Physical disintegration of gross solids in sewers
Background
Investigating the process of gross solid disintegration in sewer systems is critical for increasing the sustainability of these systems and the efficiency in their operation. This process is however poorly understood because it entails a complex interplay between the properties of these solids and hydrodynamics, which can lead to fragmentation and erosion. Gross solids are usually defined as solids bigger than 6mm in two dimensions (i.e. captured by a 6 mm mesh screen). Their specific gravity is usually in the range of 0.9-1.2 and they include fecal stools, toilet paper and “sanitary refuse” such as women’s sanitary protection, condoms, bathroom litter, etc. Gross solids are of particular concern for sewer systems since they can cause maintenance problems such as blockages and their sedimentation can increase the formation of toxic gases (e.g. sulphide and methane). They can further cause blinding of screens at waste water treatment plants. Reduction in wastewater discharges (as a result of e.g., steep population decrease and/or implementation of domestic water saving measures), results in lower flow velocities in sewer stretches which is expected to increase the impacts of fecal matter and other gross solids material.
Goal of the project
In the proposed Master research project, we aim at quantifying the physical disintegration of gross solids, specifically feces, under realistic hydrodynamic conditions. Based on the experimental data, we will devise a model which will constitute a module in a simulation aiming at assessing the effects of reduction in domestic water consumption and transition to decentralized wastewater treatment systems on the operation of sewer systems.
Objective and suggested tasks
The objective is to characterize physical disintegration of gross solids in different turbulent conditions.
The research will consist of three main steps:
- Laboratory experiments for the determination of the rate of disintegration of synthetic feces under different intensities of turbulence. Measurements will be conducted in a turbulence generator with synthetic feces of different physical properties.
- The evolution of the particle size distribution in time (i.e. the physical disintegration of the feces) will be measured from image analysis.
- Verification of results of the measurements conducted with artificial feces by repeating the experiments with real feces - this step will be conducted under well-defined and safe conditions.
Requirements
- Interest in sewer hydraulics and fluid mechanics
- Comprehensive knowledge in Matlab
- High motivation and initiative
Timing and schedule
The thesis starts immediately and lasts 16 weeks. Meetings with the advisors will be scheduled frequently, e.g. weekly or bi-weekly, whereas there will be two meetings with the supervisor.