Monitoring and Assessment of Microbiological Quality
Session Objectives
· To describe the
process of planning monitoring and surveillance activities and the need for
progression through a number of stages starting with a pilot phase.
· To describe the development of
analytical ranges in water quality monitoring.
· To introduce the critical
parameters concept and emphasise the need for monitoring to focus on health
related parameters of water quality.
· To describe the design of
sampling networks and frequencies of sampling in routine monitoring programmes.
· To discuss the linkage of
monitoring to water supply improvement.
Introduction
The routine monitoring and assessment of the microbiological
quality of water is the key priority for both water suppliers and surveillance
agencies. Microbiological quality is of principal concern because of the acute
risk to health posed by viruses, bacteria and helminths in drinking-water.
Therefore, monitoring and assessment of drinking-water is primarily a
health-based activity which emphasises the protection of public health through
ensuring that the water supplied is of a good quality.
Because monitoring is a health-based activity, other parameters
of water supply should also be assessed: quantity, continuity, coverage and
cost. All these parameters will affect public health. The water supplier should
aim to monitor all aspects of water supply within their area of responsibility
and aim for a continuous water supply which is of sufficient quantity and
quality at an affordable cost to be available to all the population connected to
the supply. The surveillance body should monitor the entire population and
identify unserved groups and actively promote universal access to adequate water
supplies.
Strategies for monitoring of microbiological quality of safe
water should also include hazard identification and risk assessment, processes
commonly incorporated within sanitary inspection. It is important that these are
systematic and quantifiable and can be used to facilitate decision making at
local, regional and national levels on preventative and remedial actions. In
addition, minimum treatment requirements and source protection should be
emphasised as essential complementary activities to monitoring and assessment.
Planning monitoring and assessment
Monitoring water supply quality will only be effective and
efficient if it is properly planned and implemented. In many countries where
there has not been routine surveillance and surveillance programmes being
developed there may be uncertainty as to what standards should be adopted, the
number of water supplies that should be covered, how many samples should be
taken, what should be analysed, frequency of inspection etc. These may vary with
time and it is important that the surveillance programme remains flexible and
open to modification in response to evolving water quality priorities.
In many cases, WHO guideline values are adopted initially as the
national standards for drinking-water quality. However, with time these may be
superseded by national or regional standards depending on water quality
priorities.
When designing a surveillance programme and planning its
implementation, it is important that achievable aims and objectives are set. It
is useful to clarify these terms: aims are general expression of targets, the
'end' result which is desired, are not generally time constrained. Objectives
are indicators of the rate of success in achieving the aim and are specific
goals set with definite time scales with indicators of achievement to provide a
means of measuring success.
Extensive use of indicator bacteria will be required to monitor
microbiological quality and the relative merits of these are discussed in the
background paper on the microbiological aspects of water quality and in the
Guidelines Volume 1. Thermotolerant (faecal) coliforms are the indicator
most widely used for routine monitoring of water quality, although extensive use
is also made of total coliforms. In addition to indicator monitoring, routine
monitoring of turbidity and chlorine residual (in chlorinated supplies) is
recommended in order to ensure that any deterioration of water quality post
treatment is rapidly identified.
The rest of this paper will discuss the development of
strategies for water quality monitoring and assessment with specific reference
to microbiological risks.
Aims and objectives
The aim of surveillance has been defined in Guidelines for
drinking-water quality. Volume III (2nd edition) as follows:
"Surveillance is an investigative activity which is undertaken in order to
identify and evaluate factors associated with drinking-water quality which could
pose a risk to health. Surveillance contributes to the protection of public
health by promoting the improvement of water supply with respect to quality,
quantity, coverage, cost and continuity". Guidelines Volume III also defines
the aim of quality control in the water supply sector (which may be seen as an
integral part of surveillance) as being: "to ensure that water services meet
national standards and institutional targets."
In order to achieve these aims, a number of objectives may be
identified, for example:
· the formulation of
working methodologies for information gathering, decision making and
communication;
· the review of existing quality
standards and modifications of these as appropriate;
· the identification of
appropriate analytical techniques;
· the identification of
appropriate equipment and facilities (including evaluation of the use of on-site
equipment) required to conduct a surveillance programme;
· identification of analytical
quality control procedures for laboratories and on-site techniques and the
identification of national (and possibly regional) analytical reference centres;
· establishing staff
requirements and assessing skills of current employees, identification of
training needs for staff, recruitment needs for the sector;
· to establish a protocol for
approval of water sources as fit for drinking;
· to establish whether there are
any particular problems in terms of sources, treatment technology, designs,
operation and maintenance regimes etc. which are leading to persistent
contamination problems.
