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Home > Projects> Tasiast, Africa, Mauritania, Tasiast Gold Mine Expansion Project, Mauritania 

Tasiast, Africa, Mauritania, Tasiast Gold Mine Expansion Project, Mauritania

Project Summary:

Project Type:

Design, Build and Service

Project Category:

Domestic Sewage

Project Purpose:

To treat domestic sewage from the Tasiast mining worker villages
Design Flow: 1200 Cubic Metres/day

Peak Flow:

4800 Cubic Metres/day
Year of completion: 2012


Full Description:

Background:
The Tasiast Gold Mine is owned by Kinross Gold Corporation, a leading gold mining company with headquarters in Toronto. Tasiast Gold Mine required two sets of domestic sewage treatment system for two new worker villages in different locations. The larger village has 9000 residents, and smaller village has 100 residents. Both sewage treatment systems have similar treatment process.

The Treatment Process

Influent sewage is pumped to equalization tank through a screw screen to protect downstream equipment. The screw screen performs the combined functions of screen, conveyor and classifier. Screened sewage is stored in equalization tank to obtain relatively constant influent characteristics, such as flow rate and influent quality. The sewage is then pumped to Sequencing Batch Reactor (SBR) tank, where Bio-Batch process takes place by activated sludge to remove BOD, TN and partial TP. In the SBR tank, each operating cycle takes approximately 4 hours and contains 3 stages: Filling/Aeration, Settling and Decanting. In the Filling/Aeration stage, the tank is fulfilled by sewage by submersible pump. Aeration system provides oxygen through fine bubble diffusers in the tank and mixes sewage with activated sludge until uniform. According to the design criteria of TN, TP and pH, chemical solutions of Alum and Soda Ash are added to the tank at this stage to decrease TN to 10 mg/l and TP to 2 mg/l. In the Settling stage, the mixed liquor is separated to clarified effluent and settled sludge. In the Decanting stage, a Telescopic Decanter is automatically controlled to draw clarified water out of SBR tank.

In the disinfection process, NaClO is added into contact with the clarified water. Effluent is then stored in effluent storage tank for further reuse or discharge.

Surplus sludge from the SBR tank is pumped to the sludge holding tank, and then to Belt Filter Press to be dewatered. Filtrate flows back to pump station by gravity to be retreated with influent, while dewatered sludge is discharged and incinerated.

Performance Data:

Parameters (flow rate = 1200 m3/day) Unit Influent Effluent
BOD5 mg/L 250-350 <30
TSS mg/L 300-400 <50
pH - - 6-9
COD mg/L - <125
TN mg/L - <10
TP mg/L - <2
Oil and Grease mg/l - <10
Total Coliforms MPN/100ml - <100

Scope of Supply:

All tanks and structures in this project are made of epoxy coated steel.

1. Sewage Pumping Station

An underground pump tank& cover, submersible sewage transfer pumps, odour control system and float level switches.

2. Intake Screen

Automatically cleaned screen, above-ground screen channel, manual bypass bar screen with channel and isolation slide gates.

3. Equalization Tank

Above-ground equalization tanks, aeration/odour control system, aeration blower assemblies, submersible sewage transfer pumps, float level switches for pump control and magnetic flow meter.

4. Biological Treatment System_Sequencing Batch Reactor Trains

SBR tanks, EDI MiniPanel disc fine-bubble aeration system, submersible waste sludge pump, float level switches, dissolved oxygen analyzer, telescopic decanter, decanter drive-systems, aeration blower assemblies, butterfly valves, alum solution feed system and soda ash feed system.

5. Disinfection (Sodium Hypochlorite) System

Chlorination contact chamber, chemical injection system and online chlorine monitor.

6. Effluent Storage Tank with float level switches


7. Sludge Holding Tank

Supernatant decanting assembly, sludge discharge connection and float level switches.

8. Sludge Dewatering System

Belt filter press, inlet gate valve, polymer tank and mixer, dosing pumps, wash pumps, dedicated local control panel and inlet feeding pumps.

9. MCC and PLC Control Panel (in Control Room)

Photographs:


SBR tank

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