Runoff quantity and quality relationships for the industrial harbours of Liguria Region, Italy: Implication for control

Size: px

Start display at page:

Download "Runoff quantity and quality relationships for the industrial harbours of Liguria Region, Italy: Implication for control"

Roger McKenzie
6 years ago
Views:

1 RESUME Runoff quantity and quality relationships for the industrial harbours of Liguria Region, Italy: Implication for control Relations entre la quantité et la qualité des eaux pluviales dans les ports industriels de la Region Liguria, Italie : Implications pour la gestion Gnecco Ilaria, Lanza Luca G., La Barbera Paolo, Sansalone John Department of Environmental Engineering - University of Genova Via Montallegro 1, Genova, Italy Department of Environmental Engineering Science, University of Florida, 217 Black Hall Gainesville, Florida 3265 USA ignecco@diam.unige.it Depuis avril 25, le Département de la Faculté d Ingénieurs de l Environnement de Gênes a effectué une campagne de mesure pour caractériser la charge polluante des eaux pluviales dans les ports industriels de la Région Liguria (Italie) en fonction des différentes activités portuaires. Les mesures de la qualité de l'eau et du débit ont été effectuées depuis le terminal à conteneurs (Port de La Spezia) et les terminaux des cargaisons de marchandises et voyageurs (Port de Gênes). L étude a porté sur les éléments contaminants suivant : MES, TOC, ph, conductivité et les métaux lourds (dissouts et sous forme de fractions d'agrégat particulaire). Ce papier illustre les résultats des différents sites de surveillance et l étude de l évolution des masses de pollution (principalement des métaux) au cours d un événement pluvieux. ABSTRACT Since April 25 the Department of Environmental Engineering of Genoa has carried on a monitoring program within the industrial Ports of Liguria Region (Italy) to investigate storm runoff pollutants as a function of the different port activities. Both water quality and flow measurements data have been collected from the container terminal site (Port of La Spezia), dry bulk terminal and car ferries terminal sites (Port of Genoa). Laboratory testing has been performed to analyse TSS, TOC, ph, conductivity and heavy metals (dissolved and particulate bound fraction). This paper aims at illustrating results from the different monitoring sites and at investigating the pollutant delivery behaviour, mainly focusing on the partitioning of metal across the event as a function of the hydrologic aspects and general water quality parameters. KEYWORDS Metals, monitoring, partitioning, runoff quality. NOVATECH

2 1 INTRODUCTION The deterioration of receiving water quality due to pollutants transported by stormwater after wash-off on the paved surfaces of commercial ports and harbors has become a major concern due to their impact on the coastal area. Such concern has led to the characterization of stormwater quantity and quality transport and the resulting implication for effective BMPs in the port and harbor environment, as well as for coastal regions of Italy impacted by urbanization. A wide range of human activities from tourism to port industry are carried out on these large impervious surfaces, thus producing a significant build-up of the pollutant load. In addition, stormwater drainage systems in harbor and port areas generally convey runoff directly in the receiving water body without any treatment. In order to investigate the pollutant load connected to different terminal activities and to evaluate the most effective BMPs to integrate in the stormwater drainage system, the Department of Environmental Engineering at the University of Genova has installed a series of instrumented sites to characterize stormwater runoff quality within port areas of the Liguria Region (Italy). In particular this paper aims at illustrating results from a monitoring campaign carried out in three different experimental sites and at investigating the pollutant delivery behaviour, mainly focusing on the partitioning of metal between the dissolved and particulate-bound phases across the rainfall-runoff event. 2 EXPERIMENTAL SITES Since April 25 the Department of Environmental Engineering of Genoa has carried on a monitoring program within the industrial Ports of Liguria Region (Italy) to investigate storm runoff pollutants as a function of the different port activities. In particular both water quality and flow measurement data have been collected from the following sites: the container terminal site (Port of La Spezia), dry bulk terminal and car ferries terminal sites (Port of Genoa). Each monitoring station is equipped with an automatic sampler to collect discrete runoff sample (12 bottles with capacity.95 l) for water quality aspects coupled with an hydraulic device for continuous flow measurements. In the following sections, a short description of the different sampling sites is provided. 2.1 The container terminal site (La Spezia, Italy) The monitoring site is located within the container terminal (Port of La Spezia). The site is used for container handling and storage and it has a total watershed area of ten hectares. The monitored area is an asphalt surface of about one hectare suitably selected within the terminal. The sampling station is equipped with an area-velocity (A-V) sensor for continuous flow monitoring; before installation, the A-V sensor has been calibrated in laboratory in particular for low flow rate characterising the initial runoff (1 1 L/s). The A-V sensor and the sampler intake suction line have been installed directly into the drainage system (concrete pipe D=.4m). 2.2 The car ferries terminal site (Genova, Italy) The experimental site, located within the car ferries terminal (Port of Genova), includes the access road for private and commercial vehicles to/from the car ferries embarkation point and the parking lot for vehicles and trucks before embarkation. The monitored area is a concrete paved surface with an extension of about 5 ha and the sampling station was installed in the terminal section of the storm water drainage pipeline. The gauge station is equipped with an area-velocity sensor to continuous 1516 NOVATECH 27

