Siderúrgica Sevillana SA is a company which operates in the non-integral siderurgy sector, which transforms raw ferrous material obtained from recycling and recovering waste material into products which may be used in other basic sectors of the economic activity of the country. Since the mid-sixties, their activity has centred upon founding and rolling hot steel.

In August, the MP Environment Area was awarded the project to modernise the rainwater treatment plant of the factory the company has in the municipality of Alcalá de Guadaira in Seville.

In general, the problem regarding waste in this factory is a result of the productive process itself: dust from steel that is settling in the immediate surroundings of the iron and steel factory is swept away by rainwater.

The rainwater is characterised as follows: basic water containing metals and the possibility of oil and grease. Basing on the surface area of the factory and the quantity of rain in the area, it is considered sufficient to treat 110 m3 of rainwater.

In general, the problem regarding waste in this factory is a result of the productive process itself: dust from steel that is settling in the immediate surroundings of the iron and steel factory is swept away by rainwater

In order to treat this water, three existing tanks will be refurbished. Rainwater will be stored in the first one; mixed with the process water in the second; in the third tank, a degreasing and pumping process will be carried out on the water from the second tank. The treatment system to be used is a physiochemical system by settling followed by sand filtration. The treatment capacity is 30 m3/ h, both for settling and filtration. A polypropylene lamella plate static clarifier has been selected to avoid atmospheric corrosion. Filtration will be performed with sand, in 1.2 metres diameter enclosed filters, which are made from carbon steel.

The plant is completely mechanised by PLC and touch screen monitor. It is also equipped with a SCADA system for remote control. However, supervision of the plant operations by qualified technicians is still recommended.

The pH level for the clarifier has been established at 9, depending on the fall of zinc and lead. The remaining metals do not require treatment since they are present in concentrations well under the established limits.

The following reagents are used in the process: polyaluminium chloride coagulant, for possible concentrations of suspended solids and oils and grease, lime slurry and sulphuric acid to adjust the pH and anionic flocculants to help precipitation.

Siderúrgica Sevillana belongs to the Riva Group, which is a leading multinational in the iron and steel sector and includes several companies operating in the steel and iron production industry, as well as related activities. It is the leading company in the Italian sector, the third operator in the European market and is positioned tenth in the international market.

José Félix Inchausti
Head of Modernisation Department