 |
|
Water and Wastewater Plant Directory
L
|
|
|
|
Moray Place, Dunedin, New Zealand
|
|
Green Island Wastewater Treatment Plant
Post Office Box 5045
Moray Place, Dunedin, 9058
New Zealand
Contact Information:
Contact:
Email:
Telephone: 03 477 4000
Fax: 03 474 3594
Plant Operation: Municipal
Processing: Wastewater
|
|
|
Web site:
http://www.dunedin.govt.nz/services/waste-water/treatment-plants/green-island
|
Plant/Process Description:
The Green Island Wastewater Treatment plant is
to the south of Green Island and borders the
Green Island Landfill and the Kaikorai Estuary.
How the Green Island plant works
Grit and plastics etc within the wastewater are
removed by grit traps and 1 mm milli-screens.
The wastewater then goes through several
processes before it reaches the secondary
treatment process, uv disinfection.
'A' process
The screened liquid enters the first of three
aeration tanks. Rotary lobe air compressors
supply process air through a series of pipes and
diffusers. The diffusers emit air as tiny
bubbles into the wastewater from the base of the
aeration tank. A surface aerator is also used in
the 'A' process tank.
A bacterial mass or "floc" is formed containing
large numbers of very active bacteria, together
with ciliates, rotifers and protozoa. The
bacteria grow rapidly under these ideal
conditions, consuming the organic material in
the wastewater.
After leaving the activated sludge tanks, the
mixed liquor suspended solids flow to a large
circular tank known as a clarifier. The sludge,
which settles to the floor of Clarifier No 1 is
removed and a proportion returned to the inlet
end of the activated sludge reactor where
it "seeds" the incoming influent.
B process
The process is repeated again with the liquid
from Clarifier No 1 being pumped into aeration
tanks 2 & 3. After passing through these two
tanks, the liquid flows to Clarifier No
2.
Activated sludge
A proportion of the sludge produced in the A & B
processes is returned to the aeration tank it
came from. This is known as returned activated
sludge.
The other portion of sludge, called waste
activated sludge, is sent to the thickener. The
thickener concentrates the sludge by removing
excess water. This sludge is then transferred to
the thermophylic digester and then to the
mesophylic digester.
Sludge from the mesophylic digester is
transferred to one of two centrifuges.
After passing through the centrifuge the sludge
has a dry solids content of 22.
Disposal and discharge
Centrate is returned to the wastewater stream
for processing. Sludge is mixed with lime and
disposed of at the Green Island Landfill.
The final treated effluent from clarifier No 2
is UV disinfected and discharged via diffusers
at the end of an 850m long ocean outfall.
|
Owner:
Dunedin City Council
Web site:
http://www.dunedin.govt.nz/
|
Operating Company:
Dunedin City Council
Web site:
http://www.dunedin.govt.nz/
|
Directions:
|
|
|
|
|
|
|
|
|
|
Disclaimer:
Water and Wastewater.com provides the information on
this page for reference purposes only. We do not certify
the accuracy of the information provided by third-party
individuals for this listing.
|
|
|
|
|
|
|
|
