Theoretical analysis of municipal solid waste treatment by leachate recirculation under anaerobic and aerobic conditions

Abstract

Long-term emissions of Municipal Solid Waste (MSW) landfills are a burden for future generations because of the required long-term aftercare. To shorten aftercare, treatment methods have to be developed that reduce long-term emissions. A treatment method that reduces emissions at a lysimeter scale is re-circulation of leachate. However, its effectiveness at the field scale still needs to be demonstrated. Field scale design can be improved by theoretical understanding of the processes that control the effectiveness of leachate recirculation treatment. In this study, the simplest and most fundamental sets of processes are distilled that describe the emission data measured during aerobic and anaerobic leachate recirculation in lysimeters. A toolbox is used to select essential processes with objective performance criteria produced by Bayesian statistical analysis. The controlling processes indicate that treatment efficiency is mostly affected by how homogeneously important reactants are spread through the MSW during treatment. A more homogeneous spread of i.e. oxygen or methanogens increases the total amount of carbon degraded. Biodegradable carbon removal is highest under aerobic conditions, however, the hydrolysis rate constant is lower which indicates that hydrolysis is not enhanced intrinsically in aerobic conditions. Controlling processes also indicate that nitrogen removal via sequential nitrification and denitrification is plausible under aerobic conditions as long as sufficient biodegradable carbon is present in the MSW. Major removal pathways for carbon and nitrogen are indicated which are important for monitoring treatment effectiveness at a field scale. Optimization strategies for field scale application of treatments are discussed.

Characterization of controlled landfill leachate from the city of Guaratinguetá - SP, Brazil

“…All this information justifies the low COD (1,013 mg L -1 ) value and the negligible value of BOD (< 5.0 mg L -1 ), once the former controlled landfill of Guaratinguetá -SP had been active for about 30 years, on the date the leachate studied was collected. Also verified were the concentrations of the total inorganic and organic solids, which, despite not considering specificity, the results help to analytically assess the untreated landfill slurry (Peng, 2017;Van Turnhout, 2018;Zhang et al, 2017b). Table 2 includes the STF/STV ratio, which shows that the total inorganic fraction found in the leachate is 3.6 times as great as the total organic fraction.…”

“…The addition and analyte recovery tests verify a minimum 90% recovery in all the analytical methodologies used, which therefore ensures the reliability of the spectrometric and spectrophotometric analytical results presented in Table 2. For being predominantly anaerobic environments, sanitary landfills produce effluents with considerably low nitrite and nitrate concentrations (Klein et al, 2017;Mandal et al, 2017;Van Turnhout, 2018). Conversely, the great biological activity found both in the waste mass and in the drainage system causes most of the organic nitrogen to be converted into ammoniacal nitrogen within the very landfill.…”

“…The main chemical element used to control eutrophication is phosphorous, since the cyanobacteria are capable of fixing atmospheric nitrogen, not allowing the reduction in nitrogen concentration with the reduction in affluent load (Von Sperling, 2005;Peng, 2017). Practically the whole of the phosphorus found in leachates is in the form of orthophosphates (Van Turnhout, 2018). They act as an alkaline cover, contributing to the partial alkalinity (pH=8.05, Table 2).…”

“…BOD5/COD ratio values below 0.05 are characteristic of stabilized leachates, nontreatable by biological methods (Deng, 2007). The fraction of organic matter oxidizable by potassium dichromate, in the COD technique, was obtained by the TOC/COD ratio, with a 0.28 response (Li et al, 2017;Peng, 2017;Van Turnhout, 2018).…”

“…Although the controlled landfill has been deactivated, the slurry and wastewater keep being generated once the landfill keeps presenting decomposition reactions of the organic parcel until the wastes disposed of have been fully stabilized (Klein et al, 2017;Mandal et al, 2017;Van Turnhout, 2018). However, the liquid waste generated will be a polluting source of underground waters of the whole region circumscribed for a number of years, owing to the toxic character of the slurry gradually liberated with the decomposition of the organic matter and of the inorganic load leaching, since the effluent is not adequately collected by means of blanket and lateral ducts (Peng, 2017;Zhang et al, 2017a;2017b).…”