1) Biological tractability of urban sewage and WWP
management.
2) Finishing, recovery and reuse of treated urban
wastewater.
3) Wastewater discharge in inland/coastal waters and effects on
aquatic ecosystems.
4) On site systems for wastewater treatment and reuse in small
urban settlements.
THEME 1 - The research concerning biological treatment of
urban sewage is developed by three main survey line research:
a) the role of quality and dilution variations of incoming
wastewater in conditioning treatment efficiency and output
concentrations: main research field is the Bologna WWTP where
arecarried out experimentations with the aim to realize a
comparison between efficiency foreseen for eachtreatment phases
andreal organic matter (BOD)removal, tested, during full scale
functioning, indifferent rainy anddilution conditions.
Dlgs.152/2006 provides for wastewater collection in drainage system
and secondary treatment for all Italian residential built-up area
and discharge regulation defines tables of parameter limits. So,in
case of combined piping system, collecting such sewage as rain
water, becomes important to receive, in primary treatment phases,
in rainy weather conditions, a large amount of collected water
volumes. Results made possible a precise mathematic formulation to
control WWTP input, during critical rainy events, and numerical
simulations are developed about active sludge WWTP performances in
function of incoming and bypass fluxes.
b) investigations about effects of sewage composition in
conditioning nitrogen removal efficiency and biomass health in
predenitre-nitre plant: on the wastewater treatment plant of
Bologna it has been also studied the effect of BOD/N ratio and
presence of grease and oil on nitrification efficiency. By controls
about health and activity state of biomass we have defined a
mathematical model for description of oxidization-nitrification
phenomena based on evaluation of sludge production in function of
sludge retention time. Limitation on oxygen transfer efficiency due
to oil releases of filamentous microorganisms has been detected as
main critical factor for nitrification phase. Sludge retention time
as regulation factor for plant management and as an important
parameter in conditioning denitrification velocity has been studied
in Ravennamunicipal wastewater plant. Results present the behavior
of denitrification velocity in function of sludge age in a
denitre-nitre plant scheme, using internal and endogenous carbon.
According with Pavia University it has been verified the effect of
daily variation in organic loadings on biological nitrogen removal.
This is a largely diffused problem in Northern Italy where often
plants receive weak wastewater or pretreated water by Imhoff
tanks.
c) the capability of automatic WWTP management by artificial
intelligence technique aimed to provide and minimize system
disturbances: variation of incoming loadings is probably the main
critical factor for steady functioning of great active sludge
treatment plants. The related transitory phases are often cause of
decrease in efficiency or even of crash in treatment function. The
survey tests innovative techniques for control of active-sludge
plants manage-ment based on automatic interpretation of on-line
measured data and is carried out in partnership with DEIS
Department of Bologna and water section of ENEA Bologna. In ENEA
laboratory have been mounted and endowed with on-line measuring
instruments one SBR pilot plant and one active sludge steady
functioning pilot plant. In collaboration with HERA Bologna are in
progress works on full scale plants of Trebbo and Calderara di Reno
for mounting on-line data acquisition system in order to make
possible to test results at real scale. Treatment of municipal
wastewaters usually requires a simple sequence of two biological
processes, denitrification that occurs in anoxic conditions,
whereas nitrification in aerobic conditions. The automatic
detection of the end of such processes allows to optimize the
duration of the operational cycles, which usually would be set on a
worst-case basis, and thus to reduce costs. Moreover, the
recognition of both process-level events is necessary to validate
the effectiveness of a cycle, in order to ensure that the effluent
is conforming to the required standards. The well-known criteria
for on-line monitoring of biological processes (nitrification and
denitrification) in a Sequencing Batch Reactor (SBR) for municipal
wastewater treatment, are based on the analysis of acquired online
signals such as pH, oxide-reduction potential (ORP) and dissolved
oxygen (DO).
THEME 2 - a In a pilot plant in Imola (BO) a few interesting
natural systems, utilizable in treatment and wastewater finishing,
have been tested about efficiency in disinfection and in phosphorous, nitrogen and BOD
removal. Continuous analysis of organic parameters reveal good
removal rates for fragmites australis on all parameters and for
lemna fragilis on dissolved nitrogen phases with hydraulic
retention time more or equal to 2 days. Results point out useful
management information about maintenance of steady condition by
control of growing transient and biomass extraction.
b)· Experimentations in reclamation and irrigation reuse of
large flowrate of domestic wastewater are carried out in
Cagliarisystem for treatment-storage-reuse of urban wastewater. The
investigation analyzes the removal effect in organic and microbial
parameters due to bacterial-algal activity typical of a facultative
pond and discuss results in order to test reliability and
efficiency with reference to the existing Italian laws about
discharge (D.lgs.152/2006) and reuse (D.M.2/5/2006). Data reveal
that Simbirizzi artificial basin make possible agricultural
recycling and reuse realizing adequate retention time for storage
and final finishing of wastewater, and at the same time permits to
avoid every discharge in seawater during summer. A mathematical
model, just developed by the research components, has been
calibrated and utilized in order to describe the evolution of
quality of water storage into the Simbirizzi basin and to control
the respect of existing law limits about irrigation reuse.
