CO-TREATMENT OF LANDFILL LEACHATE IN SBR SYSTEM: LAB-SCALE CASE STUDY REPORT

SUMMARY: Landfill leachate represents nowadays one of the most controversial topics in the waste management cycle. A possible alternative for treating aged landfill leachate is represented by the co-treatment with municipal wastewater (MWW) that provides the necessary amount of biodegradable substances to enhance the development of bacteria metabolism. The correct tradeoff between landfill leachate and MWW represent a key factor in order to avoid inhibition of biomass activity. The paper reports the results of an experimental research carried out on two lab-scale Sequencing Batch Reactors (SBRs) fed with synthetic wastewater and landfill leachate in different percentages (SBR1 fed with 20% v/v and SBR2 fed with 40% v/v of landfill leachate, respectively). The experimental campaign lasted almost 200 days and was divided into two phases (named phase I and II, respectively) characterized by different operational parameters of the SBRs cycle with the aim to investigate the influence of aeration phase duration on the biological removal of organic carbon and ammonium. Periodical sampling of inlet, mixed liquor, supernatant and effluent allowed investigating the biological process involved by measuring process parameters such as COD, TOC, NH4-N, NO3-N, NO2-N, TN, pH, salinity and electrical conductivity. Moreover, particle size distribution (PSD), extracellular polymeric substances (EPSs) and soluble microbial products (SMPs) of mixed liquor were also measured. Finally, respirometric techniques allowed the assessment of heterotrophic and autotrophic biomass viability. Achieved results allowed to notice a significant influence of landfill leachate in carbon removal (mean efficiency close to 60 % and 40% for SBR1 and SBR2 respectively). With reference to ammonium nitrogen oxidation, SBR1 was not affected by the leachate whereas in SBR2 significant inhibition phenomena occurred during the whole experimentation with temporary accumulation of NO2-N (due to nitrobacter inhibition). Moreover, during the last days of phase I, an aerobic granulation process occurred in SBR2, with a mean diameter of granules close to 0.2 mm.