IMPROVING DISINFECTION EFFICIENCY IN SMALL DRINKING WATER TREATMENT PLANTS Report to the Water Research Commission by MNB Momba † , CL Obi ♠ and P Thompson ♣ † Department of Environmental, Water and Earth Sciences, Tshwane University of Technology, Arcadia Campus, P/Bag X680, Pretoria 0001 ♠ School of Agricultural and Life Sciences, University of South Africa, Sunnyside Campus, Pretoria, PO Box 392, UNISA 0003, South Africa ♣ Umgeni Water, PO Box 30800, Mayville 4058 WRC Report No 1531/1/08 ISBN 978-1-77005-683-1 Set No 978-1-77005-682-4 JULY 2008
Transcript
IMPROVING DISINFECTION EFFICIENCY IN SMALL DRINKING
WATER TREATMENT PLANTS
Report to the
Water Research Commission
by
MNB Momba†, CL Obi♠ and P Thompson♣
† Department of Environmental, Water and Earth Sciences, Tshwane University of Technology,
Arcadia Campus, P/Bag X680, Pretoria 0001
♠ School of Agricultural and Life Sciences, University of South Africa, Sunnyside Campus,
Pretoria, PO Box 392, UNISA 0003, South Africa
♣ Umgeni Water, PO Box 30800, Mayville 4058
WRC Report No 1531/1/08 ISBN 978-1-77005-683-1 Set No 978-1-77005-682-4
JULY 2008
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This report forms part of a series of two reports. The other report is Guidelines for the Improved Disinfection of Small Water Treatment Plants (WRC Report TT 355/08).
DISCLAIMER
This report has been reviewed by the Water Research Commission (WRC) and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of
the WRC, nor does mention of trade names or commercial products constitute endorsement or recommendation for use
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EXECUTIVE SUMMARY
1. BACKGROUND OF THE STUDY AND PROBLEM STATEMENT
In South Africa, water infrastructure is well developed in urban areas as opposed to rural areas
where the infrastructure is either poorly developed or non-existent. Supply of water to rural
communities is usually effected through small water treatment plants. Small water treatment plants
(SWTPs) are defined as water treatment systems that are installed in areas which are not well
serviced and which do not normally fall within the confines of urban areas. They include water
supplies from boreholes and springs that are chlorinated, treatment plants of small municipalities
and establishments such as rural hospitals, schools, clinics and forestry stations. However, the
efficacy of drinking water treatment by small water treatment plants is fraught with several
technical and management problems. This is corroborated by the extensive documentations on the
supply of water of poor microbiological quality which is unsafe for human consumption in different
provinces of South Africa.
In order to unravel the intricacies around the operational and management parameters
impinging on the disinfection efficiency of small water treatment plants and to ensure sustainability
of potable water supply to rural communities, this study involved 181 small water treatment plants
across seven provinces of South Africa. The goal was to determine the nature and full extent of the
problems and provide practical and user-friendly guidelines for intervention.
2. PROJECT OBJECTIVES
The objectives of the project were as follows:
To identify and characterize the various types of disinfection equipment currently employed
at small water treatment systems, as well as systems that could potentially be used.
To identify the means of disinfection (i.e. the physical and/or chemical processes) employed
at these systems, as well as the performance, chemical and electrical inputs, and ongoing
maintenance requirements of each type.
To identify or determine the current quality of treated water, procedures followed to monitor
and control the disinfection processes and the adequacy and consistency of the levels of
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disinfectant added. To identify the frequency and adequacy of microbiological tests
performed on the final treated water.
To identify the main reasons for disinfection problems experienced at small water systems –
both technical and non-technical.
To estimate the cost of drinking water disinfection appropriate for the required standards in
water sector using the required equipment, instrumentation and manpower.
To identify major problems resulting in water quality changes in the distribution system by
conducting a comprehensive study in the Fort Beaufort, Seymour and Alice distribution
systems.
To provide guidelines for the improved disinfection of final water at small water treatment
plants which also include installation and operating costs for the different disinfection
systems and chemicals.
3. METHODOLOGY
In order to collect sufficient data on technical and management issues of small water treatment
plants in South Africa, a detailed survey of 181 small water treatment plants across seven provinces
was conducted. The seven provinces namely Limpopo, Mpumalanga, North-West, Free State,
KwaZulu-Natal, Eastern Cape and Western Cape were selected on the basis of familiarity with the
areas, economic status and rural areas experiencing technical and management problems. The
geographic position system (GPS) co-ordinates of each site were logged during the survey to
facilitate future incorporation into a geographical information system (GIS) that is being developed
for the country. On-site visits of small water treatments plants in the designated provinces were
conducted from June 2004 to December 2005. Wherever possible, some plants were visited at least
twice during the study period. The methodology was two-pronged: use of a questionnaire and visual
inspection, and determination of physicochemical and microbiological quality of drinking water.
The questionnaire was used to gather information on the ownership and design capacity of
each water treatment plant, the type of raw water sources and related characteristics, various
methods of water treatment, the equipment currently employed, the performance of the plants,
knowledge and skills of the operators as well as other technical and management issues.
Physico-chemical and microbiological analyses of water samples collected from the raw
water and final water at the points of treatment and consumption were performed using standard
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methods. Briefly, the chlorine residual concentrations and pH, the temperature, the turbidity and the
conductivity of water samples were measured on-site using a multi-parameter ion specific meter
(Hanna-BDH laboratory supplies), thermometer, microprocessor turbidity meter (Hanna
instruments) and conductivity meter (Hanna instruments) respectively. Total and faecal coliforms
were used to monitor bacteriological quality as stated in the South African National Standards
(SANS 241:2005) and South African Water Quality Guidelines for Domestic Use (DWAF, 1996;
Water Research Commission, 1998).
To identify the major problems resulting in water quality changes in distribution systems, an
on-site evaluation of the operating conditions at Fort Beaufort, Seymour and Alice water treatment
plants in the Eastern Cape Province was conducted. This commenced with a reconnaissance visit to
the plants and the network of smaller reservoirs in villages that were serviced by these plants. The
relationship between the performance of the plant dosing systems and the water quality in the bulk
distribution systems was established. To ensure effective free residual chlorine throughout the
reticulation systems and the consumer’s taps, the chlorine dosages applied at the dosing points in
each plant were assessed. The sampling regime for bacteriological quality of drinking water was
designed to include points furthest to the satellite reservoirs servicing specific villages in order to
provide a broad overview of the quality compliance of the water that got to the end users at these
locations. The evaluation of these water treatment plants and their reticulation systems was
performed from October to November 2005.
4. SUMMARY OF MAJOR FINDINGS AND CONCLUSIONS REACHED
Small water treatment plant ownership – Four categories of the plant ownership were identified,
viz Local/District Municipality, Department of Water Affairs and Forestry (DWAF), Department of
Health (DOH) and Water Board (private company). Overall, 81% of the small water treatment
plants surveyed in South Africa were owned by Local/District Municipality.
Design capacity of small water treatment plants – The capacity of the plants surveyed during the
investigation varied between 0.3 ML/d and 120 ML/d. Most of the plants were operating below the
design capacity.
Type of raw water sources – Overall 86% of the small water treatment plants surveyed abstracted
their raw water from surface water, 10% used groundwater and 4% a combination of both water
sources.
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Water treatment practices – Conventional water treatment processes were generally used in the
majority of the plants surveyed. In terms of coagulation, it was noted that polyelectrolyte (66%)
was commonly used, followed by alum (18%) and ferric chloride (6%). Sixty percent of the small
water treatment plants used rapid gravity filtration system while a further 24%, 9% and 2% of the
plants made use of pressure filters, slow sand filtration and diatomaceous earth filters in that
respective order. Chlorine gas was found to be the most popular disinfectant (69%), followed by
sodium hypochlorite (15%) and calcium hypochlorite (HTH) (14%), among others.
Physicochemical quality compliance – All water samples collected at various plants fell within
SANS 241:2005 Class I in terms of pH (5 to 9.5) and conductivity (< 150 mS/m).
Turbidity – At the point of treatment, 44% and 38% of the small water treatment plants surveyed in
South Africa fell within SANS turbidity Class I (<1 NTU) and Class II (1-5 NTU), respectively. At
the point of consumption, 46% and 41% of the plants fell within Class I and Class II, respectively.
The highest turbidity compliance (Class I: 69-73%, Class II: 27 -31%) was noted in the Free State
and the lowest turbidity compliance (Class I: 27-33%, Class II: 24-45%) was recorded in the
Eastern Cape Province.
Chlorine residual – Overall, the small water treatment plants surveyed had drinking water with free
chlorine residual concentrations ranging between ≤ 0.1 and ≤ 0.5 mg/L. In most cases, the flow rate
of the water and the initial chlorine dose were not known, resulting in under-chlorinated drinking
water. During the on-site evaluation of the operating conditions at Fort Beaufort, Seymour and
Alice water treatment plants, the following major problems impacted on the effectiveness of the
disinfection process in the distributions: i) the distribution systems of the pipe network did not show
acceptable levels of residual chlorine while the plant chlorination systems gave adequate dosage at
the dosing points; ii) most of the chlorine dosed at the treatment plants was consumed by the floc
sludge that accumulated in the reservoirs and the deposits that were present in the distribution
networks .
