To keep overflows of raw effluent to a minimum during wet weather conditions, we investigated the ability of a secondary clarifier of an activated sludge treatment plant to accept hydraulic overloads without being washed out. The experiments, which were conducted on a full scale 8000 p.e. treatment plant, showed the feasibility of the project, and suggested some features, which were included in a one-dimensional model designed to study the behavior of the sludge blanket in the clarifier. This model takes into account the effect of convection currents, suspected to play an important part in the rising of sludge blankets. The sensitivity of the model to sludge settleability prevented its use with long times-series, unless a continuous recalibration was performed. Nevertheless, this model appears very interesting for a better understanding of the dynamics of the clarifier, as described by measured data. It could be used in relation with sensors to improve the operation of the treatment plant.

No abstract

No abstract

No abstract

Monitoring systems for measuring rainfall, as well as flow rates and pollutant quantities conveyed by sewers and/or discharged by stormwater overflow devices, have become a common feature in many municipal sewer services, in part spurred by recent regulatory requirements. However, the state of measurement conditions in sewer facilities does not always ensure reliable results. For this reason, it is essential that measured values be carefully screened prior to their use, since many sources of disruption capable of skewing data can be encountered. The present article describes a method for validating dry-weather data a posteriori. This method relies upon flow rate forecasts, a combination of standard daily wastewater flow profiles and an estimation of infiltration flows. Measurement results are then compared with this forecast and an appropriate series of statistical tests are run to detect all major data anomalies. A number of diagnostic rules are then applied in order to derive an initial interpretation of these anomalies and, in particular, to identify the influence of rainfall events.