TREATMENT OF BIODIGESTER EFFLUENT : CATALYTIC THERMAL TREATMENT (CATALYTIC THERMOLYSIS) WITH ENERGY RECOVERY FOLLOWED BY WET OXIDATION

Parmesh Kumar Chaudhari*, Bidyut Majumdar¹, Raj Kumar Singh² and Shri Chand³

1. Department of Chemical Engineering, National Institute of Technology, Raipur-492001 (INDIA)
2. Department of Chemistry, National Institute of Technology, Raipur-492001 (INDIA)
3. Department of Chemical Engineering, Indian Institute of Technology, Roorkee-247667 (INDIA)

*E-mail : pkchaudhari@rediffmail.com

Received on August 18, 2009 and accepted on December 04, 2009

ABSTRACT

The organic wastewater having Chemical Oxygen Demand (COD) = 34 kg/m³ and Biochemical Oxygen Demand (BOD) = 6.3 kg/m³ from the alcohol biodigester reactor was catalytically thermally treated at 140 oC under autogenous pressure (0.86 MPa) at initial pH (pH₀) 1 in absence of air. The catalyst (CuO) mass loading (C_W) was 3 kg/m³. The reduction of organics was due to formation of solid residues. These residues were separated by filtration. The residues have property similar to lignite in term of its heating value. The supernatant of filtration having COD = 10.2 kg/m³ and BOD = 1.075 kg/m³ was subjected to wet oxidation process, which further reduced the COD to 3.06 kg/m³ and BOD to 0.190 kg/m³. The two step process catalytic thermolysis followed by wet oxidation (at T = 140 oC, = 4 bar, pH0 = 1.5) was able to overall 90.6 % COD reduction, 96 % BOD reduction and 95 % colour reduction. The oxidation was found to be two step process, first fast then slower in second step. The pH of effluent was increased to 1.5 from 1.0 after thermolysis, which, further increased to 2.47 after wet oxidation process.

Keywords : Thermal treatment, Catalytic thermolysis, Wet oxidation, Biodigester effluent, COD reduction, Residues.