Microbiological compliance – For coliforms, 67% and 72% of the plants complied with the South
African drinking water recommended limits for total coliforms and faecal coliforms at the point of
treatment, respectively. The Eastern Cape Province produced the lowest drinking water quality in
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terms of both total (28% of the plants) and faecal (34% of the plants) coliforms while the Free State
produced the best water quality (100% compliance).
Control and monitoring – Generally, 50% of the operators and supervisors interviewed did not
exude knowledge of the flow-rates at which their plants operated and more than 78% were unaware
of the chemical doses used or how to correlate the required dose to the flow rate. In terms of
instrumentation, only 46% of plants surveyed had the instruments to measure turbidity, pH and
chlorine residual. Ninety–five percent of the plants reported that an external monitoring group
visited the plants approximately once a month; however most plants complained about a lack of
feedback.
Non technical (management) aspects – Non technical issues affecting the efficiency of water
supply by small water treatment plants included: inadequate training of manpower, poor
maintenance practices, poor working conditions, insufficient financial capacity, poor recording,
poor documentation and communication of data and information, as well as inadequate community
involvement.
Estimated cost of chlorination – The survey indicated that chlorine was commonly used in small
water treatment plants. To improve the chlorination efficiency in water sector, this study suggests
the following estimated costs for chlorine gas, sodium hypochlorite, and calcium hypochlorite,
which are commonly used in rural small water treatment:
For the improved disinfection of final water at small water treatment plants and distribution
systems, a guide document was drawn up. It included practical steps and also installation and
operating costs for the different disinfection systems and chemicals. This guide document is
Cost Comparison of Disinfection Alternatives
Gas/liquid
Chlorination
Sodium
Hypochlorite
Calcium
Hypochlorite
Capital Cost R194 800 R317 455 R90 000
Direct Operating Cost c/kl 9.50 33.86 17.02
Maintenance c/kl 1.10 1.10 0.55
Total Operating Cost c/kl 13.77 34.79 36.01
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intended for use at operational and management levels by plant managers, supervisors, plant
operators and plants owners, consultants and Municipal Water Local Authorities.
5. RECOMMENDATIONS
Small water treatment plants should be equipped with a flow meter, jar stirrer, turbidity meter, pH
meter and a chlorine meter for enhancement of disinfection efficiency.
A programme for monitoring the physicochemical (at least pH, temperature, turbidity and free
chlorine residual) and bacterial (coliform bacteria, especially faecal coliforms) quality of water at
the point of treatment and various sites of the distribution systems should be established.
Regular competency assessments and appropriate training programmes for water service providers
and regulators should be conducted.
The development and implementation of operational checklists and protocols are equally essential
to ensure timely ordering of materials (particularly chemicals) and the maintenance of equipments.
Increased funding of small water treatment plants and enhancement of working conditions of
personnel are also recommended.
6. RECOMMENDATION FOR FUTURE STUDY
A future investigation has to be conducted on the compliance of non-metropolitan South African
potable water providers with the required management guidelines and norms including reasons for
non-compliance.
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7. LIST OF PRODUCTS
7.1 Book
Momba MNB, Thompson P and Obi CL (2006). Practical and user-friendly guidelines for
improving the efficiency of disinfection in small water treatment plants of South Africa
7.2 Article
Momba MNB, Tyafa Z, Makala N, Brouckaert BM and Obi CL ( 2006 ) Safe drinking water still
a dream in rural areas of South Africa. Case Study: The Eastern Cape Province. Water SA 32 (5):
715-720
Obi CL, Momba MNB, Samie A, Igumbor JO, Green E and Musie E (2007) Microbiological,
physico-chemical and management parameters impinging on the efficiency of small water treatment
plants in the Limpopo and Mpumalanga Provinces of South Africa. Water SA 33(2): 1-9
7.3 Conference Presentation
Obi CL, Samie A, Green E, Musie E, Masebe T, Mashota M, Ndou S, Momba MNB, Thompson P,
Charles K (2004) The efficiency of Disinfection of the Drinking Water in Small Water Treatment
Plants in Limpopo and Mpumalanga Provinces of South Africa: Preliminary report. The 2nd
International Conference on Safe Water, November 4-7, Johannesburg, South Africa.
Z Tyafa, MNB Momba, N Makala, BM Brouckaert and CL Obi (2006) Safe drinking water still a
dream in rural areas of South Africa - Case study: The Eastern Cape Province. The Water Institute
of South Africa, Biennial conference and exhibition, Durban, May, South Africa.
Obi CL, Momba MNB, Samie A, Green E, Musie E, Masebe T, Mashota M, Igumbor JO and Ndou
S (2006) Water Quality Indicator Indices and Management Issues of Small Water Treatment Plants
in Limpopo and Mpumalanga Provinces of South Africa. The International Water Association
World Congress, China, September.
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ACKNOWLEDGEMENTS
The following persons and organisations are thanked for their contribution to this report: Financial Support Water Research Commission Members of the Steering Committee Dr G Offringa Water Research Commission (Chairman) Prof D Key University of Western Cape Mr C Swartz Chris Swartz Engineer Mr K Charles CSIR Ms M du Preez CSIR Mr M Ramba Emanti Mr PL Chimloswa Amatola Water
Project Team and Technical Support Prof M Momba Tshwane University of Technology (Project Leader) Mr P Thompson Umgeni Water (Project Team)
Prof CL Obi University of South Africa (Project Team) Ms ZN Makala University of Fort Hare (Project Team) Ms Tyafa University of Fort Hare (Project Team) Mr K Charles CSIR (Project Team) Dr A Okoh University of Fort Hare (Technical Support) Dr BM Brouckaert University of KwaZulu-Natal (Technical Support) Mr C Mfenyana University of Fort Hare (Technical Support) Miss A Okeyo University of Fort Hare (Technical Support) Mr N Sibewu University of Fort Hare (Technical Support) Mr A Bosrotsi University of Fort Hare (Technique Support) Mr A Samie University of Venda (Technical Support) Mr E Green University of Venda (Technical Support) Mr E Musie University of Venda (Technical Support) Xolani Ngcemu Umgeni Water (Technical Support)
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TABLE OF CONTENTS EXECUTIVE SUMMARY..............................................................................................................................iii
LIST OF TABLES..........................................................................................................................................xiv
LIST OF FIGURES.........................................................................................................................................xv
CHAPTER I: GENERAL INTRODUCTION……………..…………………………..…………………….1
CHAPTER II: LITERATURE REVIEW………………….………..……………………………………….4
2.1: BACKGROUND ON RURAL WATER SUPPLY AND SMALL WATER SYSTEMS IN
SOUTH AFRICA ………………………………………………………………………………….4 2.2: GENERIC UNIT PROCESSES AND BARRIERS IN WATER TREATMENT ….……………5
2.2.1: Selection of water sources………………………………………………………………………5
2.4 WATER DISTRIBUTION AND STORAGE……………………………………………………….23 2.5: MICROBIOLOGICAL QUALITY OF THE FINAL WATER & PUBLIC HEALTH
SIGNIFICANCE ……………………………………………………………………………….….24 2.5.1: Monitoring the safety of water supplies ……………………………………………….…25
2.5.2: Quality at water works and in distribution systems…………………………………………….26
2.5.3: Impact of microbiological quality of treated water on public health…………………………...26
2.6: IMPROVING DISINFECTION EFFICIENCY IN SMALL WATER TREATMENT PLANTS.....28 2.6.1: In-service training of water personnel and management…………………………………..…...28
2.6.2: Hygiene education and community based management……………………………………..…29
CHAPTER III: SURVEY OF DISINFECTION EFFICIENCY OF SMALL DRINKING WATER
TREATMENT PLANTS…………………………………………………………………………...31
3.1: SURVEY AREA…………………………………………………………………………………….31 3.2: SURVEY METHODOLOGY……………………………………………………………………….31 3.3: RESULTS OF THE SURVEY AND DISCUSSION………………………………………………..32
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3.3.1: Small water treatment plant ownership…………………………………………………………32
3.3.2: Design capacity of small water treatment plants………………………………………………..32
3.3.3: Type of raw water sources………………………………………………………………………34
3.3.4: Water treatment practices……………………………………………………………………….35
3.3.5: Quality of drinking water produced by small water treatment plants……………………….….38
Fig. 3.10 Free Chlorine Histogram at Point of use across all Provinces
3.3.5.2 Microbiological compliance
It is important to note that the quality of water reaching consumers depends not only on operating
conditions at the treatment plant but also on changes that can occur in the distribution system.
During the survey period, it was noted that final drinking water of the highest quality might be
leaving some plants but its condition deteriorated to some extent before it reached the consumers
(Appendix 3.4). Given sufficient time, the chlorine residual concentration decreased to a very low
level that did not comply with the South African standard. High turbidity in the finished water, old
pipes, breaks in distribution pipelines, biofilm growth, sludge accumulation in the storage reservoirs
and the availability of nutrients for microbiological growth could be among the factors that
accelerate the chlorine residual decay of final drinking water at the point of use (Momba et al.,
2000).
