Tourism Cervia Municipality

Cervia waste water purification plant: safeguarding the sea

The recent tourist development has modified the whole coastal area, influencing its environment. This resulted in difficult environmental and hygienic-sanitary conditions which are constantly worsened by the continuous production of polluting elements. Urban waste, highly-organic sewage and the resulting modification of chemical-physical and biological-bacterial parameters in the sea water alter the marine environment in a very short time.

Cervia municipality was among the first to deal with the problem of waste waters in order to avoid the pollution of the sea facing the tourist resort. The city administration started to discuss this issue in the early '60s and commissioned the project to Prof. Marzolo from Padua University “one of the most important Italian scholars on that subject“and to Galimberti group from Padua.

The general project was approved by the city council in August 1965. It included a city sewer net divided in white and black, as well as a purification plant that was able to process 360 l every second.

TECHNICAL DETAILS

The sewage produced in the municipal area are led into the centralised purification plant through a separate branch sewers net. A general wash stokes the first stage of the process, which includes a double micro-sifting (fine grey) and a mechanical dysoiling and degritting treatment. The constant stoking flow to the following stages is regulated by a drain that let the surplus sewage flow into an equalising accumulation tank. From here they are brought back into the general wash process through an automatic solenoid system, only when the flows of the main sewer tend to decrease. By previous pre-aeration process aimed at increasing their oxidoreducing potential, the waters are divided into three separate purification lines, each composed by:

• Primary sedimentations for the elimination of the sedimenting material that is demolished at the rate of 50% of total COD;

• Pre-denitrification necessary for the reduction of the nitrous and nitric nitrogen concentration for an anoxic environment where the activated sludges are re-circulated at the rate of 200% of the alimentation flow;

• Biological oxidation that helps the nitrification and degradation of the organic substance;

• Final decantation where the biological mass (activated sludges) is separated from the depurated fluid phase;

• While the sludges are treated anaerobically through digesting processes with biogas production, the waters “which have undergone a further treatment of biological dephosphorization aimed at decreasing the present phosphorus by reducing it at levels under 2 mg/l“undergo a seepage process on a sand and anthracite bed, before being conditioned by a final disinfection process with peracetic acid.