pva-gel beads for immobilization of...
TRANSCRIPT
PVA-gel beads for immobilization of microorganisms
Conventional biological wastewater treatment- Activated sludge (AS) method -
Solid-liquidseparation
Microbialdegradation
Wastewater(organic
contaminant)Sedimentation tank
Sludge return
Discharge supernatant
Air[Excess sludge]
Activated sludge method’s problems
Treatment tank is big
Bulking phenomenon occurs by layer change of microorganism resulting from a load change
It is necessary to draw a large amount of sludge
Large operating costs
Removal and treatment of sludge is high
Commonly-used bio-media method
Bio-media is added to AS tank as adjuvant to increase AS performance. (developed in latter half of the 1980s)
Bio-media added activated sludge method
Effluent from primary sedimentation tank
Return sludge
Excess sludge
Aeration tank
Treated water
Final sedimentation tank
Various types of bio-medias
From each carrier manufacture’s website
Most of them do not have porous structures like PVA-gel beads. (bacteria is retained only on the surface with protozoa and metazoa.)
Basic flow of PVA-gel beads method under aerobic conditions
*Sludge is not returned to PVA-gel tank.
Sedimentation tankAS tankPVA-gel tank
Organic biodegradationSolid-liquid separation
Treated water by PVA-gel beads
Effluent
EffluentInfluent
Sludge
Organic biodegradation
Principle of Autolysis as sludge reduction using PVA-gel beads
Less excess sludge generation
PVA-gel tank Sludge reduction tank
Autolysis Autolysis ⇒⇒ Use of microbiological metabolismUse of microbiological metabolism
Proprietary technology that eliminates or reduces sludge
Advantages of PVA-gel beads Easy retrofit (water quantity, loading up)
– Add a PVA-gel tank to an AS one or retrofit an existing treatment (AS) tank to PVA-gel one
Small footprint– Reduce tank volume due to high load designing
Low running cost– Reduce the cost of excess sludge disposal– Reduce the cost of low-biodegradable substances disposal
because of its biodegradation– Reduce energy from dewatering and drying
Increased capacity up to 5 times
0
1
2
3
4
活性汚泥 PVAゲル
有機物分解能力
kg/m3-槽・日
x5
kg/m3・d
Activated sludge
PVA-gelVo
lum
e lo
ad
Features of PVA-gel beads
Stable immobilization of bacteria → High load operation– Aerobic (organic treatment) – Nitrification, Denitrification (Nitrate treatment) – Anaerobic (Methane fermentation)
Bacteria rich flora → Lower excess sludge – Aerobic treatment – Autolysis treatment
High biodegradability of organic substances → Treatment of low degradable substances – Aerobic treatment
Features of PVA-gel beads High load operation
– Aerobic (organic treatment) :standard 25 kg BOD/m3 gel・d (2.5 kg BOD/ m3 tank volume・d)
– Nitrification, Denitrification (Nitrate treatment) :standard 3 kg N/m3 gel・d (0.3 kg N/m3 tank volume・d )
– Anaerobic (Methane fermentation) :standard 3 kg N/m3 gel・d (0.3 kg N/m3 tank volume・d )
Lower excess sludge– Aerobic treatment : 30% or less of removed BOD– Autolysis treatment: 5 to 10% of removed BOD
*It differs according to water qualities.
Treatment of low degradable substances– Oil and grease, PVA and so on
Conventional
PVA-gel method
Sedimentation tank
EffluentAS Excess sludge
100%Return sludge
Autolysis(mineralization)tank
Effluent
Reuse
ASEffluent
Excess sludge 40%
(Many references)
Return sludge
Excess sludge5-10%
KURARAY PVA-gel method
Standard method
Excess sludge reduction autolysis method