Domestic slurry transportability
This project proposal addresses the transportability of domestic slurries, which is the missing link for future sanitation systems. Many investigators of future treatment concepts have claimed that a low dilution is beneficial for the treatment efficiency and essential for the success of future sanitation systems. But the minimum required dilution and other properties of domestic slurries (i.e. toilet flushing and biodegradable “kitchen” slurries) are yet to be determined. A preliminary assessment of transportation concepts for future sanitation systems shows that the most promising transportation concepts are single phase slurry transport (comparable to pressurized sewer transport systems “drukriolering”) and a two-phase (air-water) transportation concept. The Dutch Foundation for Applied Research on Water Management and Wastewater Treatment (STOWA) has recently recommended to further investigate new black water transport concepts. Future domestic slurries are likely to contain a significant fraction (> 50%) of kitchen waste. A domestic slurry is a non-Newtonian mixture of cohesive solids (faeces), fibers (toilet paper, hair, etc.), non-cohesive solids with a wide particle size distribution and relatively low density ( ~1200 kg/m3, kitchen waste from a grinder) and liquids (water, urine). A number of transportability issues for new sanitation concepts, related to the dilution, or equivalently the solids content, has been largely neglected. These include:
- Rheological characterization of domestic slurries (i.e. black water and biodegradable “kitchen” slurries) as a function of solids content, including cohesive properties
- Transportability of domestic slurries as a single phase slurry or a two-phase (air-slurry) mixture in relation to the slurry dilution.
- Feasibility of different transportation concepts (e.g. intermittent pressure transport, two-phase flow with air addition and air pressure) in relation to the scale of the transportation system and the dilution of different domestic slurries.
Key elements in the Research proposal include:
- Rheological characterization of domestic slurries, including cohesive properties, as a function of solids content, particle size and other parameters. To this end 500 samples of domestic sludges are analysed with respect to viscosity, cohesion, surface tension, density at two temperatures (10 and 20 degree Celcius).
- Experiments on artifi cial sludges will be set-up and carried out in large-scale lab facilities (ALPHA Loop at Deltares). The reasons for not using real life sludge in these experiments is that domestic sludges are not stable due to bio-chemical breakdown processes, repeatability of experiments and ARBOregulations.
- Development of a 1D multi-phase simulation model for the transportation of a domestic slurry.
- A limited number verifi cation lab-experiments with real domestic sludges.
- Monitoring of transient fl ow properties in the lab and possibly a full-scale vacuum sewer, resulting in slurry slug length, velocity, driving pressure per slug and possibly rheological properties in reality.
- The transport of domestic slurries will be monitored in small-scale pilots (e.g. DESAH Sneek). These data, including fl ow regimes, pressure drop, void fraction and water content, will be used for model validation.
Partners
TU Delft, Deltares
Funded by
STW Watertech2013, Deltares, STOWA/Rioned, Waternet, Waterschap Zuiderzeeland, XYLEM BV, Grontmij BV, Desah BV.
TU coordinator
Ivo Pothof
Period
May 2014 – May 2018