For over three years various high-performance processes for the removal of nitrates from drinking water, including two in-house developments from WABAG, were tested in Mashhad, which, with 2.6 million inhabitants, is Iran’s second largest city. The successful completion of this international research project was marked by a celebration in Mashhad on 15 January 2009, attended by over 300 guests. Representatives from the Iranian water authorities and all of the country’s most important municipal authorities gathered on-the-spot information and participated in the celebrations.
Mashhad is located in an arid zone of north-eastern Iran. The city is known as a national, religious centre and is the destination for millions of pilgrims every year, who, like the inhabitants, need a secure supply of drinking water. This is largely obtained from groundwater reserves, which can be in short supply, especially in summer. In addition, probably as a result of inadequate wastewater treatment, increased inputs of nitrogen have led to a rise in the level of nitrates in the water from numerous wells. These nitrates cannot be dealt with using standard drinking water treatment and therefore more far-reaching processes are needed in order to reduce the nitrate content to the WHO stipulated value of 50mg/l and below.
The related research project was initiated and realised within the scope of German/Iranian co-operation with the ministries, research companies and WABAG. As the technology leader, together with German research institutes, WABAG selected four suitable processes, designed and delivered all pilot plants, put them into operation on site and also provided operational management support. The following processes have been tested in continuous operation:
- Biological denitrification (the WABAG BIODEN® process)
- Reverse osmosis
- Ion exchange
- Electrodialysis process (the WABAG ENR® process)
Although nitrate removal plants have been in operation in Europe for a number of years, the project in Mashhad represented a special challenge due to the changed environmental conditions, e.g. higher groundwater salinity. Various parameters such as efficiency and process stability, investment and operating costs, technology and personnel efforts, drinking water quality and environmental effects were evaluated and rated in the final report.
The results showed that all four processes could meet the desired requirements; the nitrate content was reduced from approximately 120mg/l to 40mg/l and below. The best overall ratings were achieved by the BIODEN and reverse osmosis processes. Moreover, the test series also demonstrated that WABAG’s proven, in-house developed BIODEN and ENR technologies for nitrate removal are capable of safely turning groundwater with a high saline content into clean drinking water, and that the reverse osmosis and ion exchange desalination processes are also able to furnish safe nitrate removal.
The BIODEN process stands out due to its ability to provide selective nitrate removal and special environmental friendliness, owing to the fact that it does not produce any saline concentrates and that practically full water recovery can be achieved. Therefore, WABAG is well prepared for the realisation of large-scale plants in Mashhad, as well as in additional Iranian cities and provinces, not to mention other countries within the region.