a city of cape town perspective - welcome to mile enhancement... · the western cape water supply...
TRANSCRIPT
ACHIEVING THE BLUE DROP
A City of Cape Town Perspective
Overview of City of Cape Town Water Supply System
Challenges
Adopted Elements of Best Practice
Water Safety Planning
Blue Drop Assessments
Conclusions
CONTENTS
BULK SUPPLY SYSTEM
The City’s Bulk Water Supply System
is planned and operated as an
integrated system;
Integrated operation: (CoCT BW &
WCWSS);
Maximisation of the storage in the
WCWSS for both the urban and
agricultural demands through
minimizing spillage from the dams;
The water resource planning,
development and operation of the
WCWSS is done by the City in
conjunction with DWA and the other
users.
The Western Cape Water Supply System:
Supplied from 14 Dams
o Capacity of 6 major dams is 898 300 000 m3
o 11 owned and operated by the City
o 2 owned and operated by the DWA
o 1 owned by TCTA and operated by DWA;
12 Water Treatment Plants;
o Total treatment capacity of 1 600 Ml/d
26 Bulk Reservoirs;
o Total storage capacity of 2 740 Ml
Atlantis Groundwater Scheme – artificially
recharged
Large diameter bulk conveyance pipelines –
o 605 km of up to 2.4m diameter pipelines
Reticulation system > 10 000 kms with 256
reservoirs and Distribution points in formal
and informal settlements.
Current City Demand ≈ 340 million m3 pa;
BULK WATER SYSTEM
PROFILE
Raw water quality - cost of treatment of potable water.
o Algal proliferation in dams impacts treatment - taste, odour and toxins e.g. (TWK, VV)
o Colour, soft, acidic, aluminium
Monitoring Capacity & Capability
o 80% vs 100% SANS 241 determinands (Antimony, Cadmium, Selenium and Uranium)
o Sampling points in informal settlements, quality and reliability of results
Availability of suitably trained staff to meet DWA Regs
o Process controllers - RPL
Maintaining acceptable DWQ throughout extensive integrated retic system
o disinfection challenge
o Stabilization challenge – CO2
Aging infrastructure
o Asset management plan
CHALLENGES
ISO Systems
Catchment Management – Drinking Water Resources
DWQ Monitoring – In house Accredited Laboratory
Training – PCs, Samplers
Taste, Odour and Toxin Control
Chemical Usage in Treatment Processes
Disinfection & Stabilization
Incident Management Protocol
Asset Management
Water Safety Planning
ADOPTED ELEMENTS OF “BEST PRACTICE”
Began with Bulk Water ISO 9001: 2000 QMS certification in 2003
Re-certification and roll-out to entire W & S Department
Enables a controlled environment for quality management and
continual improvement
Structured approach
Electronic Document Management System
IMPLEMENTATION OF ISO 9001 QMS
Pristine resources
Manage the catchments
Limit human activity – detrimental to WQ
Contain nutrients and contaminants to acceptable levels
Control vegetation – removal of alien species
Monitor raw water quality in the streams and dams
Hydrobiology
o Algae count
o Geosmin/MIB
o Microcystin
Raw Water Quality – Treatment Cost
CATCHMENT MANAGEMENT
DRINKING WATER QUALITY REQUIREMENTS
Risk Assessment of Water Safety plan is mainly based on
compliance of Drinking Water Quality.
SANS 241 requires tests to be performed throughout the entire
value chain of Water Supply
Development of Sampling frequency and protocol is based on the
outcome of the test performed
Population sampling coverage is defined as 1:20 000 for Metros
Sampling Coverage cannot be defined through water supply
system since the entire system is INTEGRATED.
Shortage of sampling point to cover the required ratio of 1:20 000
identified in 2010 during the assessment.