The time in which it is expected to achieve these objectives
must be outlined and indicators selected to measure progress, for instance
definition of appropriate chemical assay equipment or type of on-site equipment
required.
Routine monitoring of water supplies
In many circumstances, there is a desire to attempt to apply all
aspects of surveillance to all the water supplies immediately. Whilst this is a
laudable ideal, it is rarely possible to achieve successfully and may lead to
resources being over-stretched and the failure of surveillance to provide the
expected improvements in water supply quality. This may in turn lead to
disappointment and increasing apathy towards surveillance.
Surveillance should be introduced progressively and at each
stage objectives set which are achievable and which positively promote the
continued development of surveillance. The experience from earlier stages should
be used to improve surveillance and lead to a progressively more efficient and
comprehensive surveillance programme. Thus, in the initial stages of
surveillance, activities may be restricted to sanitary inspections and critical
parameter analysis on a restricted number of water supplies. As the programme
develops, the number of water supplies covered will be increased, frequency of
sampling and inspections increased and the analytical range increased.
Sanitary inspections can be carried out relatively cheaply and
easily and can be implemented on all water supplies from the start of
surveillance. Sanitary inspection is as much a tool for the supplier or
community as the surveillance agency for determining state of the water supply
infrastructure and the identification of actual or potential faults and should
be carried out on a regular basis by the supplier. The surveillance agency
should conduct some independent inspections to verify the reliability of the
supplier's information but this does not need to be as frequent.
In the long-term it is desirable that all water supplies should
be included in a surveillance programme. However, it is important to be
realistic in planning initial surveillance activities taking into account
infrastructure, available trained personnel, the number of water supplies in the
country and the ability to fund on-going surveillance activities.
Initial surveillance activities may be limited. However, it is
important that short, medium and long tern achievable aims and objectives are
included in the planning stage of surveillance. There should also be a set of
clearly defined indicators that can be used to assess whether targets have been
met. The establishment of credible indicators of a monitoring and evaluation
programme at the start of the planning process is central to good planning of
implementation. Time scales should be attached to each objective and aim and a
proposed strategy for achieving these outlined.
Planned surveillance activities will only be possible if there
are funds to pay for them and budgets for surveillance require careful
preparation. In most cases, there are limited funds available and this
inevitably will affect how many supplies can be included, how often they can be
visited and how many samples can be analysed. It is therefore imperative that
the following are identified and the cost calculated: the number and location of
water supplies to be included in each stage of surveillance; staff time;
consumable requirements; equipment purchase and maintenance costs; fuel costs;
the cost of reporting results to suppliers and communities; and the cost of
follow-up activities. It is vital that all these elements are accurately
budgeted for and cost-effectiveness achieved.
Pre-surveillance activities
Prior to the start of a surveillance programme, there are a
number of activities which should be undertaken to ensure that the planners have
access to all baseline data to design the surveillance programme. The
pre-surveillance activities should provide the information concerning current
status of water supply and surveillance in the country, and will include the
following:
Current surveillance activities: scope;
analytes; reliability; who is responsible; geographical spread.
Inventory of supplies: type
(borehole/spring/gallery/surface etc); treatment technologies; age; population
served; existing quality data; source approval;
Staff assessment: numbers available; skills available;
recruitment requirements; training requirements;
Surveillance infrastructure: available laboratories;
laboratory equipment; on-site equipment; consumables; transport; geographical
spread; computer availability; database availability.
Once this information is available the programme can be designed
and will include recommendations for improving on all the above and to test
appropriate methods. It is usual to run a pilot project to evaluate the approach
to be adopted and to identify any parts of the programme which require
improvement.
Pilot project
There are essentially two approaches to the establishment of a
pilot phase that can be adopted:
1. the use of a pilot project concentrated within
one geographical area;
2. establishing surveillance on small scale national basis, with
a small number of supplies included from each region.
Selected supplies may be restricted to those with large
populations (for instance over 10,000 people or provincial capitals) or may
include supplies that serve all types of population centre.
The first of these approaches allows a more intensive allocation
of resources and it may be easier to measure the effectiveness of the approach
adopted. However, there is a risk that the area selected may not be
representative or that successful approaches may not be replicable in other
parts of the country. This may be due to different types of source or treatment
used, different staffing structure or resource base. It may be difficult to
develop and sustain the level of support available for a small regional,
pilot-scale project on a national scale in the short term. Different regional
water suppliers may have different priorities based on the principal threats to
water quality in each region, the surveillance infrastructure available, the
expertise available and the number of people served.
