Performance of a novel vertical-flow settler: a comparative study.
By increasing particle concentration and G value (root-mean-square velocity gradient) to enhance flocculation, a novel vertical-flow settler was designed to increase sedimentation effectiveness, and to simultaneously improve operational stabilization. Due to the gradual decrease in upward flow-rate of raw water, a flocs blanket would form and suspend in the middle section of the settler, not at the bottom as in a conventional clarifier. Enough large flocs, resulted from flocculation or filtration, would continuously settle out of the flocs blanket, and simultaneously, the flocs in raw water or those forming above the blanket would ceaselessly enter the flocs blanket. As a result, the flocs concentration in the blanket could keep a dynamic balance. The hydrodynamic shear in the blanket was improved by flow separation, which was induced by the abrupt change in flow channel. Due to the floes blanket and improved hydrodynamic shear, flocculation would be enhanced, which was helpful for removing fine particles in raw water. A comparative study showed that the novel vertical-flow settler had a much better performance in the removal of the particles in raw water than a conventional one, when they treated kaolin suspensions of different concentrations (500, 100 and 50 mg/L, respectively) coagulated by polyaluminum chloride(PAC1) at the up-flow rates of I and 2 mm/s, respectively.
The design and operation of a double-V compartment vertical-flow settler
This paper descriptionbes the development of a vertical-flow settler for underground pumping installations in the mines of Gold Fields of South Africa Ltd. The recommended settler employs the principle of 'dynamic filtration': the solids that are in suspension in mine water are filtered through a stable horizontal bed of flocculated particles, a technique that was established in about 1958.
Using Streaming Current Detectors in Water Treatment
An independent assessment of streaming current detectors (SCDs) was carried out, including laboratory studies, a survey of SCD users, and on-site studies at water treatment plants. In accordance with theory, streaming current was found to be proportional to zeta potential, although a reading offset was observed. Users rated the SCD highly in most respects. The most commonly reported difficulty was clogging of the instrument or of sample lines. An analysis of periods before and after SCD installation at 10 treatment plants showed significant reductions in chemical expenses, particularly during times of changing raw water conditions. Water quality was not significantly improved, but this may have been because plant flows had increased between the periods being compared. Practical aspects of SCD use are discussed.