To ensure the absence of bacterial pathogens, the drinking water should be free of faecal
organisms. The primary bacterial indicator recommended for this purpose is the coliform group of
organisms (DWAF, 1996; WHO, 2004; SANS 241, 2005). Total and faecal coliforms are used
much more than any other indicator group for monitoring drinking water quality because they
address both health and treatment efficiency objectives. Although as a group, they are not
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exclusively of faecal origin, they are universally present in large numbers in the faeces of human
and other warm blooded animals. The presence of faecal coliforms in treated water indicates poor or
inadequate treatment of drinking water. Higher concentrations of faecal coliforms in treated water
indicate a high risk of contracting waterborne disease, even if small amounts of the water are
consumed (DWAF, 1996).
Figures 3.17-3.18 and Appendix 3.4 illustrate the microbiological quality of water supplied
by plants surveyed. It must however be stressed that these results were once off surveys which were
repeated in some provinces. Due to logistics and the costs involved, repeated analyses could not be
done over the entire country. Despite these shortcomings it must be emphasized that once off
surveys are a good indicator of the microbiological quality of the water produced by the plants
surveyed. In many instances this was also the first time water samples from these all treatment
plants were being analyzed and this is an indicative of major shortcomings in the legislation in
South Africa. Recent developments within DWAF do however show that there is now increased
emphasis on monitoring of drinking water quality. The Delmas incident in South Africa in 2005
resulted in 600 cases of typhoid, five documented deaths, and 3300 cases of diarrhoea. Escherichia
coli were found in one of the town’s reservoirs and the lack of treatments, especially chlorination,
was found to be a major contributing factor to the tragedy (Water Wheel, November/December
2005).
In Mpumalanga, 95% of the plants at the point of treatment and 84% at point of use
complied with the South African water quality standard in terms of total colifoms. Seventy four
percent of the plants were within the limits recommended by South African standards in terms of
faecal coliforms at both the point of treatments and the point of use. Total coliform counts ranged
between 0 and 380 cfu/100 ml at the point of treatment and between 0 and 180 cfu/100 ml at the
point of use, while faecal coliform counts ranged between 0 and 3 cfu/100 ml at the point of
treatment and between 0 and 12 cfu/100 ml at the point of use.
In Limpopo, 64% of the plants at the pint of treatment and 94% at point of use of the plants
complied with the South African recommended standard in terms of total coliforms. The total
coliform counts ranged between 0 and 3.6 × 103 cfu/100 ml at the point of treatment and between 0
and 250 cfu/100 ml at the point of use. In terms of faecal coliforms, 73% and 88% of the plants
complied with South African drinking water recommended limits at the point of treatment and at
the point of use, respectively. Faecal coliform counts ranged between 0 and 60 cfu/100 ml and
between 0 and 7 cfu/100 ml at the point of treatment and at the point of use, respectively.
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33
1911
17
28
53
12
173
0
20
40
60
80
100
120
Limpopo Mpumalanga Free State North West KZN Eastern Cape Western Cape RSA
Name of Province
0
20
40
60
80
100
120
140
160
180
200
Total Coliform Compliance (%) (<10 cfu/100ml) Faecal Coliform Compliance (%)(<1 cfu/100 ml) Total Plants Surveyed
%
No of Plants Surveyed
Fig. 3.11 Bacteriological Compliance at the Point of Treatment
In the North-West province, 76% of the samples from the plants at point of treatment and 53% at
the point of use complied with the South African recommended limits in terms of total coliforms.
Total coliforms ranged between 0 and 83 cfu/100 ml at the point of treatment and between 0 and
288 cfu/100 ml at the point of use. A total of 94% and 83% of the plants were found within the
recommended limits for faecal coliforms at the point of treatment and at the point of use
respectively. Faecal coliform counts ranged between 0 to 5 cfu/100 ml and between 0 to 13 cfu/
100 ml at the point of treatment and at the point of use, respectively.
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33
1911
17
28
53
13
174
0
20
40
60
80
100
120
Limpopo Mpumalanga Free State North West KZN Eastern Cape Western Cape RSA
Name of Province
0
20
40
60
80
100
120
140
160
180
200
Total Coliform Compliance (%) (<10 cfu/100ml) Faecal Coliform Compliance (%)(<1 cfu/100 ml) Total Plants Surveyed
%
No of Plants Surveyed
Fig. 3.12 Bacteriological Compliance in Distribution System The microbiological data of the plants visited in the Free State province resulted in 100%
compliance with the SANS Standard in terms of total coliforms and faecal coliforms at the point of
treatment. At the point of use 92% compliance was obtained in terms of total coliforms and 85%
compliance in terms of faecal coliforms. The above non-compliance represented two points in the
distribution system and it must be noted that overall the plants in the Free State were producing
excellent water quality.
In KwaZulu-Natal, 57% of the plants at point of treatment complied with the SANS
Standard in terms of total coliforms and 61% complied in terms of faecal coliforms. At the point of
use, 64% plant compliance was obtained in terms of total and faecal coliforms. Total coliform
counts ranging up to 866 cfu/100 ml were detected at one site at the point of treatment with
corresponding faecal coliform counts of 53 cfu/100 ml. At the point of use an alarmingly high total
coliform count of 2419 cfu/100 ml was detected at one of the sites with a corresponding faecal
coliform count of 36cfu/100 ml. The primary cause of this failure was due to either lack of
chlorination facilities or under-dosing of chlorine.
In the Eastern Cape Province, at the point of treatment 28% of the plants complied with the
SANS standard in terms of total coliforms and 34% complied in terms of faecal coliforms. At the
point of use 20% of the plants complied in terms total coliforms and 29% complied in terms of
faecal coliforms. Total coliform counts ranging up to 240 cfu/100 ml were noted at the point of
treatment of one of the plants and 223 cfu/100 ml at one of the points in the distribution system. A
maximum faecal coliform count of 25 cfu/100 ml was detected at one of the points of treatment
while 98 cfu/100 ml was noted at one of the points in the distribution system.
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In the Western Cape, at the point of treatment 50% of the plants complied in terms of total
coliforms and 25% complied in terms of faecal coliforms. In the distribution system, there was 25%
compliance in terms of both total and faecal coliforms. Total coliform counts ranged between 0 and
59 cfu/100 ml at the point of treatment and between 1 and 67 cfu/100 ml at the point of use, while
the faecal coliform counts ranged between 0 and 25 cfu/100 ml and between 0 and 50 cfu/100 ml at
the point of treatment and at the point of use, respectively.
Compared to other provinces, the Eastern Cape Province produced the lowest potable
drinking water quality in terms of both total and faecal coliforms while the Free State produced the
best drinking water quality. These results confirm the poor microbiological quality of the drinking
water in the Eastern Cape that was also noted by Momba and co-workers (2004) in a previous study
conducted in the Alice Water Treatment plant.
3.3.6 Control and monitoring
Water treatment plant operators are all aware that the characteristics of the raw water they are
treating changes from time to time. While the quality of borehole water tends to remain fairly
constant, the quality of raw water extracted directly from rivers can change drastically, especially in
terms of suspended solids. Even the change in temperature from winter to summer can also
influence the treatment of drinking water (e.g. it is harder to form floc in cold water than in
summer). Furthermore, there are variations in water demand which may require changes in raw
water flow rate. Consequently, operators need to make adjustments to the operation of the plant
from time to time in order to meet changing treatment requirements. They also need to check that
the adjustments made are consistent with the desired effect (Momba and Brouckaert, 2005).
In Limpopo and Mpumalanga, most of the operators and supervisors interviewed did not
have a good knowledge of the flow rate at which their plants were being operated. Generally the
chemical dosing rates were determined by experience. Very few knew what their chemical dose
rates were or how to calculate them. Coagulant doses were adjusted manually, usually based on the
appearance of the floc and sometimes also based on the taste of the water when alum was used.
Chlorine doses were set manually and some plants were overdosing chlorine. Nearly all of the
plants reported that an external monitoring group (the District Municipality, BNK, MMP or some
private company) visited the plants approximately once a month although most plants complained
about a lack of feedback from the external monitors. Most of the plants were partially automated
which facilitated the operator's work and limited some overdosing errors and ensured that remote
reservoirs were kept full. In Mpumalanga, most plants had instruments to measure turbidity, pH and
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chlorine residual although these were not always used. The maintenance of equipment in some
plants was not taken into account.
In the North-West Province, 60% of the plants were equipped with raw water flow meters;
however readings were only recorded in plants owned by Water Boards and in three of the
municipal owned plants. It was noted that 66% of the plants had jar stirrers on-site; however these
were only used in four of the plants. Less than 20% of the supervisors and operators knew the
required chemical dosing rates or how to calculate them. Chemical dosages were adjusted based on
the appearance of the floc and the colour of the finished water. All the plants were measuring
chlorine residuals, however less than half of them were measuring turbidity and pH. Only one plant
was testing the general chemical and microbiological quality of water. Four municipal plants were
monitored by local health inspectors; however the plant staffs were not getting any feedback on the
water quality results. Nearly all of the plants reported that an external monitoring group visited the
plants approximately once a month, but they did not know what kind of tests they were doing and
they were not getting any feedback. The Botshelo water owned plants were equipped with a
telemetry system and Supervisory Control And Data Analysis (SCADA) system for the monitoring
of the whole plant.
