CITY OF CAPE TOWN

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CITY OF CAPE TOWN
WASTEWATER TREATMENT
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FOLLOWING 1997 RE-STRUCTURING
LOCATION OF WORKS
Treatment Works locations, Catchment Areas, Bulk
Conveyance System
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PROBLEMS ASSOCIATED WITH 1997 INBUNDLING

• 11 Previous owners
• Different systems
• Lack of investment
• Different efficiencies

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STRATEGIC INVESTIGATION

• Assess condition of facitilies
• Assess process performance
• Examine catchments
• Assess long term development
• Identify a programme of upgrading

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IDENTIFIED REQUIREMENTS

• Upgrade of existing facilities
• Capacity extensions
• Water re-use
• Compliance with standards
• Odour control
• Sludge management

All of which resulted in a R1.5 bn requirement
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TYPICAL UPGRADINGS
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ATHLONE WWTW CONSTRUCTION OF NEW INLET WORKS
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ZANDVLIET WWTW ARCHIMEDIAN INLET SCREW PUMP
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BELLVILLE WWTW TESTING THE NEW AERATION SYSTEM
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ZANDVLIET WWTW SLUDGE DE-WATERING FACILITY
INSTALLATION OF NEW BELT PRESS
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BORCHEDRS QUARRY WWTW SLUDGE HOPPERS
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CAPE FLATS WWTW GAS HOLDER
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MACASSAR WWTW SST CONSTRUCTION
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CAPE FLATS WWTW SLUDGE DEWATERING
(PELLETISATION) INSTALLATION
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MACASSAR WWTW SLUDGE DEWATERING BUILDING
CONSTRUCTION
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SPECIAL PROBLEMS

• Introduction of 2010 standards
• Introduction of waste discharge charge system
• Odour control
• Sludge disposal

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BUDGETS

• Annual Capital Budget R86 million
• Operating Budget
• R 178 million excl capital charges
• R 285 million incl capital charges

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TYPICAL UPGRADINGS FROM 1997
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TREATMENT CAPACITY INCREASES SINCE 1997

• Cape Flats 50 Ml/day
• Bellville 5 Ml/day
• Macassar 5 Ml/day
• Wildevoëlvlei 8 Ml/day
• Potsdam 5 Ml/day
• Scottsdene 2,5 Ml/day
• Zandvliet 10 Ml/day

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MECHANICAL SLUDGE DE-WATERING INSTALLATIONS

• Athlone Belt presses
• Cape Flats Centrifuge de-watering equipment
  and Pelletisation plant
• Bellville Belt presses
• Borcherds Quarry Belt press and Centrifuge
• Mitchells Plain Centrifuge
• Potsdam Belt presses
• Zandvliet Belt presses
• Macassar Belt presses

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SLUDGE LAGOON REDUCTION

• Cape Flats 1 lagoon completed
• Zandvliet All lagoons cleaned
• Bellville 1 lagoon completed

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MAJOR PROCESS IMPROVEMENTS

• New inlet works at Athlone Wastewater Treatment
  Works inclusive of automatic screens and grit
  removal
• New inlet screens at Cape Flats, Macassar,
  Zandvliet, Bellville and Borcherds Quarry
  Wastewater Treatment Works
• Replacement air diffusers in biological
  reactors at Athlone, Bellville and Cape Flats
  Wastewater Treatment Works
• New primary and secondary clarifier tanks at
  Athlone, Zandvliet, Macassar, Bellville and
  Cape Flats Wastewater Treatment Works

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CURRENT ADDITIONAL UPGRADE/ INTENTIONS

• Potsdam Capacity Extension
• Wesfleur Capacity Extension
• Kraaifontein Capacity Extension
• Athlone Capacity Extension
• Melkbosstrand Capacity Extension
• Fisantekraal New Works

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REDUCTION IN STAFF LEVELS OVER THE LAST 5 YEARS
32 Reduction
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AIM OF WASTEWATER DEPARTMENT

• To provide an effective service delivery though
  appropriate planning implementation
• To minimise negative impacts
• To be cost effective
• To promote effluent re-use

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Upgrade of Domestic Waste Water Effluent for
Industrial Use
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Water Conservation In Industry

• Good Housekeeping
• Water Minimization
• Effluent Recycle and Re-use
• Domestic Waste Water Effluent Upgrade and Re-use

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Stakeholders in Wastewater Re-use

• DWAF/DEAT
• Reduce pollution loading
• Local Council
• Strategic Intent of Zero Effluent Discharge
• Industry
• SHE Intentions
• Economic

