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The wastewater arrives into the
inlet channels at Ringsend from Ringsend Main Lift Pumping Station,
Dodder Valley Gravity Sewer and Sutton and Dun Laoghaire Pumping
Stations. The wastewater passes through fine screens (6mm) to
remove paper, plastics and large solids. Grit is removed in special
tanks. 12 No. lamellae primary settlement tanks which allow most
of the suspended solids in the wastewater to settle. The settled
wastewater is pumped to 24 Sequencing Batch Reactors (SBR’s)
for secondary treatment. Micro-organisms developed in the process
are used to take organic matter out of the wastewater, along
with ammonia and nitrogen. SBR technology is used to achieve
BOD/COD removal and nitrification.
The SBR’s at Ringsend are the largest in the world and, uniquely,
are contained in a two storey structure, due to site limitations.
The 24 SBR’s are divided into 6 units, built three on top of
three. Each unit consists of 4 tanks, operating in sequence.
While one tank is filling with wastewater, a second is aerating
wastewater with oxygen to accelerate the natural biological secondary
treatment. The third tank is settling wastewater and the fourth
tank is decanting treated wastewater to the next treatment stage.
The treated water receives tertiary treatment in the form of
ultraviolet disinfection, to meet Bathing Water Standards, before
being discharged into the Bay. The entire treatment process at
Ringsend is totally natural. Oxygen from the air is used to treat
the wastewater and heat is used to treat the sludge. The outputs
from the treatment works are:
• Clean water
• Biofert (fertiliser)
• Energy
Over 50% of the energy needed to run the plant is generated from
the sludge treatment.
Sludge is a by-product of the treatment of wastewater generated
from the primary and secondary stages. At Ringsend it is treated
using hydrolysis and digestion before being thermally dried,
killing pathogens and producing a pasteurised, organic based
fertiliser. 25,000 tonnes of Biofert is produced at the Ringsend
Treatment Works each year. A by-product of the sludge digestion
process is biogas, which supplies over 50% of the heat and electricity
required at the Ringsend works.
| KEY DATA: |
|
| Population
Equivalent: |
1.7 million |
| Dry Weather Flow: |
4.65 m3/s |
| Flow to
Full Treatment: |
11.1 m3/s |
| Maximum flow to storm: |
11.5 m3/s |
| Maximum
flow to works: |
22.6
m3/s |
| BOD: |
98,400 kg/d |
| TSS: |
101,000
kg/d |
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