Impact of volatile solids destruction on the shear and solid-liquid separation behaviour of anaerobic digested sludge.

Systematic and comprehensive characterisation of shear and solid-liquid separation properties of sludge across a wide range of solids concentration and volatile solids destruction (VSD) is critical for design and optimization of the anaerobic digestion process. In addition, there is a need for studies at the psychrophilic temperature range as many unheated anaerobic digestion processes are operated under ambient conditions with minimal self-heating. In this study, two digesters were operated at different combinations of operating temperature (15-25 °C) and hydraulic retention time (16-32 d) to ensure a wide range of VSD in the range of 0.

Shear and solid-liquid separation behaviour of anaerobic digested sludge across a broad range of solids concentrations.

Due to the non-homogeneous and multiphase nature of anaerobic lagoon constituents, CFD modelling for process optimisation requires continuous functions for shear and solid-liquid separation properties across a large range of solids concentrations. Unfortunately, measurement of existing material properties of anaerobic sludges is limited to only shear or solid-liquid separation, or to a limited solids concentration. In this work, the shear properties of an anaerobic sludge were measured from 0.

Formation mechanisms and mechanical properties of anaerobic lagoon scum.

The formation of a floating scum layer on the liquid surface of covered anaerobic lagoons prevents optimal and efficient lagoon operation. Scum can reduce hydraulic retention time, inhibit biogas capture and cause damage to lagoon covers. Managing the negative impact of scum requires understanding what scum is, how it forms and how it consolidates.

Characterising sedimentation velocity of primary waste water solids and effluents.

Sedimentation in waste water is a heavily studied topic, but mainly focused on hindered and compression settling in secondary sludge, a largely monodispersed solids, where bulk sedimentation velocity is effectively described by functions such as double Vesilind (Takacs). However, many waste water solids, including primary sludge and anaerobic digester effluent are polydispersed, for which application of velocity functions is not well understood. These systems are also subject to large concentration gradients, and poor availability of settling velocity functions has limited design and computational fluid dynamic (CFD) analysis of these units.

Rheological characterisation of synthetic and fresh faeces to inform on solids management strategies for non-sewered sanitation systems.

In order to obviate the economic issues associated with pit latrine emptying and transport such as high water additions and rheologically difficult sludge properties, the implications of prompt solid/liquid separation were investigated. This was achieved through rheological characterisation of fresh human faeces and synthetic faeces, and comparison with aged faecal sludges. Shear yield stress, thixotropy and post-shear structural recovery were characterised for a total solids (TS) concentration range of 5-35% total solids (TS) and stickiness yield stress was determined for concentrations up to 100% TS.

On the compressional rheology of fresh faeces: Evidence for improving community scale sanitation through localised dewatering.

Non-sewered sanitation is currently dependant upon pit latrine emptying, the safety of which is compromised by the high costs of faecal sludge transport to centralised treatment facilities. Transport in turn is hindered by the complex rheology of pit latrine sludge. This study therefore characterised the compressional rheology of fresh faeces and modelled the implications for passive (gravity) or mechanical (forced) solid/liquid separation.

Compartmentalization of extracellular polymeric substances (EPS) solubilization and cake microstructure in relation to wastewater sludge dewatering behavior assisted by horizontal electric field: Effect of operating conditions.

Sludge treatment and disposal have become important environmental issues in China. Mechanical dewatering is widely used to reduce the amount of sludge to be disposed and relieve the rapid growth pressure of waste sludge. In comparison to traditional sludge dewatering processes, pressure electro-osmotic dewatering has many advantages on sludge dewatering efficiency, low conditioner dosage and concentrated cake are both beneficial to further recycling of waste sludge.

Quantification of wastewater sludge dewatering.

Quantification and comparison of the dewatering characteristics of fifteen sewage sludges from a range of digestion scenarios are described. The method proposed uses laboratory dewatering measurements and integrity analysis of the extracted material properties. These properties were used as inputs into a model of filtration, the output of which provides the dewatering comparison.