projects. As a result, the Diocese had to meet a set of stringent specifications for the removal of a variety of pollutants, including metals, bacteria and oils.

In addition to performance, cost savings was a top priority in the selection of the stormwater treatment system. The city of Huntington Beach initially approved a plan that included a radial cartridge filter, but civil engineering firm Truxaw & Associates convinced the city to consider an alternative, more cost-effective solution: a compact, modular filtration system from Hydro International.

The Up-Flo Filter, based on upflow filtration technology developed at the University of Alabama, incorporates multiple elements of a treatment train — screening, sedimentation and high-rate filtration — in a compact, modular device.

According to the engineering firm, Hydro's filter system offered a cost savings of about 25% over the other unit, a cost reduction made possible by the filter's high treatment efficiency in a small footprint. It uses a sedimentation sump and screening system to pretreat stormwater runoff before it flows up through the filter media where final filtration occurs. A high-capacity siphoning bypass safeguards against upstream ponding or flooding during high-flow events. The siphon also serves as a floatables baffle to prevent the escape of floatable trash.

Upflow technology sends flow in an upward direction, countering gravitational forces to fluidize the media and allow the entire depth of the media bed to be used. This results in extended run times before clogging. In contrast, the media in down-flow, or radial-flow, filters is compressed at shallow depths, reducing flow rate and treatment capacity.

The differences in design between the first specified unit and the Up-Flo Filter helped convince both the engineer and Huntington Beach environmental officials of the system's long-term benefits. The first unit consisted of two structures, with treatment being conducted in one and water being bypassed into a second unit. By contrast, the Up-Flo Filter combines these processes into one unit, creating a streamlined system that has fewer parts to malfunction and needs less regular maintenance.

California regulations require stormwater to be treated on the first flush, removing up to 80% of all total suspended solids. Independent laboratory tests from a variety of sources, including the highly regarded New Jersey Corporation for Advanced Technology, have verified the Up-Flo Filter's ability to remove pollutants under a variety of conditions.

The site contractors, Van Diest Brothers Construction, installed the first filter during the initial phase of construction. Two or more systems are planned in the second and third phases, which are expected to be undertaken sometime in the next decade.

About the Author:

David Scott is the stormwater products manager for Hydro International. He has over a decade of experience working in the field of stormwater in the areas of consulting, regulatory relations and products.

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