Internal Task Force Tom Rtjer, Head of Internal Task Force 9 April, - - PowerPoint PPT Presentation

Tom Røtjer, Head of Internal Task Force 9 April, 2018

Internal Task Force

The refining process to extract alumina

The input factors, processes and output at the Alunorte alumina refinery

2 Bauxite Pressure vessel 170-180 oC Crystall- ization Rotating

• ven

Filtering

Caustic soda

Bauxite residue

Crushing Milling

Water

• 2.4 kilo bauxite is turned into 1 kilo

alumina and 1.4 kilo bauxite residue

• Stored in bauxite residue deposits
• Process water treated before release

The refining process

Bauxite Alumina

Bauxite Alumina

Bauxite residue

The bauxite residue deposits (1 and 2)

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Effluent water treatment plant (Area 82) Area 45 DRS1 (Bauxite residue deposit 1) Albras (primary aluminium plant) Alunorte alumina refinery area Alunorte bauxite and coal storage area Canal Novo and Canal Velho Pará river Mixing box

24 February, 2018

Rainfall volumes

The event of intense rainfall 16-17 February 2018 resulted in 231mm in 12hr and 239mm in 24hr. Total February rainfall was 901mm

Key findings

• Extreme rainfall resulting in large amounts of

water needing treatment upon release

• Internal power outage due to lightning reducing

water treatment capacity

• External power voltage dip into refinery caused

a spill of process water containing caustic soda inside the process area, that impacted the effluent water treatment plant capacity

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319.4mm

6 days

Daily rainfall in mm

Alunorte Effluent Water Treatment System

Measurements in Pará River within average pH and Suspended Solids limits

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Canal Velho DRS2 effluent steel pipe DRS1 effluent concrete pipe DRS1 effluent concrete pipe

Effluent water treatment plant

Alunorte/Albras

X

X

Measurement point

Mixing box

Outlet from Alunorte

Pará River

Gate

• Process area water
• Stormwater

X

Gate

Return to process area Canal Novo

X

Measurement point

Area 45 storm water flooding

• Used for contractors and laydown area.
• As part of the Alunorte Water Management

improvement project that is already sanctioned, a new storm water system including new holding pond and sufficient pumping system will be constructed in Area 45 Flooding contained within the walls of the surrounding pipe channels

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No overflow from DRS1

Freeboard development during event

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• Water retained in DRS1 in order to let Effluent

Treatment Plant prioritize plant area

No overflow from DRS2

Freeboard development during event

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Alleged «overflow» - photo «evidence» used in media to «prove» spillover from DRS2. The same «overflow» showing that water moves from a dry zone to a wet zone within the deposit, as it is supposed to.

• DRS2 had good capacity, and DRS2 basins

contributed to relieving pressure on DRS1

4,01 4,09 3,89 2,83 2,79 2,73 2,55 2,20 2,11 1,98 1,66 1,63 1,60 1,60 1,40 1,40 1,76 1,86 2,14 2,31 2,41 2,70 2,83 3,03 3,26 3,38 0,00 0,50 1,00 1,50 2,00 2,50 3,00 3,50 4,00 4,50 5,00

15-fev 16-fev 17-fev 18-fev 19-fev 20-fev 21-fev 22-fev 23-fev 24-fev 25-fev 26-fev 27-fev 28-fev 1-mar 2-mar 3-mar 4-mar 5-mar 6-mar 7-mar 8-mar 9-mar 10-mar 11-mar 12-mar 13-mar 14-mar 15-mar 16-mar 17-mar 18-mar 19-mar 20-mar 21-mar 22-mar 23-mar 24-mar 25-mar 26-mar 27-mar 28-mar 29-mar 30-mar 31-mar

Borda livre m

Borda livre DRS2 (m)

Real Previsão chuva extrema Previsão base chuvas clima tempo Alvo

Summary

• The operational integrity of the bauxite residue

deposits 1 and 2 was maintained during the event, and there were no overflow from the deposits

• In order to avoid risks of harm to the

environment, not fully treated effluent was released through Canal Velho into the Para River − Average effluent concentration in the river was within

the prescribed limits between pH 6-9

• Recommendations have been identified to

increase capacity and improve the integrity of the

• verall effluent water treatment system of

Alunorte No overflow from the Bauxite residue deposits

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Recommendations

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Increase effluent treatment capacity:

• By 50% before next rainy season
• Holding basin and pump capacity Area 45
• New transfer pipes and pumping facilities

(DRS1 to ETP)

• Integrate holding basins at the Bauxite

Residue deposits

• Upgrade mixing box system
• Better separation of clean storm water from

water needing treatment

New Water Balance Study Update emergency plans and training Finalize closure of DRS1 Ensure good dialogue with authorities

Plant improvements Environmental improvements

Initiate and perform an environmental baseline and effect study as basis for future monitoring Invite academia in Pará Brazil/Norway to high quality environmental R&D program Review and improve the environmental monitoring Reduce external water consumption through reuse of internal water

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