Water Management
Developing Company:
Environment and Urban Planning Office

Waste Water Treatment Plant in Arjona

Designing, Programming and Setting a waste water treatment plant in motion in the town of Arjona, developed by the Environment and Urban Planning Office and managed by SOMAJASA.


The plant has been designed to treat an average water level up to 2,257 m3 daily in a set year. The organic load has been design for the equivalent of up to 12,000 inhabitants in the worst possible scenario.

The process line consists of a traditional treatment using extended aeration with two process lines.

Sludge treatment is carried out using mechanical dehydration in centrifuging tanks.


A control system is required to monitor and manage all the operations involved in primary water treatments in order to achieve the required levels and protect operators, plant equipment and the environment.


A decentralised control system based on PLCs and SCADA supervision system on the Citec of Schneider Electric industrial platform means a solid, efficient and effective solution and thus, a fast response against possible events and it prevents the plant from stopping and not operating.


The main benefits of these solutions are amongst others:

  • Constant and automatic supervision of the plant.
  • Energy efficiency in the water treatment process.
  • Control and registration of all the measured parameters.
  • Actions aimed to allow high availability of the infrastructure.

Technical Data

Two waste water sewer pipes, a 3.9 kilometre-long pipe in the North area and another 2.9 kilometre-long pipe in the South part that passes near the waste-water treatment plant. There, they will join into a sewer manhole connected to the Waste-Water Treatment Plant as one single connecting pipe.

The plant can take 130.75 litres as daily maximum water volume per second; it will operate with an extended aeration system and thus, it will have two treatment lines working simultaneously; one for water treatment and another one for sludge treatment.

In addition, it can treat 26.15 litres per second as average waste-water daily volume and thus, it ensures sewage disposal for current and future populations. In 2030 it is forecast to be around 12,000 people.

Most important data


Incoming daily water level


Population Design


Investment in euros