Extension to the Segovia WWTP

The Segovia Wastewater Treatment Plant (WWTP) went into operation in 1996. The flows treated at the facility have increased progressively due to population growth and also as a result of greater industrial activity with corresponding increases in the effluents requiring treatment.

Moreover, it would have been difficult to comply with European Directive 91/271, which sets out effluent quality parameters if the project to extend and upgrade the infrastructure had not been undertaken.

Given this scenario, state-owned enterprise Aguas de las Cuencas de España (ACUAES), which operates under the aegis of the Ministry of Agriculture, Food and Environmental Affairs, undertook the project to extend and upgrade the Segovia WWTP. The project required investment of €21 million (excluding VAT) and was co-financed by European Union Cohesion Funds. A consortium made up of GSINIMA and OHL was responsible for executing the project.


The project was completed on schedule in March of this year. It ensures the treatment of all wastewater from the city of Segovia, the surrounding municipalities of La Lastrilla and San Cristóbal de Segovia, and the “El Cerro” and “Hontoria” industrial estates. The WWTP produces effluent of sufficient quality for subsequent reuse, with minimal impact on the River Eresma, the receiving medium.

The work, which began in March 2014, consisted of:

  • The complete renovation of pretreatment, including adaptation of the large-particle well, the replacement of all equipment and the construction of a new covered building with odour control.
  • The installation of a new primary and secondary settling system, as well as a new stormwater settling system. The latter can work in tertiary treatment mode for further refining of the effluent.
  • Upgrading the bioreactor and and increasing its capacity.
  • The installation of a new extended, comprehensive sludge line for treatment, storage and evacuation of all sludge produced. Equipment is also installed for energy recovery in the form of the biogas produced at the plant.
  • The construction of new process buildings.

The work carried out to extend the existing facilities has also provided the upgraded WWTP with greater operating and functional flexibility to meet future treatment needs.

In summary, subsequent to the renovation work, the new Segovia WWTP can receive an average daily flow of 41,280 m3, guaranteeing the suitable removal of nutrients and a capacity of 147,920 population equivalent. In addition, a stormwater treatment system was built and this can also operate in tertiary treatment mode.

The main constraints on the construction work were the limited space available in the facility for the execution of the works and the marked level differences to be found on the site.

The total or partial demolition of existing elements and the subsequent construction of new elements was carried out on a very small floor space. This meant that smaller auxiliary equipment had to be selected than would normally be the case in similar projects and the construction work had to be organised “from inside to outside” for practical purposes.

The importance of not interrupting the operation of certain elements of the existing WWTP was another factor that added complexity to the execution of the work.

The need for structural rehabilitation of the pretreatment stage and the bioreactor, along with the many existing pipes, created interferences that put constraints on the construction process.

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