As solid bowl conveyor centrifuges were being adapted to municipal biosolids, refinement in optimization became necessary. The first centrifuge dewatering applications were mainly performed on primary solids that permitted coarse adjustment of the pond depth to achieve the desired performance.
As stricter environmental laws generated more secondary and finer solids, the ponds were deepened to a neutral level. This eliminated the dry beach and overcame the transportation difficulties associated with the lighter, softer settled solids. At the neutral pond level, bowl conveyor differential
control was adequate to achieve acceptable process results. Higher fuel, disposal, personnel and transportation costs increased the demands for further optimization of the centrifuge. Automatic torque control allowed high solids to be generated but pond adjustments were still required to
maximize economic operation of the dewatering process. The technology for real time pond depth control was first developed in the mid 1990's. The technology is now utilized and accepted by users primarily for thickening or swing applications where the pond setting is critical to the operation. The
evolution of dewatering technology has caused the pond levels to rise significantly above the neutral level. In many cases, the higher pressure generated by the deep pond on the solids squeezes out additional water from the cake. However, the variability of the biosolid's physical characteristics
and changes in hydraulic rates create a situation where the optimal pond setting can only be achieved with real time pond depth control.
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