Anaerobic Tratment Kinetics Of Municipal Landfill Leachate

Abstract

Landfill leachate taken from a young municipal landfill site (3.5 years old),containing high organic contaminants (Total Organic Carbon -TOC of about 5000 mg L-1), was treated in bench-scale Anaerobic Sequencing Batch Reactors (ASBR), and an Anaerobic Hybrid Bed Filter (AHBF) at 35oC. 20 months testing program has been conducted at varied influent leachate concentration of 546-4800 mgTOC L-1, Hydraulic Retention Time(HRT) of 10-1.5 days and Solid Retention Time(SRT) of 40-9 days in ASBR's and influent leachate concentration of 1250-4490 mgTOG L-1 , and HRT of 5.1-0.9 days in AHBF ASBR achieved 73.9% TOC removal at maximum organic loading rate of 2.8 kgTOC m-3 d-1 at 1.5 days of HRT and 65.3% at 0.561 kgTOC kgVSS-1 d-1 ofmaximum specific loading rate and 2 days of HRT. The AHBF maintained 74.7% TOC removal at 1.08 kgTOC m-3 d-1 of loading and 2.4 days of HRT. Methane conversion ratio averaged 0.742 m3CH4 kgTOC-1 removed at(STP). Reaction rate constants obtained from ASBR and AHBF data were ko = 483-1480 mg L-1 d-1, k1721/2=10.5-30 mg1/2L-1/2 d-1, k1 = 0.45-1.5 d-1, k2 = 3.5-10.4 d-1. Biomass yield coefficient, Y, and biomass decay coeffiıcient, kd, evaluated from ASBR data are in the range of 0.45-0.3 gVSS gTOC-1 removed and 0.003-0.022 d-1 respectively. In order to select a growth rate model relating specific growth rate, m, to substrate concentration, S, for acclimated sludge, to represent anaerobic leachate degradation, experimental data from ASBR's were fitted to the noninhibitory model (Monod) and four inhibitocy models using least square technique. The range of biokinetic constants were as follows: mm = 0.05-0.142 d-1, K8 = 1500-750 mgTOC L-1, Ki = 685,700-75,000 mgTOC L-1, n = 0.0028-0.0045, Sm, = 7500-5500 mgTOC L-1. Corresponding mm* and S* values were in the range of 0.047-0.118 d-1 and 29,800- 4030 mgTOC L-1 respectively. F-test performed between Monod (the lowest variance) and the inhibition models showed that inhibition models were not different from Monod model at both %5 and %1 significance levels. Kinetic parameters also indicated that, in this study range, anaerobic treatment of leachate presented slight inhibition.