Projects / Programmes
Geophysical and Ecological Approach to Dispersion of a Sewage Plume
Code |
Science |
Field |
Subfield |
1.02.07 |
Natural sciences and mathematics |
Physics |
Biophysics |
Code |
Science |
Field |
P500 |
Natural sciences and mathematics |
Geophysics, physical oceanography, meteorology |
sewage, coastal waters, submarine outfall, dispersion, dilution, stratification, tides
Researchers (3)
no. |
Code |
Name and surname |
Research area |
Role |
Period |
No. of publicationsNo. of publications |
1. |
05226 |
PhD Vlado Malačič |
Hydrology |
Head |
1998 - 1999 |
367 |
2. |
00112 |
PhD Rudolf Rajar |
Civil engineering |
Researcher |
1998 - 1999 |
366 |
3. |
06202 |
PhD Tomaž Vrhovec |
Physics |
Researcher |
1999 |
209 |
Organisations (3)
Abstract
The applied research project deals with the analysis of wastewater field, which spreads into the sea from two diffusers of the submarine outfall near Piran. Numerical models were developed for the simulation of diffusers'' hydraulics and of initial dilution of a buoyant plume, which spreads from the diffuser''s orifices towards the wastewater field laying above. The wastewater field is formed within the water column in a layer of neutral buoyancy in density-stratified environment. There, the secondary dilution process starts, where currents spread the wastewater patch on a larger scale.
The near-field survey of the wastewater distribution was monitored ten times from 1997 to 1998 with a fine-scale CTD probe, on which sensors for oxygen and fluorescence (chlorophyll-a) were additionaly installed. Surveys covered the area of 780 m × 740 m with 31 vertical profiles. On a central station the concentrations of nutrients and faecal coliforms were analysed in the water samples taken from at least ten depths. The vertical resolution of the free-falling CTD probe with a speed of 1 m/s is 2.5 cm, therefore anomalies in salinity (less than 0.2 PSU) and temperature (less than 0.3 °C) were detected in layers of wastewater fields which originate from two diffusers. These anomalies corresponded to a signifficant increase in ammonia and faecal coliforms. Since during the enhanced summer stratification of the shallow Gulf of Trieste the thickness of the layer of neutral buoyancy could be less than 0.5 m, the wastewater field is hardly detectable with ''standard'' CTD probes of lower resolution.
In 1999 the secondary dilution process will be estimated on the basis of current measurements. Tidal currents at the place of sewage spreading will also be analysed from the results of a 2D numerical model of the northern Adriatic Sea.