Optimizing biological treatment and electrical consumption for the wastewater treatment plant (WWTP) at San Giorgio di Piano, Bologna, Italy has required the use of both skilled engineers to understand the plant’s actual performance and novel software to improve that performance using oxygen and ammonia measurements.
Location: San Giorgio di Piano, Bologna, Italy
Date of completion: 30.09.2014
Duration: 8 months
Client: Hera S.p.A.
Contractor: ETC s.r.l.
Project manager: Claudio Modena
Challenge summary: Optimization of water quality and energy consumption in an Italian WWTP
Challenge solution: Implementation of OSCAR® process controller leads to large energy savings (-38%) and ensures high nitrogen abatement (>75%)
ETC Engineering s.r.l. is an Italian engineering company active in the field of wastewater from 2008.
From many years of experience in design and consulting activities, ETC has identified the need to control the WWTPs that are designed under one set of project conditions but often find themselves working in different loading conditions. ETC has therefore combined the design activity with the development of advanced control systems for WWTPs. The supply of advanced controllers and customer technical assistance arise from the awareness that the knowledge of specialised engineers is fundamental, not only in the design activity but also during operational life of a civil work.
The world of wastewater treatment is increasingly equipping itself with cutting-edge tools that allow the optimization of processes as regards both the quality of discharged effluent and energy consumption.
OSCAR® (Optimal Solutions for Cost Abatement in nutrients Removal) is an automation and supervisory software developed by ETC in Trento, Italy, which has been installed in more than 90 WWTPs nationwide. It controls the sewage treatment through an intermittent aeration process that alternates aerobic nitrification phases and anoxic denitrification ones.
The process logic is based on the direct monitoring of working parameters acquired in the field. Such an approach allows a plant to cope with variations of incoming pollution loads in an automated and effective manner, significantly increasing the abatement efficiency of total nitrogen and ensuring compliance with discharge limit. Automation modules by OSCAR® increase the operational flexibility of the plant, allowing it to dynamically adapt to the operator’s needs. This has a positive impact on the energy usage of the sewage treatment plant: it optimizes operations of installed equipment and avoids waste of electricity.
OSCAR® algorithms are normally based on oxygen and ammonia measurements, therefore it is necessary to have oxygen and ammonia probes in each separate treatment line.
OSCAR® software is installed on an industrial PC supplied by ETC and within a suitably equipped special electric panel, which interfaces directly with the plant automation (existing PLC). It is necessary to modify the algorithms inside the PLC to make them compatible with the commands produced by the advanced algorithms of the controller, but no changes in the process flow diagram are necessary.
The software and its communication with existent automation is normally tested by an experienced and qualified engineer. No interruptions of plant working are required for the installation. The start-up and test phase lasts from 2 to 5 days according to plant size and complexity, but during this period the plant remains completely in operation. The OSCAR® system was tested at the San Giorgio di Piano WWTP with the aim of achieving:
- 30% energy saving
- 75% nitrogen removal efficiency (wrt t-N)
The selected plant has a design treatment capacity of 9,950 PE , where PE (Population Equivalent) stands for the ratio of the sum of the pollution load produced during 24 hours by industrial facilities and services to the individual pollution load in household sewage produced by one person in the same time.. San Giorgio’s treatment plant is composed of two independent biological trains (henceforth Train 1 and Train 2), each of which includes phosphorus removal, denitrification, oxidation/nitrification, and secondary clarification; this layout provides an ideal situation for comparative experimentation.
ETC Sustainable Solutions (the service provider) installed the OSCAR® process controller on Train 1 on 01/02/2014; Train 2 was not modified and continued treatment with the original design process of intermittent aeration based on a timer. The treatment efficiency of both trains was calculated based on remote sensing data measured by Hera (the plant operator) and analyses of incoming wastewater and effluent at the discharge, also by Hera.
The results were validated by Prof. Ing. Gianni Andreottola and his team at the Department of Civil, Environmental and Mechanical Engineering of the University of Trento.
The experimental installation confirmed the reliability of the OSCAR® system in achieving the expected treatment efficiency (nitrogen removal efficiency>75%).
From the energy efficiency perspective, it has been shown how it is possible to reduce energy consumption by 38% with respect to pre-OSCAR® management, while improving treatment efficiency at the same time.
Following the experimental testing, Hera decided to use OSCAR® for the complete management of the plant by also installing it on Train 2. The experimentation then led to a close collaboration between ETC and Hera: to this date ETC has done studies and software installations for Hera on about 30 other WWTPs over four years.
Statistics obtained during these years of OSCAR® installations all over Italy show an average payback time for the implementation of the controller of between 2 and 3 years.
One of the reasons for this success lies in the awareness that the activity of the engineer must not be closed to the mere realization of the project but the engineer must think of solutions that follow the life cycle of what is designed and realised. This applies to wastewater treatment plants but also to any other civil work, be it a building or an infrastructure.
The challenge of the engineer is therefore in the development of these innovative solutions for the management and optimization of the works in their life cycle, a sector with a potential market that cannot be underestimated.