Removal of Adsorbable Organic Halides (AOX) from Recycled Pulp and Paper (P&P) Mill Effluent Using Granular Activated Carbon–Sequencing Batch Biofilm Reactor (GAC-SBBR)

Paper mills generate varieties of pollutants depending upon the type of the pulping process. The wastewaters discharged from these mills have high chemical oxygen demand (COD) and colour, in which indicating high concentrations of recalcitrant organics. This study was conducted using a Granular Activated Carbon – Sequencing Batch Biofilm Reactor (GAC-SBBR) of 3.0 L working volume, operated in an aerobic condition and packed with 200 gL-1 of 2-3 mm granular activated carbon (coconut shells) as a medium for the biofilm growth. For the six of months, the hydraulic retention time (HRT) was set at 36 hours and later it was adjusted to 24 hours in order to evaluate the performance of the system. The treated wastewater samples for these studies were taken from a recycled pulp and paper mill factory in Pahang, Malaysia with 4 different batch characteristics. The adsorbable organic halides (AOX) that had been determined and treated were pentachlorophenol (PCP), 2,3,4,5-tetrachlorophenol (2,3,4,5-TeCP), 2,4,6-trichlorophenol (2,4,6-TCP), 2,4-dichlorophenol (2,4-DCP), 2-chlorophenol (CP) and phenol at various concentration ranges. The Monod growth kinetic parameters for the process specific growth rate coefficient (µh), half saturation coefficient (Ks), endogenous decay coefficient (DH) and Yield coefficient (YH) obtained were 0.0037 hr-1, 65.23 mgL-1, 4x10-5 hr-1 and 0.36 mg/mg, respectively. Analysis of the growth kinetic parameters in GAC-SBBR had deduced that the system was suitable to operate on long biomass retention time (BRT) under anoxic condition. The results also indicated that the biofilm attached onto granular activated carbon (GAC) can substantially remove these recalcitrant organics in the wastewater, within the range of 10 – 100% AOX removal depending on the selected HRTs.