Abstract
The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. The effects of characteristics of physical conditioners on sludge compressibility and zeta potential were analyzed. The optimal rice husk-based powder was RH-SCB, which presented the highest net sludge solid yield (YN, expresses the dry mass flow by filtration) at 20.39 kg/(m2 h) for 70% dry sludge (DS). Characterization analysis indicates that the hardness and surface Fe content of powders which could influence the compressibility coefficient of sludge cake and sludge zeta potential were the major factors influencing sludge dewaterability. The comparison of feasibility and economic analysis showed that adding RH-SCB improves the quality of the sludge filtrate and reduces the pollution potential of conditioned sludge (the ratio of secondary and primary (RSP) of Cu, Zn, Cd reduces from 43.05, 144.00, 7.25 to 7.89, 14.63, 4.27, respectively), and the costs of using RH-SCB were the lowest (at 88.4% lower than that of the raw sludge). Therefore, it is feasible to use RH-SCB to improve sludge dewaterability.
Highlights
The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared
The highest Y N of 20.39 kg/(m2 h) was achieved when the dosage of RH-SCB was 70% dry sludge (DS) (0.7 kg RH-SCB/kg DS). These results indicate that, among the studied materials, RH-SCB is the optimal one for use as a physical conditioner to enhance sludge dewaterability
The reason may be that the surface iron content of RH-SCB is high, and the surface charge of the RH-SCB is positive, causing the RH-SCB to embed in flocs by charge neutralization with sludge particles before adding FeCl3 and work better as a skeleton builder during sludge dewatering[17]
Summary
The effects of rice husk flour (RHF), rice husk biochar (RHB), and rice husk-sludge cake biochar (RH-SCB, expresses sludge cake biochar deriving from a sludge that has been previously conditioned with rice husk) used as physical conditioners on sludge dewaterability were compared. Due to the increasing amount of wastewater and current efficiency of wastewater treatments, the amount of sewage sludge (moisture content higher than 90%) produced worldwide has increased This sludge must be treated and disposed appropriately because it can contain several pollutants that were removed from the wastewater[2,3]. A permeable skeleton structure is formed in the sludge cakes, increasing the removal of water and, the sludge dewaterability It is not clear what kind of waste biomass-based material is better for sludge dewatering, raw flour, biochar, or sludge cake biochar conditioned by biomass-based materials. The feasibility of adding different waste biomass-based materials including the effects of different waste biomass-based materials on the pollution potential of heavy metals in the sludge, and pH and SCOD of sludge filtrate which can significantly influence sludge disposal, and the disposal costs have not been compared
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