Evaluation of Sampling Methods Required by Oil Grit Separator Testing Protocols

Performance testing of oil grit separators requires determining how effectively they remove sediment from water. This requires sampling the effluent. This study looked at the effectiveness of two different sampling techniques: grab sampling and isokinetic sampling. A laboratory pilot plant was configured to allow for sampling under controlled conditions. A number of flow rates and sediment concentrations were tested. It was found that grab sampling is very effective at lower flow rates. At higher flow rates isokinetic sampling is required. For the sediment typically found in the effluent of an OGS truly isokinetic conditions are not required. Acceptable results are obtained as long as the ratio of tube velocity to pipe velocity is ≤ 1.3.