3 flow monitoring directly installed at the bottom of the drainage pipe; such sensor allows to measure reverse flow conditions that may be occur due to tidal flow: seawater may backflow into the drainage system through the outlet section at high tide. Finally the monitoring station is equipped with a dedicated rain gauge, properly calibrated in the laboratory according to the WMO specifications (Lanza et al. 25). 2.3 The dry bulk terminal site (Genova, Italy) The experimental site is located within the dry bulk terminal which is employed mainly for (animal) meal handling and storage operations. The area includes the rail access and it is equipped with the overhead-travelling crane and the conveyer system to transfer products from vessels to storage facility or directly to trucks and train. Cargo operations determine products build-up on the impervious surface which is washedoff during rainfall event, therefore the storm water drainage system is characterized by high storage capacity gully pots which provide a preliminary runoff sedimentation before discharging into the receiving water The delineated and monitored area has a total extension of.7 ha and the sampling station was installed directly into the harbour pipe network drainage system and samples taken directly from the drainage system. The monitoring station is equipped with a pressure gauge for continuous level measurements and the flow rate data are determined after application of a stage-discharge curve obtained from calibration in the laboratory. 3 WATER QUALITY DATA From the monitoring campaign the following data are available: one-minute rainfallrunoff data, obtained from continuous level and velocity measurements and water quality data, obtained from laboratory testing of runoff samples collected by the automatic sampler at five minutes frequency. General water quality parameters are examined: total suspended solids (TSS), chemical oxygen demand (COD) or total organic carbon (TOC), ph, electrical conductivity and total hydrocarbons. Furthermore dissolved and particulate metals (copper, zinc, lead and mercury) are investigated. As for the container terminal, the monitoring campaign has been carried out from April 25 to January 26; 14 rainfall events have been monitored and in particular for 6 of them laboratory tests of water samples were performed for both dissolved and particulate contaminants. As for the dry bulk and car embarkation sites the monitoring program was initiated in October 25 and to date respectively 5 and 4 rainfall-runoff events have been monitored. Note that due to the high delivery of total suspended solids at the dry bulk terminal site, laboratory testing have been performed only for the dissolved metals fraction. Due to the significant temporal variation of the pollutant load across the wash-off process the event mean concentration (EMC flow-weighted average of constituent concentration) has been calculated for each parameter in order to provide an estimate of pollutants based on the entire monitored event. Results that are summarized in Table 1, indicate significant TSS and TOC/COD EMC values, particularly at the dry bulk terminal site which reveals EMC mean values for TSS and TOC respectively equal to 883 and 83 mg/l. As for metals, it emerges that copper, lead and mainly zinc show high total concentration values (dissolved and particulate-bound fraction) exceeding 1 mg/l (except for the dry bulk terminal site). In particular, at the container terminal site the mean and maximum EMC values for total zinc are respectively 3.7 and 13.8 mg/l; as for total copper and lead EMC mean values are equal to.84 and.54 mg/l. NOVATECH

