Setting: A biodiverse wetland teeming with life

Opened in 1876, the Maryland Zoo in Baltimore is the third oldest zoo in the United States. The historic 135-acre site, located in Druid Hill Park, is home to over 2,000 animals with the largest area dedicated to species originating from the African continent.

The zoo's 12,000-gallon marshland aviary exhibit imitates a typical wooded freshwater marsh found on the upper eastern shore of Maryland, where numerous rivers flow into Chesapeake Bay. A type of wetland dominated by grasses, marshes are transition zones between dry land and open water. As such, they are critical to the survival of many species of resident and migratory birds, fish, reptiles, amphibians, and invertebrates.

Maryland Zoo's Marsh Aviary is home to many native bird species including turkey vulture, black vulture, wood duck, black-crowned night heron, little blue heron and cattle egret.

Challenge: High-maintenance sand filtration impaction

Zoo technicians were plagued with ongoing issues involved with impaction of the existing sand filter. A combination of algae, dissolved waterfowl diet and bacterial film had resulted in the sand in the sand filters loading up rapidly and clumping together, significantly blocking flow several times over an 18-month period.

"Because of the gelatinous nature of the biomaterial, the sand would clump into large bricks that could not be broken up during backwashing," explains Waterco's Marketing Manager and Life Support Development, Kristina Macias. "Therefore, the sand had to be removed and replaced in a matter of a few months. This negatively impacted exhibit appearance, water quality, and the overall functionality of the Life Support System."

Solution: Centrifugal water filtration combined with glass pearl purity

Joey Stokes, an engineer/technical support manager for Waterco, suggested glass pearl media in place of sand to reduce impaction of the filter media. Manufactured from 100% pure glass, Waterco Glass Pearls offer much finer filtration than conventional filter media. Whereas other filter media may contain a variety of contaminants, glass pearls are chemically inert for superior purity. They also require up to 20% less backwash water than sand, saving operators valuable time and water.

Operating on the basis of 'depth filtration', dirt is driven into the filter bed and trapped in minute spaces between the particles of filter media, allowing clean water to pass through.

Waterco's MultiCyclone 70XL, which has achieved NSF/ANSI Standard 50 certification* - one of the largest fiberglass horizontal filters on the market to do so - was also installed to improve efficiency. Based on centrifugal filtration, incoming water is guided by a diverter plate so that it enters 70 hydro cyclones that spin the sediment out to the hydro cyclone's wall. It then spirals it down to the sediment chamber, while the clean water spirals upwards and out. Subsequently, there is no filter media to clean or replace and no moving parts that cause wear and tear.

Conclusion: Finer filtration, less labour, reduced downtime

Waterco's filtration solutions have not only reduced labour and material costs, along with exhibit downtime, but also reduced the time it previously took zoo technicians to replace the filter media every few months.

"We have been running the glass pearl media for four months," says Maryland Zoo's water quality tech-operator, Kyle D. Leister. "Thus far, we have only good things to say about the new media."

The biggest improvement, Kyle explains, is that the biomaterial trapped in the filters - or 'sludge' as he refers to it - is now easily removed with a short backwash of municipal water.

"Previously, we used quartz silica sand and the sludge would become embedded in the media, making proper backwashes impossible," Kyle says. "Every few weeks we used to have to open the filters, chlorinate overnight, then use a cement mixing paddle on a drill to break up the media prior to backwashing. In eighteen months, new sand had to be replaced twice before we decided to take the plunge and switch to glass pearls."

Furthermore, with normal 0.8mm sand filter media, a 10-minute backwash with the same flows and pressures would drop the pressure from 30+psi to around 15psi, which wouldn't last long. However, with Waterco Glass Pearls, zoo technicians can achieve pre-load pressures <10psi after only a three-minute backwash from 30+psi - even when they were running the system only using one filter.

Waterco Glass Pearls have been evaluated by TUV SUD PSB and are suitable for domestic swimming pools, aquaculture, water treatment and industrial applications. TUV test reports can be made available upon request.

*All sizes of MultiCyclones have been certified by NSF/ANSI to the NSF50 standard.