Capacity to ensure resampling within 24hrs as required by the
City‟s Incident Management Protocol
WATER QUALITY MONITORINGDWQ Challenges
Monitoring by In-house accredited laboratory
SANAS Accredited in 2011
High level of technical expertise
Extremely well equipped laboratory
>110 000 phys, micro & chem analyses / year
Monitoring programme
Hourly sampling and analysis – operational at WTP laboratories
o WTP Labs also well equipped
Weekly composite and grab samples from WTP analysed at SS
o Raw and treated water
Weekly sampling at reservoirs and distribution points – SS
o Hand-held loggers – Sampling reliability
Weekly Scientific Services visit by chemist to WTP
Monitors process
Checks plant lab
Oversees equipment calibration
WATER QUALITY MONITORINGProgramme
ATLAB – Automated process lab at WTPsautomated pH, alkalinity, hardness, turbidity and residual chlorine analyses
good repeatability, traceability and accuracy
gives trends of results for operational performance
connected to central server – can view results from office
Monitor raw water quality in the streams and damsAlgae count
Geosmin
Toxins
WATER QUALITY MONITORINGATLABS
Algal Monitoring &
Identification, Chlorophyll-a
determination
Bio-monitoringELISA Toxin tests for Microcystins
Site investigations and Boat sampling
The section analyses water from various raw water
impoundments eg. Theewaterskloof Dam, and Wetlands across
the city. Work is also done for a number of external clients. Staff
also contribute to over comments to clients w.r.t Physical,
Chemical and algal monitoring
WATER QUALITY MONITORINGBiological Sciences: Hydrobiology
Membrane Filtration and HPC
Methods
Cryptosporidium and
Giardia trials are
under way
The section analyses water from Potable Water treatment plants
and Waste Water treatment plants. Test are also undertaken on
water in the various city wide reservoirs and distribution
systems, this includes the Informal settlements. Environmental
water is also monitored monthly, these include rivers and
wetlands as well as the fortnightly coastal waters, including Blue
flag beaches.
Colilert
Method
WATER QUALITY MONITORINGBiological Sciences: Microbiology
Highest qualification (PHDs, Masters, Honours,
Bachelors and Diplomas) in various water
sciences and engineering
Water Quality Data maintained in Laboratory
Information Management System (LIMS) which
went live in July 2007.
The city„s drinking water quality has consistently
achieved position 1 in SABS inter-laboratory
comparison.
SANAS: 17025 accreditation achieved in 2011.
Legislation requires drinking water quality
analyses be performed in an accredited
laboratory.
Many state of the art instruments - ICP, FIA, IC,
TOC, UV, HPLC, ELISA (> R25 million) to attain
better turnaround time on the high volume of
analyses.
WATER QUALITY MONITORINGScientific Services Laboratory Improvements
SAMPLER TRAINING
The correct procedure to collect samples is
essential.
SANS 241 Section 5.2 gives reference to the
Standard Methods that can be used for a
sampling programme.
Training of sampling officers and pollution
control officers is critical in order to minimise
contamination associated with sampling. Intense
training programme at the City.
Samples need to be handled according to the
laboratory requirements in order to minimise
incorrect results. Strict SOPs in place.
PROCESS CONTROLLER TRAINING
Process specific training
o Peculiar to the Cape soft, acidic
and coloured waters
Site specific training
o Plant specific – different processes
Specialized on-site equipment
training
Continual updating.
RPL – opportunity for older
experienced hands with lower
academic levels
TASTE, ODOUR AND TOXIN CONTROL
Monitoring protocol
Analysis(GCMS, ELISA)
Powdered activated carbon
Carefully selected to be effective
PAC dosing
CHEMICAL USAGE AT WTPs
Very stringent specifications for process
chemicals
Minimising contaminants
Ensuring sustained quality within tight
tolerances
Security of supply
Resulting in improved treated water
quality
CHEMICAL DOSING CONTROL AT WTPs
State-of-the-art dosing control systems
Change from solid to liquid chemicals
Mass-flow metering – Coriolis meters
Feed the coagulant at precise rates (0.01 mg/ℓ)
automatically adjust according to:
o flow changes
o water quality and temperature changes
UV absorbance of coloured raw water
o a good measure of the required coagulant
dosage
o Spectrophotometer used for rapid and
sensitive determination UV absorbance
11th International Gothenburg Symposium
8th – 10th November 2004Orlando, USA
Session 1: Dosage Control
“Optimization of Potable Water Quality and Chemical Usage through Specially Developed
Dosage Control Systems in the City of Cape Town”
by
Peter Flower
ISO 9001: 2000
Coagulation pH Control
When treating the coloured waters of the Cape, using aluminium sulphate, selection of the optimum pH requires a compromise between
Minimizing the residual organic content
minimizing aluminium concentration in the treated water.
