Supportative Data 2

EVALUATION OF RECYCLED CRUSHED GLASS
SAND MEDIA FOR HIGH RATE SAND FILTRATION
FINAL REPORT
PREPARED FOR:
CWC
A DIVISION OF THE Pacific North West Economic Region (PNWER)
2200 Alaskan Way, Suite 460
Seattle, WA
October 1998
PROJECT CONSULTANT
Aquatic Commercial Industries
Report No. GL-98-1
Disclaimer
CWC disclaims all warranties to this report, including mechanics, data contained within and all other aspects, wither expressed or
implied, without limitation on warranties of merchantability, fitness for a particular purpose, data integrity, or accuracy of
Results. This report was designed for a wide range of commercial, industrial and institutional facilities and a range of complexity and
Levels of data input. Carefully review the results of this report prior to using them as a basis for decision or investments.

ACKNOWLEDGMENTS:
Competitive. CWC also acknowledges support from the US Environmental Protection Agency and other
Organizations.
CWC is a non profit organization providing recycling market development services to both businesses
and governments, including tools and technologies to help manufacturers use recycled materials. CWC is an
Institute of Standards and Technology. The MEP is a growing nationwide network
of extension services to help smaller US manufacturers improve their performance and become more
Affiliate of the national Manufacturing Extension Partnership (MEP) – a program of the US Commerce
Department’s National

EXECUTIVE SUMMARY
             A field test was performed to examine the potential for using finely processed recycled glass sand as a filtration medium in high rate sand filtration. Previous CWC studies and lab tests at Pennsylvania State and San Jose State Universities have demonstrated that, when properly processed, recycled glass is an effective filtration medium as a substitute for natural sand in many applications. This field test at an athletic club swimming pool was designed to determine whether glass sand was able to attain or exceed the clarity achieved with conventional sand and to establish how the cleaning characteristics of glass sand media compared with sand in terms of frequency and water use. This project was also intended to provide the filtration industry with information for economic evaluations to be made regarding the market potential for recycled glass sand as a filtration medium.
            The test was run from July 1997 to March 1998 at the Bally Total Fitness Center in Federal Way, Washington. Three filters were used, with a filter surface area of 21.18 square feet. The maximum design flow for the filter system, at 15 gallons per minute per square foot of filter area, was 327 galloons per minute. Each filter contained 275 pounds of 1/8” x ¼” pea gravel and 650 pounds of #20 silica sand. Control data on turbidity, operating pressures and backwash efficiency was developed by observing and testing the filter’s operation through four complete runs with conventional silica sand media (US Sieve Standard #20x30)
            The conventional media was removed and replaced with …. crushed glass sand media….
            Again, data was collected during repeat filter runs with the recycled glass media. This data was then compared to the control data for silica sand.
             The field evaluation revealed the following trends that illustrate the performance of recycled glass sand media compared to conventional sand media:
             1. Improved water clarity shown by a 25% reduction in National Turbidity Unit (NTU) readings.
             2. Increased backwash efficiency shown by a 23% reduction in water used for backwashing.
             3. Approximately 20% less glass sand (by weight) required for filtration.
         …. The data supports the findings that indicate possible performance advantages in using recycled glass in high rate sand filtration. Glass appears to be able to catch more turbid particles, thereby cleaning water more effectively and efficiently. This may allow pool filters to be operated for fewer hours to achieve desired water clarity, thereby saving energy and equipment life. More efficient backwashing uses less pool water that has already been chemically treated, heated and filtered and requires less operational and staff time.

             Of particular interest is the fact that these results were achieved by using 20% less filter media by weight. In economic terms, filter media is measured and purchased by weight; cost for filter media are incurred in both the acquisition and disposal of media. Simply by the fact that glass is 20% less dense than silica sand, real savings in pool operating costs can be achieve, especially when improved water clarity and increased backwash efficiency are added considerations.
3.0 FILTER EQUIPMENT

            Filters used for this evaluation were “Triton” TR series manufactured by PacFab, Inc. These filters are common in the swimming pool industry, with an estimated 5,000 to 7,000 filter vessels located on the West Coast of the United States. Each filter contained 7.06 square feet of cross-sectional filter area. Three filters were on one manifold, for a total of 21.18 square feet of filter surface area. The maximum design flow for this installation, at 15 gallons per minute (gpm) per square foot of filter area, was 327 gpm. These filters are manufactured for flow rates between 5 and 20 gpm per square foot.
             Each filter contained 275 pounds of 1/8” x ¼” pea gravel pea and 650 pounds of #20 silica sand. The sand depth from surface to bottom drain lateral was 13.5 inches. The bottom drain laterals were proved to prevent sand particles larger than #30 silica from leaving the filter. Each filter was fitted with manual air relief valves.
            6.0 MEDIA CHANGE
           The conventional media was changes and replaced with …. Crushed glass sand media. The sand replacement took approximately one day. The 1/8”x1/4” pea gravel bed below the medium was left in place. The underdrain laterals were surrounded and covered with gravel to a height of approximately one-inch above the laterals. This gravel allowed the filter to better distribute the backwash flow to the sand bed and is required by the National Sanitation Foundation (NSF) for the filter’s approval at filter rates of 15 gpm (and higher) per square foot of filter area.
           the filter manufacturer’s specifications required 6.5 cubic feet of medium for each filter (a total of 19.5 cubic feet for the system). This would have required 1,950 pounds of silica sand. However, glass is less dense than silica sand, so only 1,500 pounds were needed, demonstrating a 20% savings in filtration media by weight. This savings would be reflective in both raw material and shipping costs. This difference is derived from two factors. First, the specific gravity of glass is 2.53, compared with approximately 2.75 for sand, a 10% difference. In addition, the newly fractured glass particles appear to not pack as tightly as the sand grains. Therefore, the interstitial spaces between the glass particles are, on average, larger and have less rounded edges than sand grains. This confirmed pervious research at Pennsylvania State University.

