The intensification of sludge digestion by the disintegration of activated sludge and the thermal conditioning of digested sludge

Abstract

The study is focused on the anaerobic degradation of different disintegrated materials containing a cell lysate. The aerobic cell lysate was produced by a disintegration of the excess activated sludge by means of a lysate-thickening centrifuge, and the anaerobic cell lysate, by a rapid thermal treatment of anaerobic digested sludge. The improvement of both the methane yield and the biodegradability of thickened activated sludge is influenced by the quality of input excess activated sludge and the parameters and efficiency of the thickening centrifuge. The improvement of the methane yield was on average 11.5-31.3% depending on the sludge quality. The relation of the stimulation effect, the disintegration rate and the anaerobic sludge activity suggest that the efficiency of the disintegration will be probably higher in the more intensive digestion process. The rapid thermal treatment of digested sludge produced a material with an active anaerobic lysate. The stimulation effect of the anaerobic lysate caused an improvement of the methane yield of raw sludge in the range of 35-49% depending on the lysate amount. The rapid thermal reactor produced a relatively very active cell lysate from anaerobic bacteria; the heat energy of the lysate can be utilised in the digester heating system.

Sewage Sludge as a Biomass Resource for the Production of Energy: Overview and Assessment of the Various Options

“…Very briefly, the various options for the recovery of energy from sewage sludge, in fact, from the organic compounds in the sludge, can be subdivided into nine groups: (1) anaerobic digestion of sewage sludge, (2) production of biofuels from sewage sludge, (3) direct production of electricity from sewage sludge in microbial fuel cells, (4) incineration of sewage sludge with energy recovery, (5) co-incineration of sewage sludge in coal-fired power plants, (6) gasification and pyrolysis of sewage sludge, (7) use of sludge as an energy and raw material source in the production of Portland cement and building materials, (8) supercritical wet oxidation of sewage sludge, and (9) hydrothermal treatment of sewage sludge.…”

“…With the standard digestion technologies, only approximately 20–30% of the organic matter is mineralized. A substantial increase of biogas production can be obtained by applying a proper physical, chemical, thermal, mechanical, or biological pretreatment step, such as hydrothermal heating, microwave heating, ultrasonic treatment, use of ozone, use of enzymes, use of liquid jets, treatment (hydrolysis) with sodium hydroxide, application of high-performance pulse techniques, or wet oxidation. – The potential of the various pretreatment processes to increase the anaerobic biodegradation rate and to produce a much larger amount of biogas is substantial. Also the smaller residual amount of the dewatered sludge, which has to be disposed in a controlled landfill or treated additionally, is an advantage.…”

Bacteriophages—potential for application in wastewater treatment processes

“…A wide range of treatments have been examined for their potential to improve WAS digestibility 13 during MAnD (Muller, 2001). Digestibility has been improved by mechanical (Dohanyos et al 2000;Winter, 2002), thermal (Li and Noike, 1992;Kepp et al 2000), chemical (Ray et al 1990;Lin et al 1997) and ultrasonic (Rooksby et al 2002) (Kalyuzhnyi and Fedorovich, 1998), thus affecting degradation processes and leading to reduced methane yields (O'Flaherty et al 1998;Ranade et al 1999). Furthermore, the associated sulphide production contributes to corrosion and odour problems and can lead to precipitation of trace metals (Stephenson et al 1994).…”

Heat Treatment Combined With Cation Addition to Improve the Dewaterability of Waste Activated Sludge

“…Heat treatment has been used previously to promote hydrolyzation of cellular structure in advance of digestion processes (Dohanyos et al, 2000). Samples were heated to 40ºC, 60ºC, or 80ºC by placing a volumetric flask containing 200 ml of sample inside a pre-heated waterbath (Fisher Scientific Isotemp model 228).…”