Chemical Oxygen Demand Balance and Energy Recovery in Wastewater Treatment Plant of Pulp and Paper Industry (Corrugated Board)

Abstract

Pulp and paper mills generate wastewater with high organic content expressed in chemical oxygen demand (COD). The organic material can be converted into biogas/methane at the Wastewater Treatment Plant (WWTP) through an anaerobic process. Besides being used to improve the quality of wastewater, WWTP can also produce energy. This study aimed to develop a model of the wastewater treatment process using the principles of COD balance and carrying out energy recovery. Model development started from COD balance analysis, energy potential calculation, and wastewater treatment process system design with a closed system to fulfill energy independently. The calculation was based on waste volume of 2,500 m³/day which can produce 1,313 kg of methane (1,970 m³) equal to 4,398.25 kg COD. By-product in the form of primary sludge was 19,897 kg equal to 3,979 kg of COD containing 2,250 kg of solids equal to 404.84 kg of COD. The resulting effluent has a COD content of 638.37 kg/day equal to  255.35 mg/l and still below the regulatory threshold of 350 mg/l. Methane gas and primary sludge are used as fuel for boiler to generate total actual steam of 43,105 kg/day. The produced energy is able to meet the needs of steam and electricity of WWTP at 773 kg/day and electricity of 1,290 kW respectively with an excess of 827 kW (64.12% surplus).

Keywords: anaerobic process, COD, energy recovery, self-sufficient energy, pulp and paper mill