The role of water in sludge dewatering

Abstract

While the dewatering of wastewater sludges has received considerable research attention, it has been assumed that the water con tinuum surrounding the sludge particles has the physical properties of bulk water. This paper suggests that such an assumption may not be valid. The existence of vicinal water, consisting of ordered and layered water molecules on the surfaces of submerged solids, is demonstrated using research from various disciplines. The meaning of "bound water" as used in sludge technology is discussed, and it is shown that bound water can be defined in several ways, depending on the test used. It seems reasonable that bound water as it is usually defined actually consists of three different types of water-water captured in the interstitial spaces within floes and within cells, vicinal water on the surfaces of solids, and water of hydration. Only some of the interstitial water can be removed by mechanical dewatering. Because of the large surface area of sludge particles, including living cells, it is likely that much of the bound water is vicinal water, and this cannot be removed mechanically. The deter mination of the various fractions of these waters may lead to a better understanding of mechanical sludge dewatering.zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Water Environ. Res., zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGF 66,4(1994).

Spatio-temporal dynamics of land use practices on rivers in tropical regions: A case study of Ruiru and Ndarugu Basins, Kiambu County, Kenya

“…This periodic input of sediment into the rivers leads to decreased water clarity, thereby inhibiting light penetration and leading to reduced biological activity. Highly turbid waters have more suspended solids and are prone to oxygen depletion (Vesilind et al, 1994).…”

Principal component analysis on sewage sludge characteristics and its implication to dewatering performance with Fe2+/persulfate-skeleton builder conditioning

“…More recently, Skinner et al (2015) proposed a model of filtration using sludge properties as inputs for quantification and comparison of dewaterability as the permeability and compressibility of sludge. In addition, moisture distribution [''free,'' ''interstitial,'' ''surface'' or ''bound'' water (Lee 1996;Vesilind 1994)] is commonly accepted as the crucial factor influencing in dewatering performance. However, the water distribution concept alone is not sufficient to elucidate the dewaterability because some characterization methods of water distribution are not able to provide quantitative results and also relatively difficult to implement (Deng et al 2011;Vaxelaire and Cezac 2004).…”

Structure modification and extracellular polymeric substances conversion during sewage sludge biodrying process

“…Firstly, SSBM were oven-dried at 75°C to destroy the bound water layers (Vesilind, 1994). Secondly, the deionized water was added into the dried SSBM to adjust the moisture content to 65% (to cover the initial 62% moisture content) to ensure that the total water in the SSBM is free water (named as SSBM free ).…”