AWWA WQTC69277

The Three Valleys Municipal Water District (TVMWD) faced several concurrent challenges at the Miramar Water Treatment Plant (MWTP). Residuals management was a cumbersome aspect of operations. On-site lagoons that collected solids-bearing streams from filter backwashes and clarification had to be cleaned on a more frequent than desired basis, which required complex logistics. The complexity of the operations required a balance of maintaining a repository for the solids-bearing streams while the MWTP remained in operation, while at the same time minimizing the impact on recycled water. TVMWD decided to simultaneously address all three of these challenges. A residuals audit was conducted, which characterized the solids-bearing streams and enumerated the amount of residuals generated by the facility. The residuals audit also evaluated management alternatives, which maximized the use of existing facilities yet utilized new processes amenable to the available space and human resource limitations. The alternatives evaluation was further calibrated by the desire to improve on-site storm water management and maximize the recharge of groundwater using storm water and the liquid fraction from residuals management. Ultimately, TVMWD selected a belt filter press as a mechanical dewatering method. The existing lagoons were retrofitted with features to provide contingency residuals management and maximize the use of existing infrastructure. A novel mixing system was retrofitted into one of the lagoons to help assure a consistent quality feed stream to the belt filter press. The area that had been used to consolidate liquid residuals was converted to an engineered infiltration basin, so that storm water collected on-site and liquid fractions from residuals management could be recharged to the local aquifer. Includes tables, figures.