8.0 GLASS SAND PERFORMANCE
….
Water Clarity
NTU readings actually dropped 25% with installation of the glass medium. This significant drop in NTU readings indicates that glass sand media may trap finer turbid particles than sand, resulting in clearer water.
Backwash
The average duration of backwash (in minutes) was 2:34 based upon ten backwashes, compared to 3:21 for silica sand based on six backwashes. Therefore, there was a reduction of as much as 23% of water used for backwashing glass sand media compared to conventional sand.
The glass media seemed to fluidize quicker and require less water for a complete backwash. This is probably a result of a combination of causes. First, glass has a lower density. The lighter material simply floats more easily with backwash flow. In addition, glass particles have a more angular shape and relatively flatter fractured sides. This may mean that glass particles pack less densely than sand and therefore require less backwash water to “unpack” during filter cleaning.
The noteworthy improvements in the backwash results in this field were consistent with trends identified in the San Jose State University study (Selvaduray) where measurements of the sand bed expansion were greater with the glass sand media than with conventional sand.
Consumption
In all cases, the amount of media required by weight was substantially less (approximately 20%) for the recycled glass sand than for silica sand. In pool operations this difference would be noted twice – first in the purchase of the filtration media and second in the disposal of spent media. Both are purchased by weight rather than by volume.
Summary
The field evaluation revealed the following trends:
     1. a 25% reduction in National Turbidity Unit readings.
     2. a 23%+ reduction in time for backwashing; and
     3. approximately 20% less glass sand (by weight) is required for filtration.
It is worthy to note that items 1, 2, and three were mirrored I the spa test data.
Applicability to other filter systems
Industries and governments use high rate filtration systems in a variety of settings. Findings from this and preceding studies show strong potential for glass to be used in commercial and municipal filtration. It is likely that the benefits concluded from this swimming pool field evaluation would be seen in other types of filtration applications, such as storm water, agricultural and industrial filtration.
9.0 CONCLUSIONS
This project was intended to be a full-scale “field test” of recycled glass for high-rate sand filtration. The work done at San Jose State University and Pennsylvania State University showed that, in laboratory scale, recycled glass had equal or better efficiency than conventional sand. Consistent with this prior research, recycled glass performed as well or better than conventional filter sand in swimming pool filtration.
The main advantages of recycled glass sand over conventional sand are:
1.Improved Water Quality. Finer particles were removed in the filter more efficiently, reflected by the 25% decrease in NRU’s. The findings show repeatedly that the recycled glass sand cleaned water more effectively. Clearer water is always desired. Being able to catch smaller turbid particles makes high-rate filtration sand even more efficient and therefore attractive over other types of filtration media. This advantage may allow pool systems to be turned off during non-use periods. This saves electrical energy and extends equipment longevity.
2.More Efficient Backwashing. Less backwash water was required to clean filter medium. As these tests results are duplicated in repeated future usage, the ability to backwash with over 20% less water is a major advantage that can prove valuable both in construction and in operation. The cost of sewer lines and holding tanks can be reduced. Most importantly, water has been saved. Beyond the value of the water resource, pool water has an added economic value when it has been chlorinated, pH adjusted, alkklinity adjusted, hardness adjusted, heated and filtered. The savings through more efficient backwashing are measured both in the cost of the water consumed and then disposed (some facilities that are charged per 100 cubic feet of water that is treated by sewage plants). Cost for chemicals and for heating water are also reduced.
3.Less Media Glass sand media is less dense and therefore lighter than conventional sand filter media. Less media by weight is required. Shipping, handling and disposal costs would be saved proportionately to the density of glass vs. silica sand media., approximately 20%.
            The benefits described in 1 and 2 above (i.e., savings in pool operation costs, energy, water usage, etc.) are achieved with 20% less material by weight.

It cannot be emphasized strongly enough that these results reflect a test of a specific glass filtration
Medium produced by a specific processor. Although they confirm the efficacy of properly processed
glass as a recirculating water filtration medium, they do not support the use of glass for this
application from any other processor, unless that processor is able to produce media that meets
Industry specifications for consistency in particle shape, size distribution, cleanliness and uniformity.
11.0 REFERENCES
Certified Pool Operator Handbook, National Swimming Pool Foundation, Lester Kowalski, Editor. 1990
Aquatic Facility Operator Handbook, National Recreation and Park Association, Kent Williams, 1994
Washington State Health and Safety Code, for Swimming Pools.
Crushed Recycled Glass as a Water Filtration Media, Pennsylvania State University, 1994, Richard Heubner PhD, Project Director.
Recycled Glass: Development of Market Potential, San Jose State University, 1994, Dr. Guna Selvaduray
Crushed Glass as a Filter Media for Onsite Treatment of Wastewater, CWC. 1995
Examination of Pulverized Waste Recycled Glass as Filter Media in Slow Sand Filtration, NYSERDA, October 1997