water Article Ultrasound-Assisted Treatment of Landfill Leachate in a Sequencing Batch Reactor Anna Grosser 1,* , Ewa Neczaj 1, Magdalena Madela 1 and Piotr Celary 2 1 Faculty of Infrastructure and Environment, Czestochowa University of Technology, 42-201 Czestochowa, Poland;
[email protected] (E.N.);
[email protected] (M.M.) 2 Central Laboratory for Measurements and Research, 44-335 Jastrzebie-Zdroj, Poland;
[email protected] * Correspondence:
[email protected]; Tel.: +48-343-250-917 Received: 8 January 2019; Accepted: 7 March 2019; Published: 12 March 2019 Abstract: Purification of leachates is currently a big challenge due to their high variability in composition and amount. The complexity of the medium, namely leachates, makes new solutions highly sought after and finds the existing ones in need of optimization. The effects of ultrasound pretreatment (20 kHz, 12 µm) on biological treatment of landfill leachates in the form of processes carried out in two sequencing batch reactors were investigated. The experiment was divided into two stages. In the first stage, leachate was treated by an ultrasonic field at different sonication times (0.5, 1, 3, 5, 10 and 15 min). Next, leachates with and without conditioning were combined with municipal wastewater in the following ratios: 5, 10, 15 and 25% v/v. For optimal processing time (3 min), 16% removal of COD was achieved. In turn, the BOD5/COD ratio was 0.3, which is higher by approximately 270% than that of the non-conditioned sample. Further elongation of sonication time did not significantly affect both parameters. Also, pretreatment of leachate resulted in a maximum increase noted in the study of specific oxygen uptake rate and dehydrogenase activity of approximately 21 and 2 times compared to the non-conditioned sample.