In the Free State, some of the operators and supervisors interviewed knew the flow rates at
which their plants operated but very few knew what their chemical dose rates were or how to
calculate them. Seventy percent of the plants had the instruments to measure turbidity, pH and
chlorine residual. Fourteen percent of the plants measured chlorine only, and 14% do not have any
on-site monitoring programme. All of those plant operators interviewed were aware of the
importance of measuring these parameters but were typically unable to persuade the municipality to
buy the instruments (however, basic instruments usually came with major upgrades). A number of
supervisors were using swimming pool test kits to measure pH and chlorine. Coagulant doses were
adjusted manually usually based on the appearance of the floc. However in one case, the dosage of
the flocculants was automatically controlled by an ion charge analyzer. Chlorine doses were also set
manually. In one case the Supervisor at a plant was reluctant to increase the chlorine dosage even
though the chlorine levels in the town were low. All of the plants visited during the survey period
were monitored by an external monitoring group (CSIR) on a monthly basis.
In KwaZulu-Natal, 15% of the plants had functioning raw water meters, 10% had installed
meters but were non-functional, and operators indicated that the meters had been non-functional for
many years. Lack of maintenance of equipment was reported in 80% of the plants. Seventy percent
of the plants were not able to calculate the chemical doses and the operators were running the plants
by visual observation of the clarifier overflow. Only 20% of the plants had on-line instruments for
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measuring turbidity and pH and 70% had bench scale equipment for measuring pH, turbidity and
chlorine. On-site jar test equipment was recorded in 5% of the plants, however only 2% were
capable of conducting a jar test. None of the plants were undertaking chlorine demand tests on site.
External Process Audits were undertaken at 30% of the plants and involved a detailed assessment of
the plant optimization. These plants were mainly plants managed by Water Boards such as Umgeni
Water and Umhlatuze Water. Seventy percent of the plants were measuring process parameters and
capturing onto daily log-sheets, however limited quality control of this data was practiced. At plants
managed by Water Boards, Process Technicians visited the plants at least once a month to assist
with optimization of the plant. The Process Technicians were responsible for a number of plants and
rotated their service between the plants. In the larger Water Boards, Process Engineers and Process
Scientists were available at short notice for trouble shooting process problems as well as to follow
up on water quality failures. Supervisors and Works Managers were only available at 20% of the
plants that were visited.
In the Eastern Cape Province, 50% of the operators and supervisors interviewed knew the
flow-rates at which their plants operated, 78% did not know the chemical doses used or how to
correlate the required dose to the flow rate, 46% had the instruments to measure turbidity, pH and
chlorine residual, 3% of the supervisors were using swimming pool test kits to measure pH and
chlorine, 95% of the plants reported that an external monitoring group visited the plants
approximately once a month; however most plants complained about a lack of feedback and 20% of
the plants were partially automated.
In the Western Cape, all the plants were equipped with raw water flow meters. Most of the
operators reported that raw water flow was adjusted if there was high demand of water or during
rain seasons. The majority of the plants owned jar stirrers. Almost all the plants were measuring
chlorine residuals and pH, however less than half of the plants were measuring the turbidity of the
water. Some of the plants were testing the general chemical quality of water and only one plant was
testing E. coli onsite. Nearly all of the plants reported that an external monitoring group visited the
plants approximately once a month and they were getting feedback. More than a half of the plants
visited during the study period were equipped with a SCADA and telemetry system to monitor the
whole plant.
To provide a guide for a simple log sheet system for effective control and monitoring, the
Tables presented below are suggested. The purpose of this type of log is to record all process
changes that take place on the plant. This helps to ensure that sufficient information is recorded to
pass onto the next operator that comes on shift. Typical details that would be recorded include,
Time of arrival on plant, condition of the plant on arrival, reservoir levels, record of person visiting
49
the plant, reasons for making process control changes, etc.
TABLE 3.2 EXAMPLE OF FILTER WASHING AND CLARIFIER SOLIDS MANAGEMENT Date Plant Name: Operator Name: Time Filter No Backwash Volume Used (m3) Clarifier No Time Desludged
06H00 6 53.5 3 5 minutes
08H00
10H00
12H00
14H00
16H00
18H00
20H00
22H00
00H00
02H00
04H00
TABLE 3.1
EXAMPLE OF A PROCESS CONTROL SHIFT LOG SHEET Date Plant Name: Operator Name: Time Raw water
Turbidity Raw water pH
Coagulant Dose
Clarifier turbidity
Chlorine dose
Final water chlorine
Lime dose
Final water pH
06H00 08H00
10H00
12H00
14H00
16H00
18H00
20H00
22H00
00H00
02H00
04H00
50
TABLE 3.3
EXAMPLE OF DAILY OPERATOR LOG Date Plant Name Operator Name
Time Description of Situation in the plant
06H00 Arrived on plant – everything in order, final water turbidity 0.3 NTU,
final chlorine 1.2 mg/l, final pH 8.4
06H35 Call received from City Engineer – Water shortage in city reservoir –
started pumps to city
07H10 Raw water turbidity increased from 45 NTU to 90NTU – undertook jar
test – optimum dose of 11 mg/l – set plant on new dose
08H30 New dose working well – good clarifier overflow turbidity
3.4 RECOMMENDATIONS FROM THE SURVEY
It is concluded that although ownership of the plants belonged to 4 categories owners such as the
District/Local Municipalities, DWAF, DOH and private companies (Water Board), over 80% of the
plants were noted to be owned by the District Municipalities. In addition, about 84% of the small
water treatment plants in the designated provinces abstracted their raw water from surface water.
Conventional water treatment processes were generally employed; over 80% of the small water
treatments employed the rapid gravity and pressure filtration systems. Chlorine gas was observed to
be the most common disinfectant used (69%), followed by sodium hypochlorite (15%) and calcium
hypochlorite (14%). Furthermore, a substantial number of the small water treatment plants engaged
operators with limited technical understanding of the treatment processes, leading to either an
overdose or an under-dose of coagulant and chlorine. Generally in terms of microbiological
parameters employed, Free State and Eastern Cape Provinces produced the safest and poorest water
quality respectively. Finally some of the small water treatment plants were devoid of basic
monitoring equipment such flow meter, pH meter, jar test apparatus, turbidity meter, chlorine meter
and colorimeter. These have led to lack of flow rate, turbidity, pH and chlorine residual
measurements.
It is strongly recommended that the following operational practices be implemented:
1. All small water treatment plants must be provided with basic functioning raw and final
water flow meters installed.
2. Accurate records of flow into and out of the plant must be recorded on a daily basis or
whenever a change in flow rate is made.
51
3. All the treatment plants must acquire jar stirrer apparatus to determine the optimum dose of
the coagulants. Jar tests must be conducted at least once per week or when the raw water
quality changes.
4. Plant operators must monitor pH at various points in the plant for coagulation control. The
turbidity of the final water must be monitored and falls within Class 1. This can only be
achieved if the operators target a filtrate turbidity of < 1NTU.
5. The chlorine dose has to be applied proportionally to the plant flow rate. To ensure effective
disinfection, measurement of the chlorine demand of water is highly recommended.
6. For a monitoring programme to be effective, each small water treatment plant must be
equipped with a jar stirrer, turbidity meter, pH meter and a chlorine meter. A programme for
monitoring the physico-chemical (at least pH, temperature, turbidity and free chlorine
residual) and bacterial (coliform bacteria, especially faecal coliform) quality of water at the
point of treatment and various sites of the distribution systems must be established.
52
CHAPTER IV
WATER QUALITY CHANGES IN THE DISTRIBUTION SYSTEM The distribution system is often vital in determining the final quality of potable water.
Deterioration of drinking water quality during storage or in distribution systems is one of the major
difficulties experienced by potable water supplies worldwide (Momba et al., 2000). The proper
understanding, characterization and prediction of water quality behavior in drinking water
distribution systems are critical in meeting regulatory requirements and ensuring customers oriented
expectation. Realizing that the water quality after treatment deteriorates with time, the distributor
cannot always guarantee the quality at the end of the distribution network. Moreover the reservoirs
which are an important part of the distribution network represent the final point at which the water
quality can be modified before it reaches the consumer (Momba et al., 2000).
This part of the study provides a reference compendium on parameters affecting the quality
of final treated drinking water in the distribution systems of three small water supplies (Seymour,
Fort Beaufort and Alice). The Fort Beaufort, Seymour and Alice water treatment plants are all
located in the Nkonkobe Municipality, in the Eastern Cape Province of South Africa. The Fort
Beaufort plant has the highest number of distribution reservoirs (26) serving 15 villages in its
distribution system. The water distribution system of Seymour consists of two storage reservoirs
located in the water treatment plant and an associated primary and secondary distribution network.
The Alice water treatment plant was selected to evaluate the effectiveness of previous operator
training that had been conducted at the plant in 2004.
4.1 METHODOLOGY
To identify the major problems resulting in water quality changes in distribution systems, an on-site
evaluation of the operating conditions at Fort Beaufort, Seymour and Alice water treatment plants
in the Eastern Cape Province was conducted by visual inspection, interviews and use of
questionnaires from October 2005 to November 2005.
4.1.1 Measurement of the flow of raw water and coagulant dose
The flow rates were recorded and in the absence of the flow meter (Seymour did not have a flow
meter while the one for Alice was malfunctioning at the time of the visit), the flow of the raw water
was calculated using the existing 90° V notch weir according to Kawamura (1991). For a 90o V-
notch weir, the total flow rate ( Q) is related to the height of the crest over the weir (H) as follows:
53
Q (m3/s) = 1.40 H2.5
The jar test was used to determine the optimum dose of the coagulant.