Generally the best organic removal is achieved around pH 5.2 – 5.4
But the solubility of aluminium increasesrapidly below pH 5,4
Need to allow for a reasonable variation in pH, which is a practical reality in all treatment plants
Optimum coagulation pH 5,6 – 5,8
Because coagulation pH control is so critical to optimum flocculation and effective colour removal, it was included in the new control system.
Features of the Dosing Control System
The heart of the system
a mass-flow metering device, (coriolis principle)
to very accurately measure
o mass
o density
o temperature of the product flowing through it.
This measuring device is integrated with:
An accurate dosing pump with a variable speed drive,
In-stream probes to monitor pH of thewater during coagulation,
Spectrophotometer readings giving the UV Absorbance levels of the water
PLC-based computer system with feedback control loops
Enables extremely accurate:
Dosing control and monitoring system
Inventory control (not easily achieved when dealing with large volumes of liquid dosed at relatively low rates)
Data Acquisition, Control and Reporting System (DACARTM)
Gives plant managers invaluable information to help optimise the processes to maintain consistent high water quality with lowest possible chemical consumptions, etc.
CONTINUOUS ONLINE GRAPHICAL DISPLAY FOR PROCESS CONTROL
A user-friendly and real-time display of process variables:
Online process viewing – simple menu system
Immediate indication of deviation from set-points (pH & dosage mg/ℓ accurate to 2 decimal places)
Live trending
Online monitoring of active chemical ingredient
Resulting in timeous implementation of corrective action – ensuring consistent quality
Power failure to pumps – current dosage rate (sec/litre) for manual operation
Benefits Derived from the Improved System
Typical Chemical Dosing
Screen
MANAGEMENT REPORTS
Effective management information (shift/day/month/ year) :
Water treated and dosage trends
o Appears to vary, but reported to 2 decimal places
Chemical dosage precision
o Actual vs target
pH control precision
o Actual vs target
Chemical mass-balance reports
o Accurate consumption reports and inventory control
Stock level
o Also expressed as “days stock remaining at current consumption”
Cost & Performance:
o Chemical costs
o Unit process costs
o Chemical savings
o Process efficiency
o Process Controller performance
Benefits Derived from the Improved System
Measured Effects and Improvements
IMPROVED COAGULATION pH CONTROL
Essential for effective coagulation and flocculation - achieved through:
Closer monitoring with a continuous graphical display of the “Actual pH vs
the Target pH” – useful tool for process controllers
Automatic adjustment of lime dosing by linking motor speed of the screw
feed at the base of the silo proportionately to the plant flow
Demonstrated by tighter grouping
of plots – less scatter
Improved Treated water
Aluminium levels after
May 2000
May 2000
Measured Effects and Improvements
REDUCED COAGULANT DOSAGE RATES
Ran trials to reduce coagulant rates
Improved consistency of concentration
Enhanced dosing control & monitoring
Reduced in 5% increments from
factors determined empirically
1st 5% ↓ for 2 months – system stability
UV Abs of t/water closely monitored
Minimal affect recorded on treated UV
2nd 5% reduction – achieved similar results, so a 3rd 5% reduction was made.
Before trial 0.04 < UV Abs <0.06; after 15% ↓, UV Abs > the City‟s upper limit of 0.1
Reverted to 5% coagulant ↓ - conservative (lime feed automation, summer UV peak)
Sodium aluminate dosed ∝ aluminium sulphate ∴ effective 5% sod alum reduction
Coagulant usage ↓, quality ➚ , treated water Al, Na & SO4↓, roll-out plan.
Improvements in the Treated Water QualityREDUCED ALUMINIUM LEVELS
Improved quality control as development process
progressed
1st significant Al concentration reduction in
Steenbras treated water:
1995 – liquid Sodium Aluminate
1996 – liquid Aluminium Sulphate
Lower levels and improved consistency:
Liquid coagulants – tight tolerances
Dosing at accurately known and consistent
concentrations
Tendency to o/dose – reduced.