4 Parameters SST (mg/l) TOC (mg/l) Container terminal site 153 (54 542) 248 a (71 a 485 a ) EMC mean (EMC min EMC max ) Car Embark. terminal site 178 (95 329) 28 (11 47) Dry bulk terminal site 883 ( ) 83 (2 192) ph mean 6.4 (5.9 7.) 7.3 (7. 7.6) 8. ( ) Cond mean (ms/cm).32 (.22.47) 1.7 ( ) 19.6 ( ) HC tot (mg/l) 3. (.4 8.5) - - Cu d (μg/l) 25.6 ( ) 11.5 ( ) 8.9 ( ) Cu p (μg/l) Pb d (μg/l) Pb p (μg/l) Zn d (μg/l) Zn p (μg/l) ( ) 26.4 ( ) ( ) ( ) ( ) ( ) 8.5 ( ) ( ) ( ) 92. ( ) ( ) (.8 23.) Hg d (μg/l) 1.2 (.4 2.) - - Hg p (μg/l) 1.9 (.4 6.4) - - a COD data Tab. 1. Event Mean Concentration (mean; minimum to maximum) of the water quality parameters monitored at the container terminal of La Spezia and at the tourism and dry bulk terminal sites of Genoa. As for metals, the subscript d indicates the dissolved fraction while the subscript p refers to the particulate fraction. - 4 HEAVY METALS PARTITIONING Metals partitioning between dissolved and particulate to suspended solids fraction is a dynamic process which is affected by several factors such as rainfall ph, alkalinity, runoff residence time and solids characteristics (Sansalone and Buchberger, 1997). Based on data collected at the container terminal site, metals partitioning across the rainfall-runoff event was examined thus relating to the hydrological aspects and the general water quality parameter (such as ph and TSS). To assess the dominant phase of each metal, the dissolved metal fraction, f d, has been calculated through the following expression: cd fd = c + c where c d and c p are respectively the dissolved and the particulate-bound concentrations. The f d value greater than.5 corresponds to a dominant dissolved fraction of metals NOVATECH 27 p d

5 Findings of the elaborations reveal a strongly dominant particulate-bound fraction for lead (all event mean f d =.21) independently of hydrologic aspects and runoff chemical-physical parameters; on the contrary copper and zinc behaviour is strongly dependent on the suspended solid concentration. To illustrate the different metal behaviour with respect to the mass delivery for total suspended solids two rainfall-runoff event are examined in the following section: the 4 September 25 event characterized by f d values for Zn, Cu and Pb respectively equal to.87,.68 and.39 and the 17 January 27 event characterized by f d values lower than.25. In Fig.1 both dissolved and particulate cumulative mass for zinc, copper and lead has been plotted as a function of the cumulative runoff volume for the 4 September 25 event. This event was characterized by the EMC value for TSS equal to 145 mg/l and by the occurrence of the first flush phenomenon, an exponential delivery behaviour of TSS mass with respect to runoff volume has been observed. As for metals mass delivery, results reveal three different behaviours: zinc show a predominant dissolved fraction across the rainfall-runoff event while the opposite behaviour is observed for lead. As for copper, it emerges a balanced partitioning between the two phases at the beginning of the wash-off process (corresponding to the most significant TSS mass delivery), afterwards the dissolved fraction predominates. Such behaviour comply with the tendency of divalent metals to hydrolyze, according to which the bonding preference of selected metal ions to iron oxides would be Pb > Cu > Zn. Cumulative Zn (g) Cumulative Cu (g) Cumulative Pb (g) Cumulative TSS (kg) TSS Fig. 1. Cumulative mass for metals (dissolved and particulate fraction) and total suspended solids as a function of the cumulative volume for the event of 4 September 25 at the container terminal of La Spezia. NOVATECH

6 On the contrary, the 17 January 26 event, illustrated in Fig.2, was characterised by a linear relationship between cumulative mass of TSS and cumulative runoff volume (no first flush occurrence) furthermore a significant transport of TSS mass was measured (EMC mean = 364 mg/l). As for each metal, such event shows a particulatebound fraction strongly predominant across the rainfall-runoff event and metals mass delivery behaviour clearly mimics the one observed for the total suspended solids. However it can be noticed that copper reveals the more balanced partitioning between the two phases. Cumulative Zn (g) Cumulative Cu (g) Cumulative Pb (g) Cumulative TSS (kg) TSS Fig. 2. Cumulative mass for metals (dissolved and particulate fraction) and total suspended solids as a function of the cumulative volume for the event of 17 January 26 at the container terminal of La Spezia. In order to investigate the temporal partitioning between metals in solution and suspended-bound fraction taking into account the TSS concentration, the behaviour of the partitioning coefficient K d during rainfall-runoff event has been analysed. K d has been determined as the ratio between metal mass normalised to the dry mass of solids to the dissolved metal concentration expressed as l/kg. Findings of the elaboration reveal that the metal partitioning coefficient K d varies by several orders of magnitude across each event and generally approaches equilibrium towards the end of the event. Furthermore it can be observed that the equilibrium coefficient significantly mimics the TSS trend manly for zinc and lead, as shown in Fig. 3. Finally, as for the events characterized by high delivery of total suspended solids (such as 29 September 5 and 17 January 6), the variation of K d is reduced in the range l/kg typical values for river and large lake (Glenn et al., 21). 152 NOVATECH 27

