Influence of process operating parameters on dryness level and energy saving during wastewater sludge electro-dewatering

Electrically assisted mechanical dewatering, known as electro-dewatering (EDW), is an alternative emerging technology for energy-efficient liquid/solids separation in the dewatering of wastewater sludge. In this study, the performance of the electro-dewatering (EDW) process for activated wastewater sludge was investigated. The influence of the operating modes; being the timing of voltage (U-EDW) or current (I-EDW) application to either or both the filtration and compression stages, and the influence of the applied pressure (in successive 30 min pressure steps) were studied. The results showed that by delaying the application of the electric field to the filter cake compression stage, there was a potential saving in power consumption of around 10–12% in the case of U-EDW and about 30–46% in the case of I-EDW. The increase of the applied pressure from 0.5 to 12 bar during the filter cake compression stage leads to an increase in electro-dewatering kinetics. The results also reveal that at a low electric field level the increase of the processing pressure has a relatively pronounced effect on the dewatering process. At high levels of the electric field, a minimum processing pressure (4–6 bar) is required to improve the electrical contact between the electrode and the sludge and thus lower the energy consumption. [Display omitted] •EDW kinetics increase with processing pressure, voltage and current.•In EDW a minimum pressure (4–6 bar) is required to improve the electrical contact.•Delaying the application of the electric field allows potential saving in power consumption.•EDW kinetic is increased by the succession of different stages of applied pressure.•The criterion (KsiEDW) provides a helpful tool to optimize the operating mode of EDW-process.