Energy Valorization of Fine Screenings from a Municipal Wastewater Treatment Plant

Abstract

The aim of this paper was to evaluate the characteristics and the energy potential for the methane production of fine screenings collected from the primary stage of a municipal wastewater treatment plant, and assess the impact on the properties and the oxygen demand of the aqueous effluents downstream from the sieves. Commercial filter bags with sieve openings of 3000, 1250, 1000, and 300 μm were used for the collection of screenings following a measurement of their biochemical methane potential. It was revealed that solid fractions from the sieves with a large size presented a high net methane production capacity exceeding 900 mL/g VS, but the gas production rate was rather slow, requiring a long time to reach the final value. However, cumulative solid fractions containing particles with a size larger than 300 μm had a lower net methane production, about 700 mL/g VS, but with a faster rate, resulting in almost 80% of the total volume released in 30 days. Aqueous samples downstream from the sieves presented decreasing organic matter content by sieve size and reduced the requirements for aeration oxygen. The installation of fine sieves in existing municipal wastewater treatment plants, therefore, may be beneficial due to the enhancement of biogas production and a reduction in the oxygen consumption of the activated sludge process.