4.1.2 Physicochemical and Microbiological Analysis
Physicochemical parameters determined on-site included: chlorine concentrations, pH, temperature
and turbidity. The initial chlorine dose and free chlorine residual concentrations were determined at
the point of the treatment and in the distribution networks using a multi parameter ion specific
meter (Hanna-BDH laboratory supplies). The pH, temperature and the turbidity were measured at
each step in the treatment processes and in the distribution networks using a pH meter, thermometer
and a microprocessor turbidity meter (HACH company, model 2100P) respectively.
For microbiological analysis, water samples were collected according to standard
procedures using sterile bottles, which contained sodium thiosulphate (ca 17.5 mg/l), placed in
cooler boxes and transported to the laboratory for analysis within 2 to 4 h after collection. Standard
methods were used to quantify total and faecal coliforms and heterotrophic plate count bacteria.
4.2 RESULTS AND DISCUSSION
4.2.1 Distribution networks
Schematic diagrams of the Fort Beaufort and Alice distribution systems are shown in Fig. 4.1 and
4.2, respectively.
The Fort Beaufort plant had three main reservoirs (No1-3) with a combined capacity of
6.3 Ml. These reservoirs were filled by high lift pumping of the clear water (Fig. 4.1). From the
main reservoirs, water was fed by either gravity or pumping to a number of service reservoirs. The
topography of the distribution allowed gravity feed from service reservoirs.
The Seymour plant had two storage reservoirs with a total capacity of about 400 m3.
Reservoirs, ventilation, scour valves and overflows were adequately designed. However, there were
no bulk sale meters or reservoir level indicators. The water was supplied by gravity to the
community in which the service levels were mainly yard and house connections. During interviews,
operators reported that the locations of the scour valves in the network were not known. Hence the
network could be flushed and it was suspected that the reservoirs had high levels of silt.
54
Fig. 4.1 Schematic diagrams of the Fort Beaufort Distribution Network (WW – Water Works, R1 – Rectangular balancing reservoir [2.3 ML], R2 - Circular Reservoir near plant [2.0 Ml], R3 – Circular reservoir near plant [2.0 Ml], R4 – Hillside reservoir, R5 – Reservoir feeding Ntobela, R7 – Bhofolo Reservoirs [2.5 Ml supply], R8 – Ntobela Reservoir supplying 14 Satellite reservoirs, R9 – Newtown Reservoir, PS1 – Pump station No 1, PS2 - Pump station No 2, PS3 - Pump station No 3, R1-3 – Has 1.6 Ml/d supply).
The Alice Plant had a capacity of 7 Ml/d. Five of the town’s seven reservoirs, including the main
reservoir were gravity fed. Float valves regulated the flows into the reservoirs and they operated
essentially at 100% capacity under normal conditions. The flow to Ntselamanzi and Mavuso
reservoirs was augmented by pumping which was initiated automatically based on the signals from
level sensors in their reservoirs.
WW
R1
R2
R3
PS2
PS3
R8
R5
R9
PS2
New town
Fort Beaufort
Town
Hillside
Bhofolo
R9
55
Fig 4.2 Schematic diagrams of the Alice distribution network
4.2.2 Water Treatment Plant operation conditions
4.2.2.1 Fort Beaufort water treatment plant
The Fort Beaufort water treatment plant abstracted its intake water from Kat River. The raw water
turbidity varied between 60 and 70 NTU, but reached 100 NTU during the rainy season. The flow
rate of the raw water measured by an ultrasonic flow meter varied between 66 and 80 l/s during the
investigation. The accuracy of the flow meter checked by measuring the height over the V-notch
weir was found to be acceptable (0.069 m3/s = 69 L/s). After coagulation with a blended polyamine,
water passed through two circular clarifiers. Settled water was then filtered in seven rapid gravity
filters followed by final chlorination. The supplier was the only person who made adjustments to
the chemical dose. The standby dosing pump had been removed for repairs a year ago.
A jar test done during the study period confirmed a dosage of 45 ml/30 s which was
adequate for the flow of 66 l/s. Dosing took place downstream of a weir proving good mixing
energy. Of concern was the fact that the operators were not in a position to measure the applied
dose while a jar stirrer was available on-site.
Calculations undertaken showed that the clarifier surface loading rates ranged between 1.8
and 2.21 m/h which was well above the design rate of 1 m/h. Sludge removal valves were
malfunctioning and the clarifier overflow turbidity ranged between 8 and 10 NTU, well above the
guideline of 5 NTU.
G olf C ourse D evelop m entM avuso
V illage
H appy R est
F orte F la ts
H illcrest
M avuso 2 .5 M L
P um p S ta tion
N ew H appy
R est 0 .7 M L
O ld H app y
R est 0 .2 M L
M eter
M eter
M eter
M eter
A W T P
V icto ria E ast
C lin ic 0 .6 M L
U F H
1 M L B alancing
T ank
N tse la-m anzi
1 .5 M L
M ain 6 M L
N tselam anzi V illage
P um p S ta tionM eter
A lice
M ain L ine
M eter
V ic to ria E ast
C lin ic
D av idson P rim ary
S am pling po in ts
56
Filtration rates were found to be between 1.2 and 1.4 m/h well below the design of 5 m/h. This
impacted on the turbidity of filtered water which was above 1 NTU. Gas chlorination was used for
disinfection. One chlorinator was available with no standby. There were no emergency stocks of
HTH. At the time of the visit the chlorinator was not working and a makeshift HTH dosing system
was in use, however there was no means of measuring the dose.
A the point of treatment, the Fort Beaufort chlorine dosing unit available read a dosing rate
of 1.2 kg/h (333.3 mg/s). The dosage in mg/l from the plant inflow when chlorine gas was being
dosed corresponded to 5.05 mg/l. Typical dosages usually do not exceed 1.5 - 2.0 mg/l. The high
dosage calculated could be due to the following reasons: i) the dosing equipment being
malfunctioning and ii) high chlorine demand of the water. The average free chlorine residual
concentration was therefore ≤ 1.5 mg/l.
4.2.2.2 Seymour Water Treatment Plant
The Seymour water treatment plant abstracted its intake water from Kat River. The raw water had
the turbidity values ranging between 50 and 70 NTU. The raw water flow measurement took place
at the head of waterworks and was found to be functional. At the time of visit, an average inflow
rate of 5.38 l/s was recorded. A blended polymeric coagulant was dosed at a weir followed by the
baffled flocculation basin and the horizontal flow rectangular sedimentation basin. The Surface
Loading Rate (SLR) of the sedimentation tanks was found to be 0.3 m/h well within the guideline
of 1 m/h. One dosing pumps was available with no standby and coagulant control was done by the
suppliers. No jar stirrer was available at the plant, but the jar tests undertaken during the study
period indicated that the dose was adequate (8.5 ml/60 s) for the flow rate of 5.38 l/s. Following
slow sand filtration, the water was chlorinated before distribution. The two slow sand filters were
operating at 0.3 m/h which was just on the upper limit for these types of filters. Filtered water had
turbidity values below 1 NTU. Filter cleaning was done monthly and the procedure was in-line with
standard practice.
On-site electrolytic chlorination using salt as a feed was used for disinfection. Operators
could not calculate the applied dose. During the visit, the chlorine dosage could not be determined
as the operation and the specification manual for the equipment were not available. However, the
free residual chlorine determined from the in-plant reservoir was 0.5 mg/l. According to the
operators, occasional shortages of salt were common. No emergency or backup HTH stock was
available. Bench pH, chlorine and turbidity meters that cost about R20 000 each were available but
were surprisingly not in use due to the lack of batteries.
57
4.2.2.3 Alice Water Treatment Plant
Raw water was abstracted from a dam, and after coagulation with a polymer the water passed
through a flocculator and horizontal sedimentation tanks. This was followed by filtration through
two valveless filters and gas chlorination. Raw water turbidity at the time of the assessment was
20 NTU. An ultrasonic flow meter was used to measure the flow rate of the raw water over a V-
notch at the head of works. The flow rate of raw water was 75 l/s and jar tests confirmed that the
applied dose was correct (15 ml/30 s). Flocculation was poor and the poor flow distribution was
overloading some of the sedimentation tanks.
The chlorination system for Alice water treatment plant was similar to that of Fort Beaufort.
Residual chlorine levels at the point of treatment ranged between 0.24 and 0.89 mg/lL after the
contact tank.
4.2.3 Drinking water quality in the distribution systems
4.2.3.1 Turbidity compliance
Figure 4.3 summarizes the turbidity results obtained in the Fort Beaufort distribution system. None
of the water samples had the turbidity values below 0.2 NTU, with 27% of the samples having a
turbidity ≤ 0.5 NTU. Most of the samples (86%) had turbidity values below 1 NTU with only 6%
being above 2.5 NTU. An uncharacteristically high turbidity was observed once from the Henrietta
control point (49.3 NTU), which was suspected to be a consequence of a damaged pipe along the
route.
In Seymour distribution networks, the turbidity of the drinking water at the various sampling
points varied very markedly in the range of 0.55 to 27 NTU. Figure 4.4 shows that none of the
samples had turbidity values below 0.2 NTU, 13% of the samples were below 0.5 NTU, 67% of the
samples had turbidity greater than 1 NTU and 14% had turbidity higher than 5 NTU.
