Related Images
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Shingle Tracer -
Seditrace Laser Detection System -
Bacillus globigii Colonies -
Faecal Streptococci Speciation -
Dye Deployment
Tracer services
Viral Tracers
Viral tracers can be used where a tracer is required to mimic bacteria survival or virus characteristics. The Serratia marscescens bacteriophage is used routinely as a tracer for investigating dispersion of bacteria/viruses over short timescales.
In contrast to spores and microspheres, the bacteriophage tracer is sensitive to environmental conditions such as sunlight, temperature and pH and therefore dies off at a comparable rate to viruses being traced. The tracer is ideal for application in survival trials and T90 determinations.
Microbial Biotyping
Emu provides additional testing services in support of tracer investigations to determine the nature and source of faecal pollution. Intestinal enterococci bacteria (part of the faecal streptococci group of bacteria) exist in the intestines of both humans and animals. However, certain species associated with animals, e.g. Streptococcus bovis, are found in cattle, but not in humans.
Emu Laboratories carry out speciation testing of faecal streptococci, isolated from water or sediment samples, to assist in discriminating human and non-human pollution sources.
Bacterial Tracers
Emu currently uses two environmental tracers to investigate bacterial movement and contamination sources:
- Bacillus globigii spores (BioTrace)
- Fluorescent microspheres
Both types of tracer are of comparable size to coliform bacteria, are highly resistant to environmental conditions and do not exist naturally in the environment.
Applications include:
- Tracking the movement of sewage from outfalls discharging into the sea or inland water courses
- Optimising the location of new submarine sewage outfalls
- Evaluating the potential impact of outfalls on bathing waters and sensitive areas
- Identifying point and diffuse pollution sources - microbial source tracking
- Determining transit times in rivers
- Establishing residence/retention times
- Analysing mixing efficiencies
- Leakage investigations
Fluorescent Microspheres
An alternative to the microbial spores is Emu’s Fluorescent Microsphere Tracer. Available in three different colours (red, blue and green), this microscopic tracer provides the opportunity to investigate multiple pollution sources simultaneously.
Emu has worked extensively with Water Plcs and regulators to apply the tracer technology in investigating bathing water pollution sources. Following release of the tracer and subsequent representative sampling, water samples are analysed for the presence of fluorescent spheres using epifluorescent microscopy. Both of Emu’s bacterial tracer systems are non-pathogenic to humans and animals, providing a “low profile” tracer system.
Dye Tracing Dilution characteristic studies
- Determination of dilution and dispersion characteristics of a water body
- Location of fractures in subsea pipelines
- Time of travel measurement of liquids through pipelines
Dye Deployment
Emu has considerable experience in the application of dye tracing for dilution and dispersion investigations. Surveys have been undertaken worldwide to assess dispersion in receiving waters for locating new submarine outfalls.
Emu’s dye tracing service is supported by a team of experienced Oceanographers and a comprehensive equipment pool. This allows tracer surveys to be combined with a range of other measurements including the monitoring of waves, currents and suspended sediment concentrations.
RB fluorescent silt tracers
Due to the small size of the particles involved, silt tracing is notoriously difficult. Emu is currently leading 3 research and development programs with the objective of improving silt tracing technology. Early work has yielded two prototype fluorescent silt tracers: one can be used for representing low density particles and the other for representing siliceous material.
Detection of the prototype tracers is achieved using SediTraceTM. As for sand tracing, the data yielded by SediTraceTM can be used to help measure sediment transport velocities and provide volumetric transport rates. Likewise, core sampling of the mobile tracer is undertaken in order to provide information on the thickness of moving sediment. Such data are of particular use for the calculation of pollutant residence times.
Environmental Tracing - Sand Tracers
Emu has developed its own unique suite of sand tracers; these mimic the detailed behaviour of natural sediments and yet are extremely cost effective. Summary details for three of the sand tracers available are presented in the following table.
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Specific Gravity
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Particle Size Range
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Resistance to Abrasion
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Number of Colours Available
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Cost
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Emu AC Tracer
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2.61
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63-2000 microns
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High
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5
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Moderate / Low
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Emu SAG Tracer
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2.57
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63-2000 microns
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High – Very High
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1
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High
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Emu RB Tracer
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1.15
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1-100 microns
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Moderate – Low
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5
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Moderate / Low
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Detection of the distribution of a tracer material at the seabed is achieved using Emu's towed laser system SediTraceTM and core samples can be taken in order to ascertain the thickness of the moving sediment layer if it is necessary to calculate sediment transport rates. In littoral environments, sampling of the exposed seabed at low tide can be undertaken in order to measure tracer distributions. In addition to tracer studies being used to measure the direction and rate of sediment transport (often to calibrate models), useful information regarding the thickness of moving sediment (and hence particle/pollutant residence times) can also be provided.
Shingle Tracers
A shingle tracer in use in a littoral environment, Emu uses magnetic techniques for shingle tracing in the littoral zone. The approach is tried and tested; it has been routinely used for the calibration of empirical sediment transport rate models, a field in which Emu has considerable experience. The material from which the shingle tracers are constructed possesses physical characteristics which match those of flint/chart exceptionally well, and yet it is versatile in terms of the size and shape of indigenous sediment it can represent.
Buried tracers can be recovered to depths of 35cm allowing transport rates to be measured effectively under a range of hydrodynamic conditions. Research work is underway with the objective of advancing shingle tracer technology; a priority is to retain the excellent reliability and value for money presently available. Emu’s expertise can, and has, been applied to develop bespoke tracers for clients with specialist requirements.