The Significance of Faecal Indicators in Water

A Global Perspective

By David Kay, Colin Fricker

The Royal Society of Chemistry

Copyright © 2012 The Royal Society of Chemistry
All rights reserved.
ISBN: 978-1-84973-169-0

Contents

Faecal Indicators and Pathogens: Expanding Opportunities for the Microbiology Community D. Kay, J. Crowther, C. Davies, A. Edwards, L. Fewtrell, C. Francis, C. Kay, A. McDonald, C. Stapleton, J. Watkins and M. Wyer, 1,
Faecal Indicators in Drinking Water – Is It Time To Move On? Margaret McGuinness, 18,
Improving Bacteriological Water Quality Compliance of Drinking Water Kate Ellis, Bernadette Ryan, Michael R. Templeton and Catherine A. Biggs, 27,
A Waterborne Outbreak Caused by a Severe Faecal Contamination of Distribution Network: Nokia Case I.T. Miettinen, O. Lepistö, T. Pitkänen, M Kuusi, L. Maunula, J Laine, J Ikonen and M-L. Hänninen, 34,
Occurrence and Growth of Coliform Bacteria in Drinking Water Distribution Systems B. Hambsch, A. Korth and H. Petzoldt, 38,
Predictive Model of Chlorine Dynamics in Water D. Kim, C. T. Le, V.V. Ha, D. Frauchiger, A. Doyen and N. Garg, 47,
Validity of Composite Sampling for Enumerating E. coli from Recreational Waters by Molecular Methods (QPCR) J. L. Kinzelman and M. Leittl, 52,
Estimating 95th Percentiles from Microbial Sampling: A Novel Approach to Standardising their Application to Recreational Waters R.S.W. Lugg, A. Cook and B. Devine, 62,
Comparison of Rapid Methods for Active Bathing Water Quality Monitoring A. Henry, G. Scherpereel, R.S. Brown, J. Baudart, P. Servais and N. Charni Ben Tabassi, 72,
Do Biofilms Developed in the River Bed Serve as Sources for Bacterial Indicators? H. Hirotani and M. Yoshino, 84,
Cost-Effective Applications of Human and Animal Viruses as Microbial Source- Tracking Tools in Surface Waters and Groundwater Silvia Bofill-Mas, Byron Calgua, Jesus Rodriguez-Manzano, Ayalkibet Hundesa, Anna Carratala, Marta Rusiñol, Laura Guerrero and Rosina Girones, 90,
Distinguishing Possum and Human Faeces using Faecal Sterol Analysis B.J. Gilpin, M Devane, D. Wood and A. Chappell, 102,
Rapid Confirmation of Presumptive Clostridium perfringens Colonies by Polymerase-Chain Reaction R. Múrtula, E. Soria, M A. Yáñez and V. Catalán, 107,
An Evaluation of Bacterial Source Tracking of Faecal Bathing Water Pollution in The Kingsbridge Estuary, UK K. R. Hussein, G. Bradleyand G. Glegg, 114,
Detection and Quantification of E. coli and Coliform Bacteria iIn Water Samples with a New Method Based on Fluorescence In Situ Hybridisation Michael Hügler, Karin Böckle, Ingrid Eberhagen, Karin Thelen, Claudia Beimfohr and Beate Hambsch, 123,
A Review of Potential Culture Independent Biological Detection Methods for the Water Industry - Challenges of Moving Beyond the Research Lab Q.I. Sheikh, J.B. Boxall and C.A. Biggs, 131,
Detection of Faecal Contamination in the Drinking Water of Small Community Water Supply Plants in Finland Tarja Pitkänen, Helvi Heinonen-Tanski, Marja-Liisa Hänninen and Ilkka T. Miettinen, 145,
Monitoring and Assessment in a Water Treatment Plant using Bankfiltrated Raw Water in Duesseldorf, Germany Vera Schumacher, Timo Binder, Hans-Peter Rohns and Christoph Wagner, 151,
Microbiology of Sustainable Water Systems; Rainwater Harvesting – A UK Perspective L. Fewtrell, C. Davies, C. Francis, H. Jones, J. Watkins and D. Kay, 167,
Subject Index, 178,

CHAPTER 1

FAECAL INDICATORS AND PATHOGENS: EXPANDING OPPORTUNITIES FOR THE MICROBIOLOGY COMMUNITY

D. Kay, J. Crowther, C. Davies, A. Edwards, L. Fewtrell, C. Francis, C. Kay, A. McDonald, C. Stapleton, J. Watkins, M. Wyer.