Figure 4.5 depicts a histogram of turbidity in the Alice distribution system. The data show
that none of the samples had turbidity below 0.2 NTU; 58% of the samples had turbidity values
≤ 1.0 NTU and 30% of the samples had turbidity values higher than 2.5 NTU. This indicates that
the consumers were receiving unsafe water and the primary reasons for this were poor plant
management as there was always a shortage of the primary coagulant and chlorine at this water
works.
58
0
5
10
15
20
25
30
35
0.1 0.2 0.5 0.75 1 1.5 2 2.5 5 10 MoreNTU
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Fig. 4.3 Histogram of Turbidity in the Fort Beaufort Drinking Water Distribution System
0
1
2
3
4
5
6
7
8
0.1 0.2 0.5 0.75 1 1.5 2 2.5 5 10 More
NTU
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Fig. 4.4 Histogram of Turbidity in the Seymour Drinking Water Distribution System
0
1
2
3
4
5
6
7
8
0.1 0.2 0.5 0.75 1 1.5 2 2.5 5 10 More
NTU
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Fig. 4.5 Histogram of Turbidity in the Alice Drinking Water Distribution System
59
4.2.3.2 Free chlorine residual concentration and microbiological characteristic in the
distribution systems
Fort Beaufort - Figure 4.6 depicts a histogram of the free chlorine concentrations and it was noted
that 28% of the results were below 0.1 mg/l, indicating that there was a large reduction in the
concentration of free chlorine residual from the treatment plant which supplied water with a free
chlorine residual concentration up to 1.5 mg/l. Ninety two percent of the samples had free chlorine
concentrations below 0.5 mg/l and were thus within the recommended levels of between 0.3 and 0.6
mg/l (Water Research Commission, 1998).
No coliform bacteria were observed in the in-plant reservoirs of the Fort Beaufort water
treatment plant during the study period. However in the distribution system, 60% of the samples
had less than 10 cfu/100 ml total coliforms. Of concern was the 7% of the samples that had more
than a 100 cfu/100 ml total coliforms (Fig. 4.7). Figure 4.8 shows a histogram of the faecal
coliforms in the Fort Beaufort system, where 4% of the samples had five or more faecal coliforms,
due to the depletion of chlorine residuals in the distribution networks.
In general 88% of the water samples had more than the DWAF (1996) limits of 100 cfu/mL
HPC (Fig.4.9). These results were an indicative of low chlorine residuals, possible regrowth of
bacteria and poor maintenance of the distribution system.
60
Figure 4.6: Fort Beaufort Free Chlorine Histogram
0
5
10
15
20
25
0.1 0.2 0.5 0.75 1 1.5 2 2.5 More
Free Chlorine
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Figure 4.7 Fort Beaufort Total Coliform Histogram
0
5
10
15
20
25
0 1 10 100 200 500 1000 More
Tot al Colif orm
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Figure 4.8 Fort Beaufort Faecal Coliforms Histogram
0
10
20
30
40
50
60
0 1 5 10 15 20 More
Faecal Coliform Bins
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Figure 4.9 Fort Beaufort Histogram of Heterotrophic Plate Counts
0
5
10
15
20
25
30
100 1000 10000 100000 1000000 More
Heterotrophic plate count
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency
Cumulative %
Figs 4.6-4.9 Histograms of Free Chlorine Residual and Indicator Bacteria in the Fort Beaufort Drinking Water
Distribution System
Seymour - In terms of free chlorine, the Seymour histogram (Fig. 4.10) shows that 20% of the
samples had a free chlorine concentration below 0.1 mg/l, a further 20% had concentrations
between 0.1 and 0.2 mg/l. Overall all the water samples had a concentration below 0.5 mg/L, while
two samples had concentrations of 0.75 and 1.0 mg/l respectively.
Eight of the 14 water samples analysed (60%) had no total coliforms, however 22% had 10
or more total coliforms (Fig.4.11). Figure 4.12 depicts the Seymour histogram for faecal coliforms
which shows that 12 of the 14 samples (85%) had no faecal coliforms whereas only two samples
had five or more.
In terms of faecal coliforms, this system showed the most promising results and was an
indicative of the smaller distribution network associated with shorter retention times. In terms of
HPC, Fig. 4.13 shows that 12% of the samples had HPC densities greater than 105 cfu/ml, 50% of
the samples had more than 104 cfu/ml HPC and 58% had more than 103 cfu/ml. Overall 65% of the
61
water samples did not meet the guideline value of 100 cfu/ml also showing that the distribution
network was in need of a good clean out.
Figure 4.10 Histogram of Free Chlorine in the Seymour Distribution System
0
1
2
3
4
5
6
7
0.1 0.2 0.5 0.75 1 1.5 2 2.5 More
Free Chlorine
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Figure 4.11 Histogram of Total Coliforms in the Seymour Distribution System
0
1
2
3
4
5
6
7
8
9
0 1 10 100 200 500 1000 More
Total Coliform
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%Frequency Cumulative %
Figure 4.12 Histogram of Faecal Coliforms in Seymour Distribution System
0
2
4
6
8
10
12
14
0 1 5 10 15 20 More
Faecal Coliform
Freq
uenc
y
75.00%
80.00%
85.00%
90.00%
95.00%
100.00%
105.00%Frequency Cumulative %
Figure 4.13 Histogram of HPC in Seymour Distribution System
0
1
2
3
4
5
6
100 1000 10000 1000001000000 More
Heterotrophic plate count
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%
Frequency Cumulative %
Fig 4.10 - 4.13 Histograms of Free Chlorine Residual and Indicator Bacteria in the Seymour Drinking Water
Distribution System
Alice - Figure 4.14 shows that 27% of the samples had residual free chlorine concentration below
0.1 mg/l, 62% below 0.2 mg/l and none of the water samples having more than 1.0 mg/l. In terms of
total coliforms (Fig. 4.15), 27% of the water samples had no coliforms with 56% having more than
the recommended limit of 10 cfu/100 ml. Of major concern was the fact that 6% of the
aforementioned samples had more than 200 cfu/100 ml, representing a major health risk to the
community.
62
Figure 4.14 Histogram of Residual Free Chlorine in Distribution system
0
1
2
3
4
5
6
7
0.1 0.2 0.5 0.75 1 1.5 2 2.5 More
Free Chlorine
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%Frequency Cumulative %
Figure 4.15 Histogram of Total Coliform in Alice Distrbution System
0
1
2
3
4
5
6
7
8
0 1 10 100 200 500 1000 More
Total Coliform
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%Frequency Cumulative %
Figure 4.16 Histogram of Faecal Coliforms in the Alice Distribution System
0
2
4
6
8
10
12
0 1 5 10 15 20 More
Faecal Coliform
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%Frequency Cumulative %
Figure 4.17 Histogram of HPC in Alice Distribution System
0
1
2
3
4
5
6
7
8
9
10
100 1000 10000 1000001000000 More
HPC
Freq
uenc
y
0.00%
20.00%
40.00%
60.00%
80.00%
100.00%
120.00%Frequency Cumulative %
Fig 4.14 - 4.17 Histograms of Free Chlorine Residual and Indicator Bacteria in the Alice Drinking Water
Distribution System
The faecal coliform histogram of the Alice distribution system in Figure 4.16 shows that 55% of the
samples had no faecal coliforms present, however 34% of the samples had more than one faecal
coliform. Of the aforementioned samples, 6% had more than 5 faecal coliforms confirming the
major consumer risk mentioned above. In terms of HPC in Alice (Figure 4.17), 6% of the samples
had more than 104 cfu/ml, 17% had more 103 cfu/ml and 50% of the samples had more than the
recommended limit of 100 cfu/ml.
Based on the chlorine rates at the dosing points and the concentrations of free residual
chlorine in networks systems, relationships were then established between both points. When in
operation, the plant chlorination systems always provided sufficient residual chlorine for areas near
the main reservoirs. For the areas that were far away from the main reservoirs, the plant chlorination
systems usually provided sufficient residual free chlorine on the days of supply/pumping to the
service reservoirs. The dosages at the plants were not sufficient enough to combat the depletion of
63
free chlorine residual in most reservoirs when the final water was detained for more than 24 h. This
was attributed to the chlorine consumption by floc/sediment accumulations in most reservoirs.
Moreover, it was found that the reservoir designs were generally adequate. They were
equipped with overflows, air vents and drainage facilities. The operation of reservoirs, however,
seemed to be inadequate. Although the plant chlorination systems gave adequate dosage at the point
of dosing, these dosages were not sustained in the distribution systems.
4.3 CONCLUSIONS
In general, the assessment of the quality of drinking water in distribution systems of Fort Beaufort,
Seymour and Alice revealed that most of the sampling points in distribution systems did not comply
with the required standards in terms of indicator bacteria such as heterotrophic plate counts, total
coliforms and faecal coliforms. This was a reflection of the inconsistency in the plant operations,
which made impossible for the plants to ensure sustainable production of good quality of drinking
water. Several factors could be responsible for this phenomenon:
i) The design and operational of the flocculation processes were not optimized at all plants.
