The OSCAR process controller was tested over eight months at a WWTP in Italy to optimize biological treatment and reduce energy consumption. It achieved an average 38% energy savings and 75.2% reduction in total nitrogen compared to the conventional treatment process. By automating the alternation of anoxic and aeration phases, OSCAR was able to efficiently adapt to varying influent loads and meet legal discharge limits while improving treatment effectiveness and lowering energy use. Based on the successful results of the experimental testing, the plant operator decided to implement OSCAR for full management of the treatment process.

1. The OSCAR®
process controller: optimizing biological
treatment and electrical consumption for the WWTP at San
Giorgio di Piano, Bologna, Italy
Claudio Modenaa
, Lorenzo Rizzolia
, Marco Viana
, Elisabetta Frestaa
, Francesco Gelminia
, GianNicola Scarcellab
, Francesco Avoliob
a. ETC Sustainable Solutions s.r.l.
b. Hera S.P.A.
This paper describes the eight-month experimental testing of the OSCAR®-Intermittent Aeration process controller at the San
Giorgio di Piano WWTP and it reports the observed results in terms of treatment efficiency and energy savings.
Objectives of the experimental testing
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)
Why use OSCAR®
-Intermittent Aeration?
OSCAR® (Optimal Solutions for Cost Abatement in nutrients
Removal) is an automation and supervisory software
developed by ETC Sustainable Solutions of Trento, Italy,
which has been installed in more than 40 WWTPs
nationwide. It optimizes the aeration of the biological
process by alternating conditions of nitrification and
denitrification within the same treatment volume. Based on
real time measurements of nitrogenous forms and dissolved
oxygen in the biological tank, the system identifies a static or
dynamic set-point for the dissolved oxygen concentration,
which is then maintained by regulating the blowers. The
advantages of this approach are:
• The duration of the anoxic phase is optimized with
respect to the real incoming load and the effluent
quality required at discharge. The protraction of the
anoxic phase during low-load periods determines a
reduction in the energy used for aeration.
• The intermittent aeration process eliminates the need
to recycle mixed liquor, so determining a further
reduction in energy consumption.
• The duration of the anoxic and aerated phases is
controlled by means of direct and indirect parameters
and it is modified in response to changes in the
incoming load. This effectively increases plant flexibility,
allowing it to adapt dynamically to treatment or
operational needs.
• When the heterotrophic biomass is subjected to
alternating anoxic and aerated conditions, a reduction
in cellular growth is observed (10-20%) and, as a
consequence, secondary sludge production is also reduced.
• The alternation of anoxic and aerated phases causes selective
conditions that favour the development of polyphosphate-
accumulating organisms in the biomass, thus increasing the
biological abatement of phosphorus of the treatment process.
Figure 1 – Example of one day of operations and monitoring
The San Giorgio di Piano WWTP
The selected plant has a design treatment capacity of 9,950 PE. It 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.
The Workgroup
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 on the basis of remote sensing data
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Consumption[kW]-N-NH4,OD[mg/L]-pH
ORP[mVv]-V[m3/h]
ORP [mV] V [m3/h] Consumption [kW]
N-NH4 [mg/L] OD [mg/L] pH

2. Contatti: www.etc-eng.it
commerciale@etc-eng.it
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.
Results
• Average energy savings of 38% for Train 1 with
respect to the Train 2
Figure 2 – Consumption and savings: OSCAR vs. conventional.
• Reduction in concentration of total nitrogen at
the discharge (75.2% average)
Figure 3 – Percentage reduction of total nitrogen Train 1
• Handling of varying incoming loads by
managing the anoxic phases with automated
regulation of blowers.
Figure 4 – Daily variation of average ammonia concentration overlaid with blower
frequency.
• Legal limits at discharge respected
Date
N-NH4
[mgN/l]
N-NO3
[mgN/l]
N-NO2
[mgN/l]
Ntot
[mgN/l]
18/02/2014 3 3.2 0.04 7.3
04/03/2014 5.2 1.8 0.08 8.3
18/03/2014 3.3 2.5 0.04 7.6
01/04/2014 0.8 2.8 0.04 5
15/05/2014 0.8 3 0.05 5
09/07/2014 7.3 0.6 0.07 10.1
23/07/2014 5.2 2 0.08 9
04/09/2014 3.4 4 0.05 8.7
18/09/2014 2.4 6.3 0.05 10.1
29/09/2014 2.6 6.2 0.06 9.4
Table 1 – Experimental results, discharge analyses of Train 1
Conclusions
The experimental installation confirmed the reliability of the
OSCAR®
system in achieving the required treatment
efficiency.
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.
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