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Water Use in Industry

• Energy
• Steam generation
• Heat Transfer
• Process
• Hygiene

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Chemistry Requirements

• Industry
• TDS 20 - 300 ppm
• SS lt 1

• Domestic Effluent
• TDS 200 - 2000 ppm
• SS 0 - 700 ppm

?
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Pilot Plant
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Chlorine
Holding Tank
Dissolved Air Flotation
Sewage Effluent
Coagulant
Compressed Air
Saturator
R O Permeate
Carbon Filter
Reverse Osmosis
Sand Filter
R O Reject
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TDS
Chlorine
820 ppm
Holding Tank
Dissolved Air Flotation
Sewage Effluent
Coagulant
30 ppm
Compressed Air
Saturator
R O Permeate
Carbon Filter
Reverse Osmosis
Sand Filter
R O Reject
820 ppm
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Suspended Solids
Chlorine
65 ppm
Holding Tank
Dissolved Air Flotation
Sewage Effluent
12 ppm (80 Reduction)
Coagulant
0.5 ppm
Compressed Air
Saturator
R O Permeate
Carbon Filter
Reverse Osmosis
Sand Filter
R O Reject
2 ppm
1 ppm
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Final Chemistries
Steam Generation
Hygiene
Heat Transfer
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Summary Benefits of Effluent Re-use

• Reduces demand for potable water
• Reduces quantity of effluent
• Reduces loading on the environment
• Financial benefits to the City and Industry
• Promotes technical innovation partnerships

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CONCLUSION

• Significant potential nationally for re-use of
  effluent in industrial applications
• As price of potable water increases, re-use of
  effluent becomes a financial incentive to both
  industry and local authorities
• In a water scarce developing country, this
  becomes a strategic environmental and business
  opportunity, which must be maximised

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Questions ?
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The End
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WATER CYCLE
WATER SUPPLY
EFFLUENT RE-USE
USAGE
WASTEWATER
TERTIARY EFFLUENT TREATMENT
CONVEYANCE
ENVIRONMENTAL IMPACTS
LIQUID FRACTION
WASTEWATER TREATMENT
EFFLUENT DISCHARGE
SLUDGE FRACTION
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OBJECTIVES
OF WASTEWATER TREATMENT

• To provide service delivery for domestic and
  industrial development
• To comply with permit requirements
• To minimise effects on the environment
• To protect public health

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CONTROLLERS
REGULATOR DWAF
DEADP
WASTEWATER TREATMENT
ENVIRONMENT
PUBLIC
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HOW IS THE WASTEWATER PURIFIED?
Screening Settlement Air flottation

• Physical processes
• Biological processes
• Chemical processes

Aerobic Anaerobic Cultivation of micro organic
agencies
Flocculation Disinfection
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PROCESS DIAGRAM
SCREENINGS AND GRIT
SUPERNATANT WATER RETURN
ODOUR CONTROLLED
SLUDGE CAKE
SLUDGE MANAGEMENT FACILITY DE-WATERING
SOLID WASTE LANDFILL SITE
SLUDGE DIGESTER
ALTERNATIVE SLUDGE USES e.g. COMPOSTING
SECONDARY SLUDGE WASTE ACTIVATED
INFLUENT FLOW RAW SEWAGE
PRIMARY SLUDGE RAW
PRIMARY SETTLING TANK
ADD OXYGEN
EFFLUENT
SECONDARY SETTLING TANK
MATURATION
DISINFECTION
SCREENING
GRIT REMOVAL
BIOLOGICAL REACTOR
ODOUR CONTROLLED
OPTIONAL PRIMARY SLUDGE TREATED ANAEROBICALLY
SLUDGE RETURN
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PRIMARY TREATMENT

• Screening
• Grit removal
• Primary settlement

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SCREENING
SIMONS TOWN HAND RAKED MECHANICAL SCREENS
BORCHERDS QUARRY WASTEWATER TREATMENT WORKS
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PRIMARY TREATMENT

• Screening
• Grit removal
• Primary settlement

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GRIT REMOVAL
MECHANICAL REMOVAL AT WESFLEUR DOMESTIC WORKS
GRIT CHANNELS AT KRAAIFONTEIN WWTW
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PRIMARY TREATMENT

• Screening
• Grit removal
• Primary settlement

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SEPARATING SOLIDS FROM LIQUID FRACTION
POSTDAM WASTEWATER TREATMENT WORKS
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SECONDARY TREATMENT

