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2.5.03 Nitrate reduction in Iran – knowledge export improves drinking water quality

Across the globe, agricultural deposition and untreated household wastewater are causing high nitrate concentrations in the groundwater. Without appropriate treatment, the resulting drinking water can be harmful to health. To reduce this risk for the inhabitants of the Iranian city Mashhad, a German- Iranian project has tested four different methods for removing nitrate from groundwater. The results will help to decide whether and with which technology drinking water treatment plants will be built in Iran in the future.

Nitrate is a nitrogen compound, low concentrations of which are naturally contained in most water sources. However, for many years now nitrate concentrations have been on the rise in numerous regions across the globe – a fact that is frequently attributed to nitrogen depositions from the agricultural sector. Groundwater is also affected by untreated household wastewater seeping into the ground. When drinking water is sourced from nitrate-containing groundwater – without sufficient treatment – the nitrate content remains in the end product. Excessive nitrate concentrations are damaging to health.

Significantly raised nitrate levels

With a population of over two million, Mashhad is Iran’s second largest city and is located in an arid zone in the north-east of the country. Untreated groundwater accounts for around 85% of the city’s water supply. The summer months in particular are characterised by severe water shortages. Over the past few years, the nitrate concentration in many of Mashhad’s wells has risen significantly – up to values of 150 mg/l (in some cases even exceeding 250 mg/l). By way of comparison: the guide value stipulated by the World Health Organisation (WHO) is 50 milligrams of nitrate per litre of drinking water. These high values are likely to be caused by untreated domestic wastewater seeping into the ground, thus causing high nitrogen deposition in the aquifer. Although the wastewater situation in Mashhad has greatly improved in recent years, the nitrate concentrations in the water resources are unlikely to diminish in the short or medium term.

To supply the population with low-nitrate drinking water in the future, the Iranian Ministry of Energy and the BMBF had agreed a joint venture in 2002; the project was entitled “Demonstration of different high-performance procedures developed in Germany for the removal of nitrate from drinking water and their adaptation to the treatment of groundwater with high concentrations of sodium nitrate and other salts using the example of drinking water purification in Mashhad, Iran”. The parties involved in the project were the IWW Water Centre (Rheinisch-Westfälisches Institut für Wasserforschung), VA TECH Wabag Deutschland GmbH, Forschungszentrum Karlsruhe (Karlsruhe Research Centre, now part of the Karlsruhe Institute of Technology (KIT)), the WETECH – Institute for Water and Environmental Protection Technology as well as the local water supplier Mashhad Water & Wastewater.

Erection of test systems on the grounds of the well pump station in Mashhadd

Erection of test systems on the grounds of the well pump station in Mashhad
Erection of test systems on the grounds of the well pump station in Mashhadd

Combined processes

The aim of the project was the first ever parallel application of four different methods for removing nitrate from drinking water; the processes employed were ion exchange, reverse osmosis, electrodialysis and biological denitrification. As these procedures were developed in Germany and had never been used with such heavily polluted groundwater, they needed to be adapted to the specific conditions in Iran – not least to ensure reliable nitrate removal in the face of similarly high sulphate concentrations. The test systems with throughputs of around three cubic metres per hour were constructed in Germany in modular format and installed in Mashhad in October 2004. A German-Iranian team (IWW, Mashhad Water & Wastewater Co.) was responsible for the operation and optimisation of the systems and performed extensive scientific research between 2004 and 2007.

Upon completion of the project at the end of May 2008, it had been established that the four procedures could be successfully applied to the situation in Mashhad. All test systems worked reliably and reduced the nitrate concentrations in drinking water to levels below the WHO guidelines. However, the project partners identified significant differences between the individual procedures – e.g. with regard to the specific wastewater volume and required resources (energy, chemicals, personnel) as well as the ecological and economic consequences. These aspects were recorded for all four processes and assessed in the form of a cost/benefit analysis. Taking the situation in Iran into account (e.g. the extremely low energy prices), biological denitrification and reverse osmosis were identified as the most suitable means of achieving the targeted water quality in Mashhad. However, these findings may be different if the boundary conditions were to change (e.g. due to increased energy prices).

Transferable results

Reactor for biological nitrate removal (denitrification))

Reactor for biological nitrate removal (denitrification)
Reactor for biological nitrate removal (denitrification))

The experiences gained over the course of this project are also relevant for new water works in Mashhad and other cities in the region, since they provide an ideal basis for Iranian experts to decide whether and with which procedures future nitrate removal plants are to be built Another important outcome of this research initiative is the new contact established between German and Iranian water experts.

The project partners have already presented their findings at numerous international conferences and trade fairs as well as in international publications. The final report entitled “Demonstration of high-performance procedures developed in Germany for the removal of nitrate from drinking water in Iran” is available online via the German National Library of Science and Technology (TIB) Hanover (http://edok01.tib.uni-hannover.de/edoks/e01fb09/590090909.pdf; 7,4 MB).

IWW Water Centre (Rheinisch-Westfälisches Institut für Wasserforschung)
Water Technology division

Dr.-Ing. Stefan Panglisch
Dipl.-Ing. Oliver Dördelmann
Moritzstraße 26
45476 Mülheim an der Ruhr, Germany
Tel.: +49(0)2 08/4 03 03-243, -321
Fax: +49(0)2 08/4 03 03-82
E-mail: s.panglisch@iww-online.de
Internet: www.iww-online.de
Funding reference: 02WT0393
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