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.
Apparatus for Observation and Analysis of Floc Blanket Formation and Performance
AbstractFloc blankets are fluidized beds of aggregated suspended particles utilized in some upflow sedimentation tanks for drinking water treatment. Floc blankets can significantly enhance particle removal and may reduce operation and maintenance costs. An experimental apparatus was built with the goal of developing an understanding of floc blanket physics and to establish a mechanistic basis for optimizing floc blanket performance. Visual insights into floc blanket mechanics are obtained by analyzing transmitted light intensity through a 1.3-cm-thick section of a floc blanket. Floc blankets were formed under simulated raw water conditions of 100 nephelometric turbidity units (NTU), an alum coagulant dose of 45  mg/L (4.1  mg/L as Al), and at sedimentation tank upflow velocities ranging from 0.4 to 1.8  mm/s. This study presents nondestructive methods for measuring floc blanket concentration and position of the floc-water interface, steady-state performance data from the experimental apparatus, and the ef...
Suitability and water quality criteria of an open drainage municipal sewage water at Coimbatore, used for irrigation.
Sanganur canal is the major open drainage system which has intricate linkage with storm water supply, domestic sewage and industrial effluent disposal. Water samples from various stations were collected and analysed for physicochemical parameters to assess the water quality of the Sanganur canal system. The study revealed that physicochemical parameters like pH, EC, TDS, DO, BOD, COD exceeded the permissible limit, clearly indicating the need of proper treatment of waste water before discharge into the Noyyal river.