A Study on the Effectiveness of Using a Bio-Physical Pilot Plan Rotating Biological Contractor-Sedimentation as a Secondary Treatment of Leachate

The main objective of this study is to carry out an investigation and evaluation on the effectiveness of using a biophysical unit treatment, which is a compacted unit combining an aerobic biological system; a rotating biological contractor (RBS) and physical system; a sedimentation tank, as a secondary treatment of leachate from Pulau Burong Landfill in Seberang Perai. The influent leachate to the unit is supplied from an aerated lagoon which is the landfill’s primary treatment of which effluent qualities do not comply to Standard B effluent parameter limits stipulated by the Environmental Quality Regulation (Sewage and Industrial Effluents), 1979 in the third schedule of the Environmental Quality Act, 1974. This pilot scale study is condected at Pulau Burong Landfill site in order to obtain operating data under real field conditions.

Evaluation of the Unit’s effectiveness is done by monitoring treatment efficiencies in the (i) unit as a whole system and (ii) and its’ individual system which is the biological –RBS system and the physical-sedimentation system. Treatment efficiencies are expressed in the form of substrate removal for parameters COD, NH3-N, SS, VSS and metals removal for parameters Fe, Mn, Ca, Mg and Ni. Charges in pH and alkalinity of the effluent are also monitored. Investigation is also carried out to identify the effect of loading rates on the unit’s treatment efficiencies; while in the biological RBC system, the relationship between loading rates and substrate removal efficiencies are obtained.

The study is also extended to the identification of microbes in the biomass of the RBC system.

Areal organic loading rate has been recognized as the major factor affecting RBC system treatment efficiency. Observations from the substrate removal trends indicate that percentage removals are reversibly related to areal organic loading rates. Meanwhile, nitrogen and metal removal trends too showed the same tendency of having percentage removals reversibly related to their respective loading rates.

Finding from this study indicate that the pilot plant is effective as secondary treatment for leachate only when it is subjected to low areal loading rates. This finding is based on the performances of removal for organic parameters, COD of which 57.3% is removed at 9.68g COD/m2 day loading rates, VSS with removal of 51.4% at 0.58g VSS/m2 day loading rate and SS with removal of 60.3% at 0.91g SS/m2 day loading rate. Meanwhile, the pilot plant performs better with nitrogen removal, which indicates a 95.5% NH3-N removal at loading rate of 6.09g NH3-N/m2 day. Removals of all the organic and nitrogen parameters involved (except for SS) are mostly from the biological RBC system. The physical sedimentation system removes SS effectively. The qualities of the effluent for these parameter (except for SS) are still very high compared to the parameter limits of the Standard B. meanwhile, metal removal for Fe, Mn and Ca are quite high with percentage of 90.0, 84.0 and 86.4% respectively at low loading rates of 0.0172, 0.0039 and 0.0050g/m2 day. Removal of Mg and Ni are fairly good at 55.7% and 66.7% with loading rates of 0.0180 and 0.0045 g/m2 day respectively. The qualities of the final effluent for these parameters complied to Standard B parameter limits.

From the microbiological analysis, two types of bacteria, Pseudomonas stutzeri and Enterobecter agglo, erans are identified in the biomass of the RBC system. The rest of the microbes present are fungus types (Staphylococcus sp. Rhizopus sp. Aspergillus sp., and Penecillum sp.) both types of bacteria identified are typical species found in the biomass of the RBC system. Basically, the optimal utilization of the reactor treatly leachate is its application with high loading rates. However, the unit treatment being studied is only capable of removing organic pollutants with low loading rates. Nevertheless, the situation can be overcome by implementing some modifications, which are suggested in detail in the conclusion of this thesis, for future study.