A national pilot project may be more expensive due to increased
travel costs and may be difficult to manage. However, there are many advantages
in this approach. It is much easier to establish a large-scale national
surveillance programme if in the pilot phase a national approach was adopted. In
this way, difference in priorities between regions will have been identified at
an early stage and can be incorporated within the national plans. It will
highlight any logistical, staffing or infrastructural problems that exist in a
region and these can be planned against in the full programme. This approach is
also likely to permit all types of water source and supply found in the country
to be represented in the pilot phase, something that may be difficult to achieve
in a single region.
Once the pilot project is complete and modifications made as
required, the surveillance programme proper can start. The implementation of
surveillance is likely to be staged over a number of years and short, medium and
long term plans will have to be drafted.
Short-term plans
The short-term aim for a water surveillance programme should be
to establish it as a perceived key priority of water supply and water resource
management and to create an environment which actively promotes surveillance.
The short-term objectives of national surveillance programmes
should be to achieve routine analysis of critical parameters covering a
representative sample of all water supplies. There are no hard and fast rules
determining this, but a figure of around 30 per cent of all water supplies has
been adopted in some circumstances. If only a proportion of supplies is to be
included initially, the supplies should be spread geographically, encompass
examples of all (or at least the principal) source types and treatment
technologies and should be concentrated on communities with larger populations.
Given that protected groundwater sources tends to have less bacteriological
contamination, it is common to include a greater proportion of surface supplies
in the early stages of surveillance. Supplies where there are known problems
with water quality should be included at this stage to try to establish the
causes, rectify these and prevent their recurrence.
Where chlorinated water supplies are surveyed, from whatever
source, turbidity and chlorine residual within the network should be tested
regularly. As the equipment and consumables required are very cheap and testing
is field based, it is feasible to test frequently and this may help reduce the
number of microbiological samples required.
The number of microbiological samples taken and their frequency
will vary depending on resources and population size, but as far as possible
samples should be taken at least quarterly by the supplier and at least annually
by the surveillance agency. The number of samples taken is largely dependent on
population supplied, time available, analytical resources and type of
distribution network. However, the more samples that are taken, the more
representative the results. Below is a very crude guide for the minimum number
of samples that should be taken:
If water supplies are from a point source, for instance a
borehole or well, not connected to a pipe network, analysis need not be as
regular. However, there should be a minimum of two analyses per year - one wet
season and one dry season - to take into account water level fluctuations and to
assess whether quality varies seasonally.
Sanitary inspections should be carried out regularly by the
supplier or the community on all water supplies and not merely those where
analysis is being carried out. Sanitary inspections may be undertaken by staff
such as systems operators or by trained community members.
Where there is a supply agency responsible for the provision of
drinking-water, the results of the sanitary inspection and any recommendations
for action should be noted and shared with the supply agency. An annual summary
of inspection results should be passed to the surveillance agency which
highlights any actions which have been recommended and the outcome of these.
Where the water supply is community managed, the results of the
sanitary inspections should be used by them to plan improvements to their supply
and an annual summary of the results should be passed to the surveillance
agency. An annual independent sanitary inspection by the surveillance agency
should also be carried out.
Training programmes should be initiated to ensure that staff are
able to carry out surveillance activities and can pass on skills in sanitary
inspection to communities. Staff from both the suppliers and the surveillance
agency are likely to require training, as are any community members involved in
surveillance.
The medium-term aim of surveillance should be to review and
consolidate the programme and expand it to cover a greater proportion of water
supplies and to ensure that adequate standards are established.
One of the medium-term objectives of water surveillance should
be to increase the coverage of the surveillance programme and to make
modifications to the programme as appropriate. The proportion of supplies that
have regular analysis of critical parameters should be increased, for example to
80 per cent. The additional water supplies included in the surveillance
programme should be distributed to reflect population distribution and the
number of groundwater supplies covered increased.
Chlorine residual and turbidity testing in the distribution
network should continue to include all chlorinated water supplies and the
frequency of testing increased. The number of samples taken from the
distribution network for microbiological analysis should be increased and the
supplier should aim to carry out microbiological analysis of samples at least
quarterly and preferably monthly on large supplies. An independent analysis by
the surveillance agency should be carried out at least annually or even more
frequently on large supplies. The analytical range may also be extended to
include other parameters such as total coliforms or other faecal indicator
bacteria.
Lines of communication should be established between supplier,
consumer and surveillance agency and the population should be kept aware of
water quality problems that arise and precautionary actions that they should
adopt.
