Question: What challenges did the construction of the Punta Gradelle plant face?
Answer: The Wastewater Treatment plant in Punta Gradelle is a case of excellence in the European and Italian wastewater technology market. The immediate need and challenge was to find a solution to protect the environment. The state of degradation of the Sorrento coast was unacceptable, with more than half of the population served discharging directly to the sea, and the other half to a purifier not reaching the required legal limits. Another target was the recovery and reuse of sludge and treated water for industrial and irrigation purposes.
The project involved the completion of the adduction and discharge works, the adaptation of the existing tunnels, a new plant tunnel, the access road, the architectural and environmental arrangement and preparation for reuse of the treated water.
Its cutting-edge technologies allow to minimize the environmental impact and to preserve a natural area of great value
Q: What differentiates this plant from similar ones in terms of technical requirements, environmental regulations and objectives to be met?
A: The plant is not comparable to standard ones due to its particular structure and environment: it is built inside a gallery in the mountain, divided into a 750-meter-long tunnel near the confluence of two sewer pipes. Its cutting-edge technologies allow to minimize the environmental impact and to preserve a natural area of great value which, especially in the high touristic season, can undergo a very intense anthropic pressure and a consequent risk for hygienic-sanitary and environmental under-protection.
To ensure the well-being of the workers involved in the system, the complex also required the opening of ventilation ducts where the air is forced by turbofans, ensuring adequate humidity and temperature conditions.
Q: How was the solution of Punta Gradelle proposed from a technical point of view?
A: Different technical solutions and state-of-the-art technologies were chosen to optimize the process, the available space, the costs and volumes. As well as to achieve the water treatment objectives.
Starting with the pre-treatment, with coarse and fine grinding that traps 1,600 kg of solid material per day that previously made its way to the sea. The water is then treated in a biological process with activated sludge to remove phosphorus and nitrogen, and then passes through the MBR (Membrane Biological Reactor) system, which combines the suspended biomass system with separation between purified water and sludge by ultrafiltration. This system represents the heart of the plant, and is composed of four reactors and a total of 40 membranes with a porosity of 0.045 microns, 10 in each reactor. A vacuum pump forces the water through the membrane; everything above 0.045 microns is retained and purified water comes out.
Rainwater treatment is carried out with an ACTIFLO® (Veolia) for the accelerated clarifloculation process.
Q: What advantages does the distributed control system offer for this type of plant, and why was the EcoStruxure Hybrid DCS solution chosen?
A: The need for efficiency and reliability in the operation of a complex system like this required a very refined supervision system, to allow for safe management of not only all the different plant sections but also all the individual operating units.
The Punta Gradelle electrical system consists of four cabinets, each managing different areas and equipped with MV switchboard plus the corresponding LV switchboards, to manage the asstes and the related Programable Automation Controllers (PAC) and Human Machine Interfaces (HMI). Cabinets are iPMCC (intelligent Power & Motor Control Centre) solution from Schneider Electric which represents the keystone of energy efficiency, guaranteeing the power supply, control and protection of electric motors and loads.
EcoStruxure HDCS, thanks to its native libraries, is a powerful instrument to achieve a quick and reliable start-up
The architecture of the solution at Punta Gradelle plant includes different PACs and a high-speed network for the exchange of information between the control units and all the cabinets. A distributed system was the best option to leverage all the interconnections and logic among the different units and to manage an important amount of information for the operating personnel.
Among the solutions available within the industrial control technologies, there is a particularly advanced one, which not only allows to have total and reliable control of the operation of this type of infrastructure, but also enables a simplification of operations and maintenance, as well as to easily identify possible improvements and savings through energy evidence on the actual consumption of the individual units. This is Ecostruxure™ Hybrid DCS (HDCS), a collective system that allows to natively integrate data and controllers into one environment, using open and standard protocols and ethernet technology: variable speed drives, power meters, intelligent cabinet (MV/LV) and PACs are merged together, interconnecting data, values and gathering information directly to the central system. EcoStruxure HDCS, thanks to its native libraries developed from our experience along many years in strong collaboration with customers, is a powerful instrument to achieve a quick and reliable start-up with the possibility of simulating and bypassing parts of the system, reducing plant downtime, supporting predictive maintenance and optimizing release times.
Q: What results / benefits were obtained?
A: From the Process Automation point of view the benefits of such a solution are the optimization of energy usage, higher reliability, secure staff safety in maintenance activities, cost reduction throughout the life cycle and simplified integration with the infrastructure on site.
From the customer point of view, the results are clear: better water quality, blue flag and guaranteed bathing in the sea, relaunching tourism and the possibility of using purified water, thanks to their chemical and bacteriological characteristics, also for irrigation, street watering and other similar usages.