Physico-chemical Investigation On Dumpsite Leachate
[A CASE STUDY OF ILORIN METROPOLIS]

    In this section, a review of the various treatments is mentioned in details. The leachate treatment processes have different effectiveness depending on the leachate from landfill of different ages. The biological treatment process has been found to be effective on leachate from young landfills (Loukidou & Zouboulis, 2000). Sometimes leachate can be treated by traditional package treatment plants on site, but this kind of treatment is expensive to build and operate (Liehr et al., 2000). An effective type of treatment is the biological process, especially for young leachate which has mainly volatile fatty acids, but it is not effective on old leachate because in many cases high COD value was found in leachate after biological treatment (Trebouet et al., 2001).
2.3.5.1 Biological treatment
A combination of aerobic, anaerobic and anoxic processes is the main processes used for biological treatment (Im et al. 2001). Biological treatment of landfill leachate usually results in low treatment efficiencies because of high chemical oxygen demand (COD), high ammonium-N content and also presence of toxic compounds such as heavy metals (Fikret et al., 2003).
Most of organic materials in leachate from young landfill (< 2yrs) are easily biodegradable by aerobic biological oxidation. However, some adjustment needs to be made to the pH by adding nutrient to optimize the process. The most common aerobic biological treatment methods are (Renou et al., 2008):-
    aerated lagoons
    activated sludge plants
    rotating biological contactors (RBC)
    trickling filter
    sequential batch plant co-treatment with sewage
    parts of the landfill body used as a reactor
    anaerobic filter
2.3.5.2 Physico-Chemical treatment
A combination of Physical, Chemical and biological methods is almost necessary for the efficient treatment of these heavily polluted leachate(Rautenbach & Mellis, 1994) Physiochemical treatments exist for not only removing refractory substances from the leachate, but also it is counted as a refining pre-step which is required before biological treatment of leachate.
These methods are like those used to reduce COD, decrease suspended solids, colloidals, particles, floating material, heavy metals, suspended soil and color (Tonni et al., 2005) by either, flotation, coagulation/flocculation, adsorption, chemical oxidation and air stripping.
Physical-chemical treatments of landfill leachate are used in addition to the treatment line (pre-treatment or last purification) or to treat a specific pollutant (stripping for ammonia) (Renoua et al., 2008). High COD and ammonium content, high COD/BOD ratio and the presence of toxic chemicals like heavy metals present difficulties in Physico-Chemical treatment of landfill leachate (Park et al., 2001). Sometimes a combination of physical, chemical and biological approaches is used for landfill leachate treatment, as it has been difficult to get efficiencies from the treatment using a single approach (Chiang et al., 2001; Ahn et al., 2002; Lin & Chang, 2000).
Most of the methods used for landfill leachate treatment include sedimentation, air stripping, adsorption and membrane filtration (Bohdziewicz et al., 2001; Marttinen et al., 2002; Trebouet et al., 2001).
On the other hand, within the chemical treatment methods which are used for the leachate treatment there are some main methods like coagulation, flocculation, chemical or electrochemical oxidation (Ahn et al., 2002; Chiang et al., 2001).
These methods have been developed and improved for landfill leachate treatment. Pressure driven membrane filtration methods have been used along with biological treatment of landfill leachate (Bohdziewicz et al., 2001). Before using biological treatment in order to improve COD removal, the Ozone pre-treatment should be used first. Also, chemical precipitation of ammonium as magnesium ammonium phosphate by adding of MgCl2 and Na2HPO4 has also improved COD removal by biological oxidation (Li & Zhao, 2001).
Another method which is the Up Flow Anaerobic Sludge Blanket (UASB) reactors had been used for landfill leachate treatment and it is efficient up to 92% COD removal (Kennedy & Lentz 2000). In addition, roughly 98% of the organic material has been removed from landfill leachate by using the combination of anaerobic-aerobic and rotating biological contactor (RBC) systems which have been used by (Park et al., 2001).