Anaerobic/Aerobic Treatment of Municipal Landfill Leachate

Abstract

Laboratory-model studies were conducted to develop design guidelines for treatment of high-strength leachate (23,000 mg COD/L, 17,500 mg BOD/L, 8,000 mg TOC/L, 1,000 mg Fe/L and 80 mg Zn/L) generated from a landfill site that serves the metropolitan area of Halifax, Canada. The selected processes included two treatment systems, I and II. System I consisted of an anaerobic fixed film reactor (AFFR1), the effluent from which was further treated by an aerated lagoon and a settling lagoon in parallel. System II consisted of a second AFFR, but was not followed by any other treatment. The AFFR’s were upflow cylindrical tanks with plastic "Tellerette" rings which provided the fixed surface. This is the first known investigation which utilized the rings (patented by Pennwalt Corporation) that are manufactured as packing material in air pollution control devices. The pH-adjusted, settled and nutrient-supplemented leachate (pre-treatment step) was added to AFFR1, and AFFR2 to maintain organic loads of about 2 and 1.6 kg COD/day.m3, respectively. The two fixed film reactors were kept at 32 ± 1°C and the two lagoons at 20 ± 2°C. The 12-week study showed that system Ia, consisting of pre-treatment, AFFR1, and aerated lagoon, resulted in the best performance; system Ib, (pre-treatment, AFFR1 and settling lagoon) generated the second best effluent, followed by System II, which produced an inferior effluent. System la resulted in greater than 99% removal of COD, BOD, TOC, Fe and Zn. System Ib removed between 98% and 99% of COD and TOC and more than 99% of BOD, Fe and Zn. System II (pre-treatment and AFFR2), however, could remove between 97% and 98% of COD and TOC, and in excess of 99% of BOD, Fe and Zn. Similar data for the remaining 36 parameters are also included. Biogas generated by the two AFFR’s ranged from about 0.4 to 0.57 m3 per kg of COD destroyed. Comparisons have been made between the performance potentials, capital and operating costs and energy requirements, of the Systems Ia, Ib and II.