PVA-gel beads for immobilization of microorganismstgwateradditives.com/documents/PVA-gel-beads-English.pdf · Advantages of PVA-gel beads Easy retrofit (water quantity, loading up)

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