2nd significant Al concentration reduction:
May 1999 – dosing control system
Clear graphical indication of state of-
, and changes in- the process with
“on-line” trending
Rapid and effective operator reaction
“Finger trouble” largely eliminated – system
auto reacts to condition changes
DISINFECTION CONTROL AND MONITORING
Pre-chlorination with dissolved gas used at the WTPs after the removal
of the organics through effective flocculation and settlement to avoid
THM formation
Final chlorination at the exit from the WTP to the service reservoir
Re-chlorination to ensure adequate residual through to the end of the
reticulation system
Chlorine residual monitored by means of on-line monitors, which are
remotely monitored with alarms and trends recorded
Chlorine residual as well as microbiological indicators are monitored at
strategic points within and at the ends of the distribution system
Special sampling taps used to ensure reliable results
Samplers undergo rigorous training and required to follow strict SOPs
DWA requires 0.2 mg/ℓ chlorine residual as indication of “acceptable drinking
water” in distribution system and point-of-delivery
CoCT aims to maintain bacteriologically safe drinking water -
o frequent analysis for E.coli and faecal coliforms together with the
measurement of free chlorine residual - “Best Practice”
o Measure E.coli and faecal coliforms weekly - frequency >than SANS 241
Residual Chlorine Levels - Not only rely on colorimetric comparator analysis
o auto-titration equipment (AT-LAB by MetrohmTM)
o on-line free chlorine analyzers (Micro 2000TM) at WTPs, bulk reservoir
outlets and distribution system
City‟s bacteriological compliance
Positive bacteriological measurement – at higher frequency
Use of technically sophisticated methods of Cl2 monitoring and analysis,
Question the need to exceed 0.2 mg/ℓ chlorine residual at point of supply
DISINFECTION CONTROL AND MONITORING
Soft, acidic coloured water
Stabilization using lime and carbon dioxide
National shortage of carbon dioxide
Compromising the stabilization process
Need to exceed the SANS 241 upper limit on pH to protect the infrastructure
STABILIZATION CHALLENGE
DWQ INCIDENT MANAGEMENT PROTOCOL
Developed a flow chart for the protocol to deal with failures of samples
taken of the treated water in terms of SANS 241 (Parts1&2): 2011
o Final treated water at the WTPs
o At the reservoir sampling points after secondary chlorination
o At the distribution sampling points
On display at all Bulk installations for quick reference to:
o Required alert levels
o Response times
o Action steps
o Contact details
Provides compact summary supplementing the detailed protocol
document.
DWQ INCIDENT MANAGEMENT PROTOCOL
DWQ INCIDENT MANAGEMENT PROTOCOL
DWQ INCIDENT MANAGEMENT PROTOCOL
DAMS
STEENBRAS UPPER &
LOWER DAMS
WEMMERSHOEK DAM
TABLE MOUNTAIN DAMSTHEEWATERSKLOOF DAM
WATER TREATMENT PLANTS
STEENBRAS WTP WEMMERSHOEK WTP VOËLVLEI WTP
BLACKHEATH WTP FAURE WTP
RESERVOIRS, PIPELINES & PUMP STATIONS
FAURE RESERVOIR
TYGERBERG RESERVOIR PLATTEKLOOF RESERVOIRFIRLANDS PUMP STATION
VOËLVLEI PUMP STATION
WITSANDS PUMP STATION
VOËLVLEI PIPELINE
VOËLVLEI PIPELINE
ASSET MANAGEMENT
The City of Cape Town based its Asset Management Plan on
the International Infrastructure Management Manual
Used the Roger Byrne tool to inform the AMP (top-down
level)
Lower level of AMP on the SAP system still in progress
(bottom-up)
The whole system still needs to be fully integrated
Current Replacement Cost: R 12 779 m
Depreciated Replacement Cost: R 5 818 m
Annual Planned Maintenance Required: R 40.1 m
DRC/CRC: 45.3%
R 0
R 500 000
R 1 000 000
R 1 500 000
R 2 000 000
R 2 500 000
R 3 000 000
R 3 500 000
R 4 000 000
2011 2013 2015 2017 2019 2021 2023 2025 2027 2029
OPEX Repair profile in 2011 Rands
R 0
R 50 000 000
R 100 000 000
R 150 000 000
R 200 000 000
R 250 000 000
R 300 000 000
2011 2013 2015 2017 2019 2021 2023 2025 2027 2029
CAPEX Repair profile in 2011 Rands
ASSET MANAGEMENTOverall R.B.S Outputs for Bulk Water:
ASSET MANAGEMENT
Asset Management Philosophy:
Manage the considerable infrastructure assets through appropriate
replacement and maintenance programmes to ensure the
sustainability of the bulk supply system.