7 1e+6 1e+5 1e+4 1e+3 4 September 25 Zn Cu Pb TSS 19 October TSS [mg/l] 1e kd [l/kg] 1e+6 29 September January e+5 1e TSS [mg/l] 1e Fig. 3. The equilibrium partition coefficient, K d, with respect to Zn, Cu and Pb as a function of the cumulative runoff volume for the container terminal of La Spezia. (In the graph K d is represented in logarithmic scale). In each graph the corresponding TSS concentration are plotted. The study of metals partitioning has a direct implication in designing suitable treatment system. Indeed particulate-bound metals require sedimentation, coagulation or filtration processes and the operational choice has to be based on the solid characteristics (in terms of particulate size distribution and density); while the effective abatement of dissolved metals fraction needs adsorpotion, ion exchange or surface complexation mechanism (Dean et al. 25). Due to the predominance of the particulate-bound metals fraction, a simple classification of solids has been carried out through the determination of total solids, suspended solids and the settleable solids under quiescent settling in an Imhoff cone. Results indicate that on a mass basis about 6% of the total solids are defined as suspended (>.45 μm) and the settleable solids constitute about 3% of the total solids. These results confirm that traditional techniques mainly based on sedimentation alone (such as a volumetrically-based first flush tank) only provide low effective pollutant load abatement: indeed storm runoff is associated with a significant fraction of dissolved pollutants thus requiring appropriate physical-chemical treatment mechanism. NOVATECH

8 5 CONCLUSIONS Results obtained through this monitoring campaign point out the relevance of heavy metals in stormwater runoff and the role of suspended solids in metal partitioning between dissolved and particulate fractions. Even as a preliminary set of results, the characterisation of runoff in commercial ports confirmed the necessity to design suitable treatment system which includes physical-chemical mechanism for dissolved pollutants coupled with filtration for particulate bound metals. The monitoring campaigns carried on within the Ports of Liguria Region provide an important database on storm runoff quality from commercial ports. The final goal of the project is to determine suitable storm water management strategies for the port urban environment in order to better control water quality in coastal areas of the Liguria Region of Italy. LIST OF REFERENCES Barrett, M.E., Zuber, R.D., Collins, E.R., Malina Jr, J.F,. Charbeneau, R.J. and Ward, G.H. (1995). A Review and Evaluation of Literature Pertaining to the Quantity and Control of Pollution from Highway Runoff and Construction. 2nd Edition, CRWR, University of Texas, Rep Bertrand-Krajewski, J.-L., Chebbo, G. and Saget, A. (1998). Distribution of pollutant mass vs volume in stormwater discharges and the first flush phenomenon. Wat. Res. 32(8), Brockbank, C.I., Batley, G.E., Ball, J.E. and Tilley, J.H. (1999). Metals and hydrocarbons in stormwater runoff from urban roads. CSIRO Rep. ET/IR98R. Dean C.M., Sansalone J.J, Cartledge F.K. and Pardue J.H. (25). Influence of Hydrology on Rainfall-Runoff Metal Element Speciation. J. Env. Eng. 131(4), Deletic, A. (1998). The first flush load of urban surface runoff. Wat. Res. 32(8), Glenn III D.W., Liu D. and Sansalone, J.J. (21). Influence of Highway Runoff Chemistry, Hydrology, and Residence Time on Non-Equilibrium Partitioning of Heavy Metals: Implications For Treatment at the Highway Shoulder. Transportation Research Record, 1755, Gnecco, I., Berretta, C., Lanza, L.G. and La Barbera, P. (25) Quality of stormwater runoff from paved surfaces of two production sites. 1th Int. Conf. On Urban Drainage, Copenhagen, Denmark (published on CD-rom) Lanza, L., Leroy, M., Alexandropoulos, C., Stagi, L. and Wauben, W. (25). WMO Laboratory Intercomparison of Rainfall Intensity Gauges. Final Report. IOM No. 84, WMO/TD No Revitt, D.M. and Morrison, G.M. (1987). Metal speciation variations within separate stormwater system. Env. Tech. Letters., 8, Sansalone, J.J., Buchberger, S.G. (1997). Partitioning and First Flush of Metals in Urban Roadway Storm Water. J. Env. Eng. 123(2), NOVATECH 27

Ilaria Gnecco, Anna Palla, Luca G.Lanza, Paolo La Barbera

Ilaria Gnecco, Anna Palla, Luca G.Lanza, Paolo La Barbera NOVATECH 200 The ESTRUS project: Performance of catch basin treatment devices in the field Le projet ESTRUS : performance des dispositifs de traitement distribués sur le terrain Ilaria Gnecco, Anna Palla,