Page 161 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SOLID-LIQUID SEPARATION AND INTERCEPTORS

SOLID-LIQUID SEPARATION AND INTERCEPTORS 3.29

To recover the precious metals, the housing is disassembled, and the filter is removed
and emptied at a remote location. The housing can be made of brass, cast iron, steel, plastic,
or any material permitted by local code.
Hair
Hair is discharged from barber shops and beauty parlors, and has the potential to accumulate
at some minor obstruction that would not ordinarily cause trouble. The hair will accumulate
and eventually cause a blockage.
An interceptor for this type of service is a small, in-line unit, using a perforated basket
strainer inserted inside a small housing. This housing is installed instead of a trap on a
fixture. To remove the accumulated hair, the housing is disassembled, and the strainer is
removed and emptied at a remote location. The housing can be made of brass, cast iron,
steel, plastic, or any material permitted by local code. The strainer is usually made of stainless
steel. Refer to Fig. 3.12 for an illustration of a typical hair trap.

Acid Neutralizers

Whenever the possibility exists that acid of any kind may be discharged into the drainage
system, an acid neutralizer must be provided. As a general rule, many authorities permit
waste with a pH of 4 or above to enter the drainage system, where it will be further diluted
with other effluent. Acid will attack ordinary piping material and cause it to fail prematurely.
One method used for small, isolated, and intermittent discharges is to percolate the acid
through a tank containing limestone chips. These chips range from 1 to 3 in (25 to 75 mm).
They are placed in a tank until it is filled to approximately 50 percent of its volume. There
is a baffle arrangement to ensure that the effluent is in continuous contact with the chips.
Generally used contact periods of between 10 and 15 min are sufficient to neutralize the
acid, with shorter times used based on the individual manufacturer’s recommendations. The
actual required contact time for proper neutralization should be based on specific interceptors,
effluent dilution, and pH values. Neutralization is accomplished by chemical reaction of the
acid with the chips. There is no residue. However, the chips must be replenished periodically,
depending on the amount of acid that is treated. General figures require 100 lb (45 kg) of chips
to treat 98 lb (44 kg) of sulfuric acid and 73 lb (33 kg) of hydrochloric acid.
Unit sizes vary, ranging from small units that can be placed under individual sinks to
tanks suitable for large facilities. They must be located in areas where their covers can be
readily removed to add new chips. The larger tanks are heavy and need additional struc-
tural support. They can be installed either above the floor or below the slab, with the cover
extending up to the finished floor above.

FIGURE 3.12 Typical hair trap.

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