Quality standards may be revised or if in the initial phase
employed the use of guideline figures for water quality, the second phase may
well include adoption of legally binding water quality standards. Standards or
guidelines for other substances of health importance, for instance nitrate,
should be drafted and analysed for as frequently as feasible.
Sanitary inspections should continue to be carried out monthly
by the supplier at all supplies and independent inspections carried out
at least annually. Larger supplies and a significant number of other supplies
should be inspected quarterly by the surveillance agency.
In addition, codes of practice and construction standards for
plumbers and builders should also be established and supported within the legal
framework. A system for licensing approved craftsmen should be established with
them regularly assessed and if consistently blow acceptable standards, a
mechanism established to revoke their licenses.
An on-going training programme for staff involved in
surveillance should be established and cover analytical techniques, sanitary
inspection techniques and community education. This should include ensuring that
appropriate courses are offered and made accessible for staff with extensive
experience but limited formal qualifications. In-service training in appropriate
topics should be provided and taught through short-courses and 'on-the-job'
training.
The national laboratory network should be increased and
appropriate AQC procedures established to ensure analytical quality is
maintained.
The long-term expansion of the surveillance programme should be
to include all water supplies in the country in the surveillance programme and
to ensure that both the supplier and the surveillance agency undertake regular
sampling and sanitary inspection. The long-term surveillance plan should include
the assessment and revision if necessary of drinking water quality standards and
these should be expanded to cover all substances of health and environmental
importance.
Samples should be taken monthly for microbiological analysis and
in larger supplies this should be expanded to weekly or daily. the surveillance
agency should aim to undertake regular independent analysis. The number of
samples taken from the distribution network for microbiological analysis should
be increased and should be representative of the entire network.
Sanitary inspections should be carried out by the suppliers on a
monthly basis on larger supplies and at least quarterly on smaller supplies with
independent inspections carried out quarterly or bi-annually. In chlorinated
supplies, the supplier should sample for turbidity and chlorine residual at
least weekly and in large supplies daily.
As in each phase of the surveillance programme, there must be
clear lines of communication between supplier, consumer and surveillance agency.
Legislation should be drafted which gives a framework of the steps to be taken
by the supplier to inform the consumers and the surveillance agency when water
quality is sub-standard. This should include time limits within which
contamination must be reported and advice given about precautionary actions that
should be taken by the consumer (for instance boiling). There should also be
time limits imposed within which the surveillance agency should be informed of
any failure to meet standards and proposed action.
Full analytical quality control and assurance procedures should
be established and all laboratories where analyses are undertaken should be part
of analytical quality control and analytical quality assurance programmes. A
national reference centre should be established, possibly supported by a network
of regional centres. There should also be clear guidelines for ensuring the
analytical quality and reliability of results obtained from on-site equipment.
A human resource development strategy should be drafted which
identifies sector training needs and how best training should be provided. This
should include in-service training and establishment if appropriate of further
and higher education courses which will produce appropriately qualified staff.
Monitoring and assessment of microbiological water quality is a
key priority in the water sector which involves water suppliers, surveillance
agencies and communities. It is a health-based activity and should include
elements of hazard identification and risk assessment, through the use of
systematic sanitary inspection, as a means of improving water supply quality.
Analysis of indicator bacteria should be supported by turbidity
and chlorine residual testing and these elements, combined with sanitary
inspection, should be used to define the sanitary status of the water supply.
Monitoring is best implemented through a series of stages to
ensure that any problems in implementation are identified and rectified during
the early stages of programme development. Initial pilot projects should test
the methodology to be used and this should then be progressively implemented on
a nation-wide basis.
Anon. Guidelines for Drinking Water Quality. Volume 3
(2nd Edition). WHO, Geneva 1997
Bartram, J. (1996) Optimising the Monitoring and Assessment
of Rural Water Supplies. PhD Thesis, University of Surrey.
