The use of hydrodynamic disintegration as a means to improve anaerobic digestion of activated sludge

Abstract

Disintegration by hydrodynamic cavitation has a positive effect on the degree and rate of sludge anaerobic digestion. By applying hydrodynamic disintegration the lysis of cells occurs in minutes instead of days. The intracellular and extracellular components are set free and are immediately available for biological degradation which leads to an improvement of the subsequent anaerobic process. Hydrodynamic disintegration of the activated sludge results in organic matter and a polymer transfer from the solid phase to the liquid phase, and an increase in COD value of 284 mg•ℓ-1 was observed, i.e. from 42 mg•ℓ-1 to 326 mg•ℓ-1. In addition the degree of disintegration changed from 14% after 15 min disintegration to 54% after 90 min of disintegration. A disruption of bacterial cells by hydrodynamic cavitation has a positive effect on the degree and rate of excess sludge anaerobic digestion. The cells of the activated sludge microorganisms rupture and addition to the digestion process leads to increased biogas production. The hydrodynamic disintegration of activated sludge leads to a higher degree of degradation and higher biogas production. Adding the disintegrated sludge (10%, 20% and 30% of volume) to fermentation processes resulted in an improvement in biogas production of about 22%, 95% and 131% respectively.

E Ffects of the Solubilisation of the Cod of Municipal Waste in Thermal Disintegration

“…The value of the reaction rate coeffi cient for the solubilisation of the solid waste fraction (hydrolysis) at 37°C calculated on the basis of designated parameters k 20 and θ amounts to 0.88 d -1 . For comparison, the values of the reaction rate coeffi cients k for the biochemical degradation reaction given in the literature amount to, e.g.…”

“…The value of the coeffi cient θ which describes the temperature effect on the reaction rate is presented in the literature in the range between 1.013 (sewage sludge) and 1.066 (hydrocarbons) [3,20,21]. The higher the value of this coeffi cient, the higher the temperature effect on the decomposition rate, and thus the substrate biodegradability.…”

“…Besides organic compounds, the raw materials must also contain the appropriate proportions of other nutrients, and be characterised by adequate hydration and pH level. A large percentage of waste with high fat and protein has a positive impact on the digestion process, while a high content of lignin and hemicellulose reduces the effi ciency of mixed waste biodegradation under anaerobic conditions [3,11,14,19,20]. In addition to the availability of organic carbon, the relationships between the other nutrients also determine the effi ciency of the methane fermentation process.…”

Improvement of anaerobic digestion of sewage sludge in a wastewater treatment plant by means of mechanical and thermal pre-treatments: Performance, energy and economical assessment

“…In general, at low applied energy only floc disintegration is observed, while high energy is required to damage microbial cells (Appels et al, 2008;Carrère et al, 2010). Although not many results are available for mechanical pre-treatments in respect to the other methods, it is demonstrated that the efficiency of most of the technologies in improving AD of sewage sludge is rather low, if not coupled with other methods (Cho et al, 2014;Grübel and Machnicka, 2009;Kampas et al, 2007;Machnicka et al, 2009).…”

“…Pre-treatments can be grouped into biological, thermal, mechanical, chemical as well as different combination of these (Appels et al, 2008;Barjenbruch and Kopplow, 2003;Bougrier et al, 2006;Carrère et al, 2010;Kavitha et al, 2014;Kim et al, 2003;Nagare et al, 2008;. In the wide scenario of lysis technologies, mechanical and thermal pretreatments are the most common systems available on the market, working in full scale plants with good results in terms of COD solubilization and AD performance improvement (Bougrier et al, 2008;Choi et al, 2006;Climent et al, 2007;Dohányos et al, 1997Dohányos et al, , 2004Ferrer et al, 2008;Grübel and Machnicka, 2009;Kampas et al, 2007;Machnicka et al, 2009;Zábranská et al, 2006). Soluble COD (SCOD), that is the amount of COD in the liquid phase (after 0.45 lm filtration), is a parameter of easy analytic determination strictly related to sludge degradability.…”