High Rate Sedimentation - Fall 2016

Ziwei (Vanessa) Qi, Aimee Owens, Ruizhe He

Abstract:

The Fall 2016 High Rate Sedimentation team investigated the effect of high upflow rates on maintaining a dense floc blanket and functional plate settlers. The team built a small-scale flocculator and tube model of the sedimentation tank in order to simplify the many experiment variation configurations.To analyze variables that effect effluent turbidity at an up- flow velocity of 3 mm/s, which is roughly triple the standard AguaClara rate. Experiment 1 varied length of the tube settlers, Experiment 2 varied length of the floc blanket, and Experiment 3 attempted to increase the density of the floc blanket by adding mass. Experiments have verified that longer tube settlers and longer floc blankets improve sedimentation tank performance.

High Rate Sedimentation - Plate Settlers, Spring 2016

Albert Cheng, Sidney Lok, Yuqi Yu, Lishan Zhu

Abstract

This semester, the goal of the High Rate sedimentation - Plate Settlers team was to maintain a suspended layer of colloidal particles (flocs) at upflow velocities higher than 1 mm/s. The suspended layer, referred to as the floc blanket, circulates flocs, enhances flocculation, and is self-cleaning. As the floc blanket grows in height, it spills over a weir into a sludge collection chamber to prevent sludge build-up inside the sedimentation tank. increasing the upflow velocity in the sedimentation tank decreases the necessary plan-view area and cost of construction. A high density floc blanket is necessary to prevent flocs from escaping the sedimentation tank at higher velocities. The High Rate Sedimentation - Plate Settlers team explored different plate settler geometries in the sedimentation tank to concentrate the floc blanket.

High Rate Sedimentation (Floc Blanket), Spring 2016

Ogechukwu (Oge) Anyene, Isha Chaknalwar, Josiah Hinterberger, Ziwei (Vanessa) Qi

Abstract

The High Rate Sedimentation - Floc Blanket team built a sedimentation tank model with the goal of increasing the upflow velocity and decreasing the plan view area, without degrading the performance of the floc blanket inside the tank reactor. Under high turbidity conditions, a stable floc blanket was maintained under upflow velocities from 1-4 mm/s. Two method of encouraging floc re-circulation, viz., in-reactor lamella plates and sludge recycling, were tested to observe effects on effluent turbidity. Results indicated that neither method had a strong enough effect to fully recommend increased upflow velocity, but future testing in improved apparatus with low turbidity influent has potential.

High Rate Sedimentation - Summer 2017

Christopher Galantino and Andrew Kang

Abstract:

The High Rate Sedimentation team designed, fabricated, and experimented on various sedimentation designs with an upflow velocity of 3 mm/s while maintaining a efficient effluent turbidity and reducing cost and space. Working off where the Spring 2017 team left off, the HRS team continued to research the effects of floc blanket height, tube settler length, varying geometries, and the size-driven floc blanket formation hypothesis. The HRS team concluded that the height of floc blanket may not provide better performance, as originally thought. Also, it has been concluded that the Trapezoidal geometry is not necessary, but provided insight on the behavior of floc on bends.

High Rate Sedimentation - Fall 2015

Oge Anyene, Larry Ge, Yuqi Yu

Abstract:

The Fall 2015 High Rate Sedimentation team aims to design a new sedimentation tank that will allow the tank upflow velocity to be significantly increased (by a factor or 2 to 10), without sacrificing particle removal performance (no increase in effluent turbidity). The motivating factors behind this velocity increase would be to decrease the plan view area of the sedimentation tanks, leading to smaller plants and lower the construction costs and to decrease the overall hydraulic retention time of the plant. One of the primary objectives of the new sedimentation tank will be to maintain a consistent floc blanket (i.e. one that allows for excess floc drainage into a floc hopper) similar to the ones found in current AguaClara plants, even with the increased upflow velocity. In order to achieve this goal our proposed design will feature two sets of plate settlers, one set near the bottom of the tank that will be suspended within the floc blanket, and one above them to capture finer particles. To test the feasibility of such a design, several small-scale experiments will be run in the lab. Such experiments will prove to demonstrate whether or not it is possible to maintain a fluidize bed within plate settlers and what the bulk flow of flocs will look like for a floc blanket maintained within plate settlers.

Sensor Development - Spring 2017

Cheer Tsang, Luna Oiwa, Jingfei Wang

Abstract:

This semester, the Sensor Development subteam modified and recalibrated the fluidized bed solids concentration sensor. This sensor enable the High Rate Sedimentation (HRS) team to determine the concentration of suspended clay particles in a running flocculation recirculator. In addition, the team fabricated a submersible sensor to determine the depth and concentration of the sludge layer in a sedimentation tank. This sensor functions in the same way as the fluidized bed solids concentration sensor, with the added characteristic that the photometer is fixed to the end of a PVC tube.