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Item type:Publication, Access status: with files , Anaerobic Digestion of Blackwater and Kitchen Refuse(2009); The main objective of this thesis was to assess the anaerobic treatment of blackwater (toilet wastewater) from vacuum toilets without and with kitchen refuse and its potential for resources management sanitation concepts. In a bench scale continuous stirred tank reactor (CSTR), the performance of mesophilic anaerobic digestion of blackwater without and with kitchen refuse was investigated at varying conditions for hydraulic retention time (HRT), ammonia concentration and pre-treatment. At HRT of 20 days, more than 60 % of the input COD was converted to biogas which represents 87 % of the maximum biodegradable COD. At these conditions, the biogas contained 75 % methane and the specific rate was 14 l CH4/cap/d. The digestion runs uninhibited despite high ammonia concentration of 1,111 mg NH4/l. When increasing ammonia artificially about two times, the inhibition by free ammonia starts at concentration of 300 mg NH3/l. Designing of the CSTR based on hydraulic criteria leads to a high unused potential of organic load. When adding kitchen refuse, the reactor can be operated at 15 days HRT and a maximum load of 5 kg COD/(m3 reaktor·d) in an uninhibited state. It results to an increase of methane production of 10 times compared to blackwater digestion. If the HRT decreases or the COD load increase, the reactor runs at an inhibited steady state at lower methane production until the process breaks down. The mesophilic anaerobic digestion process has a relevant hygienization performance of 2 log reduction for the pathogen indicator E.coli. Additionally 2 log reduction can be reached in case of post-storage of 40 days at ambient temperature. Pre-pasteurization and Pre-acidification were studied, but no treatment is able to meet safely the standard of 1.000 CFU/g TR set by WHO (2006) and US EPA (Anonymous 1993). The Anaerobic Digestion Model No. 1 (ADM1) by IWA was implemented with the software Aquasim. The model was calibrated based on the experimental results. The key parameter were the disintegration and hydrolysis constant kdis and the inhibition constants for free ammonia and pH. The calibrated model was applied for the simulation of process limits and of a technical scale reactor. This model can now be used as a tool to design and predict the performance of an anerobic CSTR for combined blackwater and kitchen refuse treatment. The finally proposed sanitation concept for household wastewaters based on anaerobic technology has major advantages in terms of energy balance and CO2 emissions compared to the conventional aerobic system.Publicationtype: Doctoral Thesis4458 1779 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Anaerobic digestion of blackwater from vacuum toilets and kitchen refuse in a continuous stirred tank reactor (CSTR)(2007-05-22); ; ; ; The objective of this research was mesophilic anaerobic digestion of blackwater from vacuum toilets (BW) and kitchen refuse (KR) in a CSTR within an ecological sanitation system. A detailed investigation of the BW characteristics was carried out. Research on anaerobic digestion was performed with CSTR of 10 I volume at HIRT of 10, 15 and 20 days. The digestion of BW at 20 days HRT showed stable performance without inhibition effects, in spite of relatively high ammonium concentrations. The removal of total and particulate COD was 61 % and 53%, respectively, and the methane yield 10 I CH4/cap/day. The addition of kitchen refuse (KR) improved the performance of the CSTR in terms of COD removal efficiency and methane yield. At 20 days HRT the removal of total and particulate COD increased up to 71 % and 67%, respectively, and the methane yield to 27 I CH4/Gap/day. The results at 15 days HRT showed similar performance. At HRT of 10 days, the anaerobic treatment was limited but reached steady state conditions at higher VFA concentrations in the effluent, with a decrease of COD removal of 30 to 33% and of methane yields of 19 to 21 %.Publicationtype: Journal Article137