Comparison of two biological treatment processes using attached-
growth biomass for sanitary land®ll leachate treatment
M.X. Loukidou, A.I. Zouboulis *
Division of Chemical Technology, Department of Chemistry, Aristotle University, GR-54006 Thessaloniki, Greece
Received 24 May 1999; accepted 15 January 2000
``Capsule'': Both methods were eective in removing nitrogen, organic matter, color and turbidity.
The objective of this investigation was to compare two biological systems using attached-growth biomass, for treatment of lea-
chates generated in a typical municipal solid waste sanitary land®ll. A moving-bed bio®lm process, which is a relatively new type of
biological treatment system, has been examined. It is based on the use of small, free-¯oating polymeric (polyurethane) elements,
while biomass is being grown and attached as bio®lm on the surface of these porous carriers. A granular activated carbon (GAC)
moving-bed bio®lm process was also tested. This method combines both physico-chemical and biological removal mechanisms for
the removal of pollutants. The presence of GAC oers a suitable porous media, which is able to adsorb both organic matter and
ammonia, as well as to provide an appropriate surface onto which biomass can be attached and grown. A laboratory-scale
sequencing batch reactor (SBR) was used for the examination of both carriers. The eects of dierent operation strategies on the
eciency of these biological treatment processes were studied in order to optimize their performance, especially for the removal of
nitrogen compounds and of biodegradable organic matter. It has been found that these processes were able to remove nitrogen
content almost completely and simultaneously, the removal of organic matter (expressed as BOD
and COD), color and turbidity
were suciently achieved. # 2000 Elsevier Science Ltd. All rights reserved.
Keywords: Attached-growth biomass; Moving-bed bio®lm; Polyurethane carriers; GAC; Land®ll leachate treatment
The method of sanitary land®ll for ultimate disposal
of municipal solid waste continues to be widely accepted
and used, especially among the Mediterranean coun-
tries. In order to minimize the negative environmental
impacts, usually created by the application of this
method, it is necessary to pay particular attention to the
selection of a disposal site, which should also be prop-
erly designed, constructed, operated and monitored
(Qasim and Chiang, 1994). The generated leachate can
cause considerable environmental problems, becoming a
major pollution hazard when contacting the surround-
ing soil, ground or surface waters. Therefore, in order to
avoid environmental deterioration, land®ll leachate
must be collected and appropriately treated before being
discharged into the environment.
Freshly produced land®ll leachates are usually high-
strength wastewaters, characterized by low pH values
(5±6), high BOD
(4000±13,000 mg/l) and COD (10,000-
60,000 mg/l) values, as well as by the presence of several
other toxic/hazardous compounds (Ehrig, 1989). Sev-
eral treatment options have been utilized for leachate
treatment, presenting varying degrees of eciency. The
main applicable methods are biological, chemical,
membrane separation and thermal treatment processes
(Forgie, 1988). Physico-chemical processes are generally
considered of higher cost and lower eectiveness. Bio-
logical processes based upon suspended-growth bio-
mass, such as conventional activated sludge processes,
were proved to be eective for the removal of organic
carbon and nutrients content. Nevertheless, the problem
of inadequate sludge settleability has usually been
encountered, as well as the need for longer aeration times,
for settling tanks of larger volume and for total biomass
recycling (Gonzalez-Martinez and Garzon-Zuniga, 1996).
Therefore, a number of innovative biological treatment
methods have been investigated.
0269-7491/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
Environmental Pollution 111 (2001) 273±281
* Corresponding author. Fax: +30-31-206-138.
E-mail address: firstname.lastname@example.org (A.I. Zouboulis).