This led to inadequate floc formation for the sedimentation process.
ii) The monitoring and adjustment of chemical dosages (coagulants and chlorine) were not
conducted on-site; operators should be capacitated to adjust dosing rates with respect to inflow and
quality changes
iii) Filtration process monitoring and control was not optimized. The filtration rate of the
SSF in Seymour was 100% higher than the accepted upper limit.
In all the plants, there was no standby dosing pumps for the coagulants and disinfection
chemicals. The stocking of disinfection chemicals was not sustainable and lack of on-site water
quality data which should assist in making critical decisions and also estimations in times of
emergency.
The above factors in water treatment plants impacted on the effectiveness of the disinfection
process in the distribution systems and the following major problems were recorded: i) the
distribution system of the pipe network did not show acceptable levels of residual free chlorine and
ii) most of the chlorine dosed at the treatment plant was consumed by the floc sludge that
accumulated in the reservoirs and the deposits that were present in the distribution pipe network.
4.4 RECOMMENDATIONS
To improve disinfection efficiency in Fort Beaufort, Seymour and Alice drinking water treatment
plants, this study suggests the following recommendations:
64
Floc sludge removal need to be done twice for the Seymour WTP and adequate flocculation
basins need to be introduced at the Fort Beaufort WTP. The quality of inflow to each filter should
be monitored to prevent overloading the filtration process and the quality of the effluent be
monitored from each filter. The concept of filtering-to-waste must be investigated after the
backwashing of the slow sand filters at Fort Beaufort and Seymour. The effectiveness of these
filters with respect to turbidity removal within 1 to 2 h after backwashing was usually low and the
filtered water should then be sent to waste until turbidity levels become acceptable (< 1 NTU).
The reservoirs need to be maintained and cleaned regularly to ensure that there is no sludge
accumulation. The sludge consumes the disinfectant thus reducing the residual chlorine and
compromising the reliability of the disinfection in the network. Some reservoirs showed leakages.
Replacement of screens on vents needs to be done annually. The pipe network system needs to be
drained or flashed as required to remove deposits that also consume disinfectants. Scour valves for
various sections of the network must be located and put to use.
A comprehensive water quality monitoring programme needs to be developed and supported
by the Municipality. Water distribution networks need to be documented in order to understand and
optimize their operation. At the time of visit, network drawings could not be obtained and there
were no records of pressure and bulk water meter readings. Record keeping and interpretations need
to be enhanced at all plants as this would assist in taking critical operation, maintenance and
management decisions.
Operators should be trained to perform key tasks such residual monitoring, adjustment of
chemical dosages, flow measurements and visual analysis of the water quality from each unit
process, independently. Each shift should have two operators; this is important to reduce the
consequences of accidents and also for morale and motivation purposes.
The Alice case is clearly one of a loss of team towards compliance of the operational
procedures, having been beneficiary of a training programme in the past year that significantly
improved the plant’s performance and the quality of the final water produced (Momba et al., 2004;
2005). This underscores the need for a regular auditing of the plants performance to ensure
continuous improvement and safe drinking water.
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CHAPTER V
MANAGEMENT ISSUES AFFECTING THE EFFICIENCY OF DISINFECTION
IN SOUTH AFRICAN SMALL WATER TREATMENT PLANTS
5.1 INTRODUCTION
The capacity of any water treatment plant to provide acceptable drinking water quality mainly
depends on the performance of each functional unit in the plant including coagulation-flocculation,
sedimentation, filtration and disinfection. Management and administration of water treatment plants
also play an important role in determining the quality of the final water. In urban areas, drinking
water quality complies with the South African National Standards (SANS) 241 Drinking Water
Specification (2005). This water, therefore, does not pose a significant risk to public health over a
lifetime of consumption. The difficulties experienced in training and retaining adequately skilled
people to run water treatment plants in impoverished rural municipalities, as well as lack of
revenues needed to hire experienced managers and to maintain and upgrade water supplies have
been among the major hurdles to providing safe and clean drinking water in these areas. Inadequate
manpower training and periodic updating of knowledge and skills affect institutional capacity to
implement sustainable water resource management. Poor maintenance practices, inadequate
improvement in working conditions and poor water programme monitoring are hallmarks of
inadequate manpower training or institutional capacity. This chapter therefore seeks to explore
management issues facing safe and reliable water supply in rural areas and some peri-urban areas of
South Africa.
5.2 METHODOLOGY
A survey of management issues of 181 small water treatment plants across seven provinces of
South Africa (including Limpopo, Mpumalanga, North-West, Free State, KwaZulu-Natal, Eastern
Cape and Western Cape) was conducted from June 2004 to December 2005. The survey started
with a short introductory meeting following by interview with the plant operators, superintendents
and supervisors of the plants. Information concerning management issues such as the training of
the operators, their salaries, benefits, decision making, maintenance practices and financial capacity
(for the purchase of chemicals/upgrading of infrastructure), data recording, documentation and
communication were sought through the use of questionnaires. The above-mentioned plant staffs
present at the time of survey were interviewed individually.
66
5.3 RESULTS AND DISCUSSION
5.3.1 Poor Maintenance Practices
Lack of maintenance of equipment was noted to be a major management problem. About 60% of
the SWTP operators interviewed in all the provinces studied (Eastern Cape, Free State, Western
Cape, Mpumalanga and Limpopo Provinces) mentioned that equipments were not regularly
maintained. This led to periodic equipment failures and the consequences of poor water quality.
Indeed some operators asserted that the culture in most SWTPs was a culture of repairs or
replacement of equipments and not maintenance of equipment. Several factors have been implicated
to fan the poor maintenance culture. Such factors included lack of technical skills and appropriate
training, inadequate or lack of relevant experience, inadequate funds and personnel. For example in
North-West, Western Cape, Free State, KwaZulu-Natal, Eastern Cape, Mpumalanga and Limpopo
Provinces, between 5.88-46.30% of the operators reportedly had educational qualifications of
standard 8, 42-62% with Matric (with the exception of KwaZulu-Natal – 80%) whereas
0-53% were enrolled in post Matric qualifications. The implications of these trends are enormous
because they typify the shortcomings and potential dangers in the water delivery system due to lack
of appropriate qualification and training. The in-service training component is exemplified by the
fact that in all the SWTPs studied, in the respective provinces, about 7-63% of the operators had not
undergone relevant and appropriate training to enable them acquire technical skills for the job
(Table 5.1).
The main role of operators is to control the equipment and processes that remove or destroy
harmful chemical compounds and micro-organisms from the water. This role is therefore mired in
controversy because most of the operators lack technical knowledge of the equipment and technical
processes. Some operators were not aware of how to determine flow rates, chlorine dosage or even
the concept of chlorination as well as maintenance of technical equipments, measurement and
documentation of processes. Above all, they lacked computational skills in an era of a rapidly
changing information technology system. The ripple effects of these shortcomings can not therefore
be ignored and should indeed be placed in the context of the reported management problems in
some Local Government Authorities (LGAs) in South Africa.
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TABLE 5.1
SOME NON-TECHNICAL ISSUES IMPACTING ON QUALITY OF WATER SERVICES DELIVERY IN SMALL WATER TREATMENT PLANTS IN SOUTH AFRICA
Training Type of Training Technical Admin Management Financial S07
Fully Partial Manual Telemetric
S08 Automation
S09 External monitoring
(Name of Company / Authority)
Section T: Filtration
T01 No of Filters
T02 Type of media
T03 Media Size
T04 Filter type
T05 Flow Pattern onto Filter
T06 Frequency of Backwash
T07 Recycle
T08 Automated
Section R: Costs
R01 Original Capital Cost of Plant
Per Annum Per m3 R02 Chemical treatment Costs
Human
Resource Costs Per Annum Per m3 R03
Per Annum Per m3 R04 Maintenance Costs
Section V: Water Quality of Treated Water
V01 Treated water turbidity NTU
V02 Treated water pH
V03 Treated water Free Chlorine mg/l as Pt/Co / Hazen /
colour units
V04 Treated water alkalinity mg/l as CaCO3
96
V05 Treated water conductivity mS/m
TDS Iron Fluoride Manganese Nitrate Hardness
V06 Chemical properties (mg/l)
V07 chlorophyll a ug/l
V08 Treated water DOC mg/l
V09 Taste and odour TON
V10 Temperature °C
V10 DO
V10 Other (specify)
V11 Total Coliforms (CFU/100 ml)
V12 Fecal Coliforms (CFU/100ml)
V13 Standard Plate
Count (CFU/100 ml)
Section W: Water Quality of Distribution System
W01 Sample Taken From Shop Garage Clinic
Other (specify)
W02 Distribution water turbidity NTU
W03 Distribution water pH
W04 Distribution water Free Chlorine mg/l as Pt/Co / Hazen /
colour units
W05 Distribution water alkalinity mg/l as CaCO3
W06 Distribution water conductivity mS/m
W07 TDS Iron Fluoride Manganese Nitrate Hardness if available
W08 Chemical
properties (mg/l)
W09 chlorophyll a ug/l
W10 Distribution water DOC mg/l
W11 Taste and odour TON
W12 Temperature °C
W13 DO
W14 Other (specify)
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Appendix 3.2
Water Treatment Processes and Equipment The Disinfection processes and equipment used by the small water treatment plants in Waterberg, Sekhukuni, Capricorn, Mopani, Vhembe (Limpopo Province) and Ehlanzeni, Nkangala (Mpumalanga Province) Districts and local municipalities.
