Waste-activated sludge disruption by dry ice: bench scale study and evaluation of heat phase transformations

Abstract

The freezing process consists of dissipating heat from the product until the final temperature is lower than the temperature of crystallisation of that product. Freezing can be used for numerous applications, including for disruption of waste-activated sludge (WAS). The aim of this study was to calculate the estimated amount of heat conveyed between the solidified carbon dioxide and the WAS, in the following ratios: 0.25:1; 0.5:1; 0.75:1 and 1:1. In heat of phase transformations, dry ice sublimation, water solidification, the amount of heat transferred by other substances and heat transferred from the sludge (dry sludge) were taken into account during the process of WAS freezing. Heat changes on the surface of WAS were registered using a thermovision camera. The effectiveness of WAS disintegration was confirmed by several biochemical parameters such as soluble chemical oxygen demand (increase over 14 times), degree of disintegration (48%), proteins (increase over 5 times), carbohydrates (increase almost 7 times), RNA (increase by 2.23 mg L−1), ammonia nitrogen (increase over 23 times), phosphates (increase almost 27 times) and turbidity (increased over 7 times). It was found that dry ice pretreatment of WAS can be an intriguing alternative for the conventional methods used.Electronic supplementary materialThe online version of this article (10.1007/s11356-019-05889-2) contains supplementary material, which is available to authorized users.

The Use of Solidified Carbon Dioxide in the Aerobic Granular Sludge Pre-Treatment before Thermophilic Anaerobic Digestion

“…(2019) [34], the COD content in the dissolved phase increased to 205 mgO 2 /dm 3 at a SCO 2 /SAS volumetric ratio of 0.25 and peaked at 889 mgO 2 /dm 3 at a SCO 2 /SAS ratio of 1.0, whereas it reached 63 mgO 2 /dm 3 in the non-pre-treated sludge. A rapid decrease in temperature directly affects the external and internal cellular structures of microorganisms.…”

Effect of Low-Temperature Conditioning of Excess Dairy Sewage Sludge with the Use of Solidified Carbon Dioxide on the Efficiency of Methane Fermentation

“…Almost double increase in the concentration of dissolved COD was demonstrated by Stabnikova et al (2008) in their study on the effect of the freezing/defrosting process on food waste [48], and by Örmeci and Vesilind (2001) in their research with sewage sludge from the North Durham Wastewater Treatment Facility, Durham, NC [49]. In turn, Machnicka et al (2019) observed a dependency between SCDO dose and the amount of COD released to the supernatant. The SCDO disintegration at the waste-activated sludge (WAS) to SCDO volumetric ratio reaching 1:0.25 led to an increase in COD concentration from the initial value of 63 mgO 2 •dm −3 (crude sludge) to 205 mgO 2 •dm −3 .…”

“…The SCDO disintegration at the waste-activated sludge (WAS) to SCDO volumetric ratio reaching 1:0.25 led to an increase in COD concentration from the initial value of 63 mgO 2 •dm −3 (crude sludge) to 205 mgO 2 •dm −3 . Increasing the SCDO/WAS ratio to 1:1 increased COD concentration to 889 mg mgO 2 •dm −3 [39].…”

Indexing energy and cost of the pretreatment for economically efficient bioenergy generation

“…Moreover, several factors depend on the destruction of microbes in WAS, such as chemical composition, freezing time, freezing temperature, and the rate of freezing. This method helps in dissociating floc structure and cells by forming ice crystals surrounding the cell walls, increasing the cytoplasmic water content and damaging the cell wall by osmotic shock, decreasing the strength of RNA and DNA, and thereby inducing cold death of microorganisms (Machnicka et al, 2019). A study by Kazimierowicz et al (2021) revealed that the chemical oxygen demand enhanced to 490.6 ± 12.3 mg dm −3 when the dry ice to WAS ratio was .3.…”