Salinity Effect on Mechanical Dewatering of Sludge with and without Chemical Conditioning

Abstract

The salinity levels of wastewater and sludge are relatively high in some coastal cities as they may use saline water for toilet flushing, and as such,the sludge dewaterability can be affected by it. The salinity effect on sludge dewaterability was therefore investigated through experimental testing of specific resistance in filtration (SRF), time to filter (TTF), and final solid content of sludge. SRF and TTF were determined using Buchner funnel tests. The final solid content was estimated by centrifuging the sludge at four levels of rotational speed. Sludge with three salinity levels (5,000, 10,000 and 20,000 ppm) were considered in this study. Coagulants such as alum, iron(II) sulfate, and organic polyelectrolytes were added to the sludgetostudythe dewaterability of such sludge with chemical conditioning. Experimental results show that doubling the salinity level of the sludge from 10,000 to 20,000 ppm shows not much change in SRF and TTF. Compared with the sludge without chemical conditioning, the addition of the coagulants to the sludge at a salinity level of 5,000 ppm drastically reduces its SRF and TTF. However, sludge with and without chemical conditioning at a salinity of 20,000 ppm has similar SRF and TTF. The final solid content of sludge increases almost linearly with salinity. Among the coagulants used in this study, the cationic polyelectrolyte is found to be better in improving sludge dewaterability, while iron(II) sulfate performs slightly better in enhancing the final solid content of the sludge.

Dewaterability of sludge conditioned with surfactant DDBAC pretreatment by acid/alkali

“…In the sludge conditioning process, both filtrate volume and filtration time were recorded to assess sludge SRF. SRF was calculated as the slope of a linear plot of volume vs. time/volume (Lo et al 2001). Protein, polysaccharide, and nucleic acid contents of the sludge supernatant were spectrophotometrically measured using a UV/visible spectrophotometer (TU-1901, PGeneral, China).…”

Effect of Ultrasound Pretreatment on Sludge Digestion and Dewatering Characteristics: Application of Particle Size Analysis

“…Filtrate volume and filtration time were recorded. SRF was calculated as the slope of the linear plot of volume vs. time/volume [18]. The water content of the sludge cake trapped by the filter paper was measured in accordance with standard methods [16].…”

Understanding the impact of chemical conditioning with inorganic polymer flocculants on soluble extracellular polymeric substances in relation to the sludge dewaterability

“…The application of chemical flocculants helps to increase the sludge particle size by agglomerating the small fines of the sludge colloids, which causes blinding, to form large flocs, which can be more easily separated from the water. The sludge flocs conditioned by organic polyelectrolytes are large and loose [2] and therefore fit for low-pressure dewatering process (centrifuge), while inorganic coagulants conditioning can produce a rigid floc, so they are often used in high-pressure process such as filter press and belt press [3,4].…”