Mpumalanga District Municipality (Local Municipality)
Surface water Coagulation Flocculation, Stabilisation Sedimentation, Filtration, Chlorination
Polyelectrolyte, Hydro-care AC 500, Milton Roy pump Open channel flocculators Lime Horizontal settling tank Rapid Gravity Sand Filters Chlorine gas, HTH, Wallace and Tierno pumps
Damani (DWAF)
Surface water Coagulation Flocculation, Stabilisation Sedimentation, Filtration, Chlorination
Alu Floc, Open channel flocculators Lime Rapid Gravity Sand filters Chlorine gas, HTH
Malamulele (DWAF)
Surface water Coagulation Flocculation, Stabilisation Sedimentation, Filtration, Chlorination
Ferric Floc HC 500, ALDOS D76327 Open channel flocculators Lime Rapid Gravity Sand Filters Chlorine gas, HTH, CONTROL MATIC M20 pump Telemetric control panel
Mudaswali (DWAF)
Surface water Coagulation Flocculation, Stabilisation Sedimentation, Filtration, Chlorination
Leave strainer Sudfloc3484 & ALLDOS pumps Soda ash and dry chemical feeder Pipe flocculation system Upflow settlers Pressure filters Chlorine gas & S10K Wallace and Terran pump
Pela Surface water-dam Coagulation pH stabilization Flocculation Sedimentation Chlorination Filtration
Aluminium sulphate and ultrafloc 5082, ALLDOS primus serie pumps Soda ash Pipe flocculation system Cyclone clarifiers Granular HTH & ALLDOS pump Rapid sand filters
Calcium chloride and ultra-floc – ALLDOS pumps Soda ash Pipe flocculation system Upflow settlers Granular HTH – ALLDOS pump Pressure filters
Mmabatho Surface water-dam Solid removal Coagulation pH stabilisation Flocculation and sedimentation Dissolved Air Flotation Filtration Chlorination
Leave strainer Ferric chloride and ALLDOS pump Soda ash-dry chemical feeders Circular scraper clarifier DAF system Rapid sand filters Chlorine gas & ALLDOS pumps
Mafikeng Ground water-boreholes and springs
Screening Filtration Chlorination
Pressure filters Chlorine gas and ALLDOS pumps
Itsoseng Ground water-boreholes
Chlorination Chlorine gas and ALLDOS pumps
Koster Surface water –dam and ground water-boreholes
Polyelectrolyte (pump) Open channel flocculation, Horizontal flow clarifiers, Rapid gravity sand filters, Sodium hypochlorite Alldos pump Sodium hypochlorite chemical pump
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KwaZulu- Natal
Plant Water source Disinfection practices Equipment Assegaai Pongola River Chlorination (Sodium hypo) 1 Dosing pump Belgrade Belgrade Dam Chlorination (Sodium hypo) 2 Dosing pumps Bethesda (umkuze) Umkuze River Chlorination (Sodium hypo) 1 Dosing pump Ceza Vungu River Chlorination (Sodium hypo) 1 Dosing pump Enyokeni Usuthu Spring Chlorination (Sodium hypo) 1 Dosing pump Frischgewaagd Pongola River Chlorination (Sodium hypo) 1 Dosing pump Greytown Merthley Lake & Spring Chlorination (gaseous Cl2) 1 Chlorinator & Injector Hlanganani No info No info No info Hlokozi No info No info No info Itshelejuba Borehole Chlorination (Sodium hypo) 1 Dosing pump Ixopo Sodbux Dam Chlorination (gaseous Cl2) 1 Chlorinator & Injector Jozini Jozini Dam Chlorination (gaseous Cl2) 1 Chlorinator & Injector Kwazibusele Kwazibusele Borehole No info No info Manguzi Shengeza River/Gezisa
Umbumbulu No info Chlorination (gaseous Cl2) No info Vulamehlo No info Chlorination (Sodium hypo) Dosing pump Wild Coast No info Chlorine dioxide Dosing pump
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Eastern Cape Province
District Municipality
Name of Plants (Owner type)
Water source
Treatment processes (Disinfection practices)
Equipment
Cacadu Graaff -Reinet Ground water and Surface water
Surface water Coagulation and pH Stabilisation, Flocculation, Sedimentation, Filtration, Chlorination
Alum and Soda ash Open channel Horizontal settlers Rapid sand filters-valveless HTH and HTH dosing pumps
Amathole Idutywa Surface water Coagulation and pH Stabilisation, Flocculation, Sedimentation, Filtration, Chlorination
Alum and Soda ash Open channel Horizontal settlers Rapid sand filters-valveless HTH and HTH dosing pumps
Elliotdale Surface water Coagulation, Chlorination
Alum HTH and HTH dosing
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Flocculation, Sedimentation, Filtration,
pumps Open channel flocculator Horizontal settlers Slow sand filter
Butterworth Surface water Coagulation, Sedimentation, Filtration, Chlorination
Alum and Primco 735 dosed by dry screw feeder and Prominent dosing pump Upflow settlers Rapid sand filters Advanced seventrew series capital contracts Model 480, chlorine gas
Cintsa Surface water Coagulation, Flocculation, Sedimentation, Filtration, Chlorination
Morgans Bay Surface water Prechlorination Coagulation, Sedimentation, Filtration, Chlorination
HTH and Siemens dosing pump Sudfloc 3890 & 475 and Milton Roy A 952-86 Circular settling tanks Pressure filters Sodium hypochlorite generated onsite
Hagahaga Surface water Pre-Sedimentation, Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Sud floc 3899, and ALLDOS 205 Pipe flocculators, Radial flow settlers, Pressure filters, HTH and CMSIC pulse meter
Komga Surface water Pre-Sedimentation, Coagulation and pH stabilization Flocculation, Sedimentation, Disinfection
Radial flow settlers, Alum and soda ash – dry chemical feeders Open channel flocculator Radial flow settlers, HTH
Cathcart Surface water Coagulation Flocculation, Sedimentation, Filtration, Disinfection
Sud floc 3880, and Concept plus pump CNPA0704 Open channel flocculator Horizontal settling tanks Rapid gravity sand filters Chlorine gas and Hydrogas pump
Adelaide Surface water Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Sud floc 3456, and ALLDOS pump Open channel flocculator Horizontal settlers Rapid gravity sand filters Chlorine gas and ALLDOS pump
Aliwal North Surface water Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Ultrafloc 5100 and ALLDOS dosing pump Open channel flocculation, Horizontal settlers and Radial flow, Slow sand filters and pressure filters Chlorine gas and ALLDOS dosing pump
Burgersdorp Surface water Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Profloc 3860, ALLDOS Open channel Horizontal settlers Rapid gravity sand filters Chlorine gas and ALLDOS dosing pump
Barkley East Surface water Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Open channel floculators Horizontal settlers Rapid valveless sand filters Chlorine gas and ALLDOS
OR Tambo Umtata Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Filtration, Chlorination
Zetafloc LP226 and Lime dosed by ALLDOS pump and dry chemical feeders Open channel floculators Upflow settlers Diatomceous filter and Rapid Gravity Sand filters Chlorine gas and ALLDOS
Mqanduli Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Filtration, Chlorination
Alum and Soda ash dosed by manually Open channel flocculation Horizontal setters Slow Sand filters HTH dosed manually
Tsolo Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Filtration, Chlorination
Sudfloc and Soda ash dosed by CMSIC pulse meter Open channel flocculation Horizontal settlers Pressure filters HTH dosed by CMSIC pulse meter
Ngqeleni Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Chlorination
Alum and Lime dosed manually Open channel flocculation Horizontal settlers HTH dosed manually
Lutsheko Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Chlorination
Zetafloc LP226 ALLDOS pump Open channel floculators Upflow settlers Diatomceous filter and Rapid Chlorine gas and ALLDOS
Libode Surface water Coagulation Flocculation, Sedimentation, Filtration, Chlorination
Polyelectriolyte (Not known) dosed by prominent pump Open channel flocculators Horizontal settlers Slow sand filters Bromine tablets (potabrom)
Umzimvibu Surface water Coagulation Flocculation, Stabilisation Sedimentation, Filtration, Chlorination
Polyelectriolyte (Not known) dosed by prominent pump Open channel flocculators Upflow settlers Pressure filters HTH dosed by ALLDOS pump
Bulolo Surface water Coagulation and pH Stabilisation Flocculation, Sedimentation, Chlorination
Profloc 3890, and lime dosed Open channel flocculation Upflow settlers Rapid gravity sand filters Chlorine gas
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Mt Ayliff Surface water Chlorination, Coagulation and pH Stabilisation Sedimentation, Filtration
Alum, Gravity feed Open channel flocculation, Horizontal Gravity sand Chlorine gas ALLDOS Lime
Ruigter Surface water Coagulation, Flocculation, Stabilization Sedimentation, Filtration, Disinfection
(Alum and Polyelectrolyte) Milton Roy Series GTM Open channel flocculation, Lime Horizontal settlers Pressure filters and rapid sand filters Chlorine gas and ALLDOS
George George Surface water (Dam) Coagulation, Flocculation, Sedimentation, Filtration, Disinfection Stabilization
Ferric Chloride (ALLDOS) Polyelectrolyte Open channel flocculation, Horizontal Rapid sand filters, Horizontal Chlorine gas,(Wallace and Tienan, regulator) Lime
