Screening Facility

MIL-HDBK-1138

notify the operator upon arrival and provide pertinent

information such as name of hauler, origin of septage, and

certification, if applicable. The monitoring of septage quantity

and quality, as described in par 6.3, should take place at the

dumping station.

6.5.3

Screening Facility. The septage typically flows

by gravity from the dumping station to the screening facility.

The purpose of the screening facility is to remove the large

solids to protect the downstream treatment processes and

associated equipment. The screens, or "bar racks," can be

manually or mechanically cleaned. Provisions should be available

to efficiently dewater and dispose of the screened materials.

This will minimize the potential for odors.

6.5.4

Grit Removal System. The screened septage will

flow by gravity to the grit removal system. The purpose of the

grit removal facility is to separate the sand, gravel, cinders,

food particles, etc., from the septage while maintaining the

organic material in the main flow for downstream treatment.

Effective grit removal systems include aerated grit chambers and

vortex-type chambers. A grit removal facility may not be

necessary if sufficient grit removal is provided as part of the

liquid or solids process treatment units.

6.5.5

Grinder Pump Stations. Grinder pumps and other

types of wastewater grinders are sometimes used for primary

treatment in lieu of screening. Grinders screen and shred

material into smaller sizes without removing the particles from

the flow. Grinders reduce odors, flies, and unsightliness often

associated with screening and essentially eliminate the steps of

screening removal and handling, which may not be practical for

smaller treatment systems.

Unfortunately, solids from grinders cause problems

downstream, including deposits of plastics in sludge handling

facilities. Pulverized synthetic materials will not decompose in

the sludge digestion process and therefore may affect some sludge

disposal methods, especially land application. Using grinders

can also result in "ropes" or "balls" of material (particularly

rags) that can clog downstream equipment such as pipes,

diffusers, pumps, and aerators.

6.5.6

Storage and Equalization. The purpose of septage

holding basins is to provide storage, equalization, and mixing

prior to further treatment. Storing the septage will help reduce

the peak loadings to the downstream processes and help maintain

the appropriate blending of septage with the raw sewage. The

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