AWWA WQTC58861

EBMUD's Upper San Leandro (USL) Reservoir began operation of its hypolimnetic oxygenation system (HOS) in May of 2002. The HOS prevented anoxia in USL Reservoir though the process took until September of 2002 to achieve even distribution of oxygen. The HOS installed in USL Reservoir utilized a bubble diffuser design using porous soaker hoses similar to ones installed by the Tennessee Valley Authority in their reservoirs. The HOS was operated in a continuous feed mode (24/7) for two months before the start of "pulse-feed" operations, which was operated at full capacity for fewer hours per day. The pulse-feed operation was intended to allow greater mixing and lateral movement of the dissolved oxygen plume. Use of noncontinuous or pulse feed operations with high oxygen flow rate beginning in July appeared to distribute oxygen more evenly than continuous feed mode and with less oxygen feed required. Without even oxygen distribution at the beginning, anoxia in some extremities could be observed, possibly resulting in higher nutrient releases from the sediments in the further locations from the HOS diffusers.