• Biological reactor
• Secondary settlement

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CULTIVATION OF MICRO ORGANISMS
SURFACE AERATION AT POTSDAM WWTW
BUBBLE AERATION AT WESFLEUR WWTW (DOMESTIC WORKS)
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SECONDARY TREATMENT

• Biological reactor
• Secondary settlement

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SECONDARY SETTLING REMOVES REMAINING SOLIDS
(SLUDGE)
POTSDAM WASTEWATER TREATMENT WORKS
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SLUDGE MANAGEMENT

• Digesters
• Lagoons
• Drying beds
• Mechanical de-watering

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SLUDGE DIGESTION
CAPE FLATS WWTW
ANAEROBIC SLUDGE DIGESTER EXAMPLES
SLUDGE DIGESTERS AT SIMONS TOWN WASTEWATER
TREATMENT WORKS
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SLUDGE MANAGEMENT

• Digesters
• Lagoons
• Drying beds
• Mechanical de-watering

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SLUDGE LAGOONS
SLUDGE LAGOONS AT ATHLONE WASTEWATER TREATMENT
WORKS
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SLUDGE MANAGEMENT

• Digesters
• Lagoons
• Drying beds
• Mechanical de-watering

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SLUDGE DRYING BEDS
SLUDGE LAGOONS AT MELKBOSSTRAND WASTEWATER
TREATMENT WORKS
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SLUDGE MANAGEMENT

• Digesters
• Lagoons
• Drying beds
• Mechanical de-watering

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MECHANICAL DE-WATERING
POTSDAM TRANSPORTING SLUDGE TO HOPPERS
POTSDAM BELT PRESS DE-WATERING OF SLUDGE
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TERTIARY TREATMENT

• Maturation ponds
• Disinfection
• Odour control

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MATURATION
PONDS AT SCOTSSDENE WASTEWATER TREATMENT WORKS
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TERTIARY TREATMENT

• Maturation ponds
• Disinfection
• Odour control

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DISINFECTION
SIMONS TOWN CHLORINE CONTACT TANK
SCOTTSDENE WWTW CHLORINE DOSING BUILDING
CONTACT DAM
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TERTIARY TREATMENT

• Maturation ponds
• Disinfection
• Odour control

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ODOUR CONTROL
POTSDAM WWTW ODOUR CONTROL IN SLUDGE DE-WATERING
FACILITY
BORCHERDS QUARRY WWTW ODOUR CONTROL IN STERCUS
FACILITY
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STRUCTURE
Admin
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33 Reduction
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PLEDGE OF WASTEWATER DEPARTMENT

• Aim to minimise the impact on the environment
  from the operation of the wastewater system
• Lower costs by reducing stormwater ingress and
  groundwater infiltration into sewers
• Aim to provide adequate wastewater treatment
  capacity

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Fe Variation
Chlorine
0.22 ppm
Holding Tank
Dissolved Air Flotation
Sewage Effluent
Coagulant
0.01 ppm
Compressed Air
Saturator
R O Permeate
Carbon Filter
Reverse Osmosis
Sand Filter
R O Reject
0.12 ppm (45 reduction)
0.26 ppm
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Phosphate Variation
7.2 ppm
Chlorine
0.81 ppm
Holding Tank
Dissolved Air Flotation
Sewage Effluent
Coagulant
0.05 ppm
Compressed Air
Saturator
R O Permeate
Carbon Filter
Reverse Osmosis
Sand Filter
R O Reject
0.56 ppm (31 reduction)
0.58 ppm
3.2 ppm (56 reduction)
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SOME MAJOR FUTURE IMPROVEMENTS
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MECHANICAL SLUDGE DE-WATERING INSTALLATIONS

• Athlone Belt presses
• Cape Flats Centrifuge de-watering equipment
  and Pelletisation plant
• Bellville Belt presses
• Borcherds Quarry Belt press and Centrifuge
• Mitchells Plain Centrifuge
• Potsdam Belt presses
• Zandvliet Belt presses
• Macassar Belt presses

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EFFLUENT RE-USE

• Councils policy to maximise effluent re-use
• Various investigations under way
• New Projects
• Steenberg/ Westlake Golf Club Irrigation
• Century City Canal irrigation
• Caltex Industrial process

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TREATMENT COST per Wastewater Treatment Works
including Capital Charges
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EFFLUENT RE-USE
EFFLUENT
MATURATION
DISINFECTION
INDUSTRIAL PROCESSES
AQUIFER RECHARGE
IRRIGATION