CONTROL OF ORGANIC LOADING RATE USING THE SPECIFIC METHANOGENIC ACTIVITY TEST DURING START-UP OF AN ANAEROBIC-DIGESTION SYSTEM

The specific methanogenic activity test (SMA) was used to determine a suitable organic loading rate during the start-up phase of a crossflow ultrafiltration membrane anaerobic reactor system (CUMAR). The SMA te st was immediately carried out after seeding the reactor with sludge t aken from a municipal wastewater treatment plant digester in order to determine the most acceptable initial organic loading rate. The initia l test results during the first week showed that the acetoclastic capa city of the reactor sludge, at an organic loading rate (OLR) of 1 kg C OD/m(3).d, was found to be low which resulted in a very poor COD remov al efficiency, i.e. 14%. Therefore the OLR was maintained at approxima tely 0.7 kg COD/m(3).d in the next two weeks of operation resulting in the COD removal efficiency of over 65% in the effluent. Based upon th e SMA tests results, the OLRs were either increased or decreased in or der to improve performance of the system and to achieve stable conditi ons which further resulted in an excellent organic matter removal, i.e . over 98% COD and almost 100% BOD removal at an OLR of over 1 kg COD/ m(3).d. At this point the ratio of actual methane production (AMP) rat e of the CUMAR system to potential methane production (PMP) rate deter mined from the SMA test was 0.45, which ensured that the CUMAR system could be loaded at higher organic loading rates for the remainder of t he operating period.