Envirotrace – Identifying the source of the problem

EnviroGene's services and DNA technology are helping to overcome the issues posed when dealing with water pollution in the face of increasing regulatory-driven demand to cut direct costs, prevent unnecessary spending and achieve performance targets.

Background to the Problem

Source tracing is a technique that uses tracers to track the movement of water and to determine the relative contribution of various sources on its composition at specific points.  For example, a tracer might be used to determine if faecal pollution from an effluent discharge pipe is passing out to sea or returning to the coast and thereby impacting water quality on the nearby beaches.  The ability to map connectivity pathways in water catchments is limited by the number of unique tracer formulations available.  EnviroGene has developed a DNA based environmental tracer system (EnviroTrace) allowing an unlimited number of tracers to be released simultaneously.  The unique tracer batches can be differentiated and quantified using quantitative molecular technology, thereby permitting the proportional contribution from each potential source of pollution to be determined.  This type of investigation can help in cutting direct costs, prevent unnecessary spending & achieve performance targets, set by regulatory driven demands.

The Environment Agency (EA) has responsibility for improvements in bathing water quality and will monitor a £4.3bn investment from water companies to improve bathing water quality between 2010 and 2015 (www.environment-agency.gov.uk).  The targeting of capital expenditure when interventions are required is obviously crucial.  EnviroGene's has a two pronged approach to identifying the sources of faecal pollution in catchments to ensure interventions are targeted correctly as is illustrated  in the hypothetical example below.

The Figure shows an estuary system and a beach that has failed a compliance test performed by a regulatory authority for bacteria associated with faecal contamination.  Initial analysis of the system suggests that there are 6 possible sources, 2 animal and 4 human.  Microbial source typing (MST) is used to determine whether the origin of the pollution is animal or human. This is done by looking for specific DNA markers that can distinguish between human and non-human sources.  If it turns out pollution is due to human source, there is no analytical technique that can further distinguish between the four human sources, so an indirect water tracing is required to determine source-pathway-receptor relationships.  Only EnviroTrace can track multiple sources simultaneously.  EnviroTrace tracers are applied at each source and samples are taken at regular intervals from the bathing waters and at other points along the beach.  These samples are analysed by quantitative molecular technology to determine the relative proportions of the different tracers. 

What is EnviroTrace?

EnviroTrace is a biodegradable nanoparticle (about 80nm in diameter) comprising identifier DNA encapsulated in a biocompatible polymer co-developed with the University of Nottingham and the University of Milan. The polymer packaging gives the particles higher stability than using naked DNA.

Benefits of using EnviroTrace

• Unlimited number of unique tracersavailable
• Track all sourcessimultaneously under same environmental conditions
• Very high sensitivity (tolerates 9-10 orders of magnitude dilution)
• No background detection
• Easy to get approval or no approvalrequired
• Non-toxic,biodegradable

Case Study

EnviroGene has performed a case study to look at the impact of various waste water treatment works (WWTW) discharging into the Clwyd and Elwy River catchments on bathing water quality at Rhyl (North Wales).  The study was undertaken in two phases (more details can be found on the website: www.envirogene.co.uk).  Six tracers were released into each of the outfalls from the nominated WWTW.  Rhodamine WT was released simultaneously with one of the tracers to compare performance of the DNA tracer system with a conventional dye tracer.  Both tracers showed very similar times of travel and degree of attenuation during transport down the river.  All 6 tracers were detected at the sampling point, however the travel times were longer than predicted from a catchment model.  Four tracers were used in the 2^nd phase.  The tracer study conclusively demonstrated connectivity between the Clwyd and the bathing beach at Rhyl. 

The case study demonstrated that the DNA tracers behaved in a similar manner to the standard dye tracers commonly used.  The six DNA tracers were used simultaneously permitting the flow from six different addition points to be performed under the same environmental conditions. This would not have been possible using Rhodamine.  The results also demonstrated that the DNA tracers acted as conservative tracers during the course of the study.

Other applications

The DNA tracers were made especially for use in surface waters and were designed to be environmentally non-persistent.  The half-life is around 16 days.  Tracer technologies are being developed for applications in other fields:

• Groundwater tracing studies
• Oil field reservoir tracers

For these applications a different formulation needs to be developed.  EnviroGene is preparing to launch a groundwater version later this summer; this will be an extension of the DNA tracer system into a variant that will be stable for much longer periods of time.  EnviroGene is also looking into producing an oil tracer, which will help to determine how fluid flows through the reservoirs.

Other applications for EnviroTrace are:

• Sewer leakage studies
• Groundwater flow
• Potable water connectivity studies
• Generation, amendment and validation of environmental flow models