Bartram, J. and Balance, R. (1996) Water Quality
Monitoring. Chapman and Hall, London
Howard, G. Developing Drinking Water Quality Monitoring in
Zimbabwe, ODA Project Reports 2-7, National Water Quality Analysis
Laboratory
Howard, G. (1997) Water Quality Monitoring: Key Issues and
Approaches. Waterlines (in press)
Lloyd, B. and Helmer, R. (1991) Surveillance of Drinking
Water Quality in Rural Areas. Longmans' London
Lloyd, B., Bartram, J., Rojas, R., Pardon, M., Wheeler, D. and
Wedgwood, K. (1991) Surveillance and Improvement of Peruvian Drinking Water
Supplies. ODA. Guildford.
|
Section |
Key points |
OHP |
|
Introduction |
· routine monitoring and
assessment of microbiological quality is the key priority for suppliers and
surveillance agencies |
1,2,3 |
|
· microbiological contamination
represents an acute risk to health and the health-based monitoring of water
quality is crucial |
|
|
· in order to safeguard health,
other parameters of water supply quality should also be monitored including
quantity, continuity, coverage and cost as well as water quality |
|
|
· the water suppliers should
monitor compliance with national standards and regulations within their area of
service |
|
|
· the surveillance agency should
monitor water supply to all the population and identify unserved or under-served
areas and promote improvements |
|
|
· hazard identification and risk
assessment should be included in sanitary inspection and should be systematic
and quantifiable |
|
|
· source protection and minimum
treatment requirements are also key complementary activities |
|
|
Planning monitoring and assessment |
· monitoring and assessment only
effective when well planned and implemented |
4,5,6 |
|
· monitoring of microbiological
quality of water supplies must have key health related objectives which aim to
maintain or improve water supply quality |
|
|
· surveillance is the
combination of sanitary inspection and water quality analysis and is essentially
health-based water supply monitoring |
|
|
· monitoring and surveillance
activities should be well planned if there are to be effective |
|
|
· it is important to develop
monitoring programmes in stages to allow refinement of the programme with time
|
|
|
· this is particularly true
where monitoring has not previously existed |
|
|
· it is important to use pilot
projects to test the approach proposed before any large scale implementation is
undertaken |
|
|
· the most sustainable approach
to monitoring is one where short, medium and long-term plans are prepared from
the outset |
|
|
· initial priority should be
given to those supplies which serve large populations |
|
|
· all monitoring should be
linked to improvements in water supply through identifying of appropriate
preventative and remedial actions |
|
|
Analytical ranges |
· this has led to the concept of
the critical parameters by WHO |
7,8 |
|
· these are: thermotolerant
coliforms, chlorine residual, turbidity and pH |
|
|
· when developing monitoring
initially concentrate on the critical parameters |
|
|
· only expand the analytical
range once full coverage of supplies with critical parameters has been achieved
|
|
|
· selection of new parameters
should be these which either directly affect health or cause water supply
rejection by consumers |
|
|
Design of networks |
· the design of sampling
networks should be well planned and done on the basis of a detailed knowledge of
the water supply |
9,10,11 |
|
· sample sites must be
representative of the: source; treatment plant; storage tank; household
connection; and point of use. |
|
|
· especially in early stages, it
is important to take samples from points where it is known or suspected that
problems exist |
|
|
· ensure samples are taken from
main lines, remote branches and dead ends |
|
|
· use supply zones in large
supplies |
|
|
· sample sites may be classified
in a number of ways |
|
|
· fixed samples are useful to
pick up long term water quality variation and thus indicate whether a source or
treatment plant is sustainable |
|
|
· variable sites will pick up
local and transient problems with water quality |
|
|
Sampling frequencies |
· minimum sampling frequencies
have been defined by WHO for piped and point water sources |
12,13 |
|
· where possible, sampling
frequency should be increased |
|
|
· it is often better to develop
a few well functioning monitoring networks which actively contribute to water
supply improvement to the basis for later development |
|
|
· costs may be reduced in piped
water supply by focusing monitoring on chlorine residual and turbidity |
|
|
· where chlorine residual is
<5TU and free chlorine residual>0.2mg/l it is very unlikely that faecal
coliforms will be present and a test may not be necessary |
|
|
· if this approach is adopted,
some random samples for faecal coliform analysis should still be taken |
|
|
Linking monitoring to improvement |
· water quality monitoring
should be linked to improvement in water supply by identifying remedial and
preventative actions |
14 |
|
· when planning interventions,
it is likely to be necessary to prioritise supplies and actions on the basis of
greatest risk |
|
|
· thus systems which classify
water quality and sanitary risk in broad quality groups are useful to identify
supplies which present the greatest risk to health |
|
|
· on larger scales (including
national) water supplies can be ranked on the basis of greatest risk and these
can be prioritised for action |
|
'...the keeping of a careful watch at all times, from the
public health point of view, over the safety and acceptability of drinking-water
supplies'
The expansion of the range of parameters must be progressive
and allow priorities to be identified
Samples must be analysed within 6 hours of taking the sample
form a water supply. In areas where transport or roads are poor and this is not
possible, portable water testing kits can be used
