Anaerobic Digestion of Nssc Pulping Effluent

Document Type : Original Research Paper


1 National University of Sciences and Technology, Islamabad (MCE-NUST), Pakistan

2 Department of Civil and Environmental Engineering, UET Taxila, Pakistan


Two UASB reactors R-I and R-II, each of 10liters capacity, made up of acryl material were
operated parallel and continuously for a period of 220 days, using actual effluent of the NSSC pulp and paper
mill, at mesophilic temperature and neutral pH. The main objective was to investigate the treatability
performance of the reactors at varying OLR and HRT in terms of TOC and lignin removal. The reactor R-I was
used by conventional procedure, whereas, for the reactor R-II methanol and activated carbon was added to
supplement its efficiency. Corresponding to an optimum OLR of 4.5kg/m3-day and HRT of 18hrs, the reactor
R-II gives 69% TOC and 60% lignin removal. But, in the reactor R-I at same operating conditions, only 56%
TOC and 51% lignin removal was noticed. However, the biogas yield in the reactor R-I was noticed relatively
more than in the R-II. The biogas yield observed was 0.28m3/kg-CODrem and 0.18m3/kg-CODrem in the reactor
R-I and R-II, respectively, with 56-58% methane content in both the reactors. The average VFAs concentration
observed in the reactor R-I and R-II is 360mg/L and 230mg/L, respectively. The results of this study suggest
that the use of methanol and activated carbon to enhance the treatability efficiency of the UASB reactor is a
viable option for the treatment of NSSC pulping effluent.