1086 SMALL FLOW WASTEWATER TREATMENT TECHNOLOGY FOR DOMESTIC AND SPECIAL APPLICATIONS
available. During earlier years of package plant usage, the
plant size was usually limited to the maximum size that
could be shipped by truck. This was about 190–228 m^3 /d
(50,000 to 60,000 gallons per day (gpd)) maximum plant
size. Currently the manufacturers fabricate the plants in the
field. Thus package plants with capacities over 3800 m^3 /d
(one million gallons a day (mgd)) can be obtained.
The earlier package plants were designed as extended
aeration plants. Currently available package plants utilize
many treatment processes. Some of these processes are
listed below.BiologicalExtended aeration
Contact stabilization
Completely mixed
Step aeration
Trickling filterRotating biological contractor
Sequencing batch reactor (SBR)ChemicalChemical precipitation
Electrochemical flotation
UltrafiltrationDetailed discussions on package plants including manu-
facturers, process alternatives, size, weight, design criteria,
and cost is extensively available in the literature. 18 – 22 These
plants have been successfully applied in the treatment of
wastewaters in the suburban areas. The range of these plants
has expanded from small establishments to large municipal
and industrial applications. Manufacturers broadly group the
models or design series into flow capacity, BOD loading,
dimensions, air supply, motor horse power, etc., which has
simplified the job of unit selection.InfluentInfluentBlowerEffluentEffluentSettling
ChamberSettling
ChamberSludgeSludgeAerationAerationTrash
Tr a pTrash
Tr a pScumScumSludgeSludgeDiffuserMechanical or
Diffused Aeration(a) Diffused aeration(b) Mechanical aerationFIGURE 3 System components of aerobic suspended growth biological treatment pro-
cess. (Adapted from Ref. 2.)C019_002_r03.indd 1086C019_002_r03.indd 1086 11/18/2005 11:06:46 AM11/18/2005 11:06:46 AM