Development and application of landfill pretreatment technologies for Asia

Abstract

Most of the local authorities in Sri Lanka and in most parts of Asia has resorted to open
dumping or controlled dumping of wastes wherein lands are becoming a limited resource,
Landfill pretreatment technologies prolong the life of landfills and thus, the research focused
on improvements to existing and new inventions, Many composting methods: windrows,
static piles of different methods and aerobic reactors were tested and experimented, In taking
advantage of energy extractions, anaerobic digesters with up and downward flow was
compared, Furthermore new designs of horizontal hydrolytic/acidogenic reactor and a hybrid
system were developed and tested, In both biological transfonnations, process conditions
were optimized kinetically, Small windrows and static piles did not satisfy WHO standards,
However, mixing ten-day old wastes with raw wastes has stabilized the decomposing waste
rapidly, Mass and volume reductions were 56% and 67%, respectively, Even in large scale
applications, windrows and static piles were too costly, In comparison, Inclined Step Grate
(ISG) performed best It can also be used for maturing and aerating remaining fibres from
anaerobic digestion, The fibre removals from the first stage vertical anaerobic digesters were
posing numerous problems, including prolonged mass retention times (MRT), In these
reactors, it was deduced that downward movement of elute (leachate) was better than up flow
and that the horizontal reactor after many modifications proved to be versatile, The reactor
was optimized by following the kinetic analysis that seven days were required to stabilize the
reactor and every three days feeding gave 2,6 times the concentration of TDS compared to
daily feeding, It reached equilibrium in less than two weeks and it was operated continuously,
The hybrid system being developed at Asian Institute of Technology (AIT) seems promising
with specific methane yields of 140,35 and 62,55 L CH4/kg VS generated for loading rate I
and 2 kgYS/m3
, respectively