The following description outlines the basic components of a
collection, treatment and reuse system for small communities and/or
developments. Typical flows are 3,000 – 100,000 gpd. Similar design
components can be applied to larger systems as well.
Small-Diameter Collection System
· Primary Treatment
provided by septic tank (1,000 or 1,500 gallons) buried underground
at each lot. ( refer to exhibit: A2 )
· Wastewater from each house delivered to
septic tank via 4” PVC drain.
· Solids and trash are settled out in
tank. An Effluent Filter minimizes solids content of tank effluent.
· Tank Material: Concrete or Fiberglass
(FRP). Polyethylene not recommended.
· Tank effluent (1” – 2” PVC lines)
either flows by gravity (STEG) or is pumped (STEP) into the Mainline. ( refer
to exhibit: A1 )
· A small Mainline (2”-4” PVC or HDPE) is
located in the streets or under sidewalk.
· Systems can contain both STEG and/or
STEP tanks.
· Manholes not required; Mainlines follow
grade at minimum depth of cover.
· Cleanouts, pigging ports and air/vacuum
release valves ensure ease of cleaning and minimize air blocks.
· Each lot has an isolation valve and
check valve after the septic tank.
· Restaurants will require additional
pretreatment using grease traps.
· Centralized large-scale pretreatment tanks may be used for commercial centers, schools, ect.
· Tanks have effluent filters and may be STEP or STEG.
Wastewater Treatment System
· Typical system includes subsurface flow
constructed wetland (w/recycle), and recirculating sand filter. ( refer to
exhibits: B1, B2 )
· Treatment system can be built in one
single or two parallel trains.
· Wetland provides Secondary Treatment -
BOD, solids and nutrient (N/P) reduction.
· Creates green space, wildlife habitat
and landscape interest.
· Recycle line can be added to increase
nutrient removal performance of the wetland.
· Sand Filter provides polishing –
including physical and biological filtration and pathogen reduction.
Improved Sand Filter lifespan due to treatment provided by
wetlands.
Reuse and or Disposal
· After the Sand Filter effluent is sent
to a reuse or disposal system.
· Subsurface Drip Irrigation
of common areas, landscaping, parks, orchards
· Subsurface Disposal Field
(pressure-dosed) under playing fields, open space
· Reuse for landscape
irrigation at individual lots (may require disinfection)
· Reuse for toilet flushing
or other uses (requires disinfection)
· Reuse lines can run
parallel to mainline collection system in order to distribute treated
effluent.
Mechanical filtration (min.
100 micron) usually required for drip irrigation systems.
*Reuse regulations governing
field sizing, application rates and disinfection requirements vary by State
and climate.
© 2005
Natural Systems, International, LLC.
www.natsys-inc.com
