Package Water Treatment Systems - Public Water Systems - page 875

Treated
Water Raw Water

Adsorption
Clarifier

Filtration

Fig. 25-7. Flow diagram of a adsorption clarifier package plant

illustrating the various operating cycles. During operation, chemically coagulated water
is introduced into the bottom of the adsorption clarifier compartment, where it passes
upward through a bed of buoyant adsorption media. The adsorption clarifier combines
the processes of coagulation, flocculation, and settling into one unit process.
In passing through the adsorption media, the chemically coagulated water is sub-
jected to: (1) mixing, (2) contact flocculation, and (3) clarification. At operating flow
rates, the mixing intensity, defined by the mean temporal velocity gradient value G ,
ranges from 150 to 300 sec 1 . Flocculation is accomplished by turbulence as water
passes through the adsorption media, and is enhanced by contact with flocculated solids
attached to the media. Estimates of the mixing parameter Gt in the adsorption clarifier
range from about 1 10 4 to 3 10 4 , depending on flow rate and the rate of headloss

development.
Turbidity removal in the adsorption clarifiers is accomplished by adsorption of the
coagulated, flocculated solids on the surfaces of the adsorption media and on previ-
ously attached solids. The adsorption clarifier provides excellent pretreatment, which
frequently is better than the performance achievable with complete flocculation and
settling processes. Turbidity removal in this stage ranges up to 95 percent.
The material used for the adsorption media was selected as a result of experimen-
tation with various materials, all with a specific gravity of less than 1 and of various
sizes and shapes. The buoyant media is retained in the adsorption clarifier by a screen
over the compartment.
Two style units are available, with capacities ranging from 350 to 4,200 gpm. The
Trimite (Fig. 25-8) models are designed for flows from 50 to 350 gpm per unit, and
the Trident (Fig. 25-9) for flows 200 to 1,400 gpm per unit. Multiple units are used
for higher flows.

Roberts Water Technologies Inc.—PACER II System
Pacer II units are also available in both steel and stainless-steel construction. Package
Pacer II units are available with flow rates up to 350 gpm, and standard modular units
are available with design flow rates of up to 1,400 gpm. Following is an operational
description of the Pacer II system.
The Pacer II Dual Treatment System is an effective surface or groundwater treat-
ment process capable of producing high-quality filtered water in varying raw-water
conditions. The Pacer provides multiple barriers of protection through the combination
of contact clarification and deep bed filtration. This combination provides a high level
of particle conditioning that has been proven through extensive testing to achieve
greater than three-log reductions of both Giardia and Cryptosporidium .