Evaluation of the working on of the Water Treatment Plant of Monte Novo.

LIFE97 ENV/P/000149

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Contact details:

Project Manager: Abílio DIAS FERNANDES
Tel: 351-66-70 31 00
Fax: 351-66-70 31 12

Project description:


The water treatment plant at Monte Novo provides drinking water to the Evora municipality, in Central Portugal. As the area suffers from irregular rainfall, most of the water comes from the Monte Novo reservoir, where it requires a costly purification process due to its low quality. Until recently, the Local Authority has used a pre-oxidation process based on pre-chlorination to degrade the organic matter from the semi-eutrophized reservoir. However, this process was suspected of leading to the formation of halogens, known as trihalomethanes that were noxious for both the consumers and the operators working in the water treatment plant. It was also costly, and did not guarantee the level of water quality required by National and EU legislation. As a result, the Council was concerned to investigate the viability of an innovative new water treatment system based on pre-oxidation process using ozone.


The aim of the project was to evaluate the effectiveness of the new water treatment system proposed for the Monte Novo plant, in providing quality drinking water at an economically viable rate. The specific objective was to compare the overall cost/benefit/quality ratio of the two systems. This would be done by verifying if the system of pre-oxidation through ozone contributed significantly to the degradation of organic matter from the reservoir water and by comparing the impact of the aluminum sulfate liquid, used instead of chlorine, as a flocculent treatment. The study would involve an exhaustive analytic control survey of the above parameters in order to compare past and present treatment systems, as well as considering the formation of bromates, acrylamides and residual ozone, which are not currently considered within National controls. The New University of Lisbon and the University of Evora would assist City Council in these analyses and in applying a computer-based mathematical modelling process to each sample in order to establish the correlation between quality/efficiency and costs. The project would make a final assessment and draw conclusions on the viability of the new system.


Although the study was initiated in August 1997 innumerable factors hampered the studies progress, namely a series of failures in the ozonisation and ozone analysis equipment, adverse weather conditions and some civil engineering errors. As a result, the study was only able to compare data from 1999 with 1996. However, a large number of detailed analyses were carried out, which allowed some useful conclusions to be drawn. Firstly, the project confirmed that the ozone system successfully contributed towards the overall quality of the water treated whilst reducing the quantity of reactive agents used in the treatment process. The use of aluminum sulfate, besides improving flocculation, was also found to contribute towards improved working conditions for the plant operators. Any Manganese found could be removed by mixing 20 parts of chlorine to 1 part manganese. The ozonisation system was confirmed to reduce the formation of trihalomethanes whilst, contrary to expectations, it did not lead to the production of bromates. The level of acrylamites recorded was also found to be very low. These benefits could be explained by the reduced dosages of poly-electrolyte. The overall conclusion was that the quality of water treated with the new ozone system fully met with the requirements of the EU and National Authorities (Decreto Lei No 236/98 de 1 de Agosto) and Community Directive 98/83/EC. Moreover, the costs were found to be similar to the previous treatment using pre-chlorination. Despite an 8 month delay and operational difficulties, the project succeeded in demonstrating the effectiveness of the innovative new water treatment system, replacing the traditional pre-bleaching by chlorine by pre-ozonization, a treatment not yet introduced in Portugal. Together with this evaluation, the project offered new methodologies for the control of parameters not yet considered by the National Authorities (bromides, acrylamites etc) which would be necessary for the effective management and control of the new water treatment system if introduced in other areas.


Environmental issues addressed:


Water - Water quality improvement


water quality improvement‚  drinking water‚  comparison

Target EU Legislation

  • Water
  • Directive 75/440 - Quality required of surface water intended for the abstraction of drinking wat ...
  • Directive 80/778 - Quality of water intended for human consumption (15.07.1980)
  • Directive 2000/60 - Framework for Community action in the field of water policy (23.10.2000)

Natura 2000 sites

Not applicable



Coordinator Câmara Municipal de Evora
Type of organisation Local authority
Description The beneficiary is the local authority responsible for the medieval walled city of Evora and outlying suburbs in Central Portugal. The city extends over an urban area of 1,643 has and supports a population of 53,754. It acts as a magnet service center in a still predominantly agricultural region, with new service sectors developing within the city itself and through the development of rural tourism. Evora is seen within Portugal, as a pioneer council in urban strategic planning. This has recently included integrated transport strategies, green belt planning and water quality strategies.
Partners New University of Lisbon University of Evora.


Project reference LIFE97 ENV/P/000149
Duration 01-MAR-1997 to 01-MAR -1999
Total budget 135,664.44 €
EU contribution 56,607.16 €
Project location Alentejo(Portugal)


Read more:

Brochure Title: Non-technical report for publication Author: Evora Municipal Council Year: 2000
Brochure Title: Informe Tecnico Author: Evora Municipal Council Year: 2000


Project description   Environmental issues   Beneficiaries   Administrative data   Read more   Print   PDF version