No abstract

This article presents an application of the Storm Water Management Model (SWMM) in order to predict the pollution in rainy weather in a combined sewer system catchment in Santander, Spain. Suspended solids (SS), chemical oxygen demand (COD) and total Kjeldahl nitrogen (TKN) were measured at the exit of the catchment and these parameters were used for the calibration and validation of the model. The process of hydraulic and quality calibration is described and the values of the adjusted parameters are presented, comparing them with those obtained from other studies. The calibrated model simulated accurately the hydrograph's shape and the time of presentation of the peak flows. The accuracy of adjustment of the volume was 96%. As for the quality validation, the accuracy of adjustment among the total simulated loads of SS, COD and TKN, and those measured at the end of the rainfall events were 93, 95 and 78% respectively, confirming the accurate confirming the relative accuracy of the model in the prediction mode. The phenomenon of the first flush was analysed, and it was determined that 65, 57 and 54% of the polluting loads of COD, SS and TKN respectively, were swept along by the first 30% of the volume in the rainfall events used for the calibration of the model.

No abstract

Peracetic acid (PAA) is the active component of a series of disinfectant products developed for the treatment of wastewater. These products have only recently been introduced onto the market so little published information exists about their efficiency. In this work the disinfection efficiency of PAA has been experimentally studied on raw wastewater, along with eventual regrowth after the ocean discharge of the treated water. Great variability has been observed in the inactivation of total coliforms by PAA, the influence of the pH of the wastewater was noteworthy. The disinfection action takes place in short times (around 5 to 10 minutes). After disinfection and mixing with real sea water the total coliforms present greater T90 values and disappearance times, having increased their concentration under laboratory conditions and in darkness.

The heavy metal pollution caused by road run-off water constitutes a problem in urban areas. The metallic load associated with road sediment must be determined in order to study its impact in drainage systems and receiving waters, and to perfect the design of prevention systems. This paper presents data regarding the sediment collected on road surfaces in the city of Torrelavega (northern Spain) during a period of 65 days (132 samples). Two sample types were collected: vacuum-dried samples and those swept up following vacuuming. The sediment loading (g m(-2)), particle size distribution (63-2800 microm) and heavy metal concentrations were determined. The data showed that the concentration of heavy metals tends to increase with the reduction in the particle diameter (exponential tendency). The concentrations ofPb, Zn, Cu, Cr, Ni, Cd, Fe, Mn and Co in the size fraction <63 microm were 350, 630, 124, 57, 56, 38, 3231, 374 and 51 mg kg(-1), respectively (average traffic density: 3800 vehicles day(-1)). By increasing the residence time of the sediment, the concentration increases, whereas the ratio of the concentration between the different size fractions decreases. The concentration across the road diminishes when the distance between the roadway and the sampling siteincreases; when the distance increases, the ratio between size fractions for heavy metal concentrations increases. Finally, the main sources of heavy metals are the particles detached by braking (brake pads) and tyre wear (rubber), and are associated with particle sizes <125 microm.