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SLOW SAND AND DIATOMACEOUS EARTH FILTRATION 9,13

suits of studies provide background data to establish design parameters and estimate fil-
ter run lengths. Data can also be used as an introduction of the process for orienting op-
erations staff.
Planning is critical to the successful implementation of the pilot program. The proto-
col must establish

• Pilot plant design and construction
• Conditions for runs
• Duration of tests
• Run parameters
• Data to be collected
• Laboratory analyses required
Some suggested water quality parameters to be monitored on the source and filtered
water include

• Turbidity
• Color
• Temperature
• Algae
• Bacteria
• Dissolved oxygen
• Iron and manganese
• Particle counts
• Filter head loss
• Flow rate
• Filter run length
It is important to collect all samples in accordance with established procedures, to min-
imize potential for contamination. Whenever possible, filter sand used for pilot studies
should be the same sand that will be used in the full-scale plant. It has also been sug-
gested that sand be installed in a "dirty" condition (similar to that delivered in construc-
tion) to determine the washing-out period during plant start-up. When tests are completed,
pilot filters can be moved into the full-scale plant for future research.
Pilot plant construction varies. Previous designs used many types of materials, in-
cluding fiberglass or concrete pipe and PVC pipe. The intent is to provide a watertight
container with room for installing sand and support media, underdrain piping, sample
ports, flow measurement equipment, and source water storage. Typical pilot plant setups
are 8 to 12 ft (2.4 to 3.7 m) high. The diameter of the pilot should be as large as possi-
ble to approximate future flow rates and facilitate operation and cleaning.

New Developments
Improvements and innovations to expand slow sand filtration treatment capabilities are
discussed in the following paragraphs.
Roughing Filters. Roughing filters serve as a pretreatment method to reduce sediment
loading to the sand filters. Many varieties are currently in use; in general they consist of