PRELIMINARY TREATMENT
Preliminary treatment of wastewater is the process by which sticks, bottles,
cans, stone, grit, rags and other large objects are remove to protect the
equipment in the plant from physical damage.
The Lynn
flow enters the facility via a 72 inch gravity interceptor where it is received
at the Lynn Influent Pumping Station and Screening Room. Acitivated carbon odor
control units scrub odors ( like sulfides a natural product of bacterial action
) out of the buildings air before it is discharged to the atomosphere.
At this point, the Lynn
flow is received with mechanically cleaned bar screens removing the screening
material (paper, sticks, rags, etc.) that are too large to pass through the
spaced bars. Once removed, these screenings are ground by comminution equipment
at which time they are ejected to the Solids Building
to be burned with the sludge.
Barscreen Drawing
& Animation
Barscreen
Room, Barscreens in blue
The screened Lynn wastewater is combined with
the Nahant, Saugus
and Swampscott flows just prior to the grit removal system. Grit is sand and
small hard inorganic material that, much like sand paper will wear down
expensive equipment if not removed in the begining of the plant. Grit removal
is the next process for which all four combined flows receive treatment. There
are four aerated grit chambers in which a mild aeration process freshens and
keeps light organic solids suspended in the wastewater while allowing the
heavier inorganic solids to settle to the bottom of the tank and be collected
by the bucket elevator system which removes these inorganic solids. Once removed,
these solids are washed, collected and ejected into covered containers. Grit is
transported in these containers to an onsite landfill, where the grit is dumped
and covered daily.
The wastewater then flow on to the Primary Treatment
process.
