Characterization of screenings from three municipal wastewater treatment plants in the Region Rhône-Alpes

The objective of this study was to analyze the composition of the screenings sampled from three municipal wastewater treatment plants (wwtp) located in the Region Rhône-Alpes, France. The plants were equipped with multi screening stages with gap sizes ranging from 60 to 3 mm. Waste production flows from each plant were monitored over at least 48 hours in each sampling campaign in order to calculate average production rates. Waste samples of at least 7 kg were collected from each screening stage in each plant at different seasons to evaluate the influence of different parameters on the composition of the waste. An overall 30 samples were thereby collected between May 2007 and February 2008, dried at 80°C for a week, and subsequently hand sorted into 10 fractions of waste materials. Results showed that the average production varied between 0.53 and 3.49 kg (wet mass) per capita per year. The highest production rates were observed during or immediately after rainy weather conditions. The dry matter content ranged between 14.4 and 29.2% of wet mass, and the volatile matter content was between 70.0 and 90.5% of dry mass. The predominant materials in the screenings were found to be sanitary textiles which accounted for 65.2% to 73.6% of dry weight and fines (<20 mm) which accounted for 15.2% to 18.2% of dry weight. These proportions were relatively similar in each plant and each sampling campaign.