Maintenance is largely re-active with cyclic and pro-active
maintenance conducted on selected strategically important elements
of the infrastructure.
A special form of asset management – very important
Stabilization of the treated water
o Raw water highly corrosive and aggressive towards metals and
cementicious materials
o Stabilize to just over a neutral point on the index – high pH
o Fine film deposit on the pipes and fittings - protection
o Provides protection to the Billions of Rands worth of infrastructure
o Maintains a sustained quality of treated water through the storage and
conveyance system.
o Stabilization level compromised by national shortage of CO2
o SANS 241 upper limit on pH
WATER SAFETY PLANNING
Risk-based approach
WSP follows the WHO guidelines
WATER SAFETY PLANNINGCITY OF CAPE TOWN WATER SAFETY PLAN COMMITTEE
NAME DESIGNATION ROLE
1. PHILEMON MASHOKO DIRECTOR: WATER & SANITATION Oversee Water Quality
Safety Plan
2. PETER FLOWER MANAGER: BULK WATER Chairperson, BD Committee
Storage, Conveyance and
treatment of Bulk Water
3. PIERRE MARITZ MANAGER: RETICULATION Distribution of Drinking
Water and Collection of
Wastewater
4. MPHARU HLOYI MANAGER: SCIENTIFIC SERVICES Water Quality Monitoring
and Quality Assurance and
Blue Drop Data Management
5. JOSIAH MPOFU MANAGER: EAM Water and Sanitation
Department Asset
Management
6. SAREL PIETERSE SECTION HEAD: WATER LAB, SCIENTIFIC
SERVICES
Drinking Water Specialist
7. ALF MOLL HEAD: OPERATIONAL LOGISTICS Drinking Water Protocol
development
8. MJIKISILE VULINDLU SECTION HEAD: BIOLOGICAL LAB,
SCIENTIFIC SERVICES
Drinking Water Specialist
9. JACO DE BRUYN HEAD: WS DEV PLANNING Information Management
10. STEVIE DARK SPO: WATER LAB, SCIENTIFIC SERVICES Scientist
11. ASA LEKKER / CARMEN JOHNSON PROFESSIONAL OFFICER: LIMS,
SCIENTIFIC SERVICES
Information Management
12. DESIREE DAMON SECTION HEAD: QUALITY ASSURANCE,
SCIENTIFIC SERVICES
Quality Assurance
13. DOUGLAS KIEWIET ACTING AREA MANAGER: PLATTEKLOOF
WTP
Process Operations
14. ARNE SINGELS SPECIALIST: BULK WATER Bulk Water System specialist
15. ZAMUXOLO TUTU MANAGER: MAINTENANCE
PROGRAMMING
Asset registers, Maintenance
plan
CONCLUSIONS – LESSONS LEARNT
BLUE DROP ASSESSMENTSYEAR OF
ASSESSMENT
No OF ASSESSMENT
CATEGORIES
BD SCORE
%
COMMENT
2009 9 100 One of only 3 municipalities to
get 100%
2010 9 98.18 2nd highest Score
2011 8 97.61 2nd highest Score
Also received Platinum Award
for 3 successive BD Awards
2012 5 ? ???
BLUE & GREEN DROP ASSESSMENT PROGRAMS
Excellent initiative on the part of DWA to focus institutions on
water quality management
Local authorities – influence politicians to allocate funding
appropriately
Provides an achievable goal for the staff in the Water &
Sanitation industry
Recognition of excellence is now possible.
I thank you for your attentionQuestions?
Mpharu Hloyi
T: 021 684 1000
M: 083 660 2300
Peter Flower
T: 021 487 2586
M: 083 375 0039