LIMING IMPACT ON GRANULES ACTIVITY OF THE MULTIPLATE ANAEROBIC REACTOR (MPAR) TREATING WHEY PERMEATE

A 19.2 l multiplate anaerobic reactor (MPAR) was used to assess the im pact of lime (Ca(OH),) on the anaerobic treatment of whey permeate eff luents. The amount of Ca(OH), required to maintain the pH of the whey permeate around 5 ranged between 3.0 and 4.5 kg/m(3), which correspond ed to concentration varying between 1.62 and 2.43 kg/m(3). Soluble che mical oxygen demand (GOD) removal efficiency exceeded 92% with a metha ne production rate of 6.7 m(3)/m(3).d. at an organic loading rate (OLR ) as high as 20 kg COD/m(3).d. Extended operation of the MPAR resulted in the accumulation of significant amounts of calcium precipitates in the sludge bed which reached after three months of operation 0.19, 0. 25 and 0.33 kg Ca2+ per kg of suspended solid (SS) in the lower, the m iddle and the upper compartment of the MPAR, respectively. The volatil e suspended solids to suspended solids ratio (VSS/SS) decreased from 0 .83 in inoculum to 0.37, 0.22 and 0.08 in the lower, the middle and th e upper compartment of the MPAR, respectively. As a result, the solubl e COD reduction and the methane production rate decreased to 31% and t o 2.3 m(3)/m(3).d. respectively, at OLR of 20 kg COD/m(3).d.