1 INTRODUCTION

Demands for a high quality science evidence-base and policy support by regulators, government and operational managers is increasing rapidly in the field of faecal indicators and pathogens. This dynamic is driven by emerging regulatory paradigms in North America, Europe and Austral-Asia underpinned by international science led organisations such as the WHO (the World Health Organisation). Central to this development is the requirement to manage microbial risks in an integrated manner at the catchment scale. This implies quantification of diverse pollutant sources with very different flux quantity and timing. The complex spatial and temporal input pattern of microbial flux then undergoes complex processes causing attenuation, and possibly regrowth, in many catchment compartments such as the land surface, soil systems, groundwater, river waters and sediments and, thence, in estuarine and near-shore systems. Notwithstanding this complexity, which has received very little research attention when compared to: for example, the nutrient parameters, regulators in North America and Europe are required to develop a catchment scale Total Maximum Daily Load (TMDL-USA) estimate or a Programme of Measures (POM-EU) respectively to ensure resource use locations in rivers, lakes and/or near-shore waters comply with microbial standards. It is these legislative drivers: namely the United States Clean Water Act (USCWA) and European Union Water Framework Directive (EUWFD) which have produced immediate and increasing pressure for high quality science policy support and research within the science community focusing on environmental microbiology.

This area is central to managing water resources at the catchment scale. The best recent evidence of this pivotal position is seen in the summary data produced by USEPA which provide a real-time summary of the reasons for water quality impairments (non-compliance in EU terminology) (Figure 1) and the numbers of resultant TMDLs completed (Figure 2). Nearly all these impairments are due to non-compliance of recreational and shellfish growing waters with faecal coliform regulatory standards designed to protect public health. The US experience offers some 20 years of catchment-scale water quality regulation prior to the implementation of parallel European Union legislation in the form of the EUWFD. The emerging US evidence-base places microbial pollution at the fore-front of water quality concerns and similar prioritisation is likely in Europe where standards also derive largely from WHO Guidelines and publications covering drinking, recreational and shellfish harvesting waters.

The emergence of this policy agenda is placing new challenges on managers of catchment activities from the farming community through to urban waste water treatment authorities. For both groups, microbial pollution is a growing concern. For the livestock farming community, the realisation that livestock contributions of faecal indicators to resource use sites is, first, highly episodic and, second, can exceed catchment-scale human sewage-derived fluxes has been challenging. For the sewage undertakers, the uncomfortable realisation that their traditional suite of regulatory parameters: namely biochemical oxygen demand, suspended sediments and ammoniacal nitrogen; do not provide an indication of microbial flux and certainly do not ensure compliance with microbial standards despite being termed the 'sanitary parameters' by the engineering profession.

2 CATCHMENT-SCALE MICROBIAL FLUX

Kay et al. have defined four principal sources of microbial loadings to rivers and coastal waters, namely:

1. human sewage disposal systems which discharge via pipes known as 'point-source' discharges. These can be further split into:

a. 'continuous discharges' of sewage effluent following various levels of treatment from simple screening of solids (e.g. rags and plastics) to full biological treatment and disinfection. The receiving waters can include rivers, lakes or coastal waters through outfall pipes; and

b. 'intermittent discharges' which occur when the sewerage system is receiving urban surface water drainage after rainfall. This can increases the flow beyond the capacity of the sewer, thus, producing short-term discharges of untreated, but diluted, raw sewage to rivers, lakes and coastal waters. This is normally discharged through:

i. 'combined sewer overflows' in the sewer line itself,

ii. 'storm tank overflows', generally sited just upstream of waste water treatment works, and

iii. 'pumping station overflows', which operate when a pumping station on the sewer line is overwhelmed because of rainfall-supplemented flow volume. These overflows may also operate during dry weather conditions in response to emergency conditions such as pumping station failure or sewer blockages.

2. livestock-derived microbial fluxes deriving from a range of catchment sources commonly termed 'diffuse-source pollution'. The pattern of this loading is site specific but includes:

a. voiding of faeces to land (and, in some, cases to water) by livestock at;

i. in-field feeding and drinking points;

ii. gates between fields used for daily stock movements, notably for dairy farming operations where stock may be moved between milking facilities and fields, particularly in the summer period;

iii. river crossing points which can be in the form of simple fords or bridges; and

iv. stream bank drinking points, where faeces may be voided directly into the watercourse or onto land which has been highly trampled and 'puddled/poached' by livestock, creating a mobile and available faecal store.

b. Faeces directly voided onto farm yards and other hardstanding areas which stock use during farming activities such as milking. Some of this loading will commonly be scraped and delivered to a dedicated manure or slurry store (see 2c below) but residues remaining after normal yard cleaning will generally be washed from the impervious farm hardstanding area, often entering small drainage ditches and watercourses, particularly where the farm hardstandings have good hydrological connectivity to the catchment drainage network.

c. Livestock manure and slurry, which accumulates from housed livestock, mainly during the winter period in temperate climates, and is commonly stored in slurry tanks or lagoons. This is spread onto fields as a fertilizer and can be timed to maximise feed crop growth. However, sometimes the imperative to spread slurry is driven by the operational requirement to increase available storage capacity after periods of high rainfall, which can encourage inappropriate spreading at high risk periods. Where slurry is applied to fields with good hydrological connectivity to adjacent streams, the microbial loading to the stream environment can be very high, with associated problems of high biochemical oxygen demand from organic-rich material input and high nutrient loadings.

3. Wildlife populations in catchment systems are another potential source of microbial pathogen loading. Generally, microbial loadings from wildlife in intensively farmed catchments are low compared to the livestock and/or human population inputs. However, this area has not received intensive research attention and some surprising findings have been reported, suggesting that roof runoff, commonly perceived to be a clean and sustainable resource, can be highly contaminated with faecal indicator organisms (FIOs), such as intestinal enterococci from avian wildlife sources.

4. Urban diffuse microbial pollution presents a further source. This comprises street drainage and associated drain flow, generally separate from the foul sewerage system, which may be contaminated with faecal matter deposited onto urban roads, pavements and roofs. Canine and feline pets certainly contribute to this loading, as do avian and rodent urban wildlife populations. This is a difficult loading to quantify because many urban areas may also have a number of inappropriate and 'informal' connections of foul sewage from individual properties into the non-foul surface water drainage systems. Links between the foul sewer and surface water drainage networks may also result from ageing and poorly maintained infrastructure. Thus, quantification of the true quality of urban diffuse microbial fluxes is problematical because identification of sites which can be guaranteed free of any such misconnections in the urban upstream infrastructure is extremely difficult.

Operational management questions required to disentangle this complex web of catchment flux and deliver health risk management through regulation of microbial parameters centres on a series of current key science agendas and questions, namely:

i. Can we quantify microbial flux given the complex catchment source patterns evident and the extreme temporal variability characteristic of microbial flux which is often driven by rainfall events and/or infrastructure breakdown?

ii. Can catchment-scale modelling tools be developed to inform (i) and (iii) and also guide complex management decisions needed to deliver cost effective attenuation of microbial flux to improve water quality compliance at the catchment scale, often involving difficult trade-offs between different users and interests?

iii. Can we determine the source species of faecal indicators at the measurement, or compliance, location using source tracking tools now available or under development and can this approach quantify the relative contribution of, for example, human and ruminant microbial contributions?

iv. Can near-real-time analytical protocols be developed to shorten the times associated with microbial culture methods and, thus, deliver operationally appropriate, and timely, information to managers seeking to limit and control health risk?

v. Can real-time prediction of microbial pollution episodes replace and/or supplement traditional sampling of faecal indicators at resource use sites?

This chapter presents evidence for UK empirical studies relevant to questions (i) and (ii). Questions (iii), (iv) and (v) are addressed subsequent chapters.

3 QUANTITATIVE MICROBIAL SOURCE APPORTIONMENT

A number of recent studies have reported catchment-scale faecal indicator (coliforms and/or enterococci) flux and sought to quantify multiple source contributions. In the United Kingdom, compliance with revised criteria for bathing waters published by the EU, which are based on WHO health-based guidelines, has driven a series of such investigations identified in Figure 3.

These studies have often focused on a key period, such as the bathing season, and the key challenge has been to design a field data acquisition protocol able to characterise the very short term changes in faecal indicator concentrations caused by episodic changes in concentration, caused by rainfall-driven events. This is challenging, particularly where aseptic sample collection is compromised by the use of automated sampling systems which are often susceptible to carry-over problems between discrete sampling events. The approach adopted in these UK studies has been station a field team on site for the project duration to ensure aseptic 'hand' collection of opportunistic event-based samples during high flow events as well as routinely planned base flow samples at all catchment outlets and at key infra-structure locations. Together with flow measurement of streams and key infrastructure sites this allows construction of flux pie charts (Figure 4) and temporal contribution plots (Figure 5) which illustrate the relative contribution of point and diffuse source fluxes on an hourly basis through the study periods or bathing season. Presentation tools as illustrated in Figure 5 provide key management information describing the flux contributions during the principal compliance stress periods: i.e. during episodic rainfall events which are a 'normal' weather-driven characteristic of many bathing waters and shellfish harvesting sites world-wide.

Studies such as the Etive investigation are complex and expensive to deliver. This has led to attempts to provide simple modelling strategies designed to use remote sensing tools to predict faecal indicator flux from infrastructure and diffuse sources. The principal infrastructure 'predictors' are the treatment type and population equivalent served by the treatment plants within the catchment and the drivers of diffuse pollution are the land use and land area under each land use. Published data on the microbiological quality of sewage effluents under different treatment regimes (Table 1) and catchment export coefficients for faecal indicators for common UK land uses types provide the base data for this type of desk-study which has been used to derive estimates of agricultural microbial source apportionment for key UK catchments draining to the coast (Figure 6).

Although empirically-based, these estimates remain approximations when applied to areas where no dedicated sampling programme has been undertaken. The experience of the studies identified in Figure 3 strongly suggests that intermittent flux from the sewerage infrastructure in the form of combined sewage overflows and storm tank overflows is a remaining area of considerable uncertainty, at least in the UK. These are rarely measured and recorded in real-time and quantitative estimates of flux from such discharges are often dependent on sewer modelling investigations which may not provide accurate estimates of flux timing and volume derived from specific overflow events.

These basic 'black-box' modelling tools have some operational utility but do not easily facilitate scenario modelling to determine the likely implications of alternative management intervention strategies. Ideally, this requires a more process-based, or 'white-box', modelling approach. However, catchment microbial science lags well behind modelling of other parameters such as dissolved oxygen, sediments and the nutrient parameters and the parameterisation of white box microbial models is in its infancy as a science agenda. Thus, empirically based parameterisation data and relationships are not available credibly to populate a process-based modelling approach at this time although progress is accelerating in this area and significant advances are underway world-wide.

4 MICROBIAL FLUX ATTENUATION AND CONTROL

Notwithstanding the lack of fully parameterised, and process-based, modelling systems, the regulatory and operational communities are faced with the challenge of achieving compliance at water use sites against microbial standards using the coliform and enterococci indicator bacteria. Many studies world-wide have addressed this problem with catchment-scale and plot scale investigations which were recently reviewed by Kay et al. They considered six broad categories of Best Management Practice (BMPs), or intervention used to reduce microbial flux to catchment outlets, namely: ponds; vegetated treatment areas; integrated constructed wetlands; woodchip corrals; vegetated riparian buffer strips; and finally in-stream ponds. Figure 7 presents the median attenuations observed and the ranges reported in the literature available.

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