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2.2.02 AQUASens analysis system – a fast and mobile method for detecting water impurities

Microbiological tests of water samples have always taken a lot of time and effort. A new analysis system, the development of which was funded by the Federal Ministry of Education and Research, could provide a solution: it is fast, mobile and accurate – and good value to boot. There are many different ways this system could be used by industries and local authorities.

Before now, tracking water impurities through microorganisms has required a specialised lab, where germs have had to be multiplied on a culture medium. While coliform (faecal) germs can be detected within a single day – as there are proven procedures in place – tests for most other bacteria still require a great deal more work and often take more than a week. However, if the water is potentially contaminated with microbes, those in charge need fast, reliable information on the degree of contamination and the potential threats.

Combined expertise

The Federal Ministry of Education and Research funded a project in order to provide a solution: “AquaSENS – Detection of micro-organisms in water with CMOS-based sensors”. Companies and science institutes combined their expertise to develop a mobile analysis system that can quickly detect micro-organisms and germs in water – without the need for timely and costly cultivations in a lab. The parties involved in the project were Siemens AG, inge watertechnologies AG, Friz Biochem Gesellschaft für Bioanalytik mbH, the Institute of Hydrochemistry (IWC) at TU Munich, the IWW Water Centre (Rheinisch-Westfälisches Institut für Wasserforschung) and the Water Technology Centre Karlsruhe (TZW). Tasks within the project:

  • Set up a compact, fully automated membrane filtration system for concentrating germs (from 10 litres of water into an eluate volume of 50 millilitres).
  • Develop two sample preparation procedures on the basis of immunomagnetic separation and affinity chromatography for further concentration and transfer of germs in a 1 millilitre measurement buffer.
  • Develop digital read-out biochips with built-in detection and analysis electronics.
  • Develop and produce the compact and user-friendly read-out device for the biochips.

Small biochip, big performance: a sensor quickly detects micro-organisms in the drinking water.

Small biochip, big performance: a sensor quickly detects micro-organisms in the drinking water.
Small biochip, big performance: a sensor quickly detects micro-organisms in the drinking water.

The AquaSENS project was able to complete all tasks set successfully: the semi-automatic device designed detected both small molecules (such as hormones, antibiotics and pesticides) and much larger bacteria: by means of an immunological test using a tiny water sample. This detection is based on the concept of the immune system: the ability of antibodies to identify foreign substances from characteristic constituents – antigens.

Biochips developed

This approach uses a biochip with a fully integrated CMOS (Complementary Metal Oxide Semiconductor). The small biochemical sensor and the associated read-out electronics are ideal for use in portable, compact and economical analysis systems. They are particularly advantageous for situations involving many different germs in a single measurement process alongside antibody-antigen interactions or the detection of specific DNA segments. The biochip and biochemical detection procedures have been developed for both of these principles.

The mobile reader provides a read-out for water impurity results

The mobile reader provides a read-out for water impurity results
The mobile reader provides a read-out for water impurity results

Because harmful germs such as legionella, salmonella and coli bacteria are usually only present in water in low concentrations and the biochips use just tiny samples of 100 microlitres, it is necessary to augment the germs being sought first. The project partners established the system required to do this by coupling a membrane filtration system with an “immunomagnetic separation column”.

The result: coli bacteria could be detected within just 90 minutes. The biochip detection limit for E.coli bacteria was determined at 2,000 germs per millilitre of sample concentrate, with a measuring time of 30 minutes. The analysis system can therefore detect bacteria within two hours.

Multiple uses available

As well as being used for the quality assurance of drinking water supplies, the analysis system could also be extremely useful for samples of process water, ultra-pure water, groundwater and surface water; tests are still underway to determine whether and how this is possible.

AQUASens could be used in public buildings and hospitals to test the process water in the sewage system or to test for harmful substances in the hot water system. The new analysis system would also be useful in the food and pharmaceutical industries, which require ultra-pure water for production.

It may even be suitable for measuring sewage sludge or for process monitoring in biotechnological fermenter. First the relevant micro-organisms would be determined, then the corresponding assays developed. The crucial thing here is to identify and produce suitable antibodies first, as they are not currently available for all use cases.

Siemens AG
Corporate Technology

Dr. Daniel Sickert
Otto-Hahn-Ring 6
81739 Munich, Germany
Tel.: +49(0) 89/63 64 50 89
Fax: +49(0) 89/63 64 85 55
E-mail: daniel.sickert@siemens.com
Internet: www.siemens.com
Funding reference: 02WU0862 - 0867
Ressource Wasser
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