c) · Another research line is developed studying the
finishing capability provided by the transitory waters regulated by
tidal oscillations, before outfalling through canal sea-mouths. On
the basis of foregoing experiences of monitoring and numerical
modelling of ecosystem phenomena carried out about Piallasse
Ravenna, three monitoring campaigns are developed into the basin of
the Canal Port in Cesenatico, where the last internal part of the
channel has been modelled as an unsteady flow reactor tank and
where variations in depth and input/output fluxes are provided by
tide, but prevalent freshwater conditions are maintained by the
high rate input of treated wastewater. Four fixed point, in output,
intermediate and input cells, are monitored in order to verify
active phenomena and finishing effects on discharged wastewater in
terms of C, and N biological removal. Modelling of oxygen and
biomass balances permits to quantify the different role of
productive and oxidizing activities, supported by mixed microalgal
and bacterial populations, during daily and nightly cycles. A few
usual formulations, utilized in aerobic lagoons design, have been
tested on the studied system and compared with model results and
monitoring data, verifying the capability of scheme plug flow
reactor+first order kinetic to interpret the finishing effect on
BOD, ammonium and nitrate residual from WWTP.
THEME 3 - Wastewater discharge in inland/coastal waters
and effects on aquatic ecosystems is focused by three research
field: the intake work of Cervia Saline, the estuary of Marano
River receiver of Riccione WWTP effluents and the outfalling system
of the Cesenatico harbour channel, which transports treated
wastewater coming from Cesena (180.000 AE) and Cesenatico (summer
100.000 AE). Generally harbour channels, having very low ground
slope, guarantee a good thermoaline turbulent mixing, for the
entire water column, if basin structure presents high pulmonary
surface/freshwater loading ratio. So discharged volumes receive a
sanitising effect by salinity and pH on microbial contamination and
vertical dispersion provides limitation of algal blooms in coastal
zone due to intrusion of nutrient in surface stratified freshwater.
On the contrary small estuaries with higher ground slope, receiving
sea water by tidal oscillations within a few hundred meters from
coastal line and high flowrate coming from WWTP, present flow
prevalently directed to sea where flush continuously freshwater in
surface. According with Bragadin e al. 2003 it has been proposed
and calibrated by data from the intake work of the Cervia Saline a
simplified scheme of calculations for hydraulic flow dividing the
channel into twenty independent cells. At each section flowrate has
been calculated in function of water surface enclosed between each
section and internal head of the channel, under the hypothesis of
negligible flow resistance, flowrate at each section is computed
from continuity equation. A different assessment, existing along
the Rimini-Cattolica coast, is investigated into the Marano estuary
near Riccione. Here higher ground slope permits direct discharge of
wastewater into estuaries of small rivers coming from near internal
hills. These estuaries receive sea water by tidal oscillations
within a few hundred meters from coastal line and present low
internal depth (max 1,6-1,8 m). Sea outfall occurs through sea
outlet only a few meter large and very low depth (60-80 cm).
Summer hydraulic flow, for high flowrate coming from WWTP and low
pulmonary available volumes, is prevalently directed to sea where
delivers continuously freshwater in surface. In summer dry weather
assessment of morphology tide and currents, it has been modelled,
along estuarine transition unsteady flow, the behaviour of
velocity, Reynolds n., salinity, dissolved oxygen, P-PO4,N-NH4,
N-NO3. Two special campaign of analysis are carried out for
calibration. A survey about seawater quality in coastal bathing
areas, interested by discharging systems of freshwater, is carried
out in the pulmonary system of Cesenatico canal harbour and in the
near coastal zone characterized by submerged breakwaters in North
direction and by emerged breakwaters in South direction. During
summer and in dry weather conditions main part of discharged
freshwater come from Waste Water Treatment Plants and from drainage
pipe systems and it has been studied dispersion area and profile
distribution of freshwater outgoing from harbour canal mouth and
discharged in the coastal area. Different effects on thermoaline
and oxygen profile, firstly modelled by a 3D numerical model, have
been registered in 2007 field experiences. Continuity and profile
of submergible breakwaters make these structures more efficient in
producing internal stratification than emerged discontinue
breakwaters which permit higher internal mixing of water column by
incoming and outgoing turbulent flux through mouths.
THEME 4 - Efficiency of small onsite domestic wastewater
treatment has been verified by monitoring of a few plant actually
active in Romagna, where small active sludge plant (combined system
Imhoff tank + Phytotreatment SFS, Imhoff tank + anaerobic filter)
are compared with reference to BOD, SS, nitrogen, phosphorous
removal. Horizontal and vertical flux systems have been analyzed
about efficiency removal, registering often nitrification deficit
caused by insufficient oxygen transfer capacity of rooted
macrophytes and showing high presence of residual BOD in effluents
due to media blockage in case of combined sewer system. Good
results are obtained by introducing biofiltration phases or
alternated vertical flux in SFS scheme with the scope of permitting
water reclamation and reuse. Pilot plant experiences, carried out in the buildings of the School of Engineering in via Terracini, have been
focused the role of hydraulic flow into the filtering medium in
conditioning removal efficiency of SFS system using fragmites
australis. Data results obtained from the pilot bed can be
correctly interpreted by model formulations using process scheme
based on first order kinetics mounted on a sequence of serial
